Lennox International Inc G61MP Continuous fan demand Unit, Ignitor is energized but unit fails to

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PROBLEM 4: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER

ENERGIZES, IGNITOR IS ENERGIZED.

Condition

Possible Cause

Corrective Action/Comments

 

 

 

4.1

4.1.1

ACTION 1 − Check line pressure at the gas valve.

 

Pressure should not exceed 13" WC for both nat-

 

 

− Unit operates with a cooling and

Check that gas is being supplied to

ural and propane. Line pressure should read a

continuous fan demand.

the unit.

minimum 4.5" WC for natural and 8.0"WC for pro-

pane.

 

 

− Combustion air inducer energizes

 

 

4.1.2

 

with Heating demand.

 

Miswiring of gas valve or loose-

ACTION 1 − Check for correct wiring and loose

 

− Ignitor is energized but unit fails to

connections. Correct wiring and/or replace any

connections at multi−pin control amp

light.

loose connections.

plugs or valve.

 

 

 

 

 

 

 

 

ACTION 1 − Check that 24V is supplied to the gas

 

4.1.3

valve approximately 35 seconds after heat de-

 

mand is initiated.

LED#1−Alternating Slow Flash

 

Defective gas valve or ignition

ACTION 2 − Replace the valve if 24V is supplied

 

LED#2−Alternating Slow Flash

control.

but valve does not open.

 

ACTION 3 − Replace the control board if 24V is

 

 

 

 

not supplied to valve.

 

 

 

PROBLEM 5: BURNERS LIGHT WITH A HEATING DEMAND BUT UNIT SHUTS DOWN

 

PREMATURELY

 

 

 

 

Condition

Possible Cause

Corrective Action/Comments

 

 

 

 

5.1.1

ACTION 1 − Check for restricted intake and ex-

 

Low pressure differential at the prove

haust vent. Remove all blockage.

 

ACTION 2: Check for proper vent sizing. See

5.1

switch.

installation instructions.

 

 

− Burners fire with a heating demand.

5.1.2

ACTION 1 − Check vent termination kit installed.

− Burners light but unit shuts off prior

Wrong concentric vent kit used for

See Placement and Installation section.

to satisfying T−stat demand.

terminating the unit.

 

− Diagnostic lights flash the pressure

 

 

 

ACTION 1 − Check condensate line for proper

switch code.

5.1.3

vent slope, and any blockage. Condensate

 

 

 

Condensate drain line is not draining

should flow freely during operation of furnace.

 

properly.

Repair or replace any improperly installed con-

LED#1−Off

densate lines.

 

LED#2−Slow Flash

5.1.4

ACTION 1 − Check for restricted intake and ex-

 

Low pressure differential at the prove

haust. Remove all blockage.

 

ACTION 2: Check for proper vent sizing. See

 

switch.

installation instructions.

 

 

 

5.2

5.2.1

ACTION 1 − Check that sensor is properly lo-

 

 

− Combustion air inducer energizes

Sensor or sense wire is improperly

cated and that the sense wire is properly at-

with a heating demand.

installed.

tached to both the sensor and the control.

 

− Burners light but fail to stay lit.

 

 

5.2.2

ACTION 1 − Check for a broken sensor.

− After 5 tries the control diagnostics

ACTION 2 − Test continuity across the sense

flash the watchguard burners failed to

Sensor or sense wire is broken.

wire. If wire or sensor are damaged replace the

ignite code.

component.

 

 

5.2.3

ACTION 1 − Check for resistance between the

 

sensor rod and the unit ground.

 

 

LED#1−Alternating Slow Flash

Sensor or sensor wire is grounded to

ACTION 2 − Check for resistance between the

sensor wire and the unit ground.

LED#2−Alternating Slow Flash

the unit.

ACTION 3 − Correct any shorts found in circuit.

 

 

 

 

 

 

 

ACTION 1 − Check the microamp signal from

 

 

the burner flame. If the microamp signal is be-

 

 

low normal, check the sense rod for proper

 

 

location or contamination.

 

5.2.4

ACTION 2 − Replace, clean, or relocate flame

 

Control does not sense 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.

 

 

 

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Contents G61MP Table of ContentsSpecifications Optional Accessories − Must be Ordered ExtraAfue Direct Vent G61MP−36B−045 Performance Less Filter Blower Data1495 2340 1285 1385 2410 Sight Blower Glass AssemblyG61MP Parts Arrangement TOP CAPIntegrated Control Board A92 Door Interlock Switch S51Circuit Breaker CB8 −Control Box Control Transformer T1Page Integrated Control Board 5 Pin Terminal TWO−STAGE Integrated Control BoardIntegrated Control Board Terminals 120VAC Neutral 120VAC LineSupply AIR Blower −Blower Compartment Blower Motor B3 and Capacitor C4Secondary Limit Controls S21 DS1 DS2 DescriptionIgnitor Bracket Burners Front View Burners TOP View −Heating Components Flame SensorIgnitor Burners FigurePrimary Limit Control S10 Flame Rollout Switches S47Combustion Air Inducer Prove Switch S18 Clamshell Heat ExchangerDual Combustion AIR Prove Switch CAI & Cold END Header BOX AssemblyFirst stage Negative Pressure Second stage Positive Combustion Air Inducer B6 Outdoor Termination Kits and Corresponding Equivalencies II−PLACEMENT and Installation−Vent Piping Guidelines −PVC Joint Cementing Procedure Minimum Vent Pipe LengthsMaximum Vent Pipe Lengths Upflow or Downflow Direct or NON-DIRECT Vent Applications − Venting PracticesTypical Exhaust Pipe Connections Reducer Direct Vent applications where combustion air is takenFrom indoors and flue gases are discharged outdoors Reducer PlugSweep ELL Carbon Monoxide Poisoning HazardPage − G61MP Vent Termination − AIR Inlet of Other Appliance Exhaust Pipe Termination Size Reduction Side View Front ViewG61MP Direct Vent Application Using Existing Chimney ANGLE−CUT in DirectionG61MP NON−DIRECT Vent Application Using Existing Chimney Condensate PipingSide View NON−DIRECT Vent Wall Ring Termination −RINGS CAP HI/LO Screws Condensate AssemblyVent Nipple TEE Screw Coupling CLEAN−OUT Access Hose clampFor Your Safety Read Before Operating −Preliminary and Seasonal Checks−Heating Start-Up −Extended Period Shutdown −Safety or Emergency ShutdownIV−HEATING System Service Checks A−C.S.A. Certification −Testing Gas Piping− Proper Combustion −Testing Gas Supply Pressure−Check Manifold Pressure − Proper Gas Flow Approximate− Condensate pH Range − High Altitude−Flame Signal −Temperature Rise−External Static Pressure −Blower Speed Taps VI−MAINTENANCEPage Page VII− Wiring and Sequence of Operation Sequence of Operation On Next Heating Sequence of Operation Normal Operation DS1 and DS2 Simultaneous Slow Flash YES See BOX a LOW Flame Signal YESEN or Heat Demand is SATISFIED. a Five Cooling Sequence of Operation Continuous LOW Speed FAN Sequence of Operation VIII− Field Wiring Applications and Jumper Settings SingleTWO Transformer Cool− Diagnostic lights flash the roll−out − Both diagnostic lights fail to light upLED#2−Off Miswiring of furnace or improper con Door interlock switch failureConnections at limit switches Uous fan demand Primary, secondary or backup secon− Diagnostic lights flash the limit failure mode LED#1−Slow Flash Miswiring of furnace or improperProve switch does not close due to a Switch failure code 2.5 minutes afterLED#1−Off Prove switch lines damaged Condensate in prove switch line− After 5 tries the control diagnostics Terminating the unit − Diagnostic lights flash the pressureSwitch code With a heating demand Installed− Combustion air inducer energizes − Roll−out switch trips during− Diagnostic lights flash roll−out fail Fails to stay lit Operation. Problem is characterizedSensor rod is contaminated Mode Er motorNostic lights flash low flame sense Burner LED#1−Slow FlashService 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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