Lennox International Inc G61MP Circuit Breaker CB8, Control Box Control Transformer T1

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I−UNIT COMPONENTS

G61MP unit components are shown in figure 1. The gas valve, combustion air inducer and burners can be ac- cessed by removing the burner access panel. Electrical components are in the control box (figure 2) found in the blower section.

G61MP units are factory equipped with a bottom return air panel in place. The panel is designed to be field removed as required for bottom air return. Markings are provided for side return air and may be cut out in the field.

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

3. Circuit Breaker (CB8)

A 24V circuit breaker is also located in the control box. The switch provides overcurrent protection to the trans- former (T1). The breaker is rated 3A at 32V. If the current exceeds this limit the breaker will trip and all unit opera- tion will shutdown. The breaker can be manually reset by pressing the button on the face. See figure 3.

CIRCUIT BREAKER CB8

PRESS TO RESET

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 dis- charge by putting the furnace, the control and the technician at the same electrostatic poten- tial. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface, such as the gas valve or blower deck, before per- forming any service procedure.

A−Control Box

1. Control Transformer (T1)

A transformer located in the control box provides power to the low voltage section of the unit. Transformers on all models are rated 40VA with a 120V primary and a 24V sec- ondary.

2. Door Interlock Switch (S51)

A door interlock switch rated 14A at 125VAC is wired in se- ries with line voltage. When the blower door is removed the unit will shut down.

CONTROL BOX G61MP

 

CIRCUIT

 

BREAKER

DOOR INTERLOCK

 

SWITCH

TRANSFORMER

 

SURELIGHT

 

CONTROL

 

BOARD

 

FIGURE 2

FIGURE 3

WARNING

Shock hazard.

Disconnect power before servicing. Integrated Control Board 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.

4. Integrated Control Board (A92)

All G61MP units are equipped with the Lennox Two−Stage Integrated control board. The system consists of a igni- tion control board (figure 4 with control terminal designa- tions in tables 3, 4 and 5) and ignitor (figure 7). The board and ignitor work in combination to ensure furnace ignition and ignitor durability. The board controls all major furnace operations. The board features two LED lights, DS1 and DS2 for troubleshooting. The board also has two accesso- ry terminals rated at (1) one amp. See table 6 for trouble- shooting diagnostic codes.

Electronic Ignition

At the beginning of the heat cycle, SureLight control moni- tors the first stage and second stage combustion air induc- er prove switch. The control will not begin the heating cycle if the first stage prove switch is closed (by−passed). Like- wise the control will not begin the second stage heating cycle if the second stage prove switch is closed, and will al- low first stage heat only. However if the second stage prove switch closes during the first stage pre−purge, the control will respond to second stage heat. Once the first stage prove switch is determined to be open, the combustion air inducer is energized on low (first stage) heat speed. When the differential in the prove switch is great enough, the prove switch closes and a 15−second pre−purge begins. If the switch is not proven within 2−1/2 minutes, the control goes into Watchguard−Pressure Switch mode for a 5−min- ute re−set period.

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 energizes during the 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 sec-

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Contents Table of Contents G61MPAfue SpecificationsOptional Accessories − Must be Ordered Extra Direct Vent Blower Data G61MP−36B−045 Performance Less Filter1495 2340 1285 1385 2410 Glass Assembly G61MP Parts ArrangementTOP CAP Sight BlowerDoor Interlock Switch S51 Circuit Breaker CB8−Control Box Control Transformer T1 Integrated Control Board A92Page TWO−STAGE Integrated Control Board Integrated Control Board Terminals 120VAC Neutral120VAC Line Integrated Control Board 5 Pin Terminal−Blower Compartment Blower Motor B3 and Capacitor C4 Secondary Limit Controls S21DS1 DS2 Description Supply AIR Blower−Heating Components Flame Sensor IgnitorBurners Figure Ignitor Bracket Burners Front View Burners TOP ViewFlame Rollout Switches S47 Combustion Air Inducer Prove Switch S18Clamshell Heat Exchanger Primary Limit Control S10First stage Negative Pressure Second stage Positive Dual Combustion AIR Prove SwitchCAI & Cold END Header BOX Assembly Combustion Air Inducer B6 II−PLACEMENT and Installation Outdoor Termination Kits and Corresponding Equivalencies−Vent Piping Guidelines Maximum Vent Pipe Lengths −PVC Joint Cementing ProcedureMinimum Vent Pipe Lengths − Venting Practices Upflow or Downflow Direct or NON-DIRECT Vent ApplicationsTypical Exhaust Pipe Connections Direct Vent applications where combustion air is taken From indoors and flue gases are discharged outdoorsReducer Plug ReducerCarbon Monoxide Poisoning Hazard Sweep ELLPage − G61MP Vent Termination − AIR Inlet of Other Appliance Exhaust Pipe Termination Size Reduction Front View Side ViewUsing Existing Chimney ANGLE−CUT in Direction G61MP Direct Vent ApplicationSide View NON−DIRECT Vent Wall Ring Termination G61MP NON−DIRECT Vent Application Using Existing ChimneyCondensate Piping Condensate Assembly Vent Nipple TEE Screw Coupling CLEAN−OUT AccessHose clamp −RINGS CAP HI/LO Screws−Heating Start-Up For Your Safety Read Before Operating−Preliminary and Seasonal Checks −Safety or Emergency Shutdown IV−HEATING System Service Checks A−C.S.A. Certification−Testing Gas Piping −Extended Period Shutdown−Testing Gas Supply Pressure −Check Manifold Pressure− Proper Gas Flow Approximate − Proper Combustion− High Altitude − Condensate pH Range−External Static Pressure −Flame Signal−Temperature Rise VI−MAINTENANCE −Blower Speed TapsPage Page VII− Wiring and Sequence of Operation Sequence of Operation On Next Heating Sequence of Operation See BOX a LOW Flame Signal YES Normal Operation DS1 and DS2 Simultaneous Slow Flash YESEN or Heat Demand is SATISFIED. a Five Cooling Sequence of Operation Continuous LOW Speed FAN Sequence of Operation TWO VIII− Field Wiring Applications and Jumper SettingsSingle Cool Transformer− Both diagnostic lights fail to light up LED#2−Off Miswiring of furnace or improper conDoor interlock switch failure − Diagnostic lights flash the roll−outUous fan demand Primary, secondary or backup secon − Diagnostic lights flash the limit failure modeLED#1−Slow Flash Miswiring of furnace or improper Connections at limit switchesSwitch failure code 2.5 minutes after LED#1−Off Prove switch lines damagedCondensate in prove switch line Prove switch does not close due to aTerminating the unit − Diagnostic lights flash the pressure Switch codeWith a heating demand Installed − After 5 tries the control diagnostics− Roll−out switch trips during − Diagnostic lights flash roll−out failFails to stay lit Operation. Problem is characterized − Combustion air inducer energizesMode Er motor Nostic lights flash low flame sense BurnerLED#1−Slow Flash Sensor rod is contaminatedService Notes

G61MP specifications

Lennox International Inc. has long been a leader in HVAC solutions, and the G61MP gas furnace exemplifies the company's commitment to innovation and energy efficiency. This high-efficiency gas furnace operates with an Annual Fuel Utilization Efficiency (AFUE) of up to 96%, allowing homeowners to save significantly on energy costs while maintaining a comfortable indoor environment.

One of the primary features of the G61MP is its modulating gas valve. This technology enables the furnace to operate at multiple levels of heating output, ensuring that it can adjust its performance according to the home’s heating demands. By modulating the heating output, the G61MP maximizes efficiency and minimizes energy waste, providing a consistent temperature and improved comfort.

The G61MP also incorporates advanced two-stage heating, which enhances its performance by reducing temperature fluctuations in the home. This feature is especially beneficial during transitional weather periods when heating needs may vary widely. With its ability to operate on a lower stage most of the time, the furnace can produce quieter operation and reduced energy consumption.

In terms of design, the G61MP includes a sealed combustion chamber that draws air from outside the home for combustion, enhancing safety and efficiency. This design feature eliminates the need for indoor air, improving indoor air quality. The furnace is also equipped with a high-efficiency ECM blower motor that not only boosts comfort but operates quietly and uses less electricity compared to traditional motors.

Further enhancing its efficiency, the G61MP utilizes a variable-speed blower, which allows for precise control of airflow throughout the home. This results in better humidity control and improved air distribution, providing an overall more comfortable environment.

The Lennox G61MP is compatible with the iComfort S30 smart thermostat, allowing homeowners to control their heating remotely, adjust settings based on their schedules, and access energy usage data. This connectivity transforms the G61MP into an integral part of a smart home ecosystem, facilitating energy conservation and comfort optimization.

Lastly, the G61MP is designed with durability in mind. Its robust construction and high-quality materials ensure reliable performance and lengthy service life. Homeowners can feel assured that they are investing in a heating solution that will meet their needs for many winters to come. In summary, the Lennox G61MP gas furnace stands out with its high efficiency, advanced technology, and user-friendly features, making it a top choice for homeowners seeking exceptional heating performance.
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