80MGF Series

80MGFService Literature 80MGF SERIES UNITS 80MGF series units are mid−efficiency gas furnaces manufactured with tubular heat exchangers formed of aluminized or stainless steel. 80MGF units are available in heating capacities of 45,000 to 140,000 Btuh and cooling applications up to 5 tons. Refer to Engineering Handbook for proper sizing. Units are factory equipped for use with natural gas. A kit is available for conversion to LPG operation. All 80MGF units built proir to September 98 use electronic (direct spark) ignition. 80MGF−11 model units are equipped with the Lennox SureLight ignition system. The 80MGFX unit meets the California Nitrogen Oxides (NOx) Standards and California Seasonal Efficiency requirements. All units use a redundant gas valve to assure safety shut−off as required by A.G.A. or C.G.A. The heat exchanger, burners and manifold assembly can easily be removed for inspection and service by simply disconnecting gas, unplugging wiring harness and spark wires and removing four screws holding the heat exchanger in place. Then the heat exchanger slides out of the cabinet. All specifications in this manual are subject to change. Procedures outlined in this manual are presented as a recommendation only and do not supersede or replace local or state codes. In the absence of local or state codes, the guidelines and procedures outlined in this manual (except where noted) are recommended only and do not constitute code. Units may be installed in upflow, downflow or horizontal position. The heat exchanger is designed for upright or horizontal use only. When the unit is installed in the downflow position, the heat exchanger is field removed and reinstalled so it is upright when the cabinet is inverted. No field conversion is required when the unit is installed in the horizontal position. Introduction . . . . . . . . . . . . . . . . . . . . . . . . Specifications . . . . . . . . . . . . . . . . . . . . . . Blower Data . . . . . . . . . . . . . . . . . . . . . . . Parts Identification . . . . . . . . . . . . . . . . . . I Unit Components . . . . . . . . . . . . . . . . . . II Installation . . . . . . . . . . . . . . . . . . . . . . . 1 2 5 7 9 19 TABLE OF CONTENTS III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . Preliminary Seasonal Checks . . . . . Heating Start Up . . . . . . . . . . . . . . . . IV Heating System Service Checks . . . V Typical Operating Characteristics . . . VI Maintenance . . . . . . . . . . . . . . . . . . . . VII Wiring and Sequence of Operation . VIII SureLight Control Troubleshooting . 19 20 20 20 22 24 26 40 Corp. 9801−L2 Revised 08−2004 Page 1 © 1998 Lennox Industries Inc. SPECIFICATIONS Model No. Input Btuh (kW) Output Btuh (kW) lA.F.U.E. California Seasonal Efficiency Flue size connection diameter Temperature rise range in. (mm) round 30 - 60 (17 - 33) in wg. (Pa) 80MGF2(X)-45 45,000 (13.2) 36,900 (10.8) 80.1% 75.4% 76.4% 3 (76) 45 - 75 (25 - 42) .50 (125) 1/2 (13) 9x7 229 x 178 1/4 (187) Tons kW 1, 1-1/2 or 2 3.5, 5.3 or 7.0 130 (59) 120 volts b LPG/propane kit Twinning Kit Up Flow/Horizontal Up−Flow/Horizontal Filter and Filter Rack Kits }No. }N & size of filt i f filters − in. ( i (mm) ) Down flow Down-flow Filter Filt Kit Catalog No. No. & Size of Filters in. (mm) 60 hertz 10 x 7 254 x 178 1/3 (224) 2, 2-1/2 or 3 7.0, 8.8 or 10.6 9x7 229 x 178 1/4 (187) 1, 1-1/2 or 2 3.5, 5.3 or7.0 135 (61) 1 phase (less than 12 amps) All models 10 x 7 254 x 178 1/3 (224) 2, 2-1/2 or 3 7.0, 8.8 or 10.6 80MGF2-60 80MGF3(X)-60 80MGF2-75 80MGF3(X)-75 60,000 (17.6) 49,200 (14.4) 80.5% 75.9% 80.1% 76.8% 4 (102) 75,000 (22.0) 61,700 (18.1) 80.0% 76.8% _F (_C) High static certified by A.G.A./C.G.A. Gas Piping Size I.P.S. Natural or LPG/propane Blower wheel nominal diameter x width di t idth Blower motor output hp (W) in. mm Nominal cooling that th t can b added be dd d Shipping weight lbs. (kg) 1 package Electrical characteristics Optional Accessories (Must Be Ordered Extra) b LB-69845L (38K84) 15L3801 5 lbs. (2 kg) Single (32J02) Ten Pack (66K64) (1) 16 x 20 x 1 (406 x 508 x 25) LB-69843A (32J01) 3 lbs. (1 kg) (2) 16 x 20 x 1 (406 x 508 x 25) LB-79239A (67J91) 79J15 10 lbs. (4 kg) Down-flow Combustible Floor Base Sidewall Power Venting Kit Hanging Bracket Kit lAnnual Fuel Utilization Efficiency based on U.S. furnaces. }Polyurethane frame type filter is furnished with kit. Filters are not furnished with kit and must be ordered extra. DOE test procedures and according to FTC 25 lbs. (11 kg) 15 lbs. (8 kg) combustion system rating for non-weatherized LB-69957 (46J66) labeling regulations. Isolated Page 2 SPECIFICATIONS continued Model No. Input Btuh (kW) Output Btuh (kW) lA.F.U.E. California Seasonal Efficiency Flue size connection diameter Temperature rise range in. (mm) round 45 - 75 (25 - 42) in wg. (Pa) .50 (125) 1/2 (13) 12 x 8 305 x 203 1/2 (373) Tons kW 2, 2-1/2, 3, 3-1/2 or 4 7.0, 8.8, 10.6, 12.3 or 14.1 140 (64) 120 volts b LPG/propane kit Twinning Kit Up Flow/Horizontal Up−Flow/Horizontal Filter and Filter Rack Kits }No. & size of filters − in. (mm) Down flow Down-flow Filter Kit Catalog No. No. & Size of Filters in. (mm) LB-79239A (67J91) Single (32J02) Ten Pack (66K64) (1) 16 x 20 x 1 (406 x 508 x 25) 60 hertz 12 x 9 305 x 229 3/4 (560) 3-1/2, 4, 5 or 6 12.3, 14.1, 17.6 or 21.1 175 (79) 1 phase (less than 12 amps) All models 80MGF4(X)-75 75,000 (22.0) 61,700 (18.1) 80.0% 76.3% 80.1% 76.5% 4 (102) 35 - 65 (19 - 36) .65 (162) 80MGF3/4(X)-100 80MGF4/5(X)-100 100,000 (29.3) 82,000 (24.0) 80.0% 77.0% _F (_C) High static certified by A.G.A./C.G.A. Gas Piping Size I.P.S. Natural or LPG/propane Blower wheel nominal diameter x width di t idth Blower motor output hp (W) in. mm Nominal cooling that th t can b added be dd d Shipping weight lbs. (kg) 1 package Electrical characteristics Optional Accessories (Must Be Ordered Extra) b LB-69845L (38K84) 15L3801 LB-69845K (81J14) 5 lbs. (2 kg) Single (46J14) Ten Pack (66K65) (1) 20 x 20 x 1 (508 x 508 x 25) 3 lbs. (1 kg) LB-69843A (32J01) (2) 16 x 20 x 1 (406 x 508 x 25) 10 lbs. (4 kg) 79J15 LB-79239B (67J92) 25 lbs. (11 kg) 15 lbs. (8 kg) combustion system rating for non-weatherized Down-flow Combustible floor Base Sidewall Power Venting Kit Hanging Bracket Kit lAnnual Fuel Utilization Efficiency based on U.S. furnaces. }Polyurethane frame type filter is furnished with kit. Filters are not furnished with kit and must be ordered extra. DOE test 10 lbs. (4 kg) LB-69957 (46J66) procedures and according to FTC labeling regulations. Isolated Page 3 SPECIFICATIONS continued Model No. Input Btuh (kW) Output Btuh (kW) lA.F.U.E. California Seasonal Efficiency Flue size connection diameter Temperature rise range _F (_C) in wg. (Pa) .50 (125) 1/2 (13) 12 x 8 305 x 203 1/2 (373) Tons kW 2, 2-1/2, 3, 3-1/2 or 4 7.0, 8.8, 10.6, 12.3 or 14.1 175 (79) 120 volts b LPG/propane kit Twinning Kit Up−Flow/Horizontal Filter and Filter Rack Kits }No. & size of filters − in. (mm Catalog No. Down-flow Filter Rack No. & Size of Filters in. mm LB-79239B (67J92) 60 hertz 12 x 9 305 x 229 3/4 (560) 3-1/2, 4, 5 or 6 12.3, 14.1, 17.6 or 21.1 190 (86) 1 phase (less than 12 amps) All models in. (mm) round 80.0% Not Available 4 (102) 45 - 75 (25 - 42) .65 (162) 80MGF3/4-120 80MGF4/5(X)-120 80MGF4/5-140 140,000 (41.0) 114,800 (33.6) 80.1% 75.5% 80.0% Not Available 5 (127) 120,000 (35.2) 98,400 (28.8) High static certified by A.G.A./C.G.A. Gas Piping Size I.P.S. Natural or LPG/propane in. (mm) Blower wheel nominal diameter x width Blower motor output hp (W) in. mm Nominal cooling that can be added Shipping weight lbs. (kg) 1 package Electrical characteristics Optional Accessories (Must Be Ordered Extra) b LB-69845K (81J14) 15L3801 Single (46J14) Ten Pack (66K65) (1) 20 x 20 x 1 (508 x 508 x 25) LB-69843A (32J01) 5 lbs. (2 kg) Single (58J93) Ten Pack (66K66) (1) 20 x 20 x 1 (508 x 508 x 25) 3 lbs. (1 kg) (2) 16 x 20 x 1 (2) 406 x 508 x 25 10 lbs. (4 kg) 79J15 LB-79239C (67J93) 12 lbs. (5 kg) Down-flow Combustible Floor Base Sidewall Power Venting Kit Hanging Bracket Kit 25 lbs. (11 kg) 15 lbs. (8 kg) LB-69957 (46J66) lAnnual Fuel Utilization Efficiency based on U.S. DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces. }Polyurethane frame type filter is furnished with kit. 2 in. x 5 in. (51 mm x 127 mm) flue adaptor furnished with -140 input furnaces for connection to furnace induced draft blower. Filters are not furnished with kit and must be ordered extra. Page 4 50 .50 . (25 mm) cleanable filter (not furnished) in place.30 .40 .g.60 .25 . 0 . Also see Filter Air Resistance table 80MGF3-60 AND 80MGF3-75 BLOWER PERFORMANCE External Static Pressure in.20 .05 . w. w.05 .20 .25 . 80MGF2-60 AND 80MGF2-75 BLOWER PERFORMANCE External Static Pressure in.30 .15 .15 .g. Also see Filter Air Resistance table Page 5 .40 . 0 .BLOWER PERFORMANCE DATA 80MGF2-45.70 NOTE Air Volume at Various Blower Speeds High cfm 1270 1245 1220 1195 1170 1140 1110 1060 990 900 800 L/s 600 590 575 565 550 540 525 500 465 425 380 Medium-High cfm 980 975 975 965 960 950 940 910 880 810 740 L/s 460 460 460 455 455 450 445 430 415 380 350 Medium-Low cfm 770 770 770 765 760 760 760 750 740 690 630 L/s 365 365 365 360 360 360 360 355 350 325 295 cfm 570 565 565 560 560 555 550 545 540 530 520 Low L/s 270 265 265 265 265 260 260 255 255 250 245 Pa 0 12 25 37 50 62 75 100 125 150 175 All air data is measured external to unit with 1 in.10 .70 NOTE Air Volume at Various Blower Speeds High cfm 1425 1415 1400 1385 1370 1350 1330 1280 1210 1135 1070 L/s 670 670 660 655 645 635 630 605 570 535 505 Medium-High cfm 1240 1230 1220 1200 1180 1160 1140 1095 1040 985 920 L/s 585 580 575 565 555 545 540 515 490 465 435 Medium-Low cfm 1000 995 990 985 980 970 955 925 900 860 800 L/s 470 470 465 465 460 460 450 435 425 405 380 cfm 800 800 795 795 790 780 770 750 720 680 630 Low L/s 380 380 375 375 375 370 365 355 340 320 300 Pa 0 12 25 37 50 62 75 100 125 150 175 All air data is measured external to unit with 1 in.10 .60 . (25 mm) cleanable filter (not furnished) in place. 23 (57) 0.40 .05 .g.70 NOTE Air Volume at Various Blower Speeds High cfm 1830 1815 1800 1875 1750 1725 1700 1650 1600 1550 1480 L/s 865 855 850 885 825 815 800 780 755 730 700 Medium-High cfm 1600 1585 1570 1550 1530 1515 1500 1460 1420 1380 1330 L/s 755 750 740 730 720 715 710 690 670 650 630 Medium cfm 1325 1320 1315 1310 1300 1290 1275 1245 1210 1170 1130 L/s 625 625 620 620 615 610 600 590 570 550 535 Medium-Low cfm 1070 1070 1070 1065 1060 1050 1040 1020 1000 980 960 L/s 505 505 505 505 500 495 490 480 470 460 455 cfm 880 880 880 875 875 870 870 860 840 820 790 Low L/s 415 415 415 415 415 410 410 405 395 385 375 Pa 0 12 25 37 50 62 75 100 125 150 175 All air data is measured external to unit with 1 in.g.20 .10 .60 .25 .15 . Also see Filter Air Resistance table FILTER AIR RESISTANCE cfm (L/s) 0 (0) 200 (95) 400 (185) 600 (280) 800 (375) 1000 (470) 1200 (560) 1400 (655) 1600 (750) 1800 (845) 2000 (935) 2200 (1030) 2400 (1125) 2600 (1220) in.g. (Pa) 0.30 .06 (15) 0.70 NOTE Air Volume at Various Blower Speeds High cfm 2450 2440 2430 2415 2400 2380 2360 2310 2260 2180 2100 L/s 1155 1150 1145 1140 1135 1125 1115 1090 1065 1030 990 Medium-High cfm 2160 2155 2150 2135 2120 2105 2090 2050 2000 1950 1890 L/s 1020 1015 1015 1010 1000 995 985 965 945 920 890 Medium cfm 1970 1965 1960 1950 1940 1930 1915 1870 1810 1750 1700 L/s 930 925 925 920 915 910 905 880 855 825 800 Medium-Low cfm 1700 1695 1690 1685 1680 1675 1670 1650 1610 1560 1520 L/s 800 800 800 795 795 790 790 780 760 735 715 cfm 1500 1500 1495 1495 1490 1480 1470 1440 1410 1370 1330 Low L/s 710 710 705 705 705 700 695 680 665 645 630 Pa 0 12 25 37 50 62 75 100 125 150 175 All air data is measured external to unit with 1 in. 80MGF3/4-100 AND 80MGF3/4-120 BLOWER PERFORMANCE External Static Pressure in. 0 .33 (82) 0.00 (0) 0. w.01 (2) 0.03 (7) 0. w.44 (110) Page 6 .40 . w.25 . (25 mm) cleanable filter (not furnished) in place.30 .50 . 0 .04 (10) 0.38 (95) 0.27 (67) 0.12 (30) 0.10 .19 (47) 0.50 .15 .20 .60 . Also see Filter Air Resistance table 80MGF4/5-100.05 .15 (37) 0. (25 mm) cleanable filter (not furnished) in place. 80MGF4/5-120 AND 80MGF4/5-140 BLOWER PERFORMANCE External Static Pressure in.09 (22) 0.80MGF4-75. 80MGF PARTS IDENTIFICATION and ORIENTATION VENT ADAPTER CABINET TOP HEAT EXCHANGER ASSEMBLY FLUE BOX COMBUSTION AIR BLOWER PRESSURE SWITCH PRIMARY LIMIT 80MGF CABINET FRONT ACCESS PANEL BURNER ASSEMBLY TRANSFORMER NOx TURBULATOR CONTROL BOARD SECONDARY LIMITS CABINET BOTTOM BLOWER ASSEMBLY DOOR INTERLOCK SWITCH FIGURE 1 HEATING COMPONENTS (shown in horizontal position) ROLLOUT SWITCH (2) PRIMARY LIMIT COMBUSTION AIR PROVE SWITCH MANIFOLD Left Bottom Back BURNERS Front Right HEAT EXCHANGER GAS VALVE COMBUSTION AIR BLOWER COLLECTOR Top FIGURE 2 Page 7 . 2− Disconnect thermostat wiring connections from furnace control board. 7− Disconnect sensor wiire from center of board. 6− Disconnect 9 pin P58 from control board. 3− Disconnect blower leads from control board.80MGF BURNER ASSEMBLY (Shown With SureLight ignitor) SURELIGHT IGNITOR BURNER BOX TOP VEST PANEL UPPER BURNER MOUNTING RAIL LOWER BURNER MOUNTING RAIL FLAME SENSOR ROLLOUT SWITCHES BURNER HEAT EXCHANGER PRIMARY LIMIT Top ORIFICE GAS VALVE Back Left Right BURNER BOX Front Bottom MANIFOLD FIGURE 3 80MGF BLOWER DOOR COMPONENTS − BLOWER ACCESS (SureLight MODEL SHOWN) To Access Blower: 1− Turn off power to unit and disconnect L1 and L2 line voltage power. 4− Disconnect J1 from P1. 5− Disconnect 6 pin P156 from control board. 4 7 3 5 Top 6 8 2 1 FIGURE 4 Page 8 Back Left Bottom Right Front . 8− Remove screws (2) and lift panel from unit. The board utilizes both 120 and 24VAC. gas valve and burners can be accessed by removing the front access panel. Transformers on all models are rated 30VA with a 120V primary and a 24V secondary. If flame is not sensed after the third trial. 3) 80MGF unit components are shown in figure 1. When there is a call for heat. the combustion air blower continues to operate for 5 seconds (post-purge) before stopping. the combustion air blower begins operating. limit and gas valve operation. combustion air blower and ignition spark. The control will attempt to ignite the burners up to two more times. 1− Control Transformer (T1) A transformer located on the blower door provides power to the low voltage section of the unit. 3− Ram Control (A3) The furnace control combines burner ignition functions with blower control functions. simply replace entire control. show where side air return opening should be cut during installation. Ignition Control The ignition control is a direct spark ignition control module integral to the furnace control. the control delays ignition until combustion air blower operation has been proved and pre-purge period has elapsed. At the same time. The RAM" board is a printed circuit board which controls the blower. A separate blower access door is located behind the front access panel. Electrical control components are mounted to the blower access door. If control is inoperable. the diagnostic LED flashes at a slow steady rate. factory preset on" fan timing (45 seconds). See figure 23. Pre-purge allows the heat exchanger to be cleared of combustion products and to introduce fresh air for combustion. the furnace control (A3) and door interlock switch (S51). gas valve. If the combustion air prove switch does not close. the combustion air blower continues to run indefinitely (until the prove switch closes). the control begins monitoring the flame sensor. The control can be manually reset before the end of 60 minutes by momentarily turning off power to the unit. See figure 5. ditions. See figure 5. Indentations on side of units. Trial for ignition lasts for 7 seconds. Can cause injury or death. Postpurge allows the heat exchanger to be cleared of combustion products. Lockout means that the control shuts off the gas valve. Jackplugs allow the blower door to be easily removed for blower service. Flame current should be between 1 and 5 microamps to keep the gas valve open. Located on the blower door are the unit transformer (T1). If the flame current is too weak (less than 1 microamp) or if the burners do not ignite (within the 7 second ignition trial). Some early model 80MGF units utilize a furnace control manufactured by RAM Electronics Corporation. If the combustion air prove switch closes. the control will shut off spark and the combustion air blower and de-energize the gas valve.I−UNIT COMPONENTS (Figures 1. On a call for heat. Control is not field repairable. A−Blower Door Components (Figure 4) Electrical burner control and blower control components are located on the outside surface of the blower access door. The switch is wired in series with line voltage. Page 9 . Pre-Purge On a call for heat. When the furnace is idle (blower off and no heating or cooling demand). The control has a non−adjustable. 2−Door Interlock Switch (S51) A door interlock switch rated 16A at 125VAC is located on the blower access door. 80MGF units are factory equipped with bottom return air panels. The blower controls. The diagnostic LED lights red (not flashing) to indicate control board failure. spark and combustion air blower for 60 minutes. It also monitors the flame. Disconnect power before servicing. Furnace control (A3) combines the function of a burner ignition control and blower control. the diagnostic LED begins flashing at a fast rate and the combustion air blower is energized. it begins with a 45 second pre-purge. Each time the control restarts the ignition sequence. The LED flashes different codes to indicate problem con- DANGER Shock hazard. Spark related components contain high voltage. The board is also equipped with a diagnostic LED for use when troubleshooting the unit. 2. The panels are designed to be field removed as required for bottom air return. It then opens the gas valve and generates a spark to ignite the burners. the combustion air blower continues to operate for 45 seconds (pre-purge) before allowing ignition. At the end of 60 minutes the control completely resets and will attempt ignition up to three times. Unsafe operation will result if repair is attempted. Fan off" timings are adjustable. When the blower door is removed the unit will shut down. the control locks out. Table 3 shows how to interpret the other LED modes. Post-Purge After a demand. residual heat in heat exchanger may cause primary limit S10 to trip resulting in frequent cycling of blower. Fan ON" timing (time that the burners operate before the supply air blower starts) is fixed at 45 seconds and cannot be adjusted. adjust blower to longer time setting.8 seconds) When flame is sensed. a limit opens or the prove switch opens. This control contains field adjustable switches and also contains line voltage. flame sensor senses loss of flame. If any of these events occur during a thermostat demand. Make sure power is disconnected before making any field adjustments or performing any service procedure. Blower Control and Timings On Fast Flash DANGER On Fast Flash On Off Then On With Spark After PrePurge Electrical Shock Hazard. the indoor blower starts after a 45 second delay. Gas valve remains open and blower continues to run until demand stops. If this occurs. NOTE If fan off" time is set too low. Off Off Off 2 Flashes On Off On 5 Flashes On On On Off Off Off On On On 4 Flashes 4 Flashes 3 Flashes Page 10 .RAM CONTROL (A3) SPARK OUTPUT LINE VOLTAGE TERMINAL CONNECTIONS 24VAC VOLT TERMINAL CONNECTIONS See Table 2 for Terminal Functions See Table 2 for Terminal Functions FAN-OFF TIMING SWITCHES THERMOSTAT CONNECTIONS DIAGNOSTIC LED FIGURE 5 TABLE 1 Furnace Control A3 Limit Response During Operation Response Condition Combustion Air Blower Gas Valve Supply Air Blower Diagnostic LED Loss of Flame Sensed Before End of 45 second Blower On Delay (3 or Fewer Trials for Ignition) Loss of Flame Sensed After 45 second Blower On Delay (3 or Fewer Trials for Ignition) Loss of Flame Sensed (More Than 3 Trials for Ignition) Flame Sensed Without Demand Primary or Secondary Limit Open Rollout Switch Open Combustion Air Prove Switch Open On On (Spark Starts Within 0. the gas valve closes and the diagnostic LED registers the error condition (table 1). Spark Electrode and Wire. −4 and −6 units are shipped with a factory fan off" setting of 180 seconds. Reset or Replace Limits as Necessary. Failed to Prove Combustion Blower Operation or Blocked Vent. Check Gas Valve. TABLE 3 Furnace Control A3 Diagnostic LED LED State Steady On Slow Flash Fast Flash Meaning Control Failure Normal Operation and No Call For Heat Normal Operation with Call For Heat Remedy Replace Control ------Failed to Sense or Sustain Flame. 80MGF−1. −3. TABLE 2 FURNACE CONTROL A3 TERMINAL DESIGNATIONS Terminal Type Function Y G R W C 120VAC HOT AUX CMB BLWR ACB HEAT ACB COOL VALVE 24VAC HOT GROUND FLAME SENSE PSW Screw Strip Screw Strip Screw Strip Screw Strip Early Units 1/4" Spade Later Units Screw Strip 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade Cooling Demand Blower Demand 24VAC to Thermostat Heating Demand 24VAC Common Line Voltage In Line Voltage Out (Switched) Switched 120VAC to Combustion Air Blower Switched 120VAC to Blower Heating Tap Switched 120VAC to Blower Cooling Tap 24VAC to Gas Valve 24VAC In From Transformer To Cabinet Ground Flame Microamp Sensing 24VAC In From Pressure Switch Switch Open: Prohibits Ignition Switch Closed: Allows Ignition 24VAC In From Limits Limit Open: Closes Gas Valve Limits Closed: Allows Ignition 24VAC to Limit Train and Pressure Switch 24VAC In From Rollout Switches FAN-OFF TIME ADJUSTMENT SWITCHES LOCATED ON FURNACE CONTROL (A3) Fan-Off Timings Switch 1 2 Off Off On On Off On Off On Timing Seconds 90 120 180 240 FIGURE 6 Diagnostic LED The furnace control is equipped with a diagnostic LED used for troubleshooting the unit and the control. Check Gas Valve. Rollout Switches and Secondary Limits. If OK. 80MGF−5 and −7 units are shipped with factory "off" setting of 60 seconds. the blower stops immediately). when indoor thermostat switch is changed from ON to AUTO and heating/cooling demand is not present. Figure 6 shows the various fan off" timings and how switches should be positioned. Check Primary Limit. HI LIMIT IN HI LIMIT OUT ROLLOUT IN 1/4" Spade 1/4" Spade 1/4" Spade Page 11 .Fan OFF" timings (time that the blower operates after a heating or cooling demand has been satisfied) are determined by the arrangement of switches on the furnace control board. Burners. If all OK. gently reposition the switches to a new timing position. Replace Control If All OK. Two Flashes Control Lockout Three Flashes Pressure Switch Open Four Flashes Open Limit Five Flashes Flame Sensed and Gas Valve Not Energized. Fan off" time will affect comfort and efficiency and is adjustable to satisfy individual applications. Flame Sensor. The fan off" timing is initiated after a heating or cooling demand but not after a blower demand (that is. Find source of Overtemperature. Repair or Replace as Necessary. −2. Check Flame Sensor. LED functions are shown in table 3. To adjust fan off " timings. See figure 5. On a call for heat from the thermostat the control monitors the combustion air blower pressure switch. and allows for thermostat connection and troubleshooting. Page 12 . The control can be reset five times during one unsatisfied thermostat demand. Unit is shipped with a factory fan off" setting of 180 seconds. 120 90 FIGURE 7 Thermostat Connection Thermostat wires are connected to the terminal strip found on the EGC control board. blower operation. the entire unit will be de-energized for one hour. When the limit automatically resets. The EGC is a printed circuit board which is divided into two sections. The control monitors main valve voltage. Ignition Control 80MGF units use the EGC direct spark integrated ignition control. residual heat in heat exchanger may cause primary limit S10 to trip. After one hour the control will repeat the ignition sequence. Fan on" time is factory set at 45 seconds following the opening of the main gas valve and is not adjustable. Watchguard may be manually reset by breaking and remaking thermostat demand. *NOTE−If flame is established beyond the 10 second flame stabilization period then lost. After the fifth trial. See figure 8. the combustion air blower is energized. The EGC controls and monitors the entire sequence of operation. Once flame is established. the pressure switch closes and a 15 second pre-purge period begins. the sequence is repeated up to five times.4− EGC Control (A3) Some early model 80MGF units are equipped with an integrated ignition/blower control (EGC−1 or EGC−2) which controls ignition. After the pre-purge period. If flame is sensed when no flame should be present. If voltage is sensed when no voltage should be present. Make sure to disconnect power before changing fan off" timing. The system goes into hard lock-out which is reset only by removing power to the unit. DANGER Shock hazard. If either of the limits trip five consecutive times during one unsatisfied thermostat demand. If this occurs. During watchguard mode. the gas valve will open and ignition (spark) will be attempted for 10 seconds. Line voltage comes into the board on the 120VAC side. The flame stabilization period allows the burners to heat up and the flame to stabilize. the control will constantly monitor the burner flame using flame rectification. the control will energize the combustion and indoor blowers. FAN-OFF TIME ADJUSTMENT TIMING JUMPER To adjust fan-off timing: Remove jumper from EGC and select one of the other pin combinations to achieve the desired time. 180 60 TIMING PINS (seconds) Leave jumper off for 240 second fan-off timing. the control de-energizes the main gas valve and combustion air blower while the indoor blower remains energized. safety circuits. If the primary or secondary heating limits open. When the differential in pressure across the pressure switch is great enough. Flame failure response time is 0. the control will go into watchguard for one hour. To adjust fan off " timing. resulting in frequent cycling of blower. NOTE If fan off" time is set too low. the ignition sequence also resets. fan off timing. If the initial attempt for ignition fails. the control de-energizes the combustion air blower which terminates voltage to the valve. the control resets for five more ignition trials. Blower Operation / Fan Off Timings Fan off" timing (time that the blower operates after the heat demand has been satisfied) can be adjusted by moving the jumper on the EGC blower control board. Safety Circuits During the entire heating demand the control monitors the safety circuits. Fan off" time will affect comfort and efficiency and is adjustable to satisfy individual applications. the control initiates a ten second flame stabilization period. Figure 7 shows the various fan off" timings and how jumper should be positioned. The fan off" timing is initiated after a heating demand but not after a cooling demand. The control will not begin the heating cycle if the pressure switch is closed (by-passed). providing a maximum of 25 trials for ignition. Avoid personal injury. 120 and 24VAC. After ignition. adjust blower to longer fan off" time setting. Terminal designations are listed in tables 5 and 6. the control goes into Watchguard"*. The unit will remain locked in this sequence until the flame is no longer sensed or the main power is turned off to reset the control.8 seconds. gently disconnect jumper and reposition across pins corresponding with new timing. Once the pressure switch is determined to be open. On the EGC−1 only. pressure switch opened during operation or condensate drain blocked. NOTE: EGC−1 board will have terminal (#16) for ACB Heat speed. 6 5 4 DIAGNOSTIC LEDS DIAGNOSTIC MODULE BLOWER TIME ADJUSTMENT JUMPER THERMOSTAT TERMINAL STRIP (DETACHABLE) 1 4 7 8 EDGE CONNECTION 2 5 3 6 9 24VAC PLUG P20 3 2 1 RED DIAGNOSTIC BUTTON DIAGNOSTIC CODE ERASE JUMPER (EGC−1 only. Increased flash rate indicates there is a heating demand. Watchguard. When this button is depressed. Normal Operation. Circuit board self-check failure or ignition/blower control is wired incorrectly. Pressure Switch Watchguard. Primary or Secondary Limit Switch Open. Auto-Reset Switch. Depress button and hold (Remove power to control and short pins for for display of last failure code. Roll-out Switch Open. burners failed to ignite. the last failure code is stored in memory and may be retrieved by depressing and holding the memory recall button.) 10 seconds to erase previous code. The codes are given in table 4. Flame sensed without valve energized. Power must be restored to the control (depress blower interlock switch) within one minute of blower access panel removal in order to retain memory.Troubleshooting The EGC control board is equipped with two diagnostic green LEDs to indicate the mode of failure.) FIGURE 8 Page 13 . DIAG #2 Simultaneous Flash On TABLE 4 EGC DIAGNOSTIC CODES DIAG #1 DIagnostic Condition Simultaneous Flash Flash Power ON". The LED lights are marked DIAG #1 and DIAG #2. Manual-Reset Switch. the LEDs will signal the last failure code in memory. remove main power and short the jumper next to the diagnostic button for five seconds. To clear the memory of the stored failure code. Flash Alternate Flash Off Flash Continuous On Off Alternate Flash Flash On Continuous On EGC−2 INTEGRATED CONTROL 8 9 10 11 12 13 14 * 15 * * 16 * * * NOTE: EGC−1 board will have terminal (#15) for 7 ACB low speed. TABLE 5 BLOWER CONTROL A15 TERMINAL DESIGNATIONS Terminal Designation Type Function (See fig. If control is inoperable. The system consists of ignition control board (figure 11 with control terminal designations in table 10) and ignitor (figure 12). Unsafe operation will result if repair is attempted. 6− SureLight Ignition System A3 (−11 models) All 80MGF−11 model units are equipped with the Lennox SureLight ignition system.79 mm 3/16 in. 5. The SureLight integrated board controls all major furnace operations. simply replace entire control. NORMAL FLAME SIGNAL u 0. Make sure that the furnace is wired correctly and is properly grounded. Page 14 . 8) R G W Y C 1 2 3 4. Table 7 and 8 show jack plug terminal designations. The board finds the lowest ignitor temperature which will successfully light the burner. The sensor is fastened to burner supports and can be removed for service without removing any part of the burners. flame is sensed by current passed through the flame and sensing electrode. Disconnect power before servicing. 13 14 15 16 Screw Strip Screw Strip Screw Strip Screw Strip Screw Strip 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 1/4" Spade 24VAC to Thermostat (Red) Manual Fan Input from Thermostat (Green) Heat Demand Input from Thermostat (White) Cool Demand Input from Thermostat (Yellow) Common Ground to Thermostat 24VAC Hot from Transformer 24VAC Return to Transformer 24VAC Ground 120VAC Return − 120VAC Common 120VAC Return − 120VAC Common Input Combustion Blower (Line Voltage) Heat Only Accessory (Line Voltage) 120VAC Hot to Transformer 120VAC Hot Input Accessories (Line Voltage) ACB Cool Speed (Line Voltage) EGC−1 ACB Low Cont.7 mm FLAME SIDE VIEWSENSOR END VIEW TABLE 6 EGC CONTROL JACK/PLUG 20 TERMINAL DESIGNATIONS Pin # Function 1 2 3 4 5 6 7 8 9 Rollout Switch Out Spare Gas Valve Common Pressure Switch Return Hi Limit Return / Pressure Switch Out Flame Sensor Gas Valve Out High Limit Out Rollout Switch Return FIGURE 9 NOTE − The 80MGF furnace contains electronic components that are polarity sensitive. Speed (Line Voltage) EGC−2 ACB Heat Speed (Line Voltage) ACB Heat Speed (Line Voltage) 5−Flame Sensor (−11 models) A flame sensor is located on the left side of the burner support.7 MICROAMPS MINIMUM FLAME SIGNAL v 0. DANGER Shock hazard. 4. 7 mm 1/32 in.15 MICROAMPS 1/4 in. The SureLight ignitor is made of durable silicon−nitride. 18 mm 1/32 in. During operation. thus increasing the life of the ignitor. 0. The sensor is mounted on a bracket in the burner support and the tip protrudes into the flame envelope of the left−most burner.79 mm BURNER 11/16 in. Can cause injury or death. The board and ignitor work in combination to ensure furnace ignition and ignitor durability. The SureLight control allows the gas valve to remain open as long as flame signal is sensed. The board also features two LED lights for troubleshooting and two accessory terminals rated at (4) four amps.7 MICROAMPS LOW FLAME SIGNAL v 0. Ignitor longevity is also enhanced by voltage ramping by the control board. Control is not field repairable. See figure 9. Units equipped with the SureLight board can be used with either electronic or electro−mechanical thermostats without modification. 6 7 8 9 10 11 12. 0. See table 9 for troubleshooting diagnostic codes. Once the pressure switch is determined to be open. FIGURE 10 Page 15 . On the 256th call for heat. Fan off time will affect comfort and is adjustable to satisfy individual applications. the control goes into Watchguard−Flame Failure mode. See figure 10. 90sec. After a 60−minute reset period. After a successful ignition. After the 15−second pre−purge period. the control goes into Watchguard−Pressure Switch mode for a 5−minute re−set period. the SureLight ignitor warms up for 20 seconds after which the gas valve opens for a 4−second trial for ignition. The control will not begin the heating cycle if the pressure switch is closed (by− passed). 80MGF units with board 63K89. After a total of five trials for ignition (including the initial trial). such as the gas valve or blower deck. If ignition is not proved during the 4−second period. the SureLight control utilizes less power to energize the ignitor on successive calls for heat. the pressure switch closes and a 15−second pre−purge begins. If the pressure switch is not proven within 2−1/2 minutes. a−Electronic Ignition On a call for heat the SureLight control monitors the combustion air blower pressure switch.TABLE 7 SureLight BOARD J156 (J2) TERMINAL DESIGNATIONS PIN # 1 FUNCTION Ignitor Not Used Ignitor Neutral Combustion Air Blower Line Voltage Not Used Combustion Air Blower Neutral 2 3 4 5 6 TABLE 8 SureLight BOARD J58 (J1) TERMINAL DESIGNATIONS PIN # 1 FUNCTION Primary Limit In Gas Valve Common Roll Out Switch Out Gas Valve 24V Pressure Switch In Pressure Switch and Primary Limit Out Not Used Roll Out Switch In Ground 2 3 4 5 6 7 8 9 ELECTROSTATIC DISCHARGE (ESD) Precautions and Procedures CAUTION Electrostatic discharge can affect electronic components. Units with board 97L48: ignitor stays energized for the full 4−second trial for ignition. The SureLight control board has an added feature that prolongs the life of the ignitor. flip dip switch to desired setting. the control and the technician at the same electrostatic potential. FAN-OFF TIME ADJUSTMENT 60sec. b−Fan Time Control The fan on time of 45 seconds is not adjustable. 180sec. 120sec. Precautions will help to avoid control exposure to electrostatic discharge by putting the furnace. 24L85 or 56L83: the ignitor stays energized for the first second of the 4−second trial. before performing any service procedure. To adjust fan−off timing. Take precautions during furnace installation and service to protect the furnace’s electronic controls. the control will again ramp down until the lowest power is determined and the cycle begins again. The control continues to ramp down the voltage to the ignitor until it finds the lowest amount of power that will provide a successful ignition. the combustion air blower is energized. This amount of power is used for 255 cycles. the control will try four more times with an inter purge and warm−up time between trials of 35 seconds. When the differential in the pressure switch is great enough. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface. the control will begin the ignition sequence again. The unit is shipped with a factory fan off setting of 90 seconds. Fan off time (time that the blower operates after the heat demand has been satisfied) can be adjusted by flipping the dip switches located on the SureLight integrated control. Normal operation − signaled when heating demand initiated at thermostat. OR: Pressure switch closed prior to activation of combustion air blower. Main power polarity reversed. OR: Broken ignitor. Replace flame sense rod. OR: Condensate line blocked. LED #1 SIMULTANEOUS SLOW FLASH SIMULTANEOUS FAST FLASH LED #2 SIMULTANEOUS SLOW FLASH SIMULTANEOUS FAST FLASH DESCRIPTION Power − Normal operation Also signaled during cooling and continues fan. Measures below . OR: Blocked inlet/exhaust vent.15 microAmps SURELIGHT INTEGRATED CONTROL BOARD SureLight Ignitor SURELIGHT IGNITOR FIGURE 12 TABLE 10 TERMINAL DESIGNATIONS ACB COOL Blower − Cooling Speed (Line Volt) ACB HEAT Blower − Heating Speed (Line Volt) PARK Alternate Blower Speeds (Dead) Continuous Low Speed Blower ACB LOW Accessory Terminal (Line Volt) ACC TX 120VAC Hot to Transformer HOT 120VAC Hot Input HTG ACC Heat Only Accessory (Line Volt) 120VAC Neutrals NEUTRALS 24VAC Hot from Transformer 24VAC HOT 24VAC RTN 24VAC Return from Transformer FLAME SENSE Flame Sense Terminal FIGURE 11 Page 16 . Rollout switch open. OR: 9 pin connector improperly attached. Units with board 56L83 or 97L48: Limit must close within 3 minutes or board goes into one hour limit Watchguard. OR: Open ignitor circuit. Circuit board failure or control wired incorrectly. Pressure switch open or has opened 5 times during a single call for heat. TABLE 9 DIAGNOSTIC CODES MAKE SURE TO ID LED’S CORRECTLY: REFER TO INSTALLATION INSTRUCTIONS FOR CONTROL BOARD LAYOUT. Fast flash equals 3 Hz (three flashes per second). Flame sensed without gas valve energized. Drop out flame sense current < 0. Units with board 63K8901 or 24L85: Limit must close within 5 trials for ignition or board goes into one hour limit Watchguard. Primary or Secondary limit open. Switch line and neutral. Improper main ground or line voltage below 75 volts. The diagnostic codes are listed below in table 9. SLOW FLASH ON OFF ALTERNATING SLOW FLASH SLOW FLASH ON ON ON OFF FAST FLASH SLOW FLASH ALTERNATING FAST FLASH SLOW FLASH ALTERNATING SLOW FLASH OFF SLOW FLASH ON OFF ON SLOW FLASH FAST FLASH ALTERNATING FAST FLASH NOTE − Slow flash equals 1 Hz (one flash per second).The SureLight board is equipped with two LED lights for troubleshooting. Low flame signal. The lights are found just above the 24VAC terminal strip see figure 8. Watchguard − burners fail to ignite.7 microAmps. To manually reset a tripped switch. When excess heat is sensed in the heat exchanger. Each furnace is equipped with two identical switches. One switch is located over the leftmost burner and the other switch is located over the rightmost burner. All motors used are 120V permanent split capacitor motors to ensure maximum efficiency. See table 11 for ratings. D−Flame Rollout Switches (S47) Flame rollout switch is a high temperature limit located on top of the burner box. With either the RAM. ROLLOUT SWITCH (S47) SUPPLY AIR BLOWER AND SECONDARY LIMITSSECONDARY LIMITS (S21) Top Left Front Bottom Back Right BLOWER MOTOR MOTOR CAPACITOR To Remove Blower From Unit: Remove Bolts and Wiring Jackplugs. Rollout can be caused by a blocked flue or lack of combustion air. the pressure in the housing is nega- FIGURE 15 The primary limit (S10) on 80MGF units is located in the middle of the heating vestibule panel. Page 17 .C. However. The switch is factory set and cannot be adjusted. Then Slide Out Front of Unit. The motor operates during all heating operation and is controlled by furnace control A3. MANUAL RESET BUTTON FIGURE 14 E−Primary Limit Control (S10) LIMIT CONTROL FOR 80MGF SERIES UNITS THIS TYPE AUTO-RESET LIMIT IS USED FOR THE PRIMARY LIMIT (S10) AND RIGHT SECONDARY LIMIT (S21) (see FIGURE 13) FIGURE 13 C−Combustion Air Blower (B6) All 80MGF units use a combustion air blower to move air through the burners and heat exchanger during heating operation. The switch monitors air pressure in the blower housing. If pressure becomes less negative (signifying an obstruction) the pressure switch opens. If the limit is tripped.5MFD 370V 40MFD 370V 40MFD 370V tive. the ignition control immediately stops ignition and closes the gas valve. The setpoint will be printed on the side of the limit. The switch can be manually reset. When S47 senses rollout. The switch is factory set and cannot be adjusted. The limit is a N. the setpoint will be printed on the side of the limit.5MFD 370V 7. TABLE 11 80MGF BLOWER RATINGS 120V 1PH BLOWER MOTOR 80MGF2 80MGF3 80MGF3/4 80MGF4 80MGF4/5 80MGF5/6 HP 1/4 1/3 1/2 1/2 3/4 3/4 CAP 5MFD 370V 5MFD 370V 7. EGC or SureLight control board. When the pressure switch opens. The pre−purge time is 45 seconds for 80MGF units equipped with the RAM control and 15 seconds for units equipped with the EGC control. the motor will operate 5 seconds after the gas valve closes (post-purge). The blowers will use either a shaded pole 120V motor or a C−frame 120V motor. There are two types of primary limit. the limit will open. the furnace control (A3) immediately closes the gas valve to prevent burner operation. The switch may have a different setpoint for each unit model number. The motor also operates for a period before burner ignition (pre−purge). Shaded pole and C−frame motors do not use run capacitors. During normal operation. A pressure switch connected to the combustion air blower housing is used to prove combustion air blower operation. See figures 15 and 16. The limit automatically resets when unit temperature returns to normal. If unit is running and flame rollout is detected. the furnace control energizes the supply air blower and closes the gas valve. push the reset button located on the control. the gas valve will close and ignition control will be disabled.B−Blower Motors and Capacitors All 80MGF units use direct drive blower motors. SPST manual-reset limit connected in series with the ignition control A3. The setpoint will be printed on the side of the limit. spark electrode and burners.F−Secondary Limit Controls (S21) The secondary limit (S21) on 80MGF units is located in the blower compartment in the back side of the blower housing. A regulator adjustment screw is located on the valve. 50L98. If stick limit (Figure 16) suffers from nuisance trips and the furnace is in the horizontal position. The flame sensor uses flame rectification to sense combustion. If the limit is tripped. (18 mm) Top Right Bottom Left GROUND FLAME RETENTION RING LOWER BURNER MOUNTING RAIL FLAME SENSOR FIGURE 17 Page 18 . The switch is factory set and cannot be adjusted. replace with limit kit no. The Ram and EGC ignition control uses direct spark to ignite the rightmost burner and the burners cross-light to the left. LIMIT CONTROL (S21) (S10) FOR 80MGF SERIES UNITS INSULATING COVER SPADE CONNECTORS G−Spark Electrode and Flame Sensor (Models with EGC or Ram control only) Figure 17 shows the arrangement of flame sensor. All terminals on the gas valve are connected to wires from the electronic ignition control. If the gas valve must be replaced. When excess heat is sensed in the heat blower compartment. 24V applied to the terminals energizes the valve. A flame retention ring in the end of each burner is used to maintain correct flame length and shape and to keep the flame from lifting off the burner head. 24VAC terminals and gas control knob are located on top of the valve. THIS TYPE AUTO-RESET LIMIT IS USED FOR THE LEFT SECONDARY LIMIT (S21) (see FIGURE 13) LIMIT SPARK ELECTRODE LIMIT INSULATING COVER (s) FIGURE 16 TYPICAL BURNER/ELECTRODE ORIENTATION DIRECT SPARK MODELS ONLY 1/8"(+1/64") UPPER BURNER MOUNTING RAIL BURNER MANIFOLD ORIFICE 23/32 in. Two limits are supplied in each furnace and each limit is a different style (figures 15 and 16). the furnace control energizes the supply air blower and closes the gas valve. The kit includes burner orifices and a regulator conversion kit. Inlet and outlet pressure taps are located on the valve. the same type valve must be used. An LPG changeover kit is available from Lennox. The limit automatically resets when unit temperature returns to normal. the limit will open. Figure 18 shows the gap between tip of the electrodes and the burner surface. The valve is internally redundant to assure safety shut−off. Refer to figures 19 or 20 for location of valve features. H−Gas Valve The 80MGF uses a gas valve manufactured by Honeywell or WhiteRodgers. Never use tools. If the knob will not turn by hand. do not try to repair it.c.). The purpose of the switch is to prevent burner operation if the combustion air blower is not operating. GAS VALVE SHOWN IN OFF POSITION FIGURE 20 I−Combustion Air Blower Prove (Pressure) Switch (S64) 80MGF series units are equipped with a combustion air prove switch located on the vestibule panel. call a qualified service technician. It monitors air pressure in the combustion air blower housing. The switch is factory set and is not field adjustable. the switch senses that the combustion air blower is operating. The trip pressure is printed on the side of the limit. It is a safety shut-down control in the furnace and must not be bypassed for any reason. If the flue becomes obstructed during operation. (7 mm) The switch is a single-pole single-throw pressure switch electrically connected to the furnace control. the switch senses a loss of negative pressure (pressure becomes more equal with atmospheric pressure) and opens the circuit to the furnace control and gas valve. The switch is connected to the combustion air blower housing by means of a flexible silicone hose. OFF III−START-UP BEFORE LIGHTING smell all around the appliance area for gas. PROVE SWITCH COMBUSTION AIR BLOWER PROVE SWITCH Normally Open Closes on Negative Pressure SPARK ELECTRODE SPARK ELECTRODE FLAME SENSOR TO BURNER GAP BURNER 5/16 in. Force or attempted repair may result in a fire or explosion. Use only your hand to turn the gas control knob. The switch trip pressure is different depending on unit model number. (7 mm) Sensing Tube Attaches to Top Side Of Blower Top Right Back FLAME SENSOR PROVE SWITCH FIGURE 18 WHITE RODGERS 36E SERIES GAS VALVE MANIFOLD PRESSURE ADJUSTMENT SCREW MANIFOLD PRESSURE OUTLET Left Front Bottom FIGURE 21 On start-up. It closes a circuit to the furnace control when pressure inside the combustion air blower increases above pressure switch set point (In. The pressure sensed by the switch is relative to atmospheric pressure. Page 19 . Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.SPARK ELECTRODE TO BURNER GAP BURNER 5/16 in. GAS VALVE SHOWN IN OFF POSITION FIGURE 19 HONEYWELL VR8205 SERIES GAS VALVE MANIFOLD PRESSURE ADJUSTMENT SCREW MANIFOLD PRESSURE OUTLET II−PLACEMENT AND INSTALLATION ON Make sure unit is installed in accordance with installation instructions and applicable does. negative w. C. valve counterclockwise 9 − Replace access panel. use the manual shut−off valve before pressure testing to isolate furnace from gas supply. Compounds used on gas piping threaded joints should be resistant to action of liquefied petroleum gases.C. 3 − Turn off all electrical power to appliance.5psig (14" W. Close all gas valves (both internal and external to unit) to guarantee no gas leak into combustion chamber. Refer to the 80MGF Operation and Installation Instruction Manual Information. Do not force. D−Extended Period Shutdown Turn off thermostat or set to UNOCCUPIED" mode. follow the instructions To Turn Off Gas To Unit" and call your service technician or gas supplier./C.G.5 PSIG (14"W. 2 − Set thermostat to lowest setting.). Voltage must be within range listed on the nameplate. All access panels. Do not attempt to light manually.5"W. 2− Check voltage at disconnect switch. IV−HEATING SYSTEM SERVICE CHECKS A−A. 2 − Turn off all electrical power to unit if service is to be performed. Certification All units are A.A. 12− If the appliance will not operate. and or C. Do not try to light the burners by hand. 4 − This appliance is equipped with an ignition device which automatically lights the burners. drop in pressure between gas meter and unit. covers and vent caps must be in place and secured. If not.G.C. Follow the gas supplier’s instructions. Tighten as required. Honeywell VR8205 Gas Valve −− Turn knob on gas valve clockwise to OFF.A. C−Safety or Emergency Shutdown Turn off unit power. Do not force. 5 − Remove access panel. 11− Set thermostat to desired setting. 10− Turn on all electrical power to unit. the gas valve must be disconnected and isolated. 8 − White Rodgers 36E Gas Valve −− Switch gas valve lever to ON. 7 − Wait five (5) minutes to clear out any gas. 3 − Remove access panel. See figure 19.A−Preliminary and Seasonal Checks 1− Inspect electrical wiring. Honeywell VR8205 Gas Valve −− Turn knob on gas to ON. WARNING Shock and burn hazard. When pressure testing gas lines.C. consult the power company and have voltage condition corrected before starting unit. C−Testing Gas Piping IMPORTANT In case emergency shutdown is required.A.) CAP GAS VALVE FIELD PROVIDED LINE PRESSURE TAP FIGURE 22 Page 20 . design certified without modifications. Do not force. 80MGF units are equipped with a direct spark ignition system. Turn off power to unit.). See figure 22. B−Gas Piping Gas supply piping should not allow more than 0.G. If you do not smell gas go to next step.A. STOP! Immediately call your gas supplier from a neighbor’s phone. These controls should be properly labeled by the installer. GAS PIPING TEST PROCEDURE MANUAL MAIN SHUT−OFF VALVE WILL NOT HOLD TEST PRESSURE IN EXCESS OF 0. Supply gas pipe must not be smaller than unit gas connection. Close manual and main gas valves. See figure 20. If you then smell gas. 5 − Replace lower access panel. turn off the main shut-off valve and disconnect the main power to unit. Gas valves can be damaged if subjected to more than 0. turn knob on Honeywell valve clockwise to OFF. 6 − White Rodgers 36E Gas Valve −− Switch gas valve lever to OFF.5psig (14"W. 4 − Switch lever on White Rodgers gas valve to OFF. both field and factory installed for loose connections. B−Heating Start-Up 1 − STOP! Read the safety information at the beginning of this section. Turning Off Gas To Unit 1 − Set thermostat to lowest setting.G. If the pressure is equal to or less than 0. connect test gauge to inlet pressure tap (field provided). 3. See figure 22.) Divide by two and compare to time in table 13 below.P. with and without other units operating. Move pressure gauge to outlet pressure tap located on unit gas valve (GV1). Check gas line pressure with unit firing at maximum rate. Do not use matches.5 +0 −0.0 in. gas should burn mostly blue with some orange streaks. w. For natural gas units.0 + 0.5" W. See Corp.5 in. flame or any other source of ignition to check for gas leaks. w.c. High pressure can result in permanent damage to gas valve or overfire. candles. 8411−L10. operating pressure at unit gas connection must be a minimum of 4. W. connect a shut-off valve between the manometer and the gas tap to permit shut off of gas pressure to the manometer. Supply pressure must fall within range listed in previous paragraph. Determine time in seconds for two revolutions of gas through the meter. For L. Flame should be stable and should not lift from burner. Operating Pressure (outlet) in.P. 3− After allowing unit to stabilize for 5 minutes. notice the flame.When checking piping connections for gas leaks. 2− While waiting for the unit to stabilize. All gas valves are factory regulated. Start unit and allow 5 minutes for unit to reach steady state.P. Manifold pressure for the 80MGF can be measured at any time the gas valve is open and is supplying gas to the unit. Natural gas should burn blue. Use of a specialty Gas Leak Detector is strongly recommended. IMPORTANT For safety. It is available through Lennox under part number 31B2001. L. Manifold Adjustment Procedure: 1− Connect a test gauge to outlet pressure tap on gas valve. TABLE 12 GAS VALVE REGULATION Unit (Fuel) Natural L. each unit should be checked separately. Kitchen detergents can cause harmful corrosion on various metals used in gas piping. The gas valve is factory set and should not require adjustment. F− Proper Gas Flow (Approximate) Furnace should operate at least 5 minutes before checking gas flow.c. record manifold pressure and compare to values given in table 12.3 9. (Two revolutions assures a more accurate time. NOTE− To obtain accurate reading. NOTE−Shut unit off and remove manometer as soon as an accurate reading has been obtained. See table 12. On multiple unit installations. for further details. Low pressure may result in erratic operation or underfire. use preferred means.0" W. check manifold pressure. Normal manifold pressure for natural gas units is 3.5 Page 21 .C. D−Testing Gas Supply Pressure When testing supply gas pressure. TABLE 13 GAS METER CLOCKING CHART Seconds for One Revolution Natural LP 80mgf g Unit 1 cu ft 2 cu ft 1 cu ft 2 cu ft Dial Dial Dial DIAL −45 80 160 200 400 −60 60 120 150 300 −75 48 96 120 240 −100 36 72 90 180 −120 30 60 75 150 −140 25 50 64 128 Natural−1000 btu/cu ft LP−2500 btu/cu ft E−Check Manifold Pressure After line pressure has been checked and adjusted. For LP/propane gas the correct manifold pressure is 9. Take care to replace pressure tap plug. Adjust manifold pressure on gas valve to match time needed.C. Checks of manifold pressure are made as verification of proper regulator adjustment. gas units.C. operating pressure at unit gas connection must be a minimum of 9. shut off all other gas appliances connected to meter. (1372m) above sea level is the jurisdiction of the local authorities. W. H−Flame Signal A microamp DC meter is needed to check the flame signal on the primary ignition control. Connect the positive (+) lead of meter to B−Temperature Rise Temperature rise for 80MGF units depends on unit input. Refer to table 15 for pressure switch replacement for models at elevations of 4500 feet (1372m) and greater. blower operation is set at thermostat subbase fan switch. See table 16 for microamp reading for the various control boards used. Unit Model 80MGF−45 80MGF−60 80MGF−75 80MGF−100 80MGF−120 80MGF−140 TABLE 15 Pressure Switch Part Number No Change No Change 88J8001 18L2401 18L2401 No Change V−TYPICAL OPERATING CHARACTERISTICS A−Blower Operation and Adjustment NOTE− The following is a generalized procedure and does not apply to all thermostat controls.82) 8. WARNING Fire and explosion hazard.14) the ignition control sensor connection and the negative (−) lead of the meter to the sensor wire. blower horsepower and static pressure as marked on the unit rating plate.86) 9.G−High Altitude Derate NOTE−In Canada. Can cause a fire or explosion resulting in property damage.87) 9. Flame (microamp) signal is an electrical current which passes from the furnace control through the sensor electrode during unit operation. These instructions MUST be followed exactly.36) 3. NOTE−This is the only permissible field derate for this appliance. blower and entire unit will be off when the system switch is in OFF position. Current passes from the sensor through the flame to ground to complete a safety circuit. blower speed. No orifice change is required.29) 3.0 to 5. 3− Depending on the type of indoor thermostat.0 w. certification for installation at altitudes over 4500 ft. The minimum pressure as shown on the nameplate for natural and propane gases must be maintained. blower operates continuously on heating speed. 2− Set thermostat for a heating demand and check flame signal with unit operating.5 (2. Check gas line pressure with unit firing.0 1. RISE °F" listed on the unit rating plate.C. To Measure Flame Signal: 1− Place meter in series between furnace control and sensor wire. With fan switch in AUTO position.0 to 5. MICROAMP METER FLAME SENSOR SENSOR WIRE IGNITION CONTROL SENSE" TERMINAL FIGURE 23 TABLE 16 MICROAMP SIGNAL 1.5 (0.6 (2.4 (0. 2− Generally.80) 8.9 (2. −10 and −11 Models Table 14 shows manifold pressure settings for installations at different altitudes.0 v. See figure 23. The blower speed must be set for unit operation within the range of AIR TEMP. Page 22 . or pressure switch change when operating at elevations of 0 to 7500 ft. FLAME SIGNAL TEST D. 1− Blower operation is dependent on thermostat control system.3 (0. personal injury or loss of life. (0 to 2248m).70 DROP OUT SIGNAL t1.2 (2. blower cycles with demand or runs continuously while heating or cooling circuit cycles.2 (0.21) 3. With fan switch in ON position. 80MGF−9. 80MGF−1 through −8 Models This unit does not require gas pressure adjustment. TABLE 14 ALTITUDE feet (m) 0 − 4500 (0 − 1372) 4500 − 5500 (1372 − 1676) 5500 − 6500 (1676 − 1981) 6500 − 7500 (1372 − 2286) GAS FUEL Natural Propane/LP Natural Propane/LP Natural Propane/LP Natural Propane/LP MANIFOLD PRESSURE in.45 v.C.15 CONTROL Ram EGC SureLight Flame signal may rise above 5 microamps for the first few seconds after ignition then level off within the range. (kPa) 3. The difference should be in the range listed on the unit rating plate. Connect the zero end of the manometer to the FIGURE 24 discharge (supply) side of the system. first check the firing rate. subtract the two readings. 6 − Replace harness connector to motor. To change blower speed taps see the Blower Speed Taps section in this manual. To Change Blower Speed: 1 − Turn off electric power to furnace.C. MOTOR FIGURE 25 Page 23 . (Red = heating. Insert wire terminal until it is securely in place. observe the manometer reading. Provided the firing rate is acceptable. DEPRESS TAB TO RELEASE WIRE TERMINAL. See figure 4. Locate supply air thermometer in the first horizontal run of the plenum where it will not pick up radiant heat from the heat exchanger. If the temperature is too low.5" W. TABLE 18 BLOWER SPEED SELECTION HI LOW TAPS AVAILABLE 3 5 5 6 4 ◊ ◊ 2 ◊ 2 2 3 3 3 4 4 4 ◊ 5 MOTOR PLUG SPEED TAP DESIGNATION 5 − Depress harness connector tab to release wire terminal. On ducted systems. Blower speed selections are listed in table 17. SELECT CONNECTOR LOCATION FOR NEW SPEED (REFER TO UNIT WIRING DIAGRAM). Disconnect harness connector from motor to expose speed selectors. See figure 25. leave the other end of the manometer open to the atmosphere. BLOWER SPEED TAP SELECTION Leadless motors only HARNESS CONNECTOR D−Blower Speed Taps Leadless Motors Blower speed tap selection is accomplished by changing the taps at the blower motor harness connector. 3 − After plenum thermometers have reached their highest and steadiest readings. increase blower speed to reduce temperature. If temperature is too high. Black = cooling. 2 − Remove front panel and blower access door. INSERT WIRE UNTIL IT IS SECURELY IN PLACE. See table 17. 4 − Select desired speeds for heating and cooling. 3 − With only the blower motor running and the evaporator coil dry. Insert manometer MANOMETER hose flush with inside edge of hole or insulation. 5 − Seal around the hole when the check is complete. 2 − Set thermostat to highest setting. Seal around the hose with per80MGF UNIT magum. 2 − Punch a 1/4" diameter hole STATIC PRESSURE in supply and return air pleTEST nums. 4 − External static pressure drop must not be more than 0. White = common). TABLE 17 BLOWER SPEED SELECTION Unit Factory Connected Speed Taps Cool (Black) 80MGF2-45 80MGF2-60 80MGF3-60 80MGF2-75 80MGF3-75 80MGF4-75 80MGF3/4-100 80MGF4/5-100 80MGF3/4-120 80MGF4/5-120 80MGF4/5-140 2 2 2 2 2 2 2 2 2 2 2 Heat (Red) 4 4 4 3 4 4 4 5 3 5 3 4 4 4 4 4 5 5 5 5 5 5 Speeds Available C−External Static Pressure 1 − Measure tap locations as shown in figure 24. decrease blower speed. Adjust blower motor speed to deliver the air desired according to the job requirements. Select connector location for new speed (refer to unit wiring diagram). 3 − Disconnect blower motor harness from motor.To Measure Temperature Rise: 1 − Place plenum thermometers in the supply and return air plenums. For systems with non−ducted returns. connect the other end of manometer to the return duct as above. See table 19 for blower motor tap colors for each speed. flame or other sources of ignition to check for gas leaks. Due to dimples designed in the heatexchanger. See figure 8. 4 − Remove burners. Page 24 . Burners Burners and burner flame should be inspected at the beginning of each heating season. 8 − Check electrode gap using appropriately sized twist drills or feeler gauges. Check the following: appearance of burner flame. 5 − Clean burner insert with bottle brush as shown in figure 26.110 and 0. See table 20 for filter sizes. Do not use matches. if necessary. 10 − Restore electrical power and gas supply.E−Blower Speed Taps Leaded Motors −11 Models Blower speed tap changes are made on the SureLight control board. 3 − Remove burner retaining bracket. Replacement filters for 80MGF-45/60/75 units must have a minimum velocity rating of 400 FPM. CLEANING BURNERS BURNER BOTTLE BRUSH VI−MAINTENANCE At the beginning of each heating season. can be drawn into living space resulting in personal injury or death. 9 − Reinstall burner box top. Clean burners. 2 − Motors used on the Lennox 80MGF series units are permanently lubricated and need no further lubrication. candles.140 inches). if necessary. Make adjustments. the system should be checked as follows: Filters All 80MGF filters are installed external to the unit. as outlined below: 1 − Turn off electrical and gas supply to unit. turn off power then switch out speed tap on "ACB HEAT" with tap connected to "PARK M1" or "PARK M2". Unused taps must be secured on dummy terminals "PARK M1" and or "PARK M2" on the SureLight board. 2 − Remove burner box top. which could contain carbon monoxide. burner pressure. NOTE−Use papers or protective covering in front of furnace while cleaning furnace. CAUTION Some soaps used for leak detection are corrosive to certain metals.79 to 3. gas flow and temperature rise. See adjustments section. making sure burners are properly seated in slots on tray and orifice in manifold. Removal is for inspection only. B−Supply Air Blower 1 − Check and clean blower wheel. Replacement filters for 80MGF-100/120/140 units require a minimum velocity rating of 625 FPM. Carefully rinse piping thoroughly after leak test has been completed. To change existing heat tap. Follow lighting instructions on front of unit. cleaning is not recommended. Gas fumes. Gap should be between 2. TABLE 19 A−Cleaning Heat Exchanger and Burners NOTE−Use papers or protective covering in front of furnace while cleaning furnace. TABLE 20 MODEL NUMBER 80MGF−45/60/75 80MGF−100/120/140 FILTER SIZE 16" X 20" X 1" 20" X 20" X 1" FIGURE 26 6 − Use bottle brush to clean inside of each burner. 7 − Replace burners and burner retaining bracket. The heating tap is connected to the "ACB HEAT " terminal and the cooling tap is connected to the "ACB COOL" terminal. Filters should be inspected monthly and cleaned or replaced when necessary to assure proper furnace operation. WARNING Blower door must be securely in place when blower and burners are operating.56mm (0. The continuous blower tap is connected to the "ACB LOW" terminal. D−Electrical 1 − Check all wiring for loose connections. Check flue pipe. Some soaps used for leak detection are corrosive to certain metals. fire or explosion. chimney and all connections for tightness and to make sure there is no blockage or leaks. 2 − Check for correct voltage. HEAT EXCHANGER REMOVAL (unit shown in horizontal position) REMOVE SCREWS (4) Left Bottom Front Right SLIDE ENTIRE ASSEMBLY OUT OF CABINET Back Top FIGURE 27 Page 25 . Can cause damage to piping resulting in gas leaks.C−Flue and Chimney Flue must conform to all AGA/GAMA venting requirements. fire or explosion. 3 − Check amp−draw on blower motor. Carefully clean piping thoroughly after leak detection has been completed. Flue pipe deteriorates from the inside out and must be disconnected in order to check thoroughly. CAUTION Potential for gas leaks. the furnace control begins a 45 second delay before energizing the indoor blower. In turn.T1 supplies 24VAC to terminal 24VAC" on A3. terminal R" of A3 supplies 24VAC to terminal RC" of the indoor thermostat (not shown). Door interlock switch must be closed for A3 and T1 to receive voltage. When the combustion air blower nears full speed. 6. 5. Also.When disconnect is closed.CMB BLWR of the blower control energizes the combustion air blower (B6).When heat demand is satisfied. 120V is routed through door interlock switch (S51) to feed the line voltage side of the furnace control (A3) and transformer T1 primary.When flame is sensed. 8. the furnace control begins a 45 second time-delay (pre-purge).When S18 closes.When there is a call for heat. W1 of the thermostat de-energizes W of the furnace control and the furnace control immediately de-energizes the gas valve. The combustion air blower runs for 5 seconds (post-purge) before being de-energized.VII−WIRING AND SEQUENCE OF OPERATION 5 2 3 6 1 4 8 7 80MGF WITH RAM CONTROL 1. assuming the flame rollout switch (S47) primary limit (S10) and secondary limits (S21) are closed. Page 26 . 4. 7. 3. the furnace control simultaneously opens the gas valve and sends high voltage to the spark electrode. 2. the indoor blower runs for a designated period (90−240 seconds) as set by switches on furnace control. combustion air prove switch (S18) closes.At the end of the pre-purge cycle. W1 of the thermostat energizes W of the furnace control with 24VAC. CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL SWITCH CLOSES. INCREMENT TRIAL REGISTER.) LED: Fast flash rate. RESET PERIOD COMPLETE? LED: Fast flash rate. AIR BLOWER OFF (5 sec.80MGF TROUBLESHOOTING SEQUENCE NORMAL HEATING MODE LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE FLAME OFF? YES CONTROL SELF−CHECK OKAY? YES HI LIMIT SWITCH CLOSED? YES PRESSURE SWITCH OPEN? YES COMBUSTION AIR BLOWER ON? PRESSURE SWITCH CLOSED? YES PREPURGE (45 seconds) IGNITION TRIAL (7 seconds) −− START IGNITION SPARK. (Fixed 45−second delay) FLAME SENSE OKAY? YES FLAME CONTINUOUSLY CHECKED? ROLLOUT SWITCHES CLOSED YES HI LIMIT SWITCH CLOSED? YES PRESSURE SWITCH CLOSED? YES THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. 120. delay) FAN OFF (After selected 90. OPEN MAIN GAS VALVE. SWITCH CLOSED YES COMBUSTION FAN ON. NO MAIN VALVE AND SPARK ARE OFF. LED: 4 flashes. SYSTEM FAN OFF. MAIN VALVE OFF. NO START IGNITION SPARK (IN 0. LED: Fast flash rate. NO Page 27 . LED: 4 flashes for hi limit. SWITCH CLOSES. MAIN VALVE AND SPARK OFF. or 240 delay)? NO NO NO SEQUENCE HOLDS. LED: 4 flashes. LED: 3 flashes.? YES YES NO NO NO NO NO NO ABNORMAL HEATING MODE LOCKOUT: MAIN VALVE OFF COMB. COMBUSTION & SYSTEM FANS ON. (AFTER DELAY TO OFF INTERVAL COMPLETED. 180. HAS FLAME BEEN REGISTERED WITHIN 7 SECONDS? YES SYSTEM FAN ON. RESET OR REPLACE ROLLOUT SWITCH. SEQUENCE HOLDS UNTIL PRES. SEQUENCE HOLDS UNTIL PRES.8 SEC. SEQUENCE HOLDS UNTIL HI LIMIT CLOSES. SWITCH OPENS. COMBUSTION AND SYSTEM FANS ON. HAS FLAME BEEN DETECTED WITHIN 7 SEC. LED: 3 flashes for pressure switch. MAIN VALVE OFF. CHECK TO SEE IF MAIN VALVE IS OFF. INCREMENT TRIAL REGISTER THREE TRIALS COMPLETED? YES IGNITION RESET PERIOD COMBUSTION & SYSTEM FANS OFF. AIR AND SYSTEM FANS ON RESET THERMOSTAT LED: 5 flash if flame sensed with valve off LED: Steady on if control board failure CHECK TO SEE IF MAIN VALVE IS OFF. IS 60 MIN. MAXIMUM). . SYSTEM FAN OFF AFTER COMPLETING SELECTED DELAY INTERVAL (At dip switches). CONTROL BOARD FAILURE. COMPRESSOR OFF. FAILURE TO DETECT OR SUSTAIN FLAME. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. COOLING SEQUENCE RUNS TO COMPLETION. THERMOSTAT CALLS FOR COOLING. NO CALL FOR HEAT. HIGH LIMIT OR ROLLOUT SWITCH OPEN. THERMOSTAT CALLS FOR HEAT. FLAME SENSED AND GAS VALVE NOT ENERGIZED. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. NO SYSTEM FAN ON AT HEATING SPEED UNTIL MANUAL FAN IS SWITCHED OFF AT THERMOSTAT. CALL FOR HEAT. THERMOSTAT OPENS. SLOW FLASH FAST FLASH 2 FLASH 3 FLASH 4 FLASH 5 FLASH STEADY ON LED CODES NORMAL OPERATION. 80MGF TROUBLESHOOTING SEQUENCE − FAN ONLY LED: Slow flash rate. PRESSURE SWITCH OPEN OR CLOSED. CONTROL ENERGIZES SYSTEM FAN AT HEATING SPEED. SYSTEM LOCKOUT. REMAINS UNCHANGED THROUGHOUT SEQUENCE. NORMAL OPERATION. MANUAL FAN SELECTION MADE AT THERMOSTAT. YES SYSTEM FAN SWITCHED TO COOLING SPEED. Page 28 . NO YES SYSTEM FAN REMAINS ON HEATING SEQUENCE AND RUNS THROUGH COMPLETION.80MGF TROUBLESHOOTING SEQUENCE − COOLING LED: Slow flash rate. THERMOSTAT CALLS FOR COOLING. The combustion air blower immediately stops. After the pre−purge period the ignition control starts ignition spark and opens main gas valve. a 15 second pre−purge begins. In turn. Page 29 .80MGF WITH EGC−2 IGNITION CONTROL 1 − When disconnect is closed. 2 − T1 supplies 24VAC to terminal 24VAC" on A3. terminal R" of A3 supplies 24VAC to terminal R" of the indoor thermostat (not shown). 120V is routed through door interlock switch (S51) to feed the line voltage side of the ignition control (A3) and transformer T1 primary. 4 − CAB of the ignition control energizes the combustion air blower (B6). Door interlock switch must be closed for A3 and T1 to receive voltage. 5 − When S18 closes. ignition control (A3) energizes the indoor blower (B3). The indoor blower runs for a designated fan off" period (60−240 seconds) as set by jumper on ignition control. W1 of the thermostat energizes W of the ignition control with 24VAC. 3 − When there is a call for heat. combustion air prove switch (S18) closes. 7 − When heat demand is satisfied. assuming primary limit (S10) and secondary limit (S21) are closed. 6 − After 45 seconds. When the combustion air blower nears full speed. W1 of the thermostat deenergizes W of the ignition control and the gas valve is immediately de-energized. 80MGF WITH EGC−2 HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE CONTROL MAIN POWER ON" FLAME OFF? YES CONTROL SELF−CHECK OKAY? YES ROLL−OUT SWITCH CLOSED YES LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE COMB. DIAG. HAS CONTROL FAILED FLAME SENSE 5 TIMES DURING ONE HEAT DEMAND? IF YES. or 240 delay)? NO Page 30 .WATCHGUARD.WATCHGUARD. 90. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. IF YES. SYSTEM GOES INTO 60 MIN. DIAG. INDOOR BLOWER ON HEAT SPEED. COMB. CODE: 1−FLASHING / 2−ON (LIMIT OPEN) IS LIMIT NOW CLOSED? YES HAS PRIMARY LIMIT OPENED 5 TIMES DURING ONE UNSATISFIED HEAT DEMAND. TERM. (Fixed 45−second delay) NO NO NO GAS VALVE. FLASHING / 2−ALT. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. DIAG. DIAG.A. 2−FLASHING (C.B. CODE: 1−OFF / 2−FLASHING (C. COMB.A. CODE: BOTH ON (CONTROL SELF−CHECK FAILURE OR INCORRECT WIRING) NO ABNORMAL HEATING MODE GAS VALVE OFF. AIR BLOWER ON?" GAS VALVE. AIR BLOWER OFF (5 sec. TERM. AIR BLOWER ON?" HAS CONTROL RESET IGNITION SEQUENCE 5 TIMES IF YES. DIAG. CODE: 1−FLASHING / 2−ON IF NO. CODE: 1−ALT. DIAG. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. REMOVE POWER TO RESET CONTROL. GO TO COMB. YES PRESSURE SWITCH CLOSED WITHIN 2. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. FLASHING IF NO. 180. COMB. COMB. COMB. WATCHGUARD. COMB. COMB. DIAG.B. SEQUENCE HOLDS UNTIL PRESSURE SWITCH CLOSES OR THERMOSTAT RESETS CONTROL. COMB. SYSTEM GOES INTO 60 MIN.B. 2−FLASHING (FLAME ROLL−OUT OPEN) NO GAS VALVE. BLOWER ON. ENERGIZED.5 MIN. FLASHING / 2−ALT.5 MINUTES? YES GAS VALVE. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. CODE: 1−ON. INDOOR AIR BLOWER OFF (After selected 60. AIR BLOWER ON?" GAS VALVE OFF. BLOWER ON. CODE: 1−ALT. delay) HTG ACC. CODE: 1−OFF. SEQUENCE HOLDS UNTIL NO FLAME SENSED OR MAIN POWER IS INTERRUPTED AND RESET. BLOWER OFF. DIAG. PRESSURE SWITCH OPEN) IS 5 MINUTE RESET PERIOD COMPLETE? GAS VALVE OFF. CODE: 1− FLASHING. FLASHING IF NO. PRESSURE SWITCH OPEN) YES PRESSURE SWITCH WATCHGUARD CONDITION: GAS VALVE. 120. ARE SWITCHES CLOSED? YES PRESSURE SWITCH CLOSED? YES THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. PRESSURE SWITCH CLOSED IN 2.B.A. SEQUENCE HOLDS UNTIL ROLL−OUT SWITCH IS MANUALLY CLOSED. PRESSURE SWITCH OPEN) HAS C. AIR BLOWER PREPURGE (15 seconds) IGNITION TRIAL (10 seconds) −− START IGNITION SPARK. AIR BLOWER PRESSURE SWITCH OPEN? YES COMBUSTION AIR BLOWER ON? HTG ACC. HAS FLAME REGISTERED WITHIN 10 SECONDS AFTER IGNITION TRIAL? YES IS FLAME SENSED AFTER 10 SECOND FLAME RECTIFICATION PERIOD? YES INDOOR AIR BLOWER ON. GO TO COMB. CODE: 1−OFF / 2−FLASHING NO (C.? YES COMB.DE−ENERGIZED. GO TO COMB. DIAG.A. SYSTEM GOES INTO 60 MIN. DIAG. INDOOR BLOWER ON UNTIL LIMIT CLOSES. 2−OFF (FLAME SENSED WITHOUT VALVE ENERGIZED) NO NO NO PRIMARY/SECONDARY LIMITS MONITORED IN HEAT CYCLE. INDOOR BLOWER (WITH 45 DELAY) ON. OPEN MAIN GAS VALVE. SYSTEM FAN SWITCHES TO CONTINUOUS SPEED AND ENERGIZES ACC TERMINAL.80MGF WITH EGC−2 COOLING SEQUENCE OF OPERATION LED: Slow flash rate. SYSTEM FAN AND ACC TERMINAL OFF AFTER 0 SECONDS. BOTH REMAIN ON UNTIL CONTINUOUS FAN IS SWITCHED OFF AT THERMOSTAT. ACC TERMINAL REMAINS ENERGIZED. AIR BLOWER. CONTINUOUS FAN SELECTION MADE AT THERMOSTAT. Page 31 . 80MGF WITH EGC−2 MANUAL CONTINUOUS FAN SEQUENCE OF OPERATION LED: Slow flash rate. THERMOSTAT OPENS. REMAINS ENERGIZED. THERMOSTAT OPENS. NO SYSTEM FAN REMAINS ON HEATING SPEED AFTER SELECTED DELAY. CONTROL ENERGIZES SYSTEM FAN AT HEAT SPEED. ACC TERMINAL DE−ENERGIZED. THERMOSTAT CALLS FOR HEAT. SYSTEM FAN SWITCHED OFF AFTER DELAY. REMAINS UNCHANGED THROUGHOUT SEQUENCE. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. TERM. THERMOSTAT CALLS FOR COOLING. ACC TERMINAL ENERGIZED. ENERGIZED WITH COMB. NO YES THERMOSTAT CALLS FOR COOLING. THERMOSTAT OPENS. YES SYSTEM FAN SWITCHED TO COOLING SPEED. COMPRESSOR OFF. ACC TERM. ACC TERMINAL ENERGIZED. HTG ACC. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. 6 − After 45 seconds. The combustion air blower immediately stops. 7 − When heat demand is satisfied. W1 of the thermostat energizes W of the ignition control with 24VAC. After the pre−purge period the ignition control starts ignition spark and opens main gas valve. 3 − When there is a call for heat. a 15 second pre−purge begins. 4 − CAB of the ignition control energizes the combustion air blower (B6). 5 − When S18 closes. When the combustion air blower nears full speed. The indoor blower runs for a designated fan off" period (60−240 seconds) as set by jumper on ignition control. Door interlock switch must be closed for A3 and T1 to receive voltage.80MGF WITH EGC−1 IGNITION CONTROL 1 − When disconnect is closed. In turn. 2 − T1 supplies 24VAC to terminal 24VAC" on A3. combustion air prove switch (S18) closes. assuming primary limit (S10) and secondary limit (S21) are closed. Page 32 . ignition control (A3) energizes the indoor blower (B3). W1 of the thermostat deenergizes W of the ignition control and the gas valve is immediately de-energized. terminal R" of A3 supplies 24VAC to terminal R" of the indoor thermostat (not shown). 120V is routed through door interlock switch (S51) to feed the line voltage side of the ignition control (A3) and transformer T1 primary. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. AIR BLOWER PRESSURE SWITCH OPEN? YES COMBUSTION AIR BLOWER ON? HTG ACC. CODE: 1−OFF / 2−FLASHING (C. PRESSURE SWITCH OPEN) IS 5 MINUTE RESET PERIOD COMPLETE? GAS VALVE OFF. SYSTEM GOES INTO 60 MIN. 2−OFF (FLAME SENSED WITHOUT VALVE ENERGIZED) NO NO PRIMARY/SECONDARY LIMITS MONITORED IN HEAT CYCLE. COMB.5 MIN. 120. DIAG. COMB. AIR BLOWER ON?" GAS VALVE OFF. INDOOR BLOWER ON HEAT SPEED. BLOWER ON. CODE: BOTH ON (CONTROL SELF−CHECK FAILURE OR INCORRECT WIRING) NO ABNORMAL HEATING MODE GAS VALVE OFF. FLASHING IF NO.? YES COMB.A. CODE: 1−OFF. DIAG. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. COMB. PRESSURE SWITCH OPEN) HAS C. HAS CONTROL FAILED FLAME SENSE 5 TIMES DURING ONE HEAT DEMAND? IF YES. AIR BLOWER ON?" HAS CONTROL RESET IGNITION SEQUENCE 5 TIMES IF YES.WATCHGUARD. DIAG. COMB. SYSTEM GOES INTO 60 MIN. PRESSURE SWITCH CLOSED IN 2. INDOOR BLOWER (WITH 45 DELAY) ON. SEQUENCE HOLDS UNTIL ROLL−OUT SWITCH IS MANUALLY CLOSED.A. DIAG. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. CODE: 1−OFF / 2−FLASHING NO (C. PRESSURE SWITCH OPEN) GAS VALVE.WATCHGUARD. (Fixed 45−second delay) NO NO NO YES PRESSURE SWITCH WATCHGUARD CONDITION: GAS VALVE. CODE: 1− FLASHING. CODE: 1−FLASHING / 2−ON (LIMIT OPEN) IS LIMIT NOW CLOSED? YES HAS PRIMARY LIMIT OPENED 5 TIMES DURING ONE UNSATISFIED HEAT DEMAND. DIAG. 2−FLASHING (C. DIAG. GO TO COMB. SYSTEM GOES INTO 60 MIN. AIR BLOWER PREPURGE (15 seconds) IGNITION TRIAL (10 seconds) −− START IGNITION SPARK. AIR BLOWER OFF (5 sec. COMB. DE−ENERGIZED. BLOWER ON. FLASHING IF NO. 180. OPEN MAIN GAS VALVE. COMB. COMB. or 240 delay)? NO Page 33 . CODE: 1−ALT. AIR BLOWER ON?" GAS VALVE. 2−FLASHING (FLAME ROLL−OUT OPEN) NO GAS VALVE. DIAG. CODE: 1−FLASHING / 2−ON IF NO. WATCHGUARD. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. BLOWER AND INDOOR BLOWER (WITH DELAY) OFF. SEQUENCE HOLDS UNTIL NO FLAME SENSED OR MAIN POWER IS INTERRUPTED AND RESET. INDOOR BLOWER ON UNTIL LIMIT CLOSES. ENERGIZED? YES PRESSURE SWITCH CLOSED WITHIN 2. INDOOR AIR BLOWER OFF (After selected 60.B. FLASHING / 2−ALT. delay) HTG ACC. DIAG. IF YES. BLOWER OFF. TERM. FLASHING / 2−ALT.80MGF WITH EGC−1 HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE CONTROL MAIN POWER ON" FLAME OFF? YES CONTROL SELF−CHECK OKAY? YES ROLL−OUT SWITCH CLOSED YES LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE COMB. DIAG. HAS FLAME REGISTERED WITHIN 10 SECONDS AFTER IGNITION TRIAL? YES IS FLAME SENSED AFTER 10 SECOND FLAME RECTIFICATION PERIOD? YES INDOOR AIR BLOWER ON. DIAG. ARE SWITCHES CLOSED? YES PRESSURE SWITCH CLOSED? YES THERMOSTAT OPENS LED: SLOW FLASH RATE COMB. GO TO COMB.5 MINUTES? YES NO GAS VALVE. CODE: 1−ALT. SEQUENCE HOLDS UNTIL PRESSURE SWITCH CLOSES OR THERMOSTAT RESETS CONTROL. CODE: 1−ON. COMB.B.B.A. 90. REMOVE POWER TO RESET CONTROL. GO TO COMB.B. TERM.A. COMPRESSOR OFF. THERMOSTAT CALLS FOR COOLING. SYSTEM FAN SWITCHED OFF AFTER DELAY. ACC TERMINAL ENERGIZED. ACC TERM. HTG ACC. THERMOSTAT OPENS. SYSTEM FAN SWITCHES TO CONTINUOUS SPEED AND ENERGIZES ACC TERMINAL.80MGF WITH EGC−1 COOLING SEQUENCE OF OPERATION LED: Slow flash rate. CONTROL ENERGIZES SYSTEM FAN AT LOW SPEED. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. YES SYSTEM FAN SWITCHED TO COOLING SPEED. ENERGIZED WITH COMB. BOTH REMAIN ON UNTIL CONTINUOUS FAN IS SWITCHED OFF AT THERMOSTAT. CONTINUOUS FAN SELECTION MADE AT THERMOSTAT. SYSTEM FAN AND ACC TERMINAL OFF AFTER 0 SECONDS. AIR BLOWER. NO SYSTEM FAN SWITCHES TO HEAT SPEED AFTER SELECTED DELAY. Page 34 . 80MGF WITH EGC−1 MANUAL CONTINUOUS FAN SEQUENCE OF OPERATION LED: Slow flash rate. ACC TERMINAL REMAINS ENERGIZED. THERMOSTAT OPENS. ACC TERMINAL DE−ENERGIZED. ACC TERMINAL ENERGIZED. REMAINS ENERGIZED. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. THERMOSTAT CALLS FOR HEAT. REMAINS UNCHANGED THROUGHOUT SEQUENCE. NO YES THERMOSTAT CALLS FOR COOLING. TERM. THERMOSTAT OPENS. 5 − Gas valve opens for a 4−second trial for ignition. Page 35 . a 15−second pre−purge follows. A 20−second warm−up period begins. 7 − After 45−second delay. 4 − SureLight control energizes ignitor. W1 of the thermostat energizes W of the furnace control with 24VAC. Combustion air blower B6 continues a 5−second post−purge period. gas valve remains open for the heat call. Call for heat can continue. 8 − When heat demand is satisfied. 2 − S10 primary limit switch and S47 rollout switch are closed. Combustion air blower runs until S18 combustion air prove switch closes (switch must close within 2−1/2 minutes or control goes into 5 minute Watchguard Pressure Switch delay). 6 − Flame is sensed. W1 of the indoor thermostat de−energizes W of the SureLight control which de−energizes the gas valve. 3 − SureLight control energizes combustion air blower B6. Once S18 closes. and indoor blower B3 completes a selected OFF time delay. SureLight control energizes indoor blower B3.80MGF WITH SURELIGHT IGNITION CONTROL 1 − When there is a call for heat. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER ON HEATING SPEED. LED #1 −− OFF. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED.B. NO NO YES IS THERE PROPER GROUND? YES POLARITY REVERSED.SURELIGHT CONTROL HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE POWER ON CONTROL SELF−CHECK OKAY? NO COMBUSTION AIR BLOWER ON FOR 1 SECOND. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. GAS VALVE OFF.A. YES CONTINUED NEXT PAGE NO NO GAS VALVE OFF.) YES HAS COMBUSTION AIR PRESSURE SWITCH CLOSED IN 2. INDOOR BLOWER OFF WITH DELAY. LED #1 OFF LED #2 SLOW FLASH (Sequence holds until pressure switch closes or thermostat resets control. INDOOR BLOWER ON. COMBUSTION AIR BLOWER OFF. LED #2 −− SLOW FLASH. INDOOR BLOWER OFF WITH DELAY. LED #1 −− ON. IS 5-MINUTE RESET PERIOD COMPLETE? Page 36 . COMBUSTION AIR BLOWER ON.) NO PRESSURE SWITCH IS IN WATCHGUARD MODE. LED #1 −− FAST FLASH LED #2 −− SLOW FLASH IS VOLTAGE ABOVE 75 VOLTS? YES NO NO LOW VOLTAGE SIGNAL AT LED HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS. LED #1 ON LED #2 ON (RESET CONTROL BY TURNING MAIN POWER OFF. COMBUSTION AIR BLOWER ON. LED #1 ALTERNATING FAST FLASH LED#2 ALTERNATING FAST FLASH CHECK FOR BROKEN IGNITOR OR OPEN IGNITOR CIRCUIT GAS VALVE OFF. IS POLARITY REVERSED? SIGNAL IMPROPER GROUND AT LED. LED #2 −− SLOW FLASH. COMBUSTION AIR BLOWER OFF. ABNORMAL HEATING MODE GAS VALVE OFF. LED #1 −− SLOW FLASH LED #2 −− OFF BURNER OFF? (CONTINUOUS FLAME CHECK) YES NORMAL OPERATION: LED #1 −− SLOW FLASH LED #2 −− SLOW FLASH THERMOSTAT CALLS FOR HEAT: LED #1 −− FAST FLASH LED #2 −− FAST FLASH YES IS COMBUSTION AIR PRESSURE SWITCH OPEN? YES IS COMBUSTION AIR BLOWER ENERGIZED? (HTG ACC TERMINAL IS ENERGIZED WITH C. GAS VALVE OFF.5 MINUTES? YES 15-SECOND COMBUSTION AIR BLOWER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH.) TURN INDUCER ON FOR 1 SECOND. INDOOR BLOWER DELAY OFF. ROLLOUT SWITCH CLOSED? YES GAS VALVE OFF. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. COMBUSTION AIR INDUCER OFF.5 MINUTES? NO 5-MINUTE PRESSURE SWITCH WATCHGUARD MODE. YES 4-SECOND TRIAL FOR IGNITION. NO HAS CONTROL FAILED TO SENSE FLAME FOR FIVE CONSECUTIVE TRIES DURING A SINGLE HEAT DEMAND? NO YES IGNITION WATCHGUARD MODE. COMB. AIR INDUCER OFF.HEAT SPEED. COMBUSTION AIR INDUCER DE−ENERGIZED. OFF. COMBUSTION AIR INDUCER ON. SLOW FLASH LED 2 ALT SLOW FLASH IS 60-MINUTE RESET PERIOD COMPLETE? YES HAS CONTROL RESET IGNITION SEQUENCE FOUR TIMES? LOW FLAME SIGNAL (Does not affect operation of control) LED #1 −− SLOW FLASH LED #2 −− FAST FLASH GAS VALVE DE−ENERGIZED. LED#1−SLOW FLASH LED#2− ON. INDOOR BLOWER OFF WITH DELAY LED #1 −− ON. COMBUSTION AIR INDUCER POWER OFF. INDOOR BLOWER OFF WITH DELAY. 4 SECONDS FLAME RECTIFICATION CURRENT CHECK. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET YES GAS VALVE DE−ENERGIZED. LED #2 −− SLOW FLASH. LED #2 −− ON. INDOOR BLOWER OFF. INDOOR AIR BLOWER COMPLETES SELECTED OFF" DELAY BEFORE SHUTTING OFF. LED #2 −− SLOW FLASH. HTG ACC TERM. ACB. IS LIMIT SWITCH CLOSED? YES NO NO YES LIMIT SWITCH WATCH GUARD MODE. YES COMB. AND ACC TERM. INDOOR BLOWER OFF WITH DELAY LED #1 −− OFF.15 microamps) YES NO FLAME PRESENT? YES FLAME SIGNAL ABOVE 0.LED #1 −− SLOW FLASH.7 MICROAMPS? YES INDOOR BLOWER ON DELAY BEGINS (45 seconds. IGNITOR ENERGIZED FOR 1 SECOND AFTER VALVE OPENS.INDOOR BLOWER ON UNTIL SWITCH CLOSES. YES FLAME STABILIZATION PERIOD. NO GAS VALVE POWER OFF. GAS VALVE OPENS. (See table 9 DIAGNOSTIC CODES for limit reset operation) NO YES ROLLOUT SWITCH CLOSED? YES COMBUSTION AIR PRESSURE SWITCH CLOSED? YES THERMOSTAT DEMAND SATISFIED. BOARD 97L48 ONLY: IGNITOR ENERGIZED FOR THE FULL 4−SECOND TRIAL FOR IGNITION. AIR INDUCER CONTINUES 5-SECOND POST PURGE AFTER T’STAT DEMAND IS SATISFIED. GAS VALVE OFF. CAN FLAME BE PROVEN WITHIN 4 SECONDS AFTER GAS VALVE OPENS? (u0. YES IGNITOR WARM-UP −− 20 SECONDS.NORMAL HEATING MODE 15-SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. YES Page 37 .? YES HAS PRIMARY/SECONDARY LIMIT RESET. HAS CAB SWITCH CLOSED IN 2. INDOOR BLOWER OFF WITH DELAY LED 1 ALT. COMBUSTION AIR INDUCER ON. IS 60MINUTE RESET PERIOD COMPLETE. NO FLAME SENSED DURING THIS PERIOD.) YES PRIMARY AND SECONDARY LIMIT SWITCHES CLOSED? NO NO NO ABNORMAL HEATING MODE IS VOLTAGE ABOVE 75 VOLTS? YES IS THERE A PROPER GROUND? YES YES NO NO NO LEDS SIGNAL ALTERNATING FAST FLASH IS IGNITOR INTACT AND CONNECTED? GAS VALVE OFF. YES LED #1 & #2 SIMULTANEOUS SLOW FLASHES. GAS VALVE OFF. SYSTEM FAN AND ACC. NO GAS VALVE OFF. Page 38 . TERMINAL IS ENERGIZED. GAS VALVE OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. NO CHECK FOR MAIN BURNER FLAME SENSE. SIGNAL CIRCUIT BOARD FAILURE AT LED. COMBUSTION AIR BLOWER OFF. COMPRESSOR OFF. YES IS POLARITY REVERSED? SIGNAL IMPROPER GROUND AT LED. IS ROLLOUT SWITCH CLOSED? YES NO GAS VALVE OFF. THERMOSTAT CALLS FOR COOLING. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. ABNORMAL COOLING MODE CONTROL SELF DIAGNOSTIC CHECK. COMBUSTION AIR BLOWER OFF. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. COMBUSTION AIR BLOWER OFF. TERM.SURELIGHT CONTROL COOLING SEQUENCE OF OPERATION NORMAL COOLING MODE POWER ON IGNITION CONTROL MAIN POWER ON. IS MAIN BURNER FLAME OFF? LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT OPENS. ACB COOL SPEED AND ACC. ROLLOUT SWITCH MONITORED CONTINUOUSLY. INDOOR BLOWER OFF WITH NORMAL DELAY. INTERRUPT MAIN POWER TO RESET CONTROL. OFF WITH 0-SECOND DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED WITH 0-SECOND DELAY. NO NO YES IS THERE PROPER GROUND? IS VOLTAGE ABOVE 75 VOLTS? NO LOW VOLTAGE SIGNAL AT LET HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS. SIGNAL POLARITY REVERSED AT LED. SEQUENCE HOLDS UNTIL FLAME IS NOT SENSED. IS CONTROL OPERATING NORMALLY? YES TURN INDUCER ON FOR 1 SECOND. INDOOR BLOWER OFF WITH NORMAL DELAY. 56L83. 24L85. THERMOSTAT CALLS FOR COOLING. ACC. TERM. (AFTER OFF DELAY COMPLETED). Page 39 . 63K8901 SYSTEM FAN DE−ENERGIZED. NO YES BOARD NO. YES SYSTEM FAN SWITCHED TO ACB COOL SPEED. TERM. THERMOSTAT CALLS FOR HEAT (W). TERM.SURELIGHT CONTROL CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. (fan remains energized) MANUAL FAN SELECTION MADE AT THERMOSTAT. MANUAL FAN SELECTION MADE AT THERMOSTAT. REMAINS ON. BOARDS 24L85. ENERGIZED. ACC. TERM. OFF. AIR BLOWER. ENERGIZES WITH COMB. THERMOSTAT OPENS. COMBUSTION AIR AND HTG ACC TERMINAL DE−ENERGIZE. TERMINAL IS ENERGIZED. ACC. NO BOARD NO. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. HTG ACC. 56L83 AND 97L48: SYSTEM FAN SWITCHES TO LOW SPEED AFTER NORMAL DELAY. BOARD 63K89: SYSTEM FAN OFF. 97L48 SYSTEM FAN SWITCHES TO ACB HEAT SPEED AFTER NORMAL DELAY (fan remains energized) THERMOSTAT OPENS. ACC. SYSTEM FAN ENERGIZES ON ACB HEAT SPEED AFTER NORMAL DELAY. If no power.2. air blower does not energize. ACTION 1 − Check for 120V to combustion air blower.4 Nine pin connector failure 1.3 Miswiring Mis iring or improper connections at roll−out switch.4 Door interlock switch failure.1. ACTION 2 − Check wire connections to switch. 1.2 Roll−out switch failure. 1. ACTION 1 − If power is present at blower.1. on operation. ACTION 1 − Check continuity across roll−out switch. Replace roll−out switch if switch is reset but does not have continuity.4 1.3 − On initial power−up the comb. LED#1−On. Replace if malfunctioning ACTION 1 − Check that transformer output is 24V. ACTION 1 − Replace circuit breaker if it is reset but does not have continuity.2 Miswiring of furnace or improper connections. 1. check wire and connections. Determine cause of main power failure. OR CONTINUOUS FAN MODE Condition Possible Cause Corrective Action / Comments ACTION 1 − Check 120V main voltage.1 120V main power polarity reversed.1 1. replace board. ACTION 2 − Determine the cause of the roll−out switch activation before leaving furnace. replace blower. switch ACTION 1 − Check 9−pin connector for proper connection to control board. ACTION 2 − If circuit breaker still trips.VIII−Troubleshooting−SureLight Control PROBLEM: 1 UNIT FAILS TO OPERATE IN THE COOLING. LED#1 O LED#2 Slow LED#2−Slow Flash 1. Page 40 .2. − Diagnostic lights flash normal power circuit.2.3 Circuit breaker tripped or fails to close. 1.6 Failed control board. 1. ACTION 3 − Check continuity of switch in closed position. LED#1−Slow Flash LED#2−Slow Flash 1.1 Roll−out switch open. 1. replace loose connectors. 1.1. ACTION 1 − Manually reset the roll−out switch by pushing the top button. ACTION 2 − Check 24V wiring to control board.4. LED#1−Off LED#2−Off 1.4.5 Transformer Failure.1 − On initial power up the combustion Open combustion air blower motor air blower does not energize. ACTION 1 − Check the 120V has line and neutral correctly input into control.3. LED#1−Fast Flash.1.2. ACTION 2 − Reverse the line and neutral at the 120V field connection.1 − Both diagnostic lights fail to light up. 1. Main voltage 120V not supplied to unit.1. 1.2 − Diagnostic lights flash the roll−out code.2 Failed combustion air blower motor. LED#2−Slow Flash. Replace if malfunctioning ACTION 1 − If all the above items have been checked. HEATING. ACTION 2 − Check continuity of the multi plug pin. check for short. 1. − Diagnostic lights flash the reverse polarity code. ACTION 1 − Check wiring connections to switch.1. ACTION 1 − Check for correct wiring of 120V to power make up box and transformer. ACTION 1 − Check that door switch is activated when door is closed. 1. LED#2−Slow Flash 3.2 Miswiring of furnace or improper connections at limit switch(es). UNITS WITH CONTROL BOARDS DATE CODED AFTER NOV. Correct wiring and/or replace any loose connections. 1. Determine cause for limit activation before placing unit back in operation. Corrective Action / Comments ACTION 1 − Check that the unit is properly grounded. ACTION 1 − Check for correct wiring and loose connections in the ignitor circuit.5. Replace if malfunctioning Page 41 . ACTION 1 − Check that the pressure switch is open without the combustion air blower operating. ACTION 1 − Check for correct wiring and loose connections. d LED#1−Slow Flash.2 Broken or failed ignitor. HEATING.1 1997. PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE. Determine cause of voltage drop and supply correct voltage to the control. OR CONTINUOUS FAN MODE Condition 1. LED#1−Alternating Fast Flash LED#2−Alternating Fast Flash Possible Cause 1. − Diagnostic lights flash the limit failure g g mode. Corrective Action / Comments ACTION 1 − Check continuity across switch(es).5. Condition 2. 1.1 − Unit operates with a cooling or continuous fan demand. with a Heating demand. 3.PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING.2.3 Line voltage is below 75V.1.2. WILL OPERATE IN COOLING WITH COMBUSTION AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF. BUT NOT IN THE HEATING MODE. replace the ignitor.2 3.1 − On initial power−up the combustion air blower remains energized. combustion Nov 1 air blower will cycle 5 seconds on 55 seconds off. BUT COMBUSTION AIR BLOWER OPERATES CONTINUOUS.7 ohms.1 − Unit operates with a cooling and continuous fan demand. g − Di Diagnostic li ht fl h th i ti lights flash the improper main ground.1.1. COMBUSTION AIR BLOWER DOES NOT ENERGIZE Condition 3. 3.2 6−Pin connector is improperly attached to the circuit board. Correctly insert connector into control.1. Correct wiring and/or replace any loose connections. LED#1−Alternating Fast Flash LED#2−Alternating Fast Flash Possible Cause Corrective Action / Comments 2.1 1997. ACTION 2 − Check for restrictions on blower inlet air (including filter) and outlet air.1 Primary or secondary (if equipped) limit open.5 − On initial power−up the combustion air blower remains energized. Switches reset automatically upon cool down. − Units with control boards date coded after Nov. − Diagnostic lights flash the pressure switch failure code.2 Pressure switch stuck closed. − Diagnostic lights flash the improper main ground. Check multi − plug connections for correct installation. LED#1−Off. PROBLEM 2: UNIT FAILS TO OPERATE IN THE COOLING OR HEATING MODE. If resistance does not read between 10.5. Miswiring of furnace or improper con− Combustion air blower will not start nections to combustion air blower. ACTION 1 − Unplug ignitor and read resistance across ignitor. 2.1 Open ignitor circuit. LED#2−On Possible Cause 3.1 Improper ground to the unit. ACTION 1 − Check that the line voltage is above 75V. ACTION 2 − Install a proper main ground to the unit ACTION 1 − Check 6−pin connector for proper installation. ACTION 1 − Check for correct wiring and loose connections.9 and 19. − Combustion air blower will not start with a Heating demand. ACTION 1 − Check for correct wiring and loose connections.1.).1 Pressure switch does not close due to incorrect routing of the pressure switch tubing. COMBUSTION AIR BLOWER ENERGIZES. 4.1. with a Heating demand. − Diagnostic lights flash the pressure switch failure code 2. ACTION 1 − If all the above modes of failure have been checked.2 Combustion air blower failure. 4. 4. ACTION 1 − Check pressure switch tubing for leaks. Page 42 .1 tinuous fan demand.1.3. Condition Possible Cause Corrective Action/Comments 3. 4. Replace pressure switch and determine if unit will operate.3.7 Pressure switch failure.2 Pressure switch does not close due to obstructions in the pressure tubing.1 − Unit operates with a cooling and continuous fan demand. the pressure switch may have failed. ACTION 1 − Check the differential pressure across the pressure switch. Correctly route pressure switch tubing. COMBUSTION AIR BLOWER DOES NOT ENERGIZE (CONT. PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE. ACTION 4 − Check voltage to combustion air blower. LED#1−Off LED#2 Slow LED#2−Slow Flash Possible Cause 4. LED#1−Off. or pressure switch is out of calibration. This pressure should exceed the set point listed on the switch.6 Miswiring of furnace or improper connections at pressure switch. Correct wiring and/or replace any loose connections.PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE. replace combustion air blower.3 Pressure switch tubing damaged Corrective Action/Comments ACTION 1 − Check that the pressure switch tubing is correctly routed.1. LED#2−Slow Flash ACTION 1 − Check for correct wiring and loose connections. ACTION 1 − Remove any obstructions from the pressure tubing and/or taps. Replace any broken tubing.1. Miswiring of furnace or improper con− Combustion air blower will not start nections to combustion air blower.5 minutes after heating demand. See installation instructions. 3. 4. − Combustion air blower energizes with a heating demand demand. − Diagnostic lights flash the pressure switch failure code 2. Condition 4. 4. ACTION 2 − Check for restricted inlet and exhaust vent.4 Pressure switch does not close due to a low differential pressure across the pressure switch. ACTION 1 − Check that the proper pressure switch is installed in the unit.1.5 Wrong pressure switch installed in the unit. Remove all blockage. ACTION 1 − If there is 120V to combustion air blower and it does not operate. ACTION 3 − Check for proper vent sizing and run length.5 minutes after 25 heating demand. IGNITOR IS NOT ENERGIZED.1. Correct wiring and/or replace any loose connections.3 − Unit operates with a cooling and con3. Replace pressure switch if necessary. use steel wool or replace sensor.2. Pressure should not exceed 13" WC for both natural and propane.3 Sensor or sensor wire is grounded to the unit. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. See installation instructions. Page 43 . − Burners light but fail to stay lit B li ht b t f il t t lit. 6.PROBLEM 5: UNIT FAILS TO FIRE IN THE HEATING MODE. ACTION 2 − Replace.1 − Burners fire with a heating demand. ACTION 1 − Check for correct wiring and loose connections. IGNITOR IS ENERGIZED. 6. COMBUSTION AIR BLOWER ENERGIZES. Possible Cause 5.2. − Combustion air blower energizes with Heating demand. ACTION 1 − Check the microamp signal from the burner flame. 6.4 Control does not sense flame.1 Low pressure differential at the pressure switch. or relocate flame sense rod. Possible Cause Corrective Action/Comments 6. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash PROBLEM 6: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY Condition 6. ACTION 2 − Test continuity across the sense wire. ACTION 2 − Check for resistance between the sensor wire and the unit ground. ACTION 2 − Replace the valve if 24V is supplied but valve does not open (check for excessive gas line pressure before replacing gas valve).3 Malfunctioning gas valve or ignition control.2. ACTION 1 − Check for restricted vent inlet or exhaust. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash 6. LED#1−Off LED#2−Slow Flash 6. If wire or sensor are damaged replace the component. Correct wiring and/or replace any loose connections. DO NOT CLEAN ROD WITH SAND PAPER. clean.1.2.) Condition 5. NOTE: Do not attempt to bend sense rod. Line pressure should read a minimum 4. − Diagnostic lights flash the pressure switch code. Remove all blockage.1. 5.2 Sensor or sense wire is broken. Corrective Action/Comments ACTION 1 − Check line pressure at the gas valve.70 microamps.5" WC for natural and 8.1.1 Sensor or sense wire is improperly installed. ACTION 2: Check for proper vent sizing. check the sense rod for proper location or contamination. ACTION 1 − Check that sensor is properly located (page 10) and that the sense wire is properly attached to both the sensor and the control. (CONT. If the microamp signal is below 0. ACTION 1 − Check for a broken sensor.0"WC for propane. − Ignitor is energized but unit fails to light.1 − Unit operates with a cooling and continuous fan demand.2 − Combustion air blower energizes with a heating demand. 5.1. ACTION 3 − Replace the control board if 24V is not supplied to valve. − After 5 tries the control diagnostics flash the watchguard burners failed to ignite code. ACTION 1 − Check that 24V is supplied to the gas valve approximately 35 seconds after heat demand is initiated. ACTION 3 − Correct any shorts found in circuit. If rod is to be cleaned. ACTION 1 − Check for resistance between the sensor rod and the unit ground.1 Check that gas is being supplied to the unit. − Burners light but unit shuts off prior to satisfying T−stat demand.2 Miswiring of gas valve or loose connections at multi−pin control amp plugs or valve. ACTION 2 − For 80MGF gas furnaces. ACTION 1 − Tighten orifice until leak is sealed. LED#1−On LED#2−Slow Flash Possible Cause Corrective Action/Comments ACTION 1 − Check that the manifold pressure matches value listed on nameplate.) Condition 6.PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT. Clean assembly as outlined in instruction manual.1 Unit is firing above 100% of the nameplate input. ACTION 2 − Check for gas leakage at the threaded orifice connection.0% for natural and 6. Page 44 . 6.2 Improper burner cross−overs ACTION 1 − Remove burner and inspect the cross−overs for burrs.3. − Roll−out switch trips during the heating demand. Problem is characterized by nuisance flame failures. CO should measure below . check for proper combustion and flow. ACTION 2 − Check for correct intake and exhaust vent installation. ACTION 1 − Check that the burners are firing into the center of the heat exchanger openings. 6.1 Recirculation of flue gases. − Burners light roughly and the unit fails to stay lit. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash 6. See instructions 6.4 − Combustion air blower energizes with a heating demand. ACTION 1 − Check for sooting deposits or other restrictions in the heat exchanger assembly. 6.5% for L. 6. Remove restriction or replace burners. This condition causes rough ignitions and operation. − Diagnostic lights flash watchguard flame failure.3. See installation instructions for proper procedure.4.4 Burners are not properly located in the burner box. ACTION 2 − Verify that the installed orifice size match the size listed on the nameplate or installation instructions. ACTION 1 − Check for proper flow of exhaust gases away from intake vent. Remove any obstacles in front of the intake and exhaust vent which would cause recirculation. Correct the location of the burners if necessary. − Diagnostic lights flash roll−out failure. Use approved method for leak detection (see unit instructions).04% (400PPM) in an air−free sample of flue gases.4. 6. or any restriction or if crossover is warped.3 − Combustion air blower energizes with a heating demand. NOTE: Be careful not to strip orifice threads.P. ACTION 3 − Check gas valve sensing hose to insure no leaks are present.3 Insufficient flow through the heat exchanger caused by a sooted or restricted heat exchanger.3.3.2 Gas orifices leak at the manifold connection.0% and 8.5% and 8. − Burners light. ACTION 4 − Check the input rate to verify rate matches value listed on nameplate. CO2 should measure between 6. LED#1−Alternating Slow Flash LED#2−Alternating Slow Flash 6. "G".1 Miswiring of furnace or improper connections at control or indoor blower motor.1. Dallas Page 45 . − Diagnostic lights flash watch guard flame failure. Clean the sense rod with steel wool or replace sensor.1. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. ACTION 1 − Check for 120V at the various calls for indoor blower by energizing "Y". − NOTE" Unit might go into 60 minute Watchguard mode depending on intermittent nature of sensor signal. 8.) 6. replace the motor. or heating mode. and "W" individually on the low voltage terminal strip. If there is 120V to each motor tap but the blower does not operate. cooling.1.3 Defective control board Condition 9. PROBLEM 9: RF STATIC DURING TIME FOR IGNITION Corrective Action/Comments ACTION 1− Call Technical Support. ACTION 2 − Check that the sense wire is properly attached to both the sensor and the control.5. ACTION 1 − Check sense rod for contamination or coated surface.5 − Combustion air blower energizes with a heating demand. Check for correct wiring and loose connections. the blower is delayed 45 seconds.2 120V is not being supplied to the indoor air blower or blower motor failure. Pay extra attention to the pin connectors. Properly locate the sense rod or replace if rod cannot be located correctly.1 Loose sensor wire connection causes intermittent loss of flame signal.0 − Indoor blower fails to operate in continuous fan. HEATING.2 Ignitor operation Corrective Action/Comments ACTION 1− Correct wiring and/or replace any loose connections. or "W" is energized.PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.1 Sense rod is improperly located on the burner. ACTION 1 − Check that the sensor is properly located. − Burners light. Corrective Action/Comments ACTION 1 − Check the sense rod for proper location on the burner.0 − Unit operates correctly but the diagnostic lights flash low flame sense code code. LED#1−Slow Flash LED#2−Fast Flash Possible Cause 7. DO NOT USE SAND PAPER TO CLEAN ROD. Possible Cause 8. 8.2 Sense rod is contaminated. replace the control. OR CONTINUOUS FAN MODE Condition 8.0 − AM radio interference Possible Cause 9. ACTION 1 − If there is not 120V when "Y".1. 7. Note that when "W’ is energized. "G". PROBLEM 7: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE Condition 7.1.1. PROBLEM 8: INDOOR BLOWER FAILS TO OPERATE IN COOLING. SERVICE NOTES Page 46 .

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