Lennox MERIT ML180UH Installation Instructions Manual
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Lennox MERIT ML180UH Installation Instructions Manual

Merit series gas furnace upflow / horizontal air discharge
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E 2011 Lennox Industries Inc.
Dallas, Texas, USA
AIR FLOW
HORIZONTAL LEFT
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06/11
*2P0611*
UPFLOW
HORIZONTAL RIGHT

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INSTALLATION
INSTRUCTIONS
ML180UH
®
MERIT
SERIES GAS FURNACE
UPFLOW / HORIZONTAL AIR DISCHARGE
506816−01
06/2011
Supersedes 506778−01
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 manuals, be alert
to the potential for personal injury or death.
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a licensed professional installer (or
equivalent), service agency or the gas supplier.
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
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Litho U.S.A.
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Summary of Contents for Lennox MERIT ML180UH

  • Page 1: Table Of Contents

    INSTALLATION INSTRUCTIONS E 2011 Lennox Industries Inc. Dallas, Texas, USA ML180UH ® MERIT SERIES GAS FURNACE UPFLOW / HORIZONTAL AIR DISCHARGE 506816−01 06/2011 Supersedes 506778−01 Litho U.S.A. 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

    (406) 1−15/16 (49) 3−1/4 23−1/2 (16) (597) (83) (19) (19) Bottom Return Bottom Return Air Opening Air Opening FRONT VIEW SIDE VIEW ML180UH Model No. 045P24A 045P36A 14−1/2 13−3/8 4−3/4 070P24A 070P36A 090P36B 17−1/2 16−3/8 6−1/4 090P48B 110P48C 19−7/8 19−1/2...

  • Page 3: Parts Arrangement

    Parts Arrangement Make−Up Box Heat Exchanger Combustion Air Inducer Combustion Air Inducer Pressure Switch Burner Box (includes sensor, ignitor and rollout switches) Gas Valve Primary Limit Control Box (under (includes integrated control, combustion interlock switch and transformer) air inducer) Upper Access Panel Secondary Limits Blower Assembly Blower Access Panel...

  • Page 4: Ml180Uh Gas Furnace

    ML180UH Gas Furnace CAUTION The ML180UH unit is shipped ready for installation in the As with any mechanical equipment, personal injury upflow or horizontal right position (for horizontal left posi- can result from contact with sharp sheet metal edges. Be careful when you handle this equipment.

  • Page 5: Use Of Furnace As A Construction Heater

    Use of Furnace as Construction Heater See figure 2. With a parallel flow arrangement, a damper (or Lennox does not recommend the use of ML180UH units as other means to control the flow of air) must adequately pre- a construction heater during any phase of construction.

  • Page 6: Combustion, Dilution & Ventilation Air

    The requirements for providing air for combustion and ven- this section to install ML180UH furnaces to ensure efficient tilation depend largely on whether the furnace is installed in and safe operation. You must consider combustion air needs and requirements for exhaust vents and gas piping.
  • Page 7 Unconfined Space Air from Inside An unconfined space is an area such as a basement or If the confined space that houses the furnace adjoins a large equipment room with a volume greater than 50 cubic space categorized as unconfined, air can be brought in by feet (1.42 m ) per 1,000 Btu (.29 kW) per hour of the com- providing two permanent openings between the two...
  • Page 8 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) 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 9: Setting Equipment

    Doing so will adversely affect the operation of the safety control devices, which could result in per- sonal injury or death. The ML180UH gas furnace can be installed as shipped in either the upflow position or the horizontal position. Left Side...
  • Page 10 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 11 Removing the Bottom Panel Horizontal Applications Remove the two screws that secure the bottom cap to the The ML180UH furnace can be installed in horizontal ap- furnace. Pivot the bottom cap down to release the bottom plications. Order horizontal suspension kit (51W10) from panel.

  • Page 12: Filters

    TABLE 1 Horizontal Application Unit Installed on Platform Filter Size Furnace Line contact is permissible but not preferred Cabinet Width Side Return Bottom Return See the unit nameplate for clearances. A − 14−1/2" 16 X 25 X 1 (1) 14 X 25 X 1 (1) B −...

  • Page 13: Venting

    1 − Remove the four mounting screws (figure 15) which Venting secure the combustion air inducer / pressure switch A 4−inch diameter flue transition is factory-installed on the assembly to the orifice plate. Lift the assembly and ro- tate it 90 degrees clockwise or counterclockwise to ei- combustion air inducer outlet of all models.
  • Page 14 HORIZONTAL RIGHT POSITION HORIZONTAL LEFT POSITION Top Vent Discharge Top Vent Discharge Vent Pipe Vent Pipe Pressure Switch Pressure Flue Switch Transition Cover Plate Flue Transition FLOW FLOW Collector Box Make−Up Box Cover Plate Collector Box Make−Up Box D Disconnect pressure switch hose from barbed fitting on the D Gas supply piping must be brought into the unit from the bot- pressure switch assembly.
  • Page 15 The ML180UH is not approved for use with horizontal venting. An exterior masonry chimney that is not tile−lined must be lined with B1 vent or a listed insulated flexible metal vent.
  • Page 16 SEALED suitable materials, or replaced with a gas vent or chimney suitable for venting ML180UH series units. The chimney MAX. LENGTH −− SEE NOTE 1 passageway must be checked periodically to ensure that it BELOW.
  • 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 16 − Vent connectors serving Category I appliances shall two consecutive table size diameters over the size of not be connected to any portion of mechanical draft the draft hood outlet or flue collar outlet. systems operating under positive pressure such as 20 −...
  • Page 19 TABLE 4 Capacity of Type B Double−Wall Vents with Single−Wall Metal 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 −...
  • Page 20 TABLE 5 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) Vent Connector 3 Inch 4 Inch 5 Inch 6 Inch Height Rise Appliance Input Rating in Thousands of Btu Per Hour (feet) (feet)
  • Page 21 TABLE 7 Vent Connector Capacity Type B Double−Wall Vents with Single−Wall Metal 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) NOTE −...
  • Page 22 Removal of the Furnace from Common Vent 3 − Close all building doors and windows and all doors be- tween the space in which the appliances remaining In the event that an existing furnace is removed from a connected to the common venting system are located venting system commonly run with separate gas ap- and other spaces of the building.

  • Page 23: Caution

    4 − The piping should be sloped 1/4 inch (6.4 mm) per 15 Gas Piping feet (4.57 m) upward toward the meter from the fur- Gas supply piping should not allow more than 0.5"W.C. drop nace. The piping must be supported at proper intervals in pressure between gas meter and unit.
  • Page 24 Left Side Piping MANUAL (Standard) MAIN SHUT−OFF AUTOMATIC MANUAL VALVE GAS VALVE MAIN SHUT−OFF (With 1/8 in. NPT AUTOMATIC VALVE Plugged Tap GAS VALVE (With 1/8 in. NPT Shown) Plugged Tap Shown) GROUND JOINT UNION GROUND JOINT UNION DRIP LEG Right Side Piping FIELD (Alternate)

  • Page 25: Electrical

    Leak Check The unit is equipped with a field make−up box on the left hand side of the cabinet. The make−up box may be moved After gas piping is completed, carefully check all piping to the right side of the furnace to facilitate installation. If the connections (factory−...
  • Page 26 2 − When the ML180UH is running in the heating mode, Generator Use − Voltage Requirements the indoor blower will run on the heating speed.
  • Page 27 ML180UH Schematic Wiring Diagram and Sequence of Operation 1 − 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. S10 primary limit, S47 rollout switch and S21 secondary limit contacts are found to be closed. Call for heat can continue.

  • Page 28: Integrated Control

    TYPICAL ML180UH FIELD WIRING DIAGRAM IGNITOR *NOTE − R" REQUIRED ON SOME OUTDOOR UNITS FIGURE 33 INTEGRATED CONTROL (Automatic Hot Surface Ignition System) TERMINAL DESIGNATIONS Humidifier (120VAC) Input (120VAC) LINE Transformer (120VAC) XFMR Electronic Air Cleaner (120VAC) Blower − Cooling Speed (120VAC) COOL Blower −...

  • Page 29: Unit Start−Up

    Turning Off Gas to Unit" and call your service techni- The gas valve on the ML180UH unit will be equipped with a cian or gas supplier. gas control switch. Use only your hand to move the switch.

  • Page 30: Gas Pressure Adjustment

    Take combustion sample beyond the flue out- let and compare to the tables below. The maximum car- TABLE 10 bon monoxide reading should not exceed 50 ppm. GAS METER CLOCKING CHART TABLE 11 Seconds for One Revolution ML180UH Natural ML180UH For Nat For L.P. Unit Unit...

  • Page 31: Other Unit Adjustments

    TABLE 12 Manifold Pressure Settings at all Altitudes Line Pressure in.wg. Model 0−2000 ft 2105−4500 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 10.0 10.0 11.0 13.0 13.0 LP/propane 10.0...
  • Page 32 Blower Speeds HEAT FAN-OFF TIME IN SECONDS Follow the steps below to change the blower speeds. 1 − Turn off electrical power to furnace. 2 − Remove blower access panel. 3 − Disconnect existing speed tap at integrated control NO JUMPER speed terminal.

  • Page 33: Blower Performance Data

    BLOWER DATA ML180UH045P24A PERFORMANCE (Less Filter) ML180UH070P36A PERFORMANCE (Less Filter) Air Volume / Watts at Various Blower Speeds Air Volume / Watts at Various Blower Speeds External External Medium- Medium- Medium- Medium- Static Static High High High High Pressure Pressure in.

  • Page 34: Blower Data

    BLOWER DATA ML180UH110P48C PERFORMANCE (Less Filter) Air Volume / Watts at Various Blower Speeds External Medium- Medium- Static High High Pressure in. w.g. cfm Watts cfm Watts cfm Watts cfm Watts 0.00 2170 980 1845 792 1565 678 1270 564 0.10 2125 919 1820 747 1555 648 1300 540 0.20...

  • Page 35: Service

    OR EXPLOSION HAZARD. Filters Failure to follow safety warnings exactly could result All ML180UH filters are installed external to the unit. Filters in dangerous operation, serious injury, death or should be inspected monthly. Clean or replace the filters property damage.
  • Page 36 Carefully remove the combustion air inducer to avoid damaging blower gasket. If gasket is damaged, it must Remove NOX insert. See figure 38. be replaced to prevent leakage. ML180UH BURNER, COMBUSTION AIR INDUCER ASSEMBLY & HEAT EXCHANGER REMOVAL Gasket Flue Transition...
  • Page 37 17 −Reinstall burner box, manifold assembly and burner box FIGURE 39 cover. 18 −Reconnect all wires. ML180UH NOx INSERTS 19 −Reconnect top cap and vent pipe to combustion air in- ducer outlet. 20 −Reconnect gas supply piping. 21 −Turn on power and gas supply to unit.

  • Page 38: Planned Service

    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: ML180UH045P24A−01. All service must be performed by a licensed professional installer (or equivalent), service agency, or gas supplier.

  • Page 39: Integrated Control Diagnostic Codes

    Integrated Control Diagnostic Codes DIAGNOSTIC CODES Make sure to Identify LED’S Correctly. LED #1 (Red) LED #2 (Green) DESCRIPTION Power on − Normal operation. SIMULTANEOUS SIMULTANEOUS Also signaled during cooling and continuous fan. SLOW FLASH SLOW FLASH SIMULTANEOUS SIMULTANEOUS Normal operation − signaled when heating demand initiated at thermostat. FAST FLASH FAST FLASH Primary or secondary limit switch open.

  • Page 40: Troubleshooting

    Troubleshooting: Heating Sequence of Operation HEATING SEQUENCE OF OPERATION ABNORMAL HEATING MODE NORMAL HEATING MODE POWER ON GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER DELAY OFF. CONTROL SELF−CHECK OKAY? LED #1 ON LED #2 ON (RESET CONTROL BY TURNING MAIN POWER OFF.) POLARITY REVERSED.
  • Page 41 Troubleshooting: Heating Sequence of Operation (Continued) HEATING SEQUENCE CONTINUED NORMAL HEATING MODE ABNORMAL HEATING MODE 15-SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. LEDS SIGNAL ALTERNATING FAST FLASH UNTIL IS VOLTAGE ABOVE 90 VOLTS? IGNITOR WARM-UP −− 20 SECONDS. VOLTAGE IS ABOVE 95 VOLTS, THEN RESTARTS HEATING...

  • Page 42: Troubleshooting: Cooling Sequence Of Operation

    Troubleshooting: Cooling Sequence of Operation COOLING SEQUENCE OF OPERATION NORMAL COOLING MODE ABNORMAL COOLING MODE POWER ON IGNITION CONTROL MAIN POWER ON. GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. CONTROL SELF DIAGNOSTIC CHECK. SIGNAL CIRCUIT BOARD FAILURE AT LED. IS CONTROL OPERATING NORMALLY? INTERRUPT MAIN POWER TO RESET CONTROL.
  • Page 43 Troubleshooting: Continuous Fan Sequence of Operation CONTINUOUS HEAT SPEED FAN SEQUENCE OF OPERATION LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT HEAT SPEED. EAC TERMINAL IS ENERGIZED. HUM TERM. ENERGIZES THERMOSTAT CALLS FOR HEAT (W).

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