Preview only show first 10 pages with watermark. For full document please download

G24 Service

Rating
Date

November 2018
Size

2.2MB
Views

1,229
Categories

Home Domestic appliances Large home appliances Water heaters & boilers

Transcript

G24M Service Literature Corp. 9723-L12 Revised 07-2001 G24M SERIES UNITS G24M series units are mid-efficiency gas furnaces manufactured with tubular steel heat exchangers formed of aluminized steel. G24M 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. Early model G24M units use electronic (direct spark) ignition. Late model G24M model units feature the Lennox SureLightT silicon-nitride ignition system. The G24MX 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. 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. 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. SPECIFICATIONS Model No. G24M2(X)-45 45,000 (13.2) 36,900 (10.8) 80.1% 75.4% G24M2-60 G24M3(X)-60 G24M2-75 G24M3(X)-75 Input Btuh (kW) 60,000 (17.6) 75,000 (22.0) Output Btuh (kW) 49,200 (14.4) 61,700 (18.1) lA.F.U.E. 80.5% 80.5% 80.1% 80.0% California Seasonal Efficiency 76.4% 75.9% 76.8% 76.8% Flue size connection diameter — in. (mm) round 3 (76) 4 (102) Temperature rise range — _F (_C) 30 - 60 (17 - 33) 45 - 75 (25 - 42) High static certified by A.G.A./C.G.A. — in wg. (Pa) .50 (125) Gas Piping Size I.P.S. Natural or LPG/propane 1/2 (13) in. 9x7 10 x 7 9x7 10 x 7 Blower wheel nominal mm 229 x 178 254 x 178 229 x 178 254 x 178 diameter x width Blower motor output — hp (W) 1/4 (187) 1/3 (224) 1/4 (187) 1/3 (224) Tons 1, 1-1/2 or 2 2, 2-1/2 or 3 1, 1-1/2 or 2 2, 2-1/2 or 3 Nominal cooling kW 3.5, 5.3 or 7.0 7.0, 8.8 or 10.6 3.5, 5.3 or7.0 7.0, 8.8 or 10.6 that can be added Shipping weight — lbs. (kg) 1 package 130 (59) 135 (61) Electrical characteristics 120 volts — 60 hertz — 1 phase (less than 12 amps) All models b Optional Accessories (Must Be Ordered Extra) b LPG/propane kit LB-69845L (38K84) Twinning Kit 96J69 — 5 lbs. (2 kg) Up-Flow/Horizontal Filter and Filter Rack Kits Single (32J02) Ten Pack (66K64) }No. & size of filters - in. (mm) (1) 16 x 20 x 1 (406 x 508 x 25) Catalog No. LB-69843A (32J01) — 3 lbs. (1 kg) ¡Down-flow No. & Size of Filters — in. (mm) Filter Kit (2) 16 x 20 x 1 (406 x 508 x 25) LB-79239A (67J91) — 10 lbs. (4 kg) 79J15 — 25 lbs. (11 kg) LB-69957 (46J66) — 15 lbs. (8 kg) Down-flow Combustible Floor Base Sidewall Power Venting Kit Hanging Bracket Kit 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. ¡Filters are not furnished with kit and must be ordered extra. Page 1 ã 1998 Lennox Industries Inc. Litho U.S.A. SPECIFICATIONS Model No. G24M4(X)-75 Input Btuh (kW) Output Btuh (kW) RA.F.U.E. California Seasonal Efficiency Flue size connection diameter in. (mm) round Temperature rise range EF (EC) High static certified by A.G.A./C.G.A. in wg. (Pa) 75,000 (22.0) 61,700 (18.1) 80.0% 76.3% 80.1% 76.5% 4 (102) 80.0% 77.0% 35 - 65 (19 - 36) .50 (125) 1/2 (13) 12 x 8 305 x 203 1/2 (373) Tons kW Shipping weight lbs. (kg) 1 package Electrical characteristics 12 x 9 305 x 229 3/4 (560) 2, 2-1/2, 3, 3-1/2 or 4 3-1/2, 4, 5 or 6 7.0, 8.8, 10.6, 12.3 or 14.1 12.3, 14.1, 17.6 or 21.1 140 (64) 175 (79) 175 (79) 120 volts 60 hertz 1 phase (less than 12 amps) All models Nominal cooling that can be added H Optional Accessories (Must Be Ordered Extra) LPG/propane kit Twinning Kit Up--Flow/Horizontal Filter and Filter Rack Kits cNo. & size of filters - in. (mm) Down-flow Filter Kit G24M4/5(X)-100 100,000 (29.3) 82,000 (24.0) 45 - 75 (25 - 42) Gas Piping Size I.P.S. Natural or LPG/propane in. Blower wheel nominal diameter x width mm Blower motor output hp (W) o G24M3/4(X)-100 LB-69845L (38K84) Single ( ) Ten Pack ( ) (1) 16 x 20 x 1 (406 x 508 x 25) 66K64 Catalog No. No. & Size of Filters in. (mm) Down-flow Combustible floor Base Sidewall Power Venting Kit Hanging Bracket Kit LB-69845K 5 lbs. (2 kg) Single Ten Pack (1) 20 x 20 x 1 (508 x 508 x 25) (81J14) 96J69 32J02 H (46J14) LB-69843A (32J01) (66K65) 3 lbs. (1 kg) (2) 16 x 20 x 1 (406 x 508 x 25) LB-79239A (67J91) 10 lbs. (4 kg) LB-79239B 10 lbs. (4 kg) 25 lbs. (11 kg) LB-69957 15 lbs. (8 kg) (67J92) 79J15 (46J66) R c o Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating f or non-weatherized furnaces. Polyurethane frame type filter is furnished with kit. Filters are not furnished with kit and must be ordered extra. 3DJH SPECIFICATIONS Model No. G24M3/4-120 G24M4/5-140 G24M4/5(X)-120 Input Btuh (kW) 140,000 (41.0) 120,000 (35.2) Output Btuh (kW) 114,800 (33.6) 98,400 (28.8) RA.F.U.E. 80.0% 80.0% 80.1% California Seasonal Efficiency Not Available Not Available 75.5% oFlue size connection diameter in. (mm) round 4 (102) 5 (127) Temperature rise range EF (EC) 45 - 75 (25 - 42) High static certified by A.G.A./C.G.A. in wg. (Pa) .50 (125) .65 (162) Gas Piping Size I.P.S. Natural or LPG/propane - in (mm) 1/2 (13) in. 12 x 8 12 x 9 Blower wheel nominal mm diameter x width 305 x 203 305 x 229 Blower motor output hp (W) 1/2 (373) 3/4 (560) Tons 2, 2-1/2, 3, 3-1/2 or 4 3-1/2, 4, 5 or 6 Nominal cooling kW 7.0, 8.8, 10.6, 12.3 or 14.1 that can be added 12.3, 14.1, 17.6 or 21.1 Shipping weight lbs. (kg) 1 package 190 (86) 175 (79) Electrical characteristics 120 volts 60 hertz 1 phase (less than 12 amps) All models H LPG/propane kit Twinning Kit Up--Flow/Horizontal Filter and Filter Rack Kits cNo. and size of filters - in. (mm) Catalog No. wDown-flow No. & Size in. Filter Rack mm of Filters Optional Accessories (Must Be Ordered Extra) H LB-69845K 5 lbs. (2 kg) Single Ten Pack Single Ten Pack (1) 20 x 20 x 1 (508 x 508 x 25) 20 x 20 x 1 (508 x 508 x 25) LB-69843A 3 lbs. (1) (1 kg) (2) 16 x 20 x 1 (2) 406 x 508 x 25 LB-79239C LB-79239B 10 lbs. (4 kg) 12 lbs. (5 kg) 25 lbs. (11 kg) LB-69957 15 lbs. (8 kg) (81J14) 96J69 (46J14) (66K65) (58J93) (66K66) (32J01) Down-flow Combustible Floor Base Sidewall Power Venting Kit Hanging Bracket Kit (67J93) (67J92) 79J15 (46J66) R c o w Annual Fuel Utilization Efficiency based on U.S. DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating f or non-weatherized furnaces. Polyurethane frame type filter is furnished with kit. 2 in. x 5 in. (51 mm x127 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. BLOWER DATA G24M2-45, G24M2-60 AND G24M2-75 BLOW ER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s 0 0 1270 600 980 460 770 365 570 270 .05 12 1245 590 975 460 770 365 565 265 .10 25 1220 575 975 460 770 365 565 265 .15 37 1195 565 965 455 765 360 560 265 .20 50 1170 550 960 455 760 360 560 265 .25 62 1140 540 950 450 760 360 555 260 .30 75 1110 525 940 445 760 360 550 260 .40 100 1060 500 910 430 750 355 545 255 .50 125 990 465 880 415 740 350 540 255 .60 150 900 425 810 380 690 325 530 250 .70 175 800 380 740 350 630 295 520 245 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table 3DJH BLOWER DATA G24M3-60 AND G24M3-75 BLOWER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s 0 0 1425 670 1240 585 1000 470 800 380 .05 12 1415 670 1230 580 995 470 800 380 .10 25 1400 660 1220 575 990 465 795 375 .15 37 1385 655 1200 565 985 465 795 375 .20 50 1370 645 1180 555 980 460 790 375 .25 62 1350 635 1160 545 970 460 780 370 .30 75 1330 630 1140 540 955 450 770 365 .40 100 1280 605 1095 515 925 435 750 355 .50 125 1210 570 1040 490 900 425 720 340 .60 150 1135 535 985 465 860 405 680 320 .70 175 1070 505 920 435 800 380 630 300 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table G24M4-75, G24M3/4-100 AND G24M3/4-120 BLOWER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s cfm L/s 0 0 1830 865 1600 755 1325 625 1070 505 880 415 .05 12 1815 855 1585 750 1320 625 1070 505 880 415 .10 25 1800 850 1570 740 1315 620 1070 505 880 415 .15 37 1875 885 1550 730 1310 620 1065 505 875 415 .20 50 1750 825 1530 720 1300 615 1060 500 875 415 .25 62 1725 815 1515 715 1290 610 1050 495 870 410 .30 75 1700 800 1500 710 1275 600 1040 490 870 410 .40 100 1650 780 1460 690 1245 590 1020 480 860 405 .50 125 1600 755 1420 670 1210 570 1000 470 840 395 .60 150 1550 730 1380 650 1170 550 980 460 820 385 .70 175 1480 700 1330 630 1130 535 960 455 790 375 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table 3DJH BLOWER DATA G24M4/5-100, G24M4/5-120 AND G24M4/5-140 BLOWER PERFORMANCE Air Volume at Various Blower Speeds External Static Pressure High Medium-High Medium Medium-Low Low in. w.g. Pa cfm L/s cfm L/s cfm L/s cfm L/s cfm L/s 0 0 2450 1155 2160 1020 1970 930 1700 800 1500 710 .05 12 2440 1150 2155 1015 1965 925 1695 800 1500 710 .10 25 2430 1145 2150 1015 1960 925 1690 800 1495 705 .15 37 2415 1140 2135 1010 1950 920 1685 795 1495 705 .20 50 2400 1135 2120 1000 1940 915 1680 795 1490 705 .25 62 2380 1125 2105 995 1930 910 1675 790 1480 700 .30 75 2360 1115 2090 985 1915 905 1670 790 1470 695 .40 100 2310 1090 2050 965 1870 880 1650 780 1440 680 .50 125 2260 1065 2000 945 1810 855 1610 760 1410 665 .60 150 2180 1030 1950 920 1750 825 1560 735 1370 645 .70 175 2100 990 1890 890 1700 800 1520 715 1330 630 NOTE All air data is measured external to unit with 1 in. (25 mm) cleanable filter (not furnished) in place. Also see Filter Air Resistance table FILTER AIR RESISTANCE cfm (L/s) in. w.g. (Pa) 0 (0) 0.00 (0) 200 (95) 0.01 (2) 400 (185) 0.03 (7) 600 (280) 0.04 (10) 800 (375) 0.06 (15) 1000 (470) 0.09 (22) 1200 (560) 0.12 (30) 1400 (655) 0.15 (37) 1600 (750) 0.19 (47) 1800 (845) 0.23 (57) 2000 (935) 0.27 (67) 2200 (1030) 0.33 (82) 2400 (1125) 0.38 (95) 2600 (1220) 0.44 (110) 3DJH VENT ADAPTER G24M PARTS IDENTIFICATION CABINET TOP HEAT EXCHANGER ASSEMBLY FLUE BOX COMBUSTION AIR BLOWER PRESSURE SWITCH G24M CABINET PRIMARY LIMIT FRONT LOUVERED LOW PRESSURE SWITCH PANEL (Propane Only) NOx TURBULATOR BURNER ASSEMBLY TRANSFORMER SECONDARY LIMITS CABINET BOTTOM BLOWER ASSEMBLY CONTROL BOARD DOOR INTERLOCK SWITCH FIGURE 1 HEATING COMPONENTS (shown in horizontal position) PRIMARY LIMIT ROLLOUT SWITCH (2) COMBUSTION AIR PROVE SWITCH ORIFICES MANIFOLD BURNERS Left Bottom Front Top Right HEAT EXCHANGER GAS VALVE COLLECTOR FIGURE 2 Page 6 Back COMBUSTION AIR BLOWER G24M BURNER ASSEMBLY (shown in upflow position with SureLight ignition system) SURELIGHT ROLLOUT IGNITOR SWITCHES BURNER BOX TOP VEST PANEL UPPER BURNER MOUNTING RAIL LOWER BURNER MOUNTING RAIL FLAME BURNER SENSOR HEAT EXCHANGER PRIMARY LIMIT Top Back ORIFICE Left GAS VALVE Right Front BURNER BOX MANIFOLD Bottom FIGURE 3 G24M BLOWER DOOR COMPONENTS -- BLOWER ACCESS To Access Blower: 4 1-- Turn off power to unit and disconnect L1 and L2 line voltage power. 2-- Disconnect thermostat wiring connections from furnace control board. J135/ P135 3-- Remove screws (2) from blower panel. 4-- Disconnect J135 from P135 from limit control. 5-- Disconnect J43 from blower motor. J1/P1 6-- Remove blower panel and lift from unit. 5 Top Right Back 6 2 Left 1 3 FIGURE 4 Page 7 Front Bottom I-UNIT COMPONENTS (Figures 1, 2, 3) DANGER G24M unit components are shown in figure 1. The blower controls, gas valve and burners can be accessed by reĆ moving the front access panel. A separate blower access door is located behind the front access panel. Electrical control components are mounted to the blower access door. G24M units are factory equipped with bottom return air panels in place. The panels are designed to be field removed as reĆ quired for bottom air return. Indentations on side of units, show where side return opening should be cut during installaĆ tion. A-Blower Door Components (Figure 4) Electrical burner control and blower control components are located on the outside surface of the blower access door. Jackplugs allow the blower door to be easily reĆ moved for blower service. Located on the blower door are the unit transformer (T1), the furnace control (A3) and door interlock switch (S51). Furnace control (A3) combines the function of a burner ignition control and blower control. 1- Control Transformer (T1) A transformer located on the blower door provides power to the low voltage section of the unit. Transformers on all models are rated 30VA with a 120V primary and a 24V secĆ ondary. 2-Door Interlock Switch (S51) A door interlock switch rated 16A at 125VAC is located on the blower access door. The switch is wired in series with line voltage. When the blower door is removed the unit will shut down. SURELIGHT IGNITOR UPPER BURNER MOUNTING RAIL Shock hazard. Disconnect power before servicing. Control is not field repairable. If control is inoperable, simply replace entire control. Can cause injury or death. Unsafe operation will result if repair is attempted. 3- SureLight Ignition System (A3) Late Model G24M Units Late model G24M units are equipped with the Lennox SureLight ignition system. The system consists of ignitor (figure 5) and ignition control board (figure 6 with control terminal designations in table 1). The board and ignitor work in combination to ensure furnace ignition and ignitor durability. The SureLight integrated board controls all major furnace operations. The board also features two LED lights for troubleshooting and two accessory termiĆ nals rated at (4) four amps. See table 2 for troubleshootĆ ing diagnostic codes. Table 3 and 4 show jack plug termiĆ nal designations. Units equipped with the SureLight board can be used with either electronic or electro-meĆ chanical thermostats without modification. The SurĆ eLight ignitor is made of durable silicon-nitride. Ignitor longevity is also enhanced by voltage ramping by the control board. The board finds the lowest ignitor temperaĆ ture which will successfully light the burner, thus increasĆ ing the life of the ignitor. a-flame sensor The flame sensor uses flame rectification to sense comĆ bustion. During operation, flame is sensed by current passed through the flame and sensing electrode. Figure 7 shows the gap between tip of the electrode and the burner surface. SURELIGHT IGNITOR BURNER ASSEMBLY FLAME RETENTION RING FIGURE 5 Page 8 ORIFICE FLAME SENSOR SURELIGHT CONTROL BOARD LATE MODEL G24M UNITS TABLE 1 SURELIGHT CONTROL TERMINAL DESIGNATIONS ACB COOL Blower - Cooling Speed (Line Volt) ACB HEAT Blower - Heating Speed (Line Volt) PARK Alternate Blower Speeds (Dead) ACB LOW Continuous Low Speed Blower ACC Accessory Terminal (Line Volt) TX 120VAC Hot to Transformer HOT 120VAC Hot Input HTG ACC Heat Only Accessory (Line Volt) NEUTRALS 120VAC Neutrals 24VAC HOT 24VAC Hot from Transformer 24VAC RTN 24VAC Return from Transformer FLAME SENSE Flame Sense Terminal NORMAL FLAME SIGNAL > 0.7 MICROAMPS LOW FLAME SIGNAL < 0.7 MICROAMPS MINIMUM FLAME SIGNAL < 0.15 MICROAMPS FLAME SENSOR TO BURNER GAP 11/16 in. 18 mm ¦ 1/32 in. 0.79 mm 1/4 in. 7 mm ¦ 1/32 in. 0.79 mm BURNER 3/16 in. 4.7 mm FLAME SIDE VIEWSENSOR FIGURE 6 END VIEW FIGURE 7 TABLE 2 DIAGNOSTIC CODES MAKE SURE TO ID LED’S CORRECTLY: REFER TO INSTALLATION INSTRUCTIONS FOR CONTROL BOARD LAYOUT. LED #1 LED #2 DESCRIPTION SIMULTANEOUS SLOW FLASH SIMULTANEOUS SLOW FLASH Power - Normal operation Also signaled during cooling and continues fan. SIMULTANEOUS FAST FLASH SIMULTANEOUS FAST FLASH Normal operation - signaled when heating demand initiated at thermostat. SLOW FLASH ON Primary or Secondary limit open. Units with board 63K8901 or 24L85: Limit must close within 5 trials for ignition or board goes into one hour limit Watchguard. Units with board 56L83 or 97L48: Limit must close within 3 minutes or board goes into one hour limit Watchguard. OFF SLOW FLASH Pressure switch open or has opened 5 times during a single call for heat; OR: Blocked inlet/exhaust vent; OR: Condensate line blocked; OR: Pressure switch closed prior to activation of combustion air blower. ALTERNATING SLOW FLASH ALTERNATING SLOW FLASH Watchguard - burners fail to ignite. SLOW FLASH OFF Flame sensed without gas valve energized. ON SLOW FLASH Rollout switch open. OR: 9 pin connector improperly attached. ON ON OFF ON OFF ON Circuit board failure or control wired incorrectly. FAST FLASH SLOW FLASH Main power polarity reversed. Switch line and neutral. SLOW FLASH FAST FLASH Low flame signal. Measures below .7 microAmps. Replace flame sense rod. ALTERNATING FAST FLASH ALTERNATING FAST FLASH Improper main ground or line voltage below 75 volts; OR: Broken ignitor; OR: Open ignitor circuit. NOTE - Slow flash equals 1 Hz (one flash per second). Fast flash equals 3 Hz (three flashes per second). Drop out flame sense current < 0.15 microAmps Page 9 TABLE 3 not proven within 2-1/2 minutes, the control goes into Watchguard-Pressure Switch mode for a 5-minute re-set period. SureLight BOARD J156 (J2) TERMINAL DESIGNATIONS PIN # FUNCTION 1 Ignitor 2 Not Used 3 Ignitor Neutral 4 Combustion Air Blower Line Voltage 5 Not Used 6 Combustion Air Blower Neutral NOTE - The G24M furnace contains electronic components that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded. After the 15-second pre-purge period, the SureLight ignitor warms up for 20 seconds after which the gas valve opens for a 4-second trial for ignition. The ignitor stays energized for the first second of the 4-second trial. G24M units with 63K89, 24L85 or 56L83: the ignitor stays energized the first second of the 4 second trial. G24M units with board 97L48: ignitor stays energized during the 4-second trial until flame is sensed. If ignition is not proved during the 4-second period, the control will try four more times with an inter purge and warm-up time between trials of 35 seconds. After a total of five trials for ignition (including the initial trial), the control goes into Watchguard-Flame Failure mode. After a 60-minute reset period, the control will begin the ignition sequence again. The SureLight control board has an added feature that prolongs the life of the ignitor. After a successful ignition, the SureLight control utilizes less power to energize the ignitor on successive calls for heat. 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. This amount of power is used for 255 cycles. On the 256th call for heat, the control will again ramp down until the lowest power is determined and the cycle begins again. TABLE 4 SureLight BOARD J58 (J1) TERMINAL DESIGNATIONS PIN # FUNCTION 1 Primary Limit In 2 Gas Valve Common 3 Roll Out Switch Out 4 Gas Valve 24V 5 Pressure Switch In 6 Pressure Switch and Primary Limit Out 7 Not Used 8 Roll Out Switch In 9 Ground ELECTROSTATIC DISCHARGE (ESD) Precautions and Procedures c-Fan Time Control The fan on time of 45 seconds is not adjustable. 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. The unit is shipped with a factory fan off setting of 90 seconds. Fan off time will affect comfort and is adjustable to satisfy individual applications. See figure 8. CAUTION Electrostatic discharge can affect electronic components. Take precautions during furnace installation and service to protect the furnace’s electronic controls. Precautions will help to avoid control exposure to electrostatic discharge by putting the furnace, the control and the technician at the same electrostatic potential. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface, such as the gas valve or blower deck, before performing any service procedure. NOTE—If fan “off” time is set too low, residual heat in heat exchanger may cause primary limit S10 to trip resulting in frequent cycling of blower. If this occurs, adjust blower to longer time setting. b-Electronic Ignition On a call for heat the SureLight control monitors the combustion air inducer prove switch. The control will not begin the heating cycle if the prove switch is closed (by-passed). Once the prove switch is determined to be open, the combustion air inducer is energized. When the differential in the prove switch is great enough, the prove switch closes and a 15-second pre-purge begins. If the prove switch is Page 10 FAN-OFF TIME ADJUSTMENT 60sec. 90sec. 120sec. 180sec. To adjust fan-off timing, flip dip switch to desired setting. FIGURE 8 4-- Ram Control (A3) Early Model G24M Units Ignition Control The ignition control is a direct spark ignition control The furnace control combines burner ignition func- module integral to the furnace control. See figure 9. tions with blower control functions. When there is a call for heat, the control delays ignition Early model G24M units utilize a furnace control manufactured by RAM Electronics Corporation. The RAM board is a printed circuit board which controls the blower, gas valve, combustion air blower and ignition spark. It also monitors the flame, limit and gas valve operation. The control has a non--adjustable, factory preset on fan timing (45 seconds). Fan off timings are adjustable. The board utilizes both 120 and 24VAC. See figure 9. The board is also equipped with a diagnostic LED for use when troubleshooting the unit. When the furnace is idle (blower off and no heating or cooling demand), the diagnostic LED flashes at a slow steady rate. On a call for heat, the diagnostic LED begins flashing at a fast rate and the combustion air blower is energized. The LED flashes different codes to indicate problem conditions. The diagnostic LED lights red (not flashing) to indicate control board failure. Table until combustion air blower operation has been proved and pre-purge period has elapsed. It then opens the gas valve and generates a spark to ignite the burners. Trial for ignition lasts for 7 seconds. At the same time, the control begins monitoring the flame sensor. If the flame current is too weak (less than 1 microamp) or if the burners do not ignite (within the 7 second ignition trial), the control will shut off the spark ignitor and the combustion air blower and de-energize the gas valve. Flame current should be between 1 and 5 microamps to keep the gas valve open. See figure 21. The control will attempt to ignite the burners up to two more times. Each time the control restarts the ignition sequence, it begins with a 45 second pre-purge. If flame is not sensed after the third trial, the control locks out. Lockout means that the control shuts off the gas valve, spark and combustion air blower for 60 minutes. At the end of 60 minutes the control completely resets and 7 shows how to interpret the other LED modes. will attempt ignition up to three times. The control can Pre-Purge On a call for heat, the combustion air blower begins operating. If the combustion air prove switch closes, be manually reset before the end of 60 minutes by momentarily turning off power to the unit. DANGER the combustion air blower continues to operate for 45 seconds (pre-purge) before allowing ignition. Prepurge allows the heat exchanger to be cleared of com- Shock hazard. bustion products and to introduce fresh air for com- Spark related components contain high voltage. Disconnect power before servicing. Control is not field repairable. If control is inoperable, simply replace entire control. bustion. If the combustion air prove switch does not close, the combustion air blower continues to run indefinitely (until the prove switch closes). Can cause injury or death. Unsafe operation will result if repair is attempted. Post-Purge After a demand, the combustion air blower continues to operate for 5 seconds (post-purge) before stopping. Post-purge allows the heat exchanger to be cleared of combustion products. Page 11 EARLY MODEL G24M FURNACE CONTROL (A3) SPARK OUTPUT 24VAC VOLT TERMINAL CONNECTIONS LINE VOLTAGE TERMINAL CONNECTIONS PLUG P20 See Table 6 for Terminal Functions FAN-OFF TIMING SWITCHES THERMOSTAT CONNECTIONS DIAGNOSTIC LED FIGURE 9 TABLE 5 When flame is sensed, the indoor blower starts after a Furnace Control A3 Limit Response During Operation Response 45 second delay. Gas valve remains open and blower Condition Combustion Air Blower Gas Valve Supply Air Blower continues to run until demand stops, flame sensor Diagnostic stat demand, the gas valve closes and the diagnostic Loss of Flame Sensed Before On Delay LED registers the error condition (table 5). On End of 45 second Blower senses loss of flame, a limit opens or the prove switch opens. If any of these events occur during a thermo- LED (Spark On Starts On Fast Flash Blower Control and Timings Within 0.8 (3 or Fewer DANGER seconds) Trials for Ignition) Electrical Shock Hazard. Loss of Flame Sensed After Off Then 45 second On With Blower On On Spark Delay (3 or After Pre- Fewer Trials Purge This control contains field adjustable switches and also contains line voltage. Make sure power On is disconnected before making any field adjust- Fast Flash ments or performing any service procedure. for Ignition) NOTEIf fan off time is set too low, residual heat Loss of Flame Sensed (More Than 3 Trials Off Off Off in heat exchanger may cause primary limit S10 to 2 Flashes trip resulting in frequent cycling of blower. If this for Ignition) occurs, adjust blower to longer time setting. Flame Sensed Without On Off On 5 Flashes Demand the supply air blower starts) is fixed at 45 seconds and Primary or Secondary On Off On 4 Flashes Limit Open Rollout Switch Open Air Prove cannot be adjusted. Fan OFF timings (time that the blower operates after On Off On 4 Flashes a heating or cooling demand has been satisfied) are determined by the arrangement of switches on the fur- Combustion Switch Open Fan ON timing (time that the burners operate before On Off On 3 Flashes nace control board. See figure 9. To adjust fan off timings, gently reposition the switches to a new timing Page 12 TABLE 7 position. Figure 10 shows the various fan off timings and how switches should be positioned. Unit is shipped with a factory fan off setting of 180 seconds. Fan off LED State time will affect comfort and efficiency and is adjustable Steady On to satisfy individual applications. The fan off timing is initiated after a heating or cooling demand but not after a blower demand (that is, when indoor thermostat switch Slow Flash Fast Flash is changed from ON to AUTO and heating/cooling de- Furnace Control A3 Diagnostic LED Meaning Remedy Control Failure Replace Control Normal Operation - - - - and No Call For Heat Normal Operation - - - - with Call For Heat Failed to Sense or Sustain mand is not present, the blower stops immediately). Flame. Check Gas Valve, Two TABLE 6 Flashes Control Lockout Burners, Spark Electrode and Wire, Flame Sensor. FURNACE CONTROL A3 TERMINAL DESIGNATIONS Terminal Type Function 24VAC HOT 1/4 Spade 24VAC In From Transformer GND 1/4 Spade To Cabinet Ground Y Screw Strip Cooling Demand G Screw Strip Blower Demand Replace Control If All OK. Failed to Prove CombusThree Flashes tion Blower Operation or Pressure Switch Open Blocked Vent. Repair or Replace as Necessary. Check Primary Limit, Rollout Switches and Sec- R Screw Strip 24VAC to Thermostat Four W Screw Strip Heating Demand Flashes C Screw Strip 24VAC Common 120VAC HOT 1/4 Spade Line Voltage In ondary Limits. Find source Open Limit of Overtemperature. If all OK, Reset or Replace Limits as Necessary. Five Flame Sensed and Gas Check Gas Valve. If OK, Flashes Valve Not Energized. Check Flame Sensor. 120VAC RTN 1/4 Spade Line Voltage Neutral 120VAC TX 1/4 Spade Line Voltage Out To Transformer CMB J20/P20 Pin 1 Switched 120VAC to Combustion Air Blower B--Blower Motors and Capacitors CMB RTN J20/P20 Pin 2 120VAC Common Combustion Air Blower All G24M units use direct drive blower motors. All mo- ACB HEAT 1/4 Spade Switched 120VAC to Blower Heating Tap ACB LOW 1/4 Spade 120VAC Output to Supply Air Blower for Continuous Operation During No Demand ACB COOL 1/4 Spade Switched 120VAC to Blower Cooling Tap VLV HOT tors used are 120V permanent split capacitor motors to ensure maximum efficiency. See table8 for ratings. TABLE 8 G24M BLOWER RATINGS 120V 1PH BLOWER MOTOR HP CAP G24MQ2 1/4 5MFD 370V 5MFD 370V J20/P20 Pin 13 24VAC to Gas Valve G24MQ3 1/3 J20/P20 Pin 9 24VAC Common From Gas Valve G24MQ3/4 1/2 7.5MFD 370V 1/2 7.5MFD 370V J20/P20 Pin 10 24VAC In From Pressure Switch Switch Open: Prohibits Ignition Switch Closed: Allows Ignition G24MQ4 G24MQ4/5 3/4 40MFD 370V G24MQ5/6 3/4 40MFD 370V HIL IN J20/P20 Pin 11 24VAC In From Limits Limit Open: Closes Gas Valve Limits Closed: Allows Ignition HIL OUT J20/P20 Pin 14 24VAC to Limit Train and Pressure Switch RO OUT J20/P20 Pin 7 24VAC Out To Rollout Switches VLV RTN PSW IN SECONDARY LIMITS (S21) RO IN J20/P20 Pin 15 24VAC In From Rollout Switches SPARK ELECTRODE Male Spark Plug Type High Voltage Out To Spark Electrode FS J20/P20 Pin 12 Flame Microamp Sensing FAN-OFF TIME ADJU SUPPLY AIR BLOWER AND SECONDARY LIMITS Top Back Left Right Front STMENT SWITCHES Bottom LOCATED ON FURNACE CONTROL (A3) Fan-Off Timings Switch Timing Seconds 1 2 Off Off 90 Off On 120 On Off 180 On On 240 BLOWER MOTOR FIGURE 10 MOTOR Diagnostic LED CAPACITOR The furnace control is equipped with a diagnostic LED To Remove Blower From Unit: Remove Bolts and used for troubleshooting the unit and the control. LED Wiring Jackplugs. Then Slide Out Front of Unit. FIGURE 11 functions are shown in table 7. Page 13 C--Combustion Air Blower (B6) E--Primary Limit Control (S10) All G24M units use a combustion air blower to move LIMIT CONTROL FOR G24M SERIES UNITS air through the burners and heat exchanger during heating operation. Some early model G24M units are THIS TYPE AUTO-RESET LIMIT IS USED FOR THE PRIMARY LIMIT (S10) AND equipped with a blower that uses a PSC (Permanent RIGHT SECONDARY LIMIT (S21) (see FIGURE 11) Split Capacitor) 120VAC motor. PSC motors use run capacitors. Other early and late model G24M units are equipped with a blower that uses a shaded pole 120V FIGURE 13 motor. The motor operates during all heating opera- The primary limit (S10) on G24M units is located in the tion and is controlled by furnace control A3. For G24M middle of the heating vestibule panel. When excess heat units equipped with the Ram ignition system, the is sensed in the heat exchanger, the limit will open. If the blower will operate for 45 seconds before burner igni- limit is tripped, the furnace control energizes the supply tion (pre-purge) and for 5 seconds after the gas valve air blower and closes the gas valve. The limit automati- closes (post-purge). For G24M units equipped with the cally resets when unit temperature returns to normal. SureLight ignition system, the blower will operate for The switch is factory set and cannot be adjusted. The 15 seconds before burner ignition (pre purge) and for 5 switch may have different setpoints for each unit model seconds after the the gas valve closes (post purge). number. However, the setpoint will be printed on the A pressure switch connected to the combustion air side of the limit. blower housing is used to prove combustion air blower operation. The switch monitors air pressure in the blower housing. During normal operation, the pressure in the housing is negative. If pressure becomes less negative (signifying an obstruction) the pressure switch opens. When the pressure switch opens, the furnace control (A3) immediately closes the gas valve to prevent burner operation. F--Secondary Limit Controls (S21) The secondary limit (S21) on G24M units is located in the blower compartment in the back side of the blower housing. When excess heat is sensed in the blower compartment, the limit will open. If the limit is tripped, the furnace control energizes the supply air blower and closes the gas valve. The limit automatically resets when unit temperature returns to normal. The switch is factory D--Flame Rollout Switches (S47) Flame rollout switch is a high temperature limit located on top of the burner box. 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. The limit is a N.C. SPST manual-reset limit connected in series set and cannot be adjusted. Two limits are supplied in each furnace and each limit is a different style (figures 13 and 14). The setpoint will be printed on the side of the limit. If stick limit (figure 14) suffers from nuisance trips anf the furnace is in the horizontal position, replace with limit kit no. 50L98. SECONDARY LIMIT CONTROL (S21) with the ignition control A3. When S47 senses rollout, FOR G24M SERIES UNITS the ignition control immediately stops ignition and control will be disabled. Rollout can be caused by a factory set and cannot be adjusted. The setpoint will be printed on the side of the limit. The switch can be manually reset. To manually reset a tripped switch, push the reset button located on the control. LIMIT (S21) (see FIGURE 11) INSULATING COVER (s) FIGURE 14 ROLLOUT SWITCH (S47) MANUAL RESET BUTTON USED FOR THE LEFT SECONDARY LIMIT blocked flue or lack of combustion air. The switch is THIS TYPE AUTO-RESET LIMIT IS SPADE CONNECTORS out is detected, the gas valve will close and ignition LIMIT INSULATING COVER closes the gas valve. If unit is running and flame roll- G--Spark Electrode and Flame Sensor Early Model G24M Units Figure 15 shows the arrangement of flame sensor, spark electrode and burners. The ignition control uses direct spark to ignite the rightmost burner and the FIGURE 12 burners cross-light to the left. The flame sensor uses flame rectification to sense combustion. 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. Figure 16 shows the gap between tip of the electrodes and the burner surface. Page 14 Top TYPICAL BURNER/ELECTRODE ORIENTATION view looking at flame end of burners 1/8(+1/64) UPPER BURNER BURNER MOUNTING RAIL GROUND SPARK ELECTRODE MANIFOLD Right ORIFICE Bottom FLAME SENSOR LOWER BURNER FLAME RETENTION RING Left (SOME UNITS MAY HAVE MOUNTING RAIL SENSOR LOCATED IN MIDDLE OF BURNER) FIGURE 15 TYPICAL ACCESS TO REGULATOR SPARK ELECTRODE TO BURNER GAP FOR ADJUSTMENT AND L.P. CHANGEOVER (Honeywell VR8205 series gas valve shown) p p 11/16 in. 18 mm 1/4 in. 7 mm 1/32 in. 0.79 1/32 in. 0.79 mm BURNER mm 287/(7 3/16 in. 35(6685( 4.7 mm 7$3 ,1/(7 21 35(6685( 7$3 2)) FLAME SIDE VIEWSENSOR *$6 9$/9( 6+2:1 ,1 2)) 326,7,21 END VIEW &$3 6&5(: %ODFN FIGURE 16 H--Gas Valve The G24M uses a gas 635,1* 35(6685( valve manufactured by Honey- 7DSHUHG (QG 5(*8/$725 $'-867,1* 6&5(: 'RZQ 5HG :KLWH well (figure 17) or White Rodgers (figure 18). The valve is internally redundant to assure safety shut--off. If the ,1/(7 gas valve must be replaced, the same type valve must 35(6685( 7$3 be used. 24VAC terminals and gas control knob are located on top of the valve. All terminals on the gas valve are connected to wires from the electronic ignition control. 24V applied to the terminals energizes the valve. Inlet and outlet pressure taps are located on the valve. A *$6 ,1/(7 regulator adjustment screw is located on the valve. Refer to figure 17 or 18 for location of valve features. FIGURE 17 An LPG changeover kit is available from Lennox. The kit includes burner orifices and a regulator conversion kit. WHITE RODGERS GAS VALVE I--Combustion Air Blower Prove (Pressure) Switch (S64) 36E GAS VALVE KNOB SHOWN REGULATOR COVER SCREW IN OFF POSITION G24M series units are equipped with a combustion air prove switch located on the vestibule panel. The switch is connected to the combustion air blower housing by GAS INLET means of a flexible silicone hose. It monitors air pressure in the combustion air blower housing. 35(6685( 35(6685( 7$3 7$3 FIGURE 18 Page 15 The switch is a single-pole single-throw pressure switch electrically connected to the furnace control. The purpose of the switch is to prevent burner opera- III--START-UP A--Preliminary and Seasonal Checks 1 -- Inspect electrical wiring, both field and factory tion if the combustion air blower is not operating. installed for loose connections. Tighten as required. 2 -- Check voltage at disconnect switch. Voltage must PROVE SWITCH COMBUSTION AIR BLOWER be within range listed on the nameplate. If not, PROVE SWITCH Normally Open consult the power company and have voltage Closes on Negative Pressure condition corrected before starting unit. B--Heating Start-Up 1 -- Set thermostat to OFF position. Close manual knob on gas valve. 2 -- Wait 5 minutes. 3 -- Open manual knob on gas valve, replace burner Sensing Tube Attaches to Top access door and turn on unit electrical supply. Side Of Blower Back WARNING Top Right Shock and burn hazard. PROVE SWITCH G24M units are equipped with either a direct spark Left Front or hot surface ignition system. Do not attempt to Bottom light manually. FIGURE 19 4 -- Set fan switch to AUTO or ON and move system On start-up, the switch senses that the combustion air selection switch to HEAT. Adjust thermostat to a blower is operating. It closes a circuit to the furnace setting above room temperature. control when pressure inside the combustion air 5 -- If unit does not light the first time, the SureLight blower increases above switch setting (negative) w.c. control will attempt four more ignitions, the Ram The pressure sensed by the switch is relative to atmo- control will attempt two more ignitions before spheric pressure. If the flue becomes obstructed dur- locking out. ing operation, the switch senses a loss of negative 6 -- If lockout occurs, repeat steps 1, 2, 3 and 4. pressure (pressure becomes more equal with atmo- C--Safety or Emergency Shutdown spheric pressure) and opens the circuit to the furnace control and gas valve. The switch trip pressure is dif- Turn off unit power. Close manual and main gas valves. IMPORTANT ferent depending on unit model number. The trip pressure is printed on the side of the limit. The switch is factory set and is not field adjustable. It is In case emergency shutdown is required, turn off a safety shut-down control in the furnace and must not the main shut-off valve and disconnect the main be bypassed for any reason. power to unit. These controls should be properly II--PLACEMENT AND INSTALLATION labeled by the installer. Make sure unit is installed in accordance with installa- D--Extended Period Shutdown tion instructions and applicable codes. Turn off thermostat or set to UNOCCUPIED mode. Close all gas valves (both internal and external to unit) to guarantee no gas leak into combustion chamber. Turn off power to unit. All access panels, covers and vent caps must be in place and secured. Page 16 IV--HEATING SYSTEM SERVICE CHECKS underfire. High pressure can result in permanent dam- A--A.G.A./C.G.A. Certification age to gas valve or overfire. For natural gas units, op- All units are A.G.A. design certified without modifica- tween 5.0 W.C. and 13.0 W.C. For L.P. gas units, tions. Refer to the G24M Operation and Installation operating pressure at unit gas connection must be be- Instruction Manual for Information. tween 10.0 W.C. and 13.0 W.C. B--Gas Piping On multiple unit installations, each unit should be Gas supply piping should not allow more than 0.5W.C. checked separately, with and without other units oper- drop in pressure between gas meter and unit. Supply ating. Supply pressure must fall within range listed in gas pipe must not be smaller than unit gas connection. previous paragraph. Compounds used on gas piping erating pressure at unit gas connection must be be- threaded joints E--Check Manifold Pressure should be resistant to action of liquefied petroleum After line pressure has been checked and adjusted, gases. check manifold pressure. Move pressure gauge to out- C--Testing Gas Piping let pressure tap located on unit gas valve (GV1). When pressure testing gas lines, the gas valve must be proper regulator adjustment. Manifold pressure for the disconnected and isolated. Gas valves can be dam- G24M can be measured at any time the gas valve is aged if subjected to more than 0.5psig (14 W.C.). See open and is supplying gas to the unit. Normal manifold figure 20. If the pressure is equal to or less than 0.5psig pressure for natural gas units is 3.5 in. w.c. For LP/pro- (14W.C.), use the manual shut--off valve before pres- pane gas the correct manifold pressure is 9.5 in. w.c. Checks of manifold pressure are made as verification of sure testing to isolate furnace from gas supply. IMPORTANT GAS PIPING TEST PROCEDURE MANUAL MAIN SHUT--OFF VALVE For safety, connect a shut-off valve between the WILL NOT HOLD TEST PRESSURE manometer and the gas tap to permit shut off of IN EXCESS OF 0.5 PSIG (14W.C.) gas pressure to the manometer. TABLE 9 GAS VALVE REGULATION Unit (Fuel) Operating Pressure (outlet) in. W.C. Natural L.P. CAP 3.5 +0 --0.3 9.5 + 0.5 GAS VALVE The gas valve is factory set and should not require adFIELD PROVIDED justment. All gas valves are factory regulated. See LINE PRESSURE TAP table 9. FIGURE 20 Manifold Adjustment Procedure: When checking piping connections for gas leaks, use 1 -- Connect a test gauge to outlet pressure tap on gas preferred means. Kitchen detergents can cause harmful valve. Start unit and allow 5 minutes for unit to corrosion on various metals used in gas piping. Use of a reach steady state. specialty Gas Leak Detector is strongly recommended. It is available through Lennox under part number 2 -- While waiting for the unit to stabilize, notice the flame. Flame should be stable and should not lift 31B2001. See Corp. 8411--L10, for further details. from burner. Natural gas should burn blue. L.P. gas Do not use matches, candles, flame or any other source of ignition to check for gas leaks. should burn mostly blue with some orange streaks. 3 -- After allowing unit to stabilize for 5 minutes, re- D--Testing Gas Supply Pressure cord manifold pressure and compare to values When testing supply gas pressure, connect test gauge given in table 9. to inlet pressure tap (field provided). See figure 20. NOTE--Shut unit off and remove manometer as Check gas line pressure with unit firing at maximum soon as an accurate reading has been obtained. rate. Low pressure may result in erratic operation or Take care to replace pressure tap plug. Page 17 F- Proper Gas Flow TABLE 11 Furnace should operate at least 5 minutes before checkĆ ing gas flow. Determine time in seconds for two revoluĆ tions of gas through the meter. (Two revolutions assures a more accurate time.) Divide by two and compare to time in table 10 below. Adjust manifold pressure on gas valve to match time needed. NOTE- To obtain accurate reading, shut off all other gas appliances connected to meter. TABLE 10 GAS METER CLOCKING CHART Seconds for One Revolution Natural LP G24M 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 26 52 64 128 Natural-1000 btu/cu ft ALTITUDE feet (m) GAS FUEL MANIFOLD PRESSURE in. W.C. (kPa) Natural 3.5 (0.87) Propane/LP 9.5 (2.36) 4500 - 5500 (1372 - 1676) Natural 3.4 (0.86) Propane/LP 9.2 (2.29) 5500 - 6500 (1676 - 1981) Natural 3.3 (0.82) Propane/LP 8.9 (2.21) Natural 3.2 (0.80) Propane/LP 8.6 (2.14) 0 - 4500 (0 - 1372) 6500 - 7500 (1372 - 2286) TABLE 12 Pressure Switch Part Number No Change No Change 88J8001 18L2401 18L2401 No Change Unit Model G24M-45 G24M-60 G24M-75 G24M-100 G24M-120 G24M-140 IMPORTANT LP-2500 btu/cu ft For safety, shut unit off and remove manometer as soon as an accurate reading has been obtained. Take care to replace pressure tap plug. NOTE- To obtain accurate reading, shut off all other gas appliances connected to meter. G-High Altitude Derate H-Flame Signal NOTE-In Canada, certification for installation at altiĆ tudes over 4500 ft. (1372m) above sea level is the jurisĆ diction of the local authorities. G24M-1 through -9 Models This unit does not require gas pressure adjustment, or pressure switch change when operating at elevations of 0 to 7500 ft. (0 to 2248m). Check gas line pressure with unit firing. The minimum pressure as shown on the nameplate for natural and propane gases must be maintained. No oriĆ fice change is required. NOTE-This is the only permissible field derate for this appliance. G24M-10 and -11 Models Table 11 shows manifold pressure settings for installations at different altitudes. Refer to table 12 for pressure switch replacement for models at elevations of 4500 feet (1372m) and greater. A microamp DC meter is needed to check the flame signal on the primary ignition control. Flame (microamp) signal is an electrical current which passes from the furnace control through the sensor elecĆ trode during unit operation. Current passes from the senĆ sor through the flame to ground to complete a safety cirĆ cuit. To Measure Flame Signal: 1 - Place meter in series between furnace control and sensor wire. Connect the positive (+) lead of meter to the ignition control sensor connection and the negaĆ tive (-) lead of the meter to the sensor wire. See figure 21. 2 - Set thermostat for a heating demand and check flame signal with unit operating. For G24M series with a RAM control, a reading of 1 to 5 microamps DC should occur. The furnace control must see at least 1.0 microamps in order to keep the gas valve energized. G24M units with the SureLight control should read 0.7 microamps or more. Page 18 FLAME SIGNAL TEST RAM CONTROL SHOWN D.C. MICROAMP METER FLAME SENSOR IGNITION CONĆ TROL 1 - Place plenum thermometers in the supply and return air plenums. Locate supply air thermometer in the first horizontal run of the plenum where it will not pick up raĆ diant heat from the heat exchanger. 2 - Set thermostat to highest setting. SENSE" TERMINAL SENSOR WIRE FIGURE 21 Flame signal from the Ram control may rise above 5 microĆ amps for the first few seconds after ignition then level off within the range. WARNING Fire and explosion hazard. These instructions MUST be followed exactly. Can cause a fire or explosion resulting in property damage, personal injury or loss of life. 3 - After plenum thermometers have reached their highĆ est and steadiest readings, subtract the two readings. The difference should be in the range listed on the unit rating plate. If the temperature is too low, decrease blower speed. If temperature is too high, first check the firing rate. Provided the firing rate is acceptable, inĆ crease blower speed to reduce temperature. To change blower speed taps see the Blower Speed Taps section in this manual. C-External Static Pressure 1 - Measure tap locations as shown in figure 22. 2 - Punch a 1/4" diameter hole STATIC PRESSURE TEST in supply and return air pleĆ V-TYPICAL OPERATING CHARACTERISTICS A-Blower Operation and Adjustment NOTE- The following is a generalized procedure and does not apply to all thermostat controls. 1 - Blower operation is dependent on thermostat control system. 2 - Generally, blower operation is set at thermostat subĆ base fan switch. With fan switch in ON position, blower operates continuously on low speed. With fan switch in AUTO position, blower cycles with demand or runs conĆ tinuously while heating or cooling circuit cycles. 3 - In all cases, blower and entire unit will be off when the system switch is in OFF position. B-Temperature Rise set for unit operation within the range of AIR TEMP. RISE °F" listed in the unit rating plate. To Measure Temperature Rise: Temperature rise for G24M units depends on unit input, blower speed, blower horsepower and static pressure as marked on the unit rating plate. The blower speed must be nums. Insert manometer MANOMETER hose flush with inside edge of hole or insulation. Seal around the hose with perĆ G24M UNIT magum. Connect the zero FIGURE 22 end of the manometer to the discharge (supply) side of the system. On ducted sysĆ tems, connect the other end of manometer to the reĆ turn duct as above. For systems with non-ducted reĆ turns, leave the other end of the manometer open to the atmosphere. 3 - With only the blower motor running and the evaporator coil dry, observe the manometer reading. Adjust blowĆ er motor speed to deliver the air desired according to the job requirements. 4 - External static pressure drop must not be more than 0.5" W.C. 5 - Seal around the hole when the check is complete. Page 19 D-Blower Speed Taps Leadless Motors Blower speed tap selection is accomplished by changing the taps at the blower motor harness connector. Disconnect harĆ ness connector from motor to expose speed selectors. Blower speed selections are listed in table 13. To Change Blower Speed: 1 - Turn off electric power to furnace. SureLight board. The heating tap is connected to the "ACB HEAT " terminal and the cooling tap is connected to the "ACB COOL" terminal. The continuous blower tap is conĆ nected to the "ACB LOW" terminal. To change existing heat tap, turn off power then switch out speed tap on "ACB HEAT" with tap connected to "PARK M1" or "PARK M2". See table 14 for blower motor tap colĆ ors for each speed. TABLE 13 2 - Remove front panel and blower access door. See figure 4. 3 - Disconnect blower motor harness from motor. 4 - Select desired speeds for heating and cooling (refer to unit wiring diagram). 5 - Depress harness connector tab to release wire termiĆ nal. Select connector location for new speed (refer to unit wiring diagram). Insert wire terminal until it is seĆ curely in place. See figure 23. 6 - Replace harness connector to motor. TABLE 14 BLOWER SPEED TAP SELECĆ TION HARNESS LEADLESS MOTORS CONNECTOR VI-MAINTENANCE DEPRESS TAB TO RELEASE WIRE TERMINAL. SELECT CONNECTOR LOCATION FOR NEW SPEED (REFER TO UNIT WIRING DIAGRAM). INĆ SERT WIRE UNTIL IT IS SEĆ CURELY IN PLACE. At the beginning of each heating season, the system should be checked as follows: A-Filters A filter must be used in order to ensure long life and proper operation. The filter is located in the return air duct or return air register. Filters must be cleaned or replaced when dirty to assure proper unit operation. MOTOR FIGURE 23 B-Heat Exchanger and Burners E-Blower Speed Taps Leaded Motors Blower speed tap changes are made on the SureLight control board. See figure 6. Unused taps must be secured on dummy terminals "PARK M1" and or "PARK M2" on the NOTE-Use papers or protective covering in front of furĆ nace while cleaning furnace. Due to dimples designed in the heatexchanger, cleaning is not recommended. Removal is for inspection only. Page 20 To clean burners: CAUTION 1 -- Turn off both electrical and gas power supplies to furnace. Potential for gas leaks, fire or explosion. 2 -- Disconnect gas supply piping and remove gas Some soaps used for leak detection are corrosive manifold. to certain metals. 3 -- Disconnect ignitor and flame sensor leads. 4 -- Remove burner tray and burners. 5 -- Clean burner retention ring with wire brush. 6 -- Use test tube brush to clean inside of each burner. 7 -- Replace burners and burner tray, making sure Can cause damage to piping resulting in gas leaks, fire or explosion. burners are properly seated in slots on tray and ori- C--Supply Air Blower 1 -- Check and clean blower wheel. 2 -- Motors used on the Lennox G24M series units are permanently lubricated and need no further fice in manifold. 8 -- Reinstall burner box and gas supply piping. Reconnect ignitor and flame sense leads. 9 -- Carefully check all piping connections (factory and field) for gas leaks. Use a leak detecting solution or other preferred means. 10 -- Restore electrical power and gas supply. Follow lighting instructions on front of unit. Carefully clean piping thor- oughly after leak detection has been completed. lubrication. D--Flue and Chimney Flue must conform to all AGA/GAMA venting requirements. Flue pipe deteriorates from the inside out and must be disconnected in order to check thoroughly. Check flue pipe, chimney and all connections for tightness and to make sure there is no blockage or leaks. E--Electrical 1 -- Check all wiring for loose connections. 2 -- Check for correct voltage. 3 -- Check amp--draw on blower motor. HEAT EXCHANGER REMOVAL (unit shown in horizontal position) REMOVE SCREWS (4) Left Back Bottom Top Front Right SLIDE ENTIRE ASSEMBLY OUT OF CABINET FIGURE 24 Page 21 VII--WIRING, OPERATION SEQUENCE &TROUBLESHOOTING A--Field Wiring, Thermostat Connections ),(/' ,167$//(' &/$66 ,, 9 ),(/' ,167$//(' /,1( 92/7$*( &20%867,21 $,5 %/2:(5 35(6685( 6:,7&+ 35,0$5< /,0,7 )851,6+(' %< ,167$//(5 7<3,&$/ *0 ),(/' :,5,1* ',$*5$0 / 1 *$6 9$/9( 7+(50267$7 : 5 < * )/$0( 52//287 6:,7&+(6 75$16)250(5 6(&21'$5< /,0,76 %/$&. :+,7( < 72 &2035(6625 &217$&725 * : 5 685(/,*+7 &21752/ & '225 ,17(5/2&. 6:,7&+ ),*85( G24M and CONDENSING UNIT THERMOSTAT DESIGNATIONS (Refer to specific thermostat and outdoor unit.) Thermostat Y G24M Furnace COOLING Y Condensing Unit COMPRESSOR HS UNIT COMPRESSOR INDOOR BLOWER G G HEAT W W POWER R R COMMON COMMON C C ),*85( 3DJH HS UNIT COMMON *1' B--Early Model G24M Series With Ram Ignition Control limits (S21) are closed, the furnace control begins 1 -- When disconnect is closed, 120V is routed through a 45 second time-delay (pre-purge). door interlock switch (S51) to feed the line voltage side of the furnace control (A3) and transformer T1 primary. Door interlock switch must be closed for 6 -- At the end of the pre-purge cycle, the furnace control simultaneously opens the gas valve and sends A3 and T1 to receive voltage. high voltage to the spark electrode. 2 -- T1 supplies 24VAC to terminal 24VAC on A3. In turn, terminal R of A3 supplies 24VAC to termi- 7 -- When flame is sensed, the furnace control begins a 45 second delay before energizing the indoor nal RC of the indoor thermostat (not shown). blower. 3 -- When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC. 8 -- When heat demand is satisfied, W1 of the thermostat de-energizes W of the furnace control and the 4 -- CMB BLWR of the blower control energizes the furnace control immediately de-energizes the gas combustion air blower (B6). When the combustion valve. The combustion air blower runs for 5 se- air blower nears full speed, combustion air prove conds (post-purge) before being de-energized. switch (S18) closes. Also, the indoor blower runs for a designated peri- 5 -- When S18 closes, assuming the flame rollout switch (S47), primary limit (S10) and secondary 3DJH od (90--240 seconds) as set by switches on furnace control. C--Ram Ignition Control Troubleshooting Guide RAM CONTROL HEATING TROUBLE SHOOTING SEQUENCE NORMAL HEATING MODE ABNORMAL HEATING MODE LED: SLOW FLASH RATE THERMOSTAT CALLS FOR HEAT LED: FAST FLASH RATE FLAME OFF? NO CONTROL SELF--CHECK OKAY? NO HI LIMIT SWITCH CLOSED? NO PRESSURE SWITCH OPEN? NO YES YES YES YES COMBUSTION AIR BLOWER ON? PRESSURE SWITCH CLOSED? LOCKOUT: MAIN VALVE OFF COMB. 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. SEQUENCE HOLDS UNTIL HI LIMIT CLOSES. LED: 4 flashes. CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL PRES. SWITCH OPENS. LED: 3 flashes. NO CHECK TO SEE IF MAIN VALVE IS OFF. SEQUENCE HOLDS UNTIL PRES. SWITCH CLOSES. LED: Fast flash rate. NO MAIN VALVE AND SPARK ARE OFF. INCREMENT TRIAL REGISTER THREE TRIALS COMPLETED? YES PREPURGE (45 seconds) IGNITION TRIAL (7 seconds) ---- START IGNITION SPARK, OPEN MAIN GAS VALVE. INCREMENT TRIAL REGISTER. HAS FLAME BEEN REGISTERED WITHIN 7 SECONDS? YES IGNITION RESET PERIOD COMBUSTION & SYSTEM FANS OFF. IS 60 MIN. RESET PERIOD COMPLETE? LED: Fast flash rate. MAIN VALVE AND SPARK OFF. YES SYSTEM FAN ON. (Fixed 45--second delay) FLAME SENSE OKAY? NO NO YES START IGNITION SPARK (IN 0.8 SEC. MAXIMUM). HAS FLAME BEEN DETECTED WITHIN 7 SEC.? FLAME CONTINUOUSLY CHECKED? ROLLOUT SWITCHES CLOSED YES HI LIMIT SWITCH CLOSED? YES PRESSURE SWITCH CLOSED? YES NO LOCKOUT. MAIN VALVE OFF. COMBUSTION AND SYSTEM FANS ON. RESET OR REPLACE ROLLOUT SWITCH. LED: 4 flashes. NO THERMOSTAT OPENS MAIN VALVE OFF. COMBUSTION & SYSTEM FANS ON. SEQUENCE HOLDS UNTIL SWITCH CLOSES. LED: 4 flashes for hi limit. LED: 3 flashes for pressure switch. LED: SLOW FLASH RATE SWITCH CLOSED COMB. AIR BLOWER OFF (5 sec. delay) COMBUSTION FAN ON. SYSTEM FAN OFF. (AFTER DELAY TO OFF INTERVAL COMPLETED.) YES FAN OFF (After selected 90, 120, 180, or 240 delay)? NO NO YES LED: Fast flash rate. 3DJH YES RAM CONTROL COOLING TROUBLE SHOOTING SEQUENCE LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT CALLS FOR COOLING. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED AT COOLING SPEED AFTER 1 SECOND DELAY. ACC TERMINAL ENERGIZED. THERMOSTAT OPENS. COMPRESSOR OFF. SYSTEM FAN AND ACC TERMINAL OFF AFTER COMPLETING SELECTED DELAY INTERVAL (At dip switches). MANUAL FAN TROUBLESHOOTING SEQUENCE LED: Slow flash rate. REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL ENERGIZES SYSTEM FAN AT CONTINUOUS SPEED. ACC TERMINAL ENERGIZED. THERMOSTAT CALLS FOR HEAT. YES NO SYSTEM FAN SWITCHES TO HEATING SPEED AFTER SELECTED DELAY. ACC TERM. REMAINS ENERGIZED. THERMOSTAT CALLS FOR COOLING. YES SYSTEM FAN SWITCHED TO COOLING SPEED. ACC TERMINAL REMAINS ENERGIZED. NO THERMOSTAT OPENS. SYSTEM FAN SWITCHED OFF AFTER DELAY. ACC TERMINAL DE--ENERGIZED. THERMOSTAT OPENS. SYSTEM FAN SWITCHES TO CONTINUOUS SPEED AND ENERGIZES ACC TERMINAL. BOTH REMAIN ON UNTIL MANUAL FAN IS SWITCHED OFF AT THERMOSTAT. SLOW FLASH FAST FLASH 2 FLASH 3 FLASH 4 FLASH 5 FLASH STEADY ON LED CODES . NORMAL OPERATION. NO CALL FOR HEAT. NORMAL OPERATION. CALL FOR HEAT. SYSTEM LOCKOUT. FAILURE TO DETECT OR SUSTAIN FLAME. PRESSURE SWITCH OPEN OR CLOSED. HIGH LIMIT OR ROLLOUT SWITCH OPEN. FLAME SENSED AND GAS VALVE NOT ENERGIZED. CONTROL BOARD FAILURE. 3DJH D-Late Model G24M Series With SureLight Ignition Control TYPICAL G24M DIAGRAM (-11 MODEL SHOWN) 123- 4- When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC. S10 primary limit switch and S47 rollout switch are closed. Call for heat can continue. SureLight control energizes combustion air blower B6. 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). Once S18 closes, a 15-second pre-purge follows. SureLight control energizes ignitor. A 20-second warm-up period begins. 5- 678- Page 26 Gas valve opens for a 4-second trial for ignition. Ignitor stays energized the first second of trial. (Board 97L48 only: ignitor energized during trial or until flame is sensed. Flame is sensed, gas valve remains open for the heat call. After 45-second delay, SureLight control energizes indoor blower B3. When heat demand is satisfied, W1 of the indoor thermostat de-energizes W of the SureLight control which de-energizes the gas valve. Combustion air blower B6 continues a 5-second post-purge period, and indoor blower B3 completes a selected OFF time delay. SURELIGHT CONTROL HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE ABNORMAL HEATING MODE GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER ON. LED #1 ALTERNATING FAST FLASH LED#2 ALTERNATING FAST FLASH CHECK FOR BROKEN IGNITOR OR OPEN IGNITOR CIRCUIT POWER ON CONTROL SELF--CHECK OKAY? NO COMBUSTION AIR BLOWER ON FOR 1 SECOND. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER DELAY OFF. LED #1 ON LED #2 ON (RESET CONTROL BY TURNING MAIN POWER OFF.) YES TURN INDUCER ON FOR 1 SECOND. IS POLARITY REVERSED? NO SIGNAL IMPROPER GROUND AT LED. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. NO IS VOLTAGE ABOVE 75 VOLTS? YES IS THERE PROPER GROUND? YES NO BURNER OFF? (CONTINUOUS FLAME CHECK) POLARITY REVERSED. LED #1 ---- FAST FLASH LED #2 ---- SLOW FLASH LOW VOLTAGE SIGNAL AT LED HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS. NO ROLLOUT SWITCH CLOSED? YES NO GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 ---- ON. LED #2 ---- SLOW FLASH. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. YES NORMAL OPERATION: GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER ON HEATING SPEED. LED #1 ---- SLOW FLASH LED #2 ---- OFF LED #1 ---- SLOW FLASH LED #2 ---- SLOW FLASH THERMOSTAT CALLS FOR HEAT: LED #1 ---- FAST FLASH LED #2 ---- FAST FLASH YES NO IS COMBUSTION AIR PRESSURE SWITCH OPEN? YES IS COMBUSTION AIR BLOWER ENERGIZED? (HTG ACC TERMINAL IS ENERGIZED WITH C.A.B.) YES HAS COMBUSTION AIR PRESSURE SWITCH CLOSED IN 2.5 MINUTES? NO YES 15-SECOND COMBUSTION AIR BLOWER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. YES CONTINUED NEXT PAGE 3DJH GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 OFF LED #2 SLOW FLASH (Sequence holds until pressure switch closes or thermostat resets control.) PRESSURE SWITCH IS IN WATCHGUARD MODE. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH DELAY. LED #1 ---- OFF. LED #2 ---- SLOW FLASH. IS 5-MINUTE RESET PERIOD COMPLETE? NORMAL HEATING MODE ABNORMAL HEATING MODE 15-SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. NO IS VOLTAGE ABOVE 75 VOLTS? YES IS THERE A PROPER GROUND? YES YES YES NO IGNITOR WARM-UP -- 20 SECONDS. YES 4-SECOND TRIAL FOR IGNITION. GAS VALVE OPENS. IGNITOR ENERGIZED FOR 1 SECOND AFTER VALVE OPENS. NO FLAME SENSED DURING THIS PERIOD. BOARD 97L48: IGNITOR ENERGIZED DURING TRIAL OR UNTIL FLAME SENSED. YES FLAME STABILIZATION PERIOD. 4 SECONDS NO NO LEDS SIGNAL ALTERNATING FAST FLASH IS IGNITOR INTACT AND CONNECTED? GAS VALVE OFF. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF. NO HAS CONTROL FAILED TO SENSE FLAME FOR FIVE CONSECUTIVE TRIES DURING A SINGLE HEAT DEMAND? NO YES FLAME RECTIFICATION CURRENT CHECK. CAN FLAME BE PROVEN WITHIN 4 SECONDS AFTER GAS VALVE OPENS? (>0.15 microamps) IGNITION WATCHGUARD MODE. GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF WITH DELAY LED 1 ALT. SLOW FLASH LED 2 ALT SLOW FLASH IS 60-MINUTE RESET PERIOD COMPLETE? YES YES NO FLAME PRESENT? YES NO LOW FLAME SIGNAL (Does not affect operation of control) LED #1 -- SLOW FLASH LED #2 -- FAST FLASH FLAME SIGNAL ABOVE 0.7 MICROAMPS? YES INDOOR BLOWER ON DELAY BEGINS (45 seconds.) GAS VALVE DE-ENERGIZED. COMBUSTION AIR INDUCER DE-ENERGIZED.INDOOR BLOWER ON UNTIL SWITCH CLOSES.LED #1 -- SLOW FLASH. LED #2 -- ON. IS LIMIT SWITCH CLOSED? YES NO PRIMARY AND SECONDARY LIMIT SWITCHES CLOSED? NO HAS CONTROL RESET IGNITION SEQUENCE FOUR TIMES? YES LIMIT SWITCH WATCH GUARD MODE. GAS VALVE OFF. COMB. AIR INDUCER OFF. INDOOR BLOWER OFF WITH DELAY. LED#1-SLOW FLASH LED#2- ON. IS 60MINUTE RESET PERIOD COMPLETE.? YES NO YES HAS PRIMARY/SECONDARY LIMIT RESET. (See table 2 DIAGNOSTIC CODES for limit reset operation) NO GAS VALVE POWER OFF. COMBUSTION AIR INDUCER POWER OFF. INDOOR BLOWER OFF WITH DELAY LED #1 -- ON. LED #2 -- SLOW FLASH. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH IS RESET ROLLOUT SWITCH CLOSED? YES COMBUSTION AIR PRESSURE SWITCH CLOSED? YES THERMOSTAT DEMAND SATISFIED. YES LED #1 & #2 SIMULTANEOUS SLOW FLASHES. YES NO YES GAS VALVE DE-ENERGIZED. COMBUSTION AIR INDUCER ON. INDOOR BLOWER OFF WITH DELAY LED #1 -- OFF. LED #2 -- SLOW FLASH. HAS CAB SWITCH CLOSED IN 2.5 MINUTES? NO YES COMB. AIR INDUCER CONTINUES 5-SECOND POST PURGE AFTER T’STAT DEMAND IS SATISFIED. INDOOR AIR BLOWER COMPLETES SELECTED “OFF” DELAY BEFORE SHUTTING OFF. ACB.HEAT SPEED, HTG ACC TERM. AND ACC TERM. OFF. Page 28 5-MINUTE PRESSURE SWITCH WATCHGUARD MODE. YES SURELIGHT CONTROL COOLING SEQUENCE NORMAL COOLING MODE ABNORMAL COOLING MODE POWER ON IGNITION CONTROL MAIN POWER ON. GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. INTERRUPT MAIN POWER TO RESET CONTROL. NO CONTROL SELF DIAGNOSTIC CHECK. IS CONTROL OPERATING NORMALLY? YES TURN INDUCER ON FOR 1 SECOND. YES IS POLARITY REVERSED? SIGNAL IMPROPER GROUND AT LED. SIGNAL HOLDS UNTIL UNIT IS PROPERLY GROUNDED. SIGNAL POLARITY REVERSED AT LED. NO NO YES IS THERE PROPER GROUND? IS VOLTAGE ABOVE 75 VOLTS? ROLLOUT SWITCH MONITORED CONTINUOUSLY. IS ROLLOUT SWITCH CLOSED? LOW VOLTAGE SIGNAL AT LET HOLDS UNTIL VOLTAGE RISES ABOVE 75 VOLTS. NO GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES. NO GAS VALVE OFF. COMBUSTION AIR BLOWER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. SIGNAL CIRCUIT BOARD FAILURE AT LED. SEQUENCE HOLDS UNTIL FLAME IS NOT SENSED. YES CHECK FOR MAIN BURNER FLAME SENSE. IS MAIN BURNER FLAME OFF? NO LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT COOLING CYCLE. THERMOSTAT CALLS FOR COOLING. COMPRESSOR CONTACTOR AND SYSTEM FAN ENERGIZED WITH 0-SECOND DELAY ACB COOL SPEED AND ACC. TERM. ENERGIZED. THERMOSTAT OPENS. COMPRESSOR OFF. ACB COOL SPEED AND ACC. TERM. OFF WITH 0-SECOND DELAY. 3DJH CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. ACC. TERMINAL IS ENERGIZED. THERMOSTAT CALLS FOR HEAT (W). NO HTG ACC. TERM. ENERGIZES WITH COMB. AIR BLOWER. YES BOARD NO. 63K8901 SYSTEM FAN DE-ENERGIZED. SYSTEM FAN ENERGIZES ON ACB HEAT SPEED AFTER NORMAL DELAY. THERMOSTAT CALLS FOR COOLING. NO YES BOARD NO. 24L85, 56L83, 97L48 SYSTEM FAN SWITCHES TO ACB HEAT SPEED AFTER NORMAL DELAY (fan remains energized) SYSTEM FAN SWITCHED TO ACB COOL SPEED. ACC. TERM. REMAINS ON. THERMOSTAT OPENS. COMBUSTION AIR AND HTG ACC TERMINAL DE-ENERGIZE. THERMOSTAT OPENS. BOARD 63K89: SYSTEM FAN OFF. ACC. TERM. OFF. (AFTER OFF DELAY COMPLETED). BOARDS 24L85, 56L83 AND 97L48: SYSTEM FAN SWITCHES TO LOW SPEED AFTER NORMAL DELAY. (fan remains energized) MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. ACC. TERM. ENERGIZED. Page 30 E--SureLight Ignition Control Troubleshooting Guide UPON INITIAL POWER UP, REMOVE ALL THERMOSTAT DEMANDS TO THE UNIT PROBLEM: 1 UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE Condition Possible Cause 1.1 1.1.1 Both diagnostic lights fail to light Main voltage 120V not supplied to up. unit. -- 1.1.2 Miswiring of furnace or improper connections. LED#1--Off LED#2--Off 1.1.3 Circuit breaker tripped or fails to close. Corrective Action / Comments ACTION 1 -- Check 120V main voltage. Determine cause of main power failure. ACTION 1 -- Check for correct wiring of 120V to power make up box and transformer. ACTION 2 -- Check 24V wiring to control board. ACTION 1 -- Replace circuit breaker if it is reset but does not have continuity. ACTION 2 -- If circuit breaker still trips, check for short. ACTION 1 -- Check that door switch is activated 1.1.4 Door interlock switch failure. when door is closed. ACTION 2 -- Check wire connections to switch, replace loose connectors. ACTION 3 -- Check continuity of switch in closed position. Replace if malfunctioning 1.1.5 Transformer Failure. 1.1.6 Failed control board. 1.2 Diagnostic lights flash the roll-out code. -- LED#1--On, LED#1 O LED#2--Slow LED#2 Slow Flash 1.2.1 ACTION 1 -- Check that transformer output is 24V. Replace if malfunctioning ACTION 1 -- If all the above items have been checked, replace board. ACTION 1 -- Manually reset the roll--out switch by pushing the top button. Roll--out switch open. ACTION 2 -- Determine the cause of the roll-- 1.2.2 ACTION 1 -- Check continuity across roll--out Roll--out switch failure. 1.2.3 Mis iring or improper connections Miswiring at roll--out switch. 1.2.4 Nine pin connector failure out switch activation before leaving furnace. switch. Replace roll--out switch if switch is reset but does not have continuity. ACTION 1 -- Check wiring connections to switch. ACTION 1 -- Check 9--pin connector for proper connection to control board. ACTION 2 -- Check continuity of the multi plug pin. 1.3 -- On initial power--up the comb. air blower does not energize. 1.3.1 -- Diagnostic lights flash the reverse polarity code. 120V main power polarity reversed. ACTION 1 -- Check the 120V has line and neutral correctly input into control. ACTION 2 -- Reverse the line and neutral at the 120V field connection. LED#1--Fast Flash, LED#2--Slow Flash. 1.4 1.4.1 -- On initial power up the combustion air blower does not energize. Open combustion air blower motor -- Diagnostic lights flash normal circuit. power on operation. operation ACTION 1 -- Check for 120V to combustion air blower. If no power, check wire and connections. 1.4.2 LED#1--Slow Flash LED#2--Slow Flash Failed combustion air blower motor. 3DJH ACTION 1 -- If power is present at blower, replace blower. PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE Condition 1.5 On initial power--up the combusg tion air blower remains energized. -- Diagnostic flash the iimDi ti lilights ht fl h th proper main ground. -- LED#1--Alternating Fast Flash LED#2--Alternating Fast Flash Possible Cause 1.5.1 Improper ground to the unit. 1.5.2 6--Pin connector is improperly attached to the circuit board. 1.5.3 Line voltage is below 75V. Corrective Action / Comments ACTION 1 -- Check that the unit is properly ground. ACTION 2 -- Install a proper main ground to the unit ACTION 1 -- Check 6--pin connector for proper installation. Correctly insert connector into control. ACTION 1 -- Check that the line voltage is above 75V. Determine cause of voltage drop and supply correct voltage to the control. PROBLEM 2: UNIT OPERATES IN COOLING MODE BUT NOT IN THE HEATING MODE, WITH COMBUSTION AIR BLOWER CYCLING 5 SECONDS ON 55 SECONDS OFF. Condition Possible Cause Corrective Action / Comments 2.1 On initial power--up the combustion air blower remains energized. -- Diagnostic lights flash the im proper main ground. -- Combustion air blower cycles 5 seconds on 55 seconds off. -- 2.1.1 Open ignitor circuit. 2.1.2 LED#1--Alternating Fast Flash LED#2--Alternating Fast Flash Broken or failed ignitor. ACTION 1 -- Check for correct wiring and loose connections in the ignitor circuit. Check mult--plug connections for correct installation. ACTION 1 -- Unplug ignitor and read resistance across ignitor. If resistance does not read between 10.9 and 19.7 ohms, replace the ignitor. PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT ENERGIZE Condition Possible Cause 3.1 Unit operates with a cooling or 3.1.1 continuous fan demand. Primary or secondary (if equipped) -- Combustion air blower will not limit open. start with a Heating demand. -- Diagnostic lights flash the limit failure mode. mode -- 3.1.2 LED#1--Slow Flash, LED#2--On Miswiring of furnace or improper connections at limit switch(es). Corrective Action / Comments ACTION 1 switch(es). -- Check Switches continuity reset across automatically upon cool down. ACTION 2 -- Check for restrictions on blower inlet air (including filter) and outlet air. Determine cause for limit activation before placing unit back in operation. ACTION 1 -- Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. 3.2 -- Unit operates with a cooling and continuous fan demand. -- Combustion air blower will not start with a Heating demand. -- Diagnostic lights flash the pressure switch failure code. code LED#1--Off, LED#2--Slow Flash 3.2.1 Miswiring of furnace or improper connections to combustion air blower. ACTION 1 -- Check for correct wiring and 3.2.2 ACTION 1 -- Check that the pressure switch is Pressure switch stuck closed. 3DJH loose connections. Correct wiring and/or replace any loose connections. open without the combustion air blower operating. Replace if malfunctioning PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER DOES NOT ENERGIZE (CONT.). Condition Possible Cause Corrective Action/Comments 3.3 -- Unit operates with a cooling and continuous fan demand. -- Combustion air blower will not start with a Heating demand. -- Diagnostic lights flash the pressure switch failure code 2.5 minutes after heating demand. LED#1--Off, LED#2--Slow Flash 3.3.1 Miswiring of furnace or improper connections to combustion air blower. ACTION 1 -- Check for correct wiring and 3.3.2 ACTION 1 -- If there is 120V to combustion air Combustion air blower failure. loose connections. Correct wiring and/or replace any loose connections. blower and it does not operate, replace combustion air blower. PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS NOT ENERGIZED. Condition Possible Cause 4.1 4.1.1 Unit operates with a cooling and Pressure switch does not close continuous fan demand. due to incorrect routing of the -- Combustion air blower enerpressure switch lines. gizes with a heating demand. demand 4.1.2 -- Diagnostic lights flash the presPressure switch does not close sure switch failure code 2.5 mindue to obstructions in the pressure utes after heating demand. lines. -- LED#1--Off LED#2--Slow LED#2 Slow Flash 4.1.3 Pressure switch lines damaged Corrective Action/Comments ACTION 1 -- Check that the pressure switch lines are correctly routed. Correctly route pressure switch lines. ACTION 1 -- Remove any obstructions from the the pressure lines and/or taps. ACTION 1 -- Check pressure switch lines for leaks. Replace any broken lines. ACTION 1 -- Check the differential pressure across the pressure switch. This pressure should exceed the set point listed on the 4.1.4 Pressure switch does not close due to a low differential pressure across the pressure switch. switch. ACTION 2 -- Check for restricted inlet and exhaust vent. Remove all blockage. ACTION 3 -- Check for proper vent sizing and run length. See installation instructions. ACTION 4 -- Check voltage to thre combustion air blower. 4.1.5 Wrong pressure switch installed in the unit, or pressure switch is out of calibration. 4.1.6 Miswiring of furnace or improper connections at pressure switch. 4.1.7 Pressure switch failure. 3DJH ACTION 1 -- Check that the proper pressure switch is installed in the unit. Replace pressure switch if necessary. ACTION 1 -- Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. ACTION 1 -- If all the above modes of failure have been checked, the pressure switch may have failed. Replace pressure switch and determine if unit will operate. PROBLEM 5: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS ENERGIZED. (CONT.) Condition 5.1 Possible Cause 5.1.1 -- Unit operates with a cooling and Check that gas is being supplied to continuous fan demand. the unit. -- Combustion air blower enerener 5.1.2 gizes with Heating demand. Miswiring of gas valve or loose -- Ignitor is energized but unit fails connections at multi--pin control to light. amp plugs or valve. Corrective Action/Comments ACTION 1 -- Check line pressure at the gas valve. Pressure should not exceed 13 WC for both natural and propane. Line pressure should read a minimum 4.5 WC for natural and 8.0WC for propane. ACTION 1 -- Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. ACTION 1 -- Check that 24V is supplied to the gas valve approximately 35 seconds after LED#1--Alternating Slow Flash LED#2--Alternating Slow Flash 5.1.3 Malfunctioning gas valve or ignition control. heat demand is initiated. ACTION 2 -- Replace the valve if 24V is supplied but valve does not open (check for excessive gas line pressure before replacing gas valve). ACTION 3 -- Replace the control board if 24V is not supplied to valve. PROBLEM 6: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY Condition Possible Cause Corrective Action/Comments 6.1.1 ACTION 1 -- Check for restricted vent inlet or 6.1 -- Burners fire with a heating demand. -- Burners light but unit shuts off prior to satisfying T--stat demand. -- Diagnostic lights flash the pressure switch code. Low pressure differential at the pressure switch. exhaust. Remove all blockage. ACTION 2: Check for proper vent sizing. See installation instructions. LED#1--Off LED#2--Slow Flash 6.2 6.2.1 -- Combustion air blower energizes Sensor or sense wire is improperly with a heating demand. installed. -- B Burners lilight ht b butt ffail il tto stay t lit lit. 6.2.2 -- After 5 tries the control diagnostics flash the watchguard burners Sensor or sense wire is broken. failed to ignite code. 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. ACTION 1 -- Check for a broken sensor. ACTION 2 -- Test continuity across the sense wire. If wire or sensor are damaged replace the component. ACTION 1 -- Check for resistance between LED#1--Alternating Slow Flash LED#2--Alternating Slow Flash 6.2.3 Sensor or sensor wire is grounded to the unit. the sensor rod and the unit ground. ACTION 2 -- Check for resistance between the sensor wire and the unit ground. ACTION 3 -- Correct any shorts found in circuit. ACTION 1 -- Check the microamp signal from the burner flame. If the microamp signal is below 0.70 microamps, check the sense rod for proper location or contamina- 6.2.4 Control does not sense flame. tion. ACTION 2 -- Replace, clean, or relocate flame sense rod. If rod is to be cleaned, use steel wool or replace sensor. DO NOT CLEAN ROD WITH SAND PAPER. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. NOTE: Do not attempt to bend sense rod. 3DJH PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.) Condition Possible Cause Check that the manifold pressure matches value listed on nameplate. See installation instructions for proper procedure. Verify that the installed orifice size match the size listed on the nameplate or installation instructions. Check gas valve sensing hose to insure no leaks are present. Check the input rate to verify rate matches value listed on nameplate. Tightenorifice untilleakissealed. Be careful not to strip orifice threads. Check for gas leakage at the threaded orifice connection. Use approved method for leak detection (see unit instructions). Checkforsootingdepositsorother restrictions in the heat exchanger assembly. Clean assemblyas outlined in instruction manual. For G24M gas furnaces, check for proper combustion and flow. CO2 should measure between 6.0% and 8.0% for NG and between 6.5% and 8.5% for LP. CO should measure below .04% (400PPM) in an air--free sample of flue gases for either NG or LP. Check that the burners are firing into the center of the heat exchanger openings. Correct the location of the burners if necessary. ACTION 1 -- 6.3 -- Combustion air blower energizes with a heating demand. -- Burners light. -- Roll--out switch trips during the heating demand. -- Diagnostic lights flash roll--out failure. Corrective Action/Comments 6.3.1 Unit is firing above 100% of the nameplate input. ACTION 2 -- ACTION 3 -ACTION 4 -- ACTION 1 -- LED#1--On LED#2--Slow Flash 6.3.2 Gas orifices leak at the manifold connection. NOTE: ACTION 2 -- ACTION 1 -- 6.3.3 Insufficient flow through the heat exchanger caused by a sooted or restricted heat exchanger. 6.3.4 Burners are not properly located in the burner box. 6.4 Combustion air blower energizes with a heating demand. -- Burners light roughly and the unit fails to stay lit. -- Diagnostic lights flash watchguard flame failure. -- LED#1--Alternating Slow Flash LED#2--Alternating Slow Flash 6.4.1 Recirculation of flue gases. This condition causes rough ignitions and operation. Problem is characterized by nuisance flame failures. 6.4.2 Improper burner cross--overs 3DJH ACTION 2 -- 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. Check for correct intake and exhaust vent installation. See instructions ACTION 1 -- ACTION 2 -- Remove burner and inspect the cross--overs for burrs, or any restriction or if crossover is warped. Remove restriction or replace burners. ACTION 1 -- PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.) 6.5 -- Combustion air blower energizes with a heating demand. -- Burners light. -- Diagnostic lights flash watch guard flame failure. -- NOTE Unit might go into 60 minute Watchguard mode depending on intermittent nature of sensor signal. 6.5.1 Loose sensor wire connection causes intermittent loss of flame signal. Check that the sensor is properly located. Checkthatthesense wireisproperly attached to both the sensor and the control.Payextraattentiontothe pinconnectors. ACTION 1 -ACTION 2 -- LED#1--Alternating Slow Flash LED#2--Alternating Slow Flash PROBLEM 7: CONTROL SIGNALS LOW FLAME SENSE DURING HEATING MODE Condition Possible Cause 7.0 7.1.1 -- Unit operates correctly but the diagnostic lights flash low flame sense code. code Sense rod is improperly located on the burner. Corrective Action/Comments Check the sense rod for proper location on the burner. Properly locate the sense rod or replace if rod cannot be located correctly. Check sense rod for contamination or coated surface. Clean the sense rod with steel wool or replace sensor. DO NOT USE SAND PAPER TO CLEAN ROD. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. ACTION 1 -- ACTION 1 -- 7.1.2 LED#1--Slow Flash LED#2--Fast Flash Sense rod is contaminated. PROBLEM 8: INDOOR BLOWER FAILS TO OPERATE IN COOLING, HEATING, OR CONTINUOUS FAN MODE Condition Possible Cause 8.0 8.1.1 -- Indoor blower fails to operate in continuous fan, cooling, or heating mode. Miswiring of furnace or improper connections at control or indoor blower motor. Corrective Action/Comments Correct wiring and/or replace any loose connections. Check for correct wiring and loose connections. ACTION 1-- Check for 120V at the various calls for indoor blower by energizing Y, G, and W individually on the low voltage terminal strip. Note that when W is energized, the blower is delayed 45 seconds. If there is 120V to each motor tap but the blower does not operate, replace the motor. If there is not 120V when Y, G, or W is energized, replace the control. ACTION 1 -- 8.1.2 120V is not being supplied to the indoor air blower or blower motor failure. 8.1.3 Defective control board ACTION 1 -- PROBLEM 9: RF STATIC DURING TIME FOR IGNITION Condition Possible Cause 9.0 9.1.2 -- AM radio interference. Ignitor operation 3DJH Corrective Action/Comments ACTION 1 -- Call Technical Support, Dallas.

G24 Service

Rating

Date

Size

Views

Categories

Share

Transcript

Forgot your password?.