Lennox International Inc. Furnace Merit Series Gas Furnace User Manual

Page 106/11*2P0611*506816−01*P506816-01* 2011 Lennox Industries Inc.Dallas, Texas, USAAIR FLOWUPFLOWAIR FLOWAIR FLOWHORIZONTAL RIGHTHORIZONTAL LEFTIN

Page 10Return Air −− Upflow ApplicationsReturn air can be brought in through the bottom or eitherside of the furnace installed in an upflow applicatio

Page 11Removing the Bottom PanelRemove the two screws that secure the bottom cap to thefurnace. Pivot the bottom cap down to release the bottompanel.

Page 12Horizontal ApplicationUnit Installed on PlatformFIGURE 14clearances.GASENTRYVENTPIPESee the unit nameplate forLine contact is permissible but n

Page 13VentingA 4−inch diameter flue transition is factory-installed on thecombustion air inducer outlet of all models. Figure 16shows the combustion

Page 14HORIZONTAL LEFT POSITIONTop Vent DischargeFIGURE 19  Disconnect pressure switch hose from barbed fitting on thepressure switch assembly. Rem

Page 15The ML180UH series units are classified as fan−assistedCategory I furnaces when vertically vented according tothe latest edition of National Fu

Page 16FIGURE 24Common Venting Using Metal−Lined Masonry Chimney4 in. (102 mm)minimumMIN. LENGTH −− ASSHORT AS PRACTICALMAX. LENGTH−− SEE NOTE 1BELOW.

Page 17FIGURE 25Common Venting Using Tile−Lined Interior Masonry Chimney and Combined Vent ConnectorMINIMUM LENGTH = AS SHORT AS PRACTICAL. FOR MAXIMU

Page 1816 − Vent connectors serving Category I appliances shallnot be connected to any portion of mechanical draftsystems operating under positive pre

Page 19TABLE 4Capacity of Type B Double−Wall Vents with Single−Wall Metal ConnectorsServing a Single Category I ApplianceHeightH(feet)LateralL(feet)Ve

Page 2Unit Dimensions − inches (mm)2Flue outlet may be horizontal but furnace must bevented vertically3Optional external side return air filter kit ca

Page 20TABLE 5Vent Connector CapacityType B Double−Wall Vents with Type B Double−Wall ConnectorsServing Two or More Category I AppliancesVentHeightH(f

Page 21TABLE 7Vent Connector CapacityType B Double−Wall Vents with Single−Wall Metal ConnectorsServing Two or More Category I AppliancesHeightH(feet)L

Page 22Removal of the Furnace from Common VentIn the event that an existing furnace is removed from aventing system commonly run with separate gas ap-

Page 23Gas PipingGas supply piping should not allow more than 0.5"W.C. dropin pressure between gas meter and unit. Supply gas pipemust not be sma

Page 24GROUNDJOINTUNIONAUTOMATICGAS VALVEFIELDPROVIDEDAND INSTALLEDGROUNDJOINTUNIONLeft Side Piping(Standard)Right Side Piping(Alternate)AUTOMATICGAS

Page 25Leak CheckAfter gas piping is completed, carefully check all pipingconnections (factory− and field−installed) for gas leaks. Usea leak detectin

Page 26Before connecting the thermostat, check to make sure thewires will be long enough for servicing at a later date. Makesure that thermostat wire

Page 271 − When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC.2 − Integrated control runs a self−check.

Page 28TYPICAL ML180UH FIELD WIRING DIAGRAMFIGURE 33IGNITOR*R*NOTE − R" REQUIRED ON SOME OUTDOOR UNITSFIGURE 34INTEGRATED CONTROL(Automatic Hot

Page 29Unit Start−UpFOR YOUR SAFETY READ BEFORE LIGHTINGWARNINGDo not use this furnace if any part has been under-water. A flood−damaged furnace is ex

Page 3Parts ArrangementFIGURE 1Secondary LimitsBlower AssemblyControl Box(includes integrated control,interlock switch and transformer)Gas ValveBurner

Page 3011 − Are flame rollout switches tripped? If flame rolloutswitches are tripped, call the service technician for in-spection.Heating Sequence Of

Page 31TABLE 12Manifold Pressure Settings at all AltitudesModelInput SizeGas 0−2000 ft 2105−4500 ft. 4501−7500 ft 7501 − 10,000 ftLine Pressure in.wg.

Page 32HEAT FAN-OFF TIME IN SECONDSTo adjust fan−off timing, reposition jumper across pins toachieve desired setting.NO JUMPERFIGURE 36609012018060901

Page 33BLOWER DATAML180UH045P36A PERFORMANCE (Less Filter)External Static Pressure in. w.g.Air Volume / Watts at Various Blower SpeedsHighMedium-HighM

Page 34ML180UH110P60C PERFORMANCE (Less Filter)External Static Pressure in. w.g.Air Volume / Watts at Different Blower SpeedsBottom Return Air, Side

Page 35ServiceWARNINGELECTRICAL SHOCK, FIRE,OR EXPLOSION HAZARD.Failure to follow safety warnings exactly could resultin dangerous operation, serious

Page 36Cleaning the Heat Exchanger and BurnersNOTE − Use papers or protective covering in front of the fur-nace during cleaning.1 − Turn off both elec

Page 37 9 − Remove screws from both sides, top and bottom ofvestibule panel.10 −Remove heat exchanger. It may be necessary tospread cabinet side t

Page 38Planned ServiceThe following items should be checked during an annual inspection. Power to the unit must be shut off for the service techni-cia

Page 39Integrated Control Diagnostic CodesDIAGNOSTIC CODESMake sure to Identify LED’S Correctly.LED #1 (Red) LED #2 (Green) DESCRIPTIONSIMULTANEOUSSLO

Page 4ML180UH Gas FurnaceThe ML180UH unit is shipped ready for installation in theupflow or horizontal right position (for horizontal left posi-tion t

Page 40Troubleshooting: Heating Sequence of OperationHEATING SEQUENCE OF OPERATIONNORMAL HEATING MODEABNORMAL HEATING MODECONTROL SELF−CHECK OKAY?NOR

Page 41Troubleshooting: Heating Sequence of Operation (Continued)HEATING SEQUENCE CONTINUEDNORMAL HEATING MODE ABNORMAL HEATING MODEFLAME RECTIFICATIO

Page 42Troubleshooting: Cooling Sequence of OperationCOOLING SEQUENCE OF OPERATIONNORMAL COOLING MODE ABNORMAL COOLING MODEIGNITION CONTROL MAIN POWER

Page 43Troubleshooting: Continuous Fan Sequence of OperationCONTINUOUS HEAT SPEED FAN SEQUENCE OF OPERATIONLED: SLOW FLASH RATE REMAINSUNCHANGED THROU

Page 5Installed in Combination with a Cooling CoilWhen this furnace is used with cooling units, it shall beinstalled in parallel with, or on the upstr

Page 6 Do not install the furnace where drafts might blow direct-ly into it. This could cause improper combustion and un-safe operation. Do not bloc

Page 7Unconfined SpaceAn unconfined space is an area such as a basement orlarge equipment room with a volume greater than 50 cubicfeet (1.42 m3) per 1

Page 8EQUIPMENT IN CONFINED SPACEALL AIR FROM OUTSIDE(Inlet Air from Crawlspace and Outlet Air to Ventilated Attic)NOTE−The inlet and outlet air openi

Page 9Setting EquipmentWARNINGDo not install the furnace on its front or its back. Donot connect the return air ducts to the back of the fur-nace. Doi