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© 2024 Lennox Industries Inc.
Dallas, Texas USA
WARNING
This furnace is equipped with an ignition control
factory enabled for use with Lennox A2Lrefrigerant
sysytems.
Disabling
functionality on A2L system is prohibited by safety
codes. Refer to furnace installation instructions for
non-A2L and non-Lennox refrigerant system setup.
Contents
Unit Dimensions - inches (mm) ......................................2
ML180DFE(K) Gas Furnace ...........................................3
Shipping and Packing List ..............................................3
Safety .............................................................................3
Use of Furnace as a Construction Heater ......................4
General ...........................................................................4
Combustion, Dilution, Ventilation Air...............................5
Setting Equipment ..........................................................9
Filters ............................................................................10
Duct System ................................................................. 11
Venting ......................................................................... 11
Gas Piping ....................................................................17
Electrical .......................................................................19
the
refrigerant
detection
INSTALLATION
INSTRUCTIONS
ML180DFE(K)
MERIT
SERIES GAS FURNACE
®
UPFLOW / HORIZONTAL AIR DISCHARGE
508543-01
11/2024
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This is a safety alert symbol and should never be
ignored. When you see this symbol on labels or in man-
uals, be alert to the potential for personal injury or death.
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer (or
equivalent), service agency or the gas supplier.
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves and
protective clothing.
Integrated Control .........................................................22
Twinning .......................................................................27
Low GWP Application ...................................................28
Unit Start-Up .................................................................31
Gas Pressure Measurement.........................................32
Proper Combustion.......................................................32
High Altitude .................................................................32
Other Unit Adjustments.................................................33
Service..........................................................................35
Repair Parts List ...........................................................37
Blower Data ..................................................................38
Start-Up and Performance Checklist ............................40
Page 1
WARNING
CAUTION
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Summary of Contents for Lennox MERIT ML180DFE045E36AK
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Page 1: Table Of Contents
Take care while handling this equipment and wear gloves and WARNING protective clothing. This furnace is equipped with an ignition control factory enabled for use with Lennox A2Lrefrigerant sysytems. Disabling refrigerant detection functionality on A2L system is prohibited by safety codes. -
Page 2: Unit Dimensions - Inches (Mm)
Unit Dimensions - inches (mm) 3-1/8 9/16 (79) (14) RETURN AIR OPENING FLUE OUTLET 19-7/16 9/16 (Top) (494) (14) 9/16 (14) TOP VIEW 27-3/4 3/4 (19) (705) Front Panel 9/16 19-7/16 9/16 (14) (494) (14) AIR FLOW ELECTRICAL INLET (Either Side) (838) 5-3/8 (137) Right GAS PIPING INLET... -
Page 3: Ml180Dfe(K) Gas Furnace
Certifications ML180DFE(K)(K) Gas Furnace ML180DFE(K) units are CSA International certified. The ML180DFE(K) gas furnace is shipped ready for in- stallation in the downflow position fueled by natural gas. A In the USA, installation of gas furnaces must conform with conversion kit (ordered separately) is required for use in local building codes. -
Page 4: Use Of Furnace As A Construction Heater
This could cause improper combus- Use of Furnace as Construction Heater tion and unsafe operation. Lennox does not recommend the use of ML180DFE(K) • Do not block the furnace combustion air openings units as a construction heater during any phase of con- with clothing, boxes, doors, etc. -
Page 5: Combustion, Dilution, Ventilation Air
CAUTION Combustion, Dilution & Ventilation Air In the past, there was no problem in bringing in sufficient Insufficient combustion air can cause headaches, outdoor air for combustion. Infiltration provided all the air nausea, dizziness or asphyxiation. It will also cause that was needed. - Page 6 When the furnace is installed so that supply ducts carry Each opening must have a minimum free area of 1 square air circulated by the furnace to areas outside the space inch (645 mm2) per 1,000 Btu (.29 kW) per hour of total in- containing the furnace, the return air must be handled by put rating of all gas-fired equipment in the confined space.
- Page 7 EQUIPMENT IN CONFINED SPACE ALL AIR FROM OUTSIDE (Inlet Air from Crawlspace and Outlet Air to Ventilated Attic) CHIMNEY OR GAS VENT VENTILATION LOUVERS (Each end of attic) OUTLET WATER FURNACE HEATER INLET VENTILATION LOUVERS (For unheated crawl space) AIR FLOW NOTE-The inlet and outlet air openings shall each have a free area of at least one square inch (645 ) per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.
- Page 8 CAUTION Downflow Installation Downflow unit installs in three ways: on non-combustible The furnace and downflow combustible flooring base flooring, on combustible flooring using a downflow com- shall not be installed directly on carpeting, tile, or other bustible flooring base, or on a reverse-flow cooling cabi- combustible material other than wood flooring.
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Page 9: Setting Equipment
Setting Equipment WARNING Do not install the furnace on its front, back or in the horizontal position. See FIGURE 12. Do not connect the return air ducts to the back of the furnace. Doing so will adversely affect the operation of the safety control COOLING COIL devices, which could result in personal injury or death. -
Page 10: Filters
Horizontal Front Back FIGURE 12 Downflow Application CAUTION Allow for clearances to combustible materials as indicated If this unit is being installed in a space serviced by an on the unit nameplate. Minimum clearances for closet or exhaust fan, power exhaust fan, or other device which alcove installations are shown in FIGURE 13. -
Page 11: Duct System
NOTE - Use these instructions as a guide. They do not specifications provided by the filter manufacturer against supersede local codes. This furnace must be vented ac- the data given in the appropriate Lennox Product cording to all local codes, these installation instructions, Specifications bulletin. Additional information is provided and the provided venting tables in these instructions in Service and Application Note ACC002 (August 2000). - Page 12 Duct Installation VENT CONNECTION “DISCONNECTED VENT” Down-Flow Unit WARNING STICKER FLUE TRANSITION COLLAR SUPPLY FIGURE 15 FIGURE 14 Common Venting Using Tile-Lined Interior Masonry Chimney and Combined Vent Connector MINIMUM LENGTH = AS SHORT AS PRACTICAL. INTERIOR TILE-LINED FOR MAXIMUM LENGTH SEE NOTE TO LEFT MASONRY CHIMNEY NOTE- Refer to provided venting tables for installations.
- Page 13 Venting Using a Masonry Chimney If type B1 double-wall vent is used inside a chimney, no other appliance can be vented into the chimney. The out- The following additional requirements apply when a lined er wall of type B1 vent pipe must not be exposed to flue masonry chimney is used to vent this furnace.
- Page 14 7 - Single appliance venting configurations with zero 13 - When the vent connector used for Category lateral lengths (TABLE 5) are assumed to have appliances must be located in or pass through a no elbows in the vent system. For all other vent crawlspace or other areas which may be cold, that configurations, the vent system is assumed to have portion of the vent connector shall be constructed...
- Page 15 TABLE 5 Capacity of Type B Double-Wall Vents with Type B Double-Wall Connectors Serving a Single Category I Appliance Vent and Connector Diameter - D (inches) Height Lateral 3 inch 4 inch 5 inch 6 inch Appliance Input Rating in Thousands of Btu Per Hour (feet) (feet) NOTE - Single appliance venting configurations with zero lateral lengths are assumed to have no elbows in the vent system.
- Page 16 TABLE 6 Vent Connector Capacity Type B Double-Wall Vents with Type B Double-Wall Connectors Serving Two or More Category I Appliances Vent and Connector Diameter - D (inches) Height Lateral 3 inch 4 inch 5 inch 6 inch Appliance Input Rating in Thousands of Btu Per Hour (feet) (feet) TABLE 7...
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Page 17: Gas Piping
Removal of the Furnace from Common Vent Gas Piping In the event that an existing furnace is removed from a Gas supply piping should not allow more than 0.5”W.C. venting system commonly run with separate gas applianc- drop in pressure between gas meter and unit. Supply gas es, the venting system is likely to be too large to properly pipe must not be smaller than unit gas connection. - Page 18 TABLE 8 Gas Pipe Capacity - ft3/hr (m3/hr) Nominal Internal Length of Pipe - feet (m) Iron Pipe Diameter Size Inches inches (3.048) (6.096) (9,144) (12,192) (15.240) (18.288) (21.336) (24.384) (27.432) (30,480) (mm) (mm) .622 (12.7) (17.799) (4.87) (3.34) (2.69) (2.29) (2.03) (1.84)
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Page 19: Electrical
Leak Check WARNING After gas piping is completed, carefully check all field-in- Fire Hazard. Use of aluminum wire with this product may stalled piping connections for gas leaks. Use a commer- result in a fire, causing property damage, severe injury cially available leak detecting solution specifically manu- or death. - Page 20 Generator Use - Voltage Requirements IMPORTANT The following requirements must be kept in mind when When matching this gas furnace with zoning, specifying a generator for use with this equipment: defrost tempering stat or other 24V accessories, • The furnace requires 120 volts + 10% (Range: 108 It is recommended to replace the factory installed volts to 132 volts).
- Page 21 FIGURE 21 Page 21...
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Page 22: Ignition Control
Indoor Blower Operation DIP Switch Settings IGNITION CONTROL The heat fan-on time of 30 seconds is not adjustable The Integrated Control DIP Switch Settings heat fan-off delay (amount of time that the blower oper- ML180DFEK units are equipped with a single-stage inte- ates after the heat demand has been satisfied) may be grated control. - Page 23 On Board Links Must NOT Be Cut To Select Thermostat Wiring Connections AC ON System Options Heat / Cool FURNACE OUTDOOR T'STAT TERM. STRIP UNIT DO NOT CUT ANY ON-BOARD LINKS FIGURE 22 Wiring Connections On Board Links Must Be Cut To Select Thermostat Heat Pump Options Dual Fuel...
- Page 24 FIGURE 24 TABLE 9 TABLE 10 1/4” QUICK CONNECT TERMINALS THERMOSTAT INPUT TERMINALS HEAT 120V HUM POWER FOR HUMIDIFIER (120 VAC COMMON GROUND LINE INCOMING POWER LINE (120 VAC) 24V AC XFMR TRANSFORMER PRIMARY (120 VAC) CIRC INDOOR BLOWER MOTOR (120 VAC) COOL ACCESSORY(120 VAC) REVERSING VALVE (when W951 is clipped)
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Page 25: Ignition Control Diagnostic Codes
IGNITION CONTROL DIAGNOSTIC CODES DIAGNOSTIC CODES / STATUS OF FURNACE CODE IDLE MODE (DECIMALBLINKS AT 1 HERTZ -- 0.5 SECONDS ON, 0.5 SECONDS OFF INDOOR BLOWER OPERATION: CONTINUOUS FAN MODE (COSTANT TORQUE ONLY) INDOOR BLOWER OPERATION: FOLLOWED BY CFM SETTING FOR INDOOR BLOWER (1 SECOND ON, 0.5 SECOND OFF) / CFM SETTING FOR MODE DISPLAYED (VARIALBE SPEED ONLY) COOLING STAGE (1 SECOND ON, 0.5 SECOND OFF) 1 OR 2 DISPLAYED / PAUSE / REPEAT CODES. -
Page 26: Performance Warning
IGNITION CONTROLDIAGNOSTIC CODES (CONTINUED) SOFT LOCKOUT FAULTS (60 MINUTES) SOFT LOCKOUT-FLAME FAILURE ON IGNITION, IGNITION RETRY>MAX, LAST FAILED RETRY DUE E270 TO FLAME FAILURE SOFT LOCKOUT-PRESSURE SWITCH OPEN, IGNITION RETRY>MAX, LAST FAILED RETRY DUE TO E271 LPSW OPEN SOFT LOCKOUT-PRESSURE SWITCH OPEN, IN RUN MODE HEATING RECYCLES>MAX, LAST FAILED E272 RETRY DUE TO LPSW OPEN SOFT LOCKOUT-FLAME FAILURE IN RUN MODE,HEATING RECYCLES>MAX, LAST FAILED RETRY... -
Page 27: Twinning
The 24 VAC secondary of the two systems must be in Twinning Two ML180DFEK Furnaces phase. All thermostat connections are made to one control The control board in this furnace is equipped with a provi- only. See diagram below. sion to ”twin” (interconnect) two(2) adjacent furnaces with The twinned furnace without thermostat connections is a common plenum such that they operate as one (1) large to have the call for heat supplied by an external 24VAC... -
Page 28: Low Gwp Application
Low GWP Application WARNING For use with Lennox approved evaporator coil and LGWP sensors only. Use original manufacturer recommended LGWP sensors if using non Lennox approved evaporator coil. CONNECTING THE FURNACE CONTROL BOARD FIGURE 26 SENSOR. See FIGURE 27 and follow steps below: TABLE 12 1 - Route sensor wire #1 through provided grommet.. - Page 29 Leak Detected TABLE 13 When the furnace control board detects a refrigerant leak: LGWP Test Button Function 1. The furnace control board shuts off the (R) input Mode of Operation Press the Test Button to: (24VAC power) to the thermostat, which de- Trigger a leak detection energizes the outdoor unit compressor and heat sources, such as gas and/or electric strip heat.
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Page 30: Start-Up Procedure
START UP PROCEDURE External Alarm (For applications with external alarms wired directly to the The furnace control board is equipped with a LGWP Test/ furnace control board) Reset button, see “Test Button Functionality”. After the The furnace control board triggers the external alarm sys- furnace control board has been mounted and wired, re- tem when it enters Leak Detected mode. -
Page 31: Unit Start-Up
7 - Wait five minutes to clear out any gas. If you then Unit Start-Up smell gas, STOP! Immediately call your gas supplier FOR YOUR SAFETY READ BEFORE LIGHTING from a neighbor’s phone. Follow the gas supplier’s instructions. If you do not smell gas go to next step. WARNING MANIFOLD MANIFOLD... -
Page 32: Gas Pressure Measurement
Heating Sequence Of Operation Supply Pressure Measurement A threaded plug on the inlet side of the gas valve provides access to the supply pressure tap. Remove the threaded 1 - When thermostat calls for heat, combustion air plug, install a field-provided barbed fitting and connect a blower starts. -
Page 33: Other Unit Adjustments
TABLE 17 Manifold Pressure Settings at all Altitudes Line Pressure in. wg. Model 0 - 4500 ft. 4501 - 7500 ft . 7501 - 10,000 ft. Input Size 13.0 LP/Propane 10.0 10.0 10.0 11.0 13.0 13.0 LP/Propane 10.0 10.0 10.0 11.0 13.0 13.0... - Page 34 Constant Torque Motor Blower Speeds ML180DFE(K) units are equipped with a permanent mag- Follow the steps below to change the blower speeds. netic indoor blower motor that provides constant torque. 1 - Turn off electrical power to furnace. The motor has five speed taps all referenced to the same 2 - Remove blower access panel.
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Page 35: Service
Perform a general system test. Turn on the furnace to At the beginning of each heating season, and to comply check operating functions such as the start-up and shut- with the Lennox Limited Warranty, your system should be off operation. checked by a licensed professional technician (or equiva-... -
Page 36: Burner Assembly Removal
Cleaning the Burners Visually inspect inside the burners and crossovers for any blockage caused by foreign matter. Remove any NOTE - Use papers or protective covering in front of the blockage. FIGURE 29 shows burner detail. furnace during cleaning. 8 - Reinstall the burner box assembly using the existing 1 - Turn off both electrical and gas power supplies to four screws. -
Page 37: Repair Parts List
Repair Parts List The following repair parts are available through independent Lennox dealers. When ordering parts, include the complete furnace model number listed on the CSA International nameplate -- Example: ML180DF110E60CK. All service must be performed by a licensed professional installer (or equivalent), service agency, or gas supplier. -
Page 38: Blower Data
BLO WER DATA ML180DF045E36AK PERFORMANCE (Less Filter) Air Volume / Watts at Various Blower Speeds External High Medium-High Medium Medium-Low Static (Black) (Brown) (Blue) (Yellow) (Red) Pressure in. w.g. Watts Watts Watts Watts Watts 0.00 1384 1164 0.10 1347 1137 0.20 1310 1110... - Page 39 BLO WER DATA ML180DF090E48BK PERFORMANCE (Less Filter) Air Volume / Watts at Various Blower Speeds External High Medium-High Medium Medium-Low Static (Black) (Brown) (Blue) (Yellow) (Red) Pressure in. w.g. Watts Watts Watts Watts Watts 0.00 1754 1547 1408 1375 1234 0.10 1711 1499...
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Page 40: Start-Up And Performance Checklist
Start-Up & Performance Check List UNIT SET UP (typical) Unit Model Number_______________ Serial Number___________________ SUPPLY Line Voltage upflow furnace shown Gas Supply Pressure Filter RETURN RETURN DUCT SYSTEM GAS SUPPLY SUPPLY AIR DUCT LP/Propane Gas Natural Gas Sealed Piping Connections Tight Insulated (if necessary) Leak Tested Registers Open and Unobstructed... -
Page 41: Unit Operation
UNIT OPERATION (typical) Combustion CO SUPPLY Thermostat Gas Manifold Pressure Temperatures upflow furnace shown Filter Blower Motor Amps Duct Static RETURN RETURN COOLING MODE HEATING MODE INDOOR BLOWER AMPS______ GAS MANIFOLD PRESSURE “W.C._____ TEMPERATURE DROP COMBUSTION SAMPLE CO CO PPM_______ ______ Return Duct Temperature _________ Supply Duct Temperature...
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