Lennox MERIT ML180UH045E36AK Installation Instructions Manual

Gas furnace upflow/horizontal air discharge

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Dallas, Texas USA

WARNING

This furnace is equipped with an ignition control

factory enabled for use with Lennox A2L refrigerant

systems.

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

ML180UHEK 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 ..........................................................8

Filters ............................................................................ 11

Duct System .................................................................12

Venting..........................................................................13

Gas Piping ....................................................................20

the

refrigerant

detection

INSTALLATION

INSTRUCTIONS

ML180UHEK

MERIT

SERIES GAS FURNACE

UPFLOW / HORIZONTAL AIR DISCHARGE

508541-01

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.

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.

IMPORTANT

DO NOT use the heat exchanger bracket to lift, drag

or pull the furnace to its installation location. Doing

so will loosen the bracket causing noise and or

unsafe operation.

Bracket

Electrical .......................................................................23

Ignition Control .............................................................25

Twinning .......................................................................30

Low GWP Application ...................................................31

Unit Start-Up .................................................................34

Gas Pressure Measurement.........................................35

Proper Combustion.......................................................35

High Altitude .................................................................35

Other Unit Adjustements...............................................36

Service..........................................................................37

Repair Parts List ...........................................................39

Start-Up Checklist.........................................................40

Page 1

CAUTION

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Summary of Contents for Lennox MERIT ML180UH045E36AK

Page 1 Bracket WARNING This furnace is equipped with an ignition control factory enabled for use with Lennox A2L refrigerant systems. Disabling refrigerant detection functionality on A2L system is prohibited by safety codes.
Page 2 Unit Dimensions - inches (mm) NOTE - 60C and 60D units that require air volumes 3−1/8 (79) over 1800 cfm must have one of the following: 1. Single side return air and Optional Return Air Base with transition that must accommodate required 20 x 25 x 1 in.
Page 3 Certifications ML180UHEK Gas Furnace ML180UHEK units are CSA International certified to ANSI The ML180UHEK unit is shipped ready for installation in the up- Z21.47. flow or horizontal right position (for horizontal left position the In the USA, installation of gas furnaces must conform with combustion air pressure switch must be moved) fueled by natu- local building codes.
Page 4 Use of Furnace as Construction Heater the requirements outlined previously, the following general recommendations must be considered when installing a Lennox does not recommend the use of ML180UHEK ML180UHEK furnace: units as a construction heater during any phase of con- •...
Page 5 • Do not install the furnace where drafts might blow CAUTION directly into it. This could cause improper combus- Insufficient combustion air can cause headaches, tion and unsafe operation. nausea, dizziness or asphyxiation. It will also cause • Do not block the furnace combustion air openings excess water in the heat exchanger resulting in rusting with clothing, boxes, doors, etc.
Page 6 Confined Space Air from Inside A confined space is an area with a volume less than 50 If the confined space that houses the furnace adjoins a cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of space categorized as unconfined, air can be brought in by the combined input rating of all appliances installed in that providing two permanent openings between the two spac- 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 Upflow Applications Setting Equipment Allow for clearances to combustible materials as indicated WARNING on the unit nameplate. Minimum clearances for closet or alcove installations are shown in FIGURE 7. Do not install the furnace on its front or its back. Do not connect the return air ducts to the back of the furnace.
Page 9 Return Air -- Upflow Applications Single Side Return Air Return air can be brought in through the bottom or either (with transition and filter) side of the furnace installed in an upflow application. If the furnace is installed on a platform with bottom return, make an airtight seal between the bottom of the furnace and the platform to ensure that the furnace operates properly and safely.
Page 10 Pivot the bottom cap down to release the bottom applications. Order horizontal suspension kit (51W10) panel. Once the bottom panel has been removed, reinstall from Lennox, or use equivalent suspension method. the bottom cap. See FIGURE 10. Allow for clearances to combustible materials as indicated on the unit nameplate.
Page 11 Combustion and flue products the data given in the appropriate Lennox Product must never be allowed to enter the return air system or Specifications bulletin. Additional information is provided the living space.
Page 12 Return Air Plenum Duct System NOTE - Return air must not be drawn from a room where Use industry-approved standards (such as those pub- this furnace, or any other gas-fueled appliance (i.e., water lished by Air Conditioning Contractors of America or Amer- heater), or carbon monoxide producing device (i.e., wood ican Society of Heating, Refrigerating and Air Condition- fireplace) is installed.
Page 13 1 - Remove the four mounting screws (FIGURE 15) Venting which secure the combustion air inducer / pressure A 4-inch diameter flue transition is factory-installed on the switch assembly to the orifice plate. Lift the assembly combustion air inducer outlet of all models. FIGURE 16 and rotate it 90 degrees clockwise or counterclockwise shows the combustion air inducer as shipped from the to either the 3 o’clock position or to 9 o’clock position.
Page 14 HORIZONTAL LEFT POSITION HORIZONTAL RIGHT POSITION Top Vent Discharge Top Vent Discharge Vent Pipe vent pipe pressure switch flue transition Pressure Switch cover plate Flue Transition FLOW FLOW collector box Cover Plate Collector Box Make-Up Box Disconnect pressure switch hose from barbed fitting on the make-up box pressure switch assembly.
Page 15 The ML180UHEK series units are classified as fan-assist- lining system or dedicated gas vent. Unlined masonry ed Category I furnaces when vertically vented according chimneys are prohibited. See FIGURE 24 and FIGURE to the latest edition of National Fuel Gas Code (NFPA 54 25 for common venting.
Page 16 When inspection reveals that an existing chimney is not Common Venting Using Metal-Lined Masonry Chimney safe for the intended purpose, it shall be rebuilt to conform to nationally recognized standards, lined or relined with SEALED suitable materials, or replaced with a gas vent or chimney MAX.
Page 17 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. NOTE - the chimney must be properly sized per provided venting tables or lined with listed metal lining system.
Page 18 17 - If vent connectors are combined prior to entering 20 - Do not install a manual damper, barometric draft the common vent, the maximum common vent regulator or flue restrictor between the furnace and capacity listed in the common venting tables must the chimney.
Page 19 TABLE 4 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 5...
Page 20 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 21 TABLE 6 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)
Page 22 Horizontal Applications Possible Gas Piping Configurations MANUAL MAIN SHUT-OFF VALVE MANUAL Horizontal Application MAIN SHUT-OFF Left-Side Air Discharge VALVE GROUND JOINT UNION GROUND JOINT DRIP LEG UNION DRIP LEG MANUAL MAIN SHUT-OFF VALVE FIELD PROVIDED GROUND JOINT INSTALLED UNION Horizontal Application NOTE - BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET DRIP LEG Right-Side Air Discharge...
Page 23 Protected by either a fuse or circuit breaker, select circuit Electrical protection and wire size according to unit nameplate. NOTE - Unit nameplate states maximum current draw. ELECTROSTATIC DISCHARGE (ESD) Maximum over-current protection allowed is 15 AMP. Precautions and Procedures CAUTION Holes are on both sides of the furnace cabinet to facilitate wiring.
Page 24 COMBUSTION BLOWER SPEED CHART AIR INDUCER FACTORY CONNECTED SPEED TAPS COMBUSTION AIR PROVING SWITCH UNIT COOL HEAT PARK 120V ACC (IF USED) 045(X)E36AK 070(X)E36BK BROWN,YELLOW 090(X)E48BK BLACK BLUE 090E60CK 110(X)E60CK BROWN BLUE 135E60DK BLACK,YELLOW GAS VALVE BLOWER SPEED SELECTION SPEED TAPS BLUE BLACK BROWN...
Page 25 IGNITION CONTROL Integrated Control DIP Switch Settings Indoor Blower Operation DIP Switch Settings The heat fan-on time of 30 seconds is not adjustable The ML180UHEK units are equipped with a single-stage inte- heat fan-off delay (amount of time that the blower oper- grated control.
Page 26 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 31 Wiring Connections On Board Links Must Be Cut To Select Thermostat Heat Pump Options Dual Fuel...
Page 27 Single Stage, Constant Torque, Non-Communicating 107792-01 FIGURE 33 TABLE 7 1/4” QUICK CONNECT TERMINALS TABLE 8 120V HUM POWER FOR HUMIDIFIER (120 VAC THERMOSTAT INPUT TERMINALS LINE INCOMING POWER LINE (120 VAC) HEAT XFMR TRANSFORMER PRIMARY (120 VAC) COMMON GROUND CIRC INDOOR BLOWER MOTOR (120 VAC) 24V AC...
Page 28 IGNITION CONTROL DIAGNOSTIC CODES DIAGNOSTIC CODES / STATUS OF FURNACE CODE IDLE MODE (DECIMAL BLINKS AT 1 HERTZ -- 0.5 SECONDS ON, 0.5 SECONDS OFF INDOOR BLOWER OPERATION: CONTINUOUS FAN MODE (CONSTANT TORQUE ONLY) INDOOR BLOWER OPERATION: FOLLOWED BY CFM SETTING FOR INDOOR BLOWER (1 SECOND ON, 0.5 SECOND OFF) / CFM SETTING FOR MODE DISPLAYED (VARIABLE SPEED ONLY) COOLING STAGE (1 SECOND ON, 0.5 SECOND OFF) 1 OR 2 DISPLAYED / PAUSE / REPEAT CODES.
Page 29 IGNITION CONTROL DIAGNOSTIC 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 30 The 24 VAC secondary of the two systems must be in Twinning Two ML180UHEK 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 31 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 SENSOR. See FIGURE 36 and follow steps below: FIGURE 35 1 - Route sensor wire #1 through provided grommet.
Page 32 FURNACE CONTROL BOARD LOW GWP MODES OF 2. The furnace control board activates the blower (high OPERATION speed). The blower purges refrigerant from the cabinet, plenum, and ductwork. The modes of operation for the furnace control board are Initializing, Normal, Leak Detected, and Fault. 3.
Page 33 LGWP TEST BUTTON FUNCTIONALITY External Alarm (For applications with external alarms wired directly to the The furnace control board is equipped with a Test/Reset furnace control board) push button. The Test button can be used to perform sev- The furnace control board triggers the external alarm sys- eral functions, depending on the mode of operation of the tem when it enters Leak Detected mode.
Page 34 Unit Start-Up MANIFOLD MANIFOLD PRESSURE PRESSURE FOR YOUR SAFETY READ BEFORE LIGHTING ADJUSTMENT OUTLET SCREW PORT WARNING Do not use this furnace if any part has been underwater. A flood-damaged furnace is extremely dangerous. Attempts to use the furnace can result in fire or explosion. INLET Immediately call a qualified service technician to inspect PRESSURE...
Page 35 11 - Are flame rollout switches tripped? If flame rollout Supply Pressure Measurement switches are tripped, call the service technician for A threaded plug on the inlet side of the gas valve provides inspection. access to the supply pressure tap. Remove the threaded Heating Sequence Of Operation (follow steps below) plug, install a field-provided barbed fitting and connect a manometer to measure supply pressure.
Page 36 TABLE 17 Manifold Pressure Settings at all Altitudes Line Pressure in. wg. Model 0 - 2000 ft. 2001 -4500 ft . 4501 - 7500 ft. 7501 - 10,000 ft Input Size 13.0 LP/Propane 10.0 10.0 10.0 10.0 11.0 13.0 13.0 LP/Propane 10.0 10.0...
Page 37 NOTE - Termination of any unused motor leads At the beginning of each heating season, and to comply must be insulated. with the Lennox Limited Warranty, your system should 4 - Place unused blower speed tap on integrated control be checked by a licensed professional technician (or “PARK”...
Page 38 7- Check the cleanliness of blower assembly and 3 - Clock gas meter to ensure that the unit is operating clean the housing, blower wheel and blower motor at the specified firing rate. Check the supply if necessary The blower motors are prelubricated pressure and the manifold pressure.
Page 39 FIGURE 39 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: ML180UH045E36AK-01. All service must be performed by a licensed professional installer (or equivalent), service agency, or gas supplier.
Page 40 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 Natural Gas LP/Propane Gas Sealed Piping Connections Tight Insulated (if necessary) Leak Tested Registers Open and Unobstructed...
Page 41 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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