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© 2023 Lennox Industries Inc.
Dallas, Texas USA
Contents
Unit Dimensions - inches (mm) ......................................2
ML180DFE 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
DOWNFLOW
AIR FLOW
Electrical .......................................................................19
Integrated Control .........................................................22
Unit Start-Up .................................................................24
Gas Pressure Measurement.........................................25
Proper Combustion.......................................................25
High Altitude .................................................................25
Other Unit Adjustments.................................................26
Service..........................................................................28
Repair Parts List ...........................................................30
Start-Up and Performance Checklist ............................31
Blower Data ..................................................................33
Page 1
INSTALLATION
INSTRUCTIONS
ML180DFE
MERIT
SERIES GAS FURNACE
®
DOWNFLOW DISCHARGE AIR
506734-03
01/2023
Supersedes 03/2022
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.
WARNING
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.
CAUTION
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.
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Summary of Contents for Lennox MERIT ML180DFE
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Page 1: Table Of Contents
INSTALLATION INSTRUCTIONS ML180DFE © 2023 Lennox Industries Inc. Dallas, Texas USA MERIT SERIES GAS FURNACE ® DOWNFLOW DISCHARGE AIR 506734-03 01/2023 Supersedes 03/2022 THIS MANUAL MUST BE LEFT WITH THE HOMEOWNER FOR FUTURE REFERENCE This is a safety alert symbol and should never be ignored. -
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 Gas Furnace
Certifications ML180DFE Gas Furnace ML180DFE units are CSA International certified. The ML180DFE gas furnace is shipped ready for instal- lation 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
Air is needed for Use of Furnace as Construction Heater proper combustion and safe unit operation. Lennox does not recommend the use of ML180DFE units • When the furnace is installed in an attic or other... -
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” WARNING Down-Flow Unit 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 I appliances must be located in or pass through a lateral lengths (tables 5 and 6) are assumed to have crawlspace or other areas which may be cold, that no elbows in the vent system.
- 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 WARNING The following requirements must be kept in mind when Electric Shock Hazard. Can cause injury or specifying a generator for use with this equipment: death. Unit must be properly grounded in • The furnace requires 120 volts + 10% (Range: 108 accordance with national and local codes.
- Page 21 ML180DFE Schematic Wiring Diagram Figure 21 Page 21...
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Page 22: Integrated Control
1/4” QUICK CONNECT TERMINALS IGNITION CONTROL 103217-03 120V HUM POWER FOR HUMIDIFIER (120 VAC LINE INCOMING POWER LINE (120 VAC) XFMR TRANSFORMER PRIMARY (120 VAC) CIRC INDOOR BLOWER MOTOR (120 VAC) ELECTRONIC AIR CLEANER (120 VAC) HUM24 POWER FOR HUMIDIFIER (24 VAC) NEUTRALS (5) NEUTRAL 3/16”... - Page 23 IGNITION CONTROL 107163-01 PARKS Heating Blower Off Diagnostic LED Push Button Delay Selector Switch Error Recall Integrated Control 107163-01 Diagnostic Codes RED LED Diagnostic Codes / Status of Furnace Flash Code No Power to Control or Board Fault Detected Board Fault Detected Fast Heartbeat Call for Heat / Burner Operation Slow Heartbeat...
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Page 24: 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 25: Gas Pressure Measurement
Heating Sequence Of Operation Supply Pressure Measurement (follow steps below and see Figure 21) 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 26: Other Unit Adjustments
TABLE 11 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 27 Electrical Blower Delay Select 1 - Check all wiring for loose connections. SW2-1 SW2-2 2 - Check for the correct voltage at the furnace operating). Correct voltage is 120VAC + 10% 3 - Check amp-draw on the blower motor with blower access panel in place.
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Page 28: Service
At the beginning of each heating season, and to comply 1 - Check the operation of the ignition system, inspect with the Lennox Limited Warranty, your system should be and clean flame sensor. Check microamps before checked by a licensed professional technician (or equiva- and after. - Page 29 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 25 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.
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Page 30: 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: ML180DF110E60C. All service must be performed by a licensed professional installer (or equivalent), service agency, or gas supplier. -
Page 31: 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 32 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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Page 33: Blower Data
BLOWER DATA TABLE 13 Allowable Heating Speeds Model Number Yellow Blue Brown Black ML180DF045E36A Not Allowed ML180DF070E36B Not Allowed Allowed Allowed Factory Setting Not Allowed Allowed ML180DF090E48B ML180DF110E60C Not Allowed TABLE 14 Allowable Circulation Speeds Model Number- Yellow Blue Brown Black All Models Factory Setting... - Page 34 BLOWER DATA ML180DF070E36A 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 1485 1297 1203 1176 1033 0.10 1444 1262 1162...
- Page 35 BLOWER DATA ML180DF090E48B 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 1372...
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