Lennox MERIT Series Installation Instructions Manual
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Lennox MERIT Series Installation Instructions Manual

Downflow air discharge
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© 2020 Lennox Industries Inc.
Dallas, Texas USA
Contents
Unit Dimensions - inches (mm) ......................................2
ML296DFV Gas Furnace................................................3
Shipping and Packing List ..............................................3
Safety .............................................................................3
General ...........................................................................5
Combustion, Dilution, Ventilation Air...............................5
Setting Equipment ..........................................................8
Filters ............................................................................12
Duct System .................................................................12
Pipe Fittings Specifications...........................................12
Venting Options ............................................................13
Joint Cementing Procedure ..........................................15
INSTALLATION
INSTRUCTIONS
ML296DFV
MERIT
SERIES
®
DOWNFLOW AIR DISCHARGE
507871-03
06/2020
Supersedes 05/2020
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.
C C C C
I I I I
HI
HI
Venting Practices ..........................................................15
Vent Piping Guidelines .................................................17
Gas Piping ....................................................................33
Electrical .......................................................................35
Blower Motor Performance ...........................................38
Integrated Control .........................................................41
Unit Start-Up .................................................................42
Gas Pressure Measurement.........................................43
Proper Combustion.......................................................44
High Altitude .................................................................44
Sequence of Operation.................................................46
Service..........................................................................47
Repair Parts List ...........................................................48
Start-Up and Performance Check list ...........................51
Page 1
WARNING
CAUTION

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  • Page 1: Table Of Contents

    INSTALLATION INSTRUCTIONS ML296DFV © 2020 Lennox Industries Inc. Dallas, Texas USA MERIT SERIES ® DOWNFLOW AIR DISCHARGE 507871-03 06/2020 Supersedes 05/2020 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) 9/16 (14) Flue Condensate Trap Assembly COMBUSTION AIR INTAKE Furnished for external field installation (178) RETURN AIR OPENING on either side of unit. EXHAUST AIR (See installation instructions OUTLET for additional information.) 2-1/16 (52) 2-1/4 9/16 (57) (14)

  • Page 3: Ml296Dfv Gas Furnace

    ML296DFV Gas Furnace Shipping and Packing List The ML296DFV Category IV gas furnace is shipped ready Package 1 of 1 contains for installation in the downflow position. 1 - Assembled ML296DFV unit The furnace is equipped for installation in natural gas 1 - Bag assembly containing the following: applications.

  • Page 4: Use Of Furnace As A Construction Heater

    Building Codes In Canada, all electrical wiring and grounding for the unit must be installed according to the current regulations of In the USA, installation of gas furnaces must conform with the Canadian Electrical Code Part I (CSA Standard C22.1) local building codes.

  • Page 5: General

    FAILURE TO FOLLOW THE ABOVE INSTALLATION IN- Chlorinated waxes and cleaners STRUCTIONS VOIDS THE MANUFACTURER’S EQUIP- Chlorine base swimming pool chemicals MENT LIMITED WARRANTY. LENNOX DISCLAIMS Water softening chemicals ALL LIABILITY IN CONNECTION WITH INSTALLER’S FAILURE TO FOLLOW THE ABOVE INSTALLATION IN- De-icing salts or chemicals STRUCTIONS.
  • Page 6 A portion of this information has been reprinted with per- Confined Space mission from the National Fuel Gas Code (ANSI Z223.1/ A confined space is an area with a volume less than 50 NFPA 54). This reprinted material is not the complete and cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of official position of the ANSI on the referenced subject, the combined input rating of all appliances installed in that...
  • Page 7 Air from Outside EQUIPMENT IN CONFINED SPACE (Inlet Air from Ventilated Crawlspace and Outlet Air to Outside) If air from outside is brought in for combustion and ventila- tion, the confined space shall be provided with two perma- nent openings. One opening shall be within 12” (305mm) Roof Terminated of the top of the enclosure and one within 12”...

  • Page 8: Setting Equipment

    EQUIPMENT IN CONFINED SPACE - ALL AIR FROM OUTSIDE (All Air Through Ventilated Attic) UNITS WITH 1/2 HP BLOWER MOTOR ROOF TERMINATED VENTILATION LOUVERS EXHAUST PIPE (Each end of attic) OUTLET RIGID LEG remove shipping bolt and washer INLET AIR SIDE WALL FURNACE (Ends 12”...
  • Page 9 WARNING SETTING EQUIPMENT Improper installation of the furnace can result in personal injury or death. Combustion and flue products must never be allowed to enter the return air system or air AIR FLOW AIR FLOW AIR FLOW in the living space. Use sheet metal screws and joint tape to seal return air system to furnace.
  • Page 10 The unit may be installed three ways in downflow applica- 3 - Set the unit over the plenum and seal the plenum to tions: on non-combustible flooring, on combustible floor- the unit. ing using an additive base, or on a reverse-flow cooling 4 - Ensure that the seal is adequate.
  • Page 11 TABLE 2 COMBUSTIBLE FLOORING BASE OPENING SIZE Front to Rear Side to Side Cabinet Catalog FURNACE Width Number B (17.5”) 11M60 18-3/4 C (21”) 11M61 22-3/4 COOLING COIL PROPERLY SIZED FLOOR FURNACE OPENING PLENUM SUPPLY AIR PLENUM PROPERLY COMBUSTIBLE SIZED FLOOR FLOORING BASE OPENING FIGURE 16...

  • Page 12: Filters

    (i.e., wood specifications provided by the filter manufacturer against fireplace) is installed. the data given in the appropriate Lennox Product When return air is drawn from a room, a negative pressure Specifications bulletin. Additional information is provided is created in the room.

  • Page 13: Venting Options

    IMPORTANT TABLE 4 PIPING AND FITTINGS SPECIFICATIONS Exhaust and intake connections are made of PVC. Use Schedule 40 PVC (Pipe) D1785 PVC primer and solvent cement when using PVC vent Schedule 40 PVC (Cellular Core Pipe) F891 pipe. When using ABS vent pipe, use transitional solvent cement to make connections to the PVC fittings in the Schedule 40 PVC (Fittings) D2466...
  • Page 14 TABLE 5 OUTDOOR TERMINATION USAGE* STANDARD CONCENTRIC Flush Mount Wall Kit 1-1/2 inch 2 inch 3 inch Vent Pipe Input Size 2 inch 3 inch Field Dia. in. 60L46 (US) 71M80 (US) 69M29 (US) Fabricated 51W11 (US) 22G44 (US) 444W92 444W92 444W93 44J40 (US)

  • Page 15: Joint Cementing Procedure

    Joint Cementing Procedure Venting Practices All cementing of joints should be done according to the Piping Suspension Guidelines specifications outlined in ASTM D 2855. NOTE - A sheet metal screw may be used to secure the SCHEDULE 40 intake pipe to the connector, if desired. Use a drill or self PVC - 5' tapping screw to make a pilot hole.
  • Page 16 2 - When furnace is installed in a residence where unit 4 - Follow the lighting instructions. Turn on the appliance is shut down for an extended period of time, such that is being inspected. Adjust the thermostat so that as a vacation home, make provisions for draining the appliance operates continuously.

  • Page 17: Vent Piping Guidelines

    NOTE - Exhaust pipe MUST be glued to furnace exhaust Vent Piping Guidelines fittings. NOTE - Lennox has approved the use of DuraVent® and NOTE - Exhaust piping should be checked carefully to Centrotherm manufactured vent pipe and terminations make sure there are no sags or low spots.
  • Page 18 TABLE 7 Maximum Allowable Intake or Exhaust Vent Length Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Intake and Exhaust must be same size. NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation. Standard Termination at Elevation 0 - 4500 ft Number 2”...
  • Page 19 TABLE 7 CONT. Maximum Allowable Intake or Exhaust Vent Length Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Intake and Exhaust must be same size. NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation. Concentric Termination at Elevation 0 - 4500 ft Number 2”...
  • Page 20 TYPICAL EXHAUST PIPE CONNECTIONS AND CONDENSATE TRAP INSTALLATION 2” 2” 2” DO NOT transition from smaller to larger pipe size in horizontal runs of exhaust pipe. 3” TRANSITION *2“ Exhaust Air Intake TOP VIEW * When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible. NOTE −...
  • Page 21 Intake Piping FIGURE 23 EQUIPMENT IN CONFINED SPACE (Inlet Air from Ventilated Crawlspace and Outlet Air to Outside) The ML296DFV furnace may be installed in either direct vent or non-direct vent applications. In non-direct vent ap- Roof Terminated plications, when intake air will be drawn into the furnace Exhaust Pipe from the surrounding space, the indoor air quality must be considered.
  • Page 22 In both Non-Direct Vent and Direct Vent applications, the TYPICAL AIR INTAKE PIPE CONNECTIONS vent termination is limited by local building codes. In the NON−DIRECT VENT APPLICATIONS absence of local codes, refer to the current National Fuel Gas Code ANSI Z223-1/NFPA 54 in U.S.A., and current INTAKE CSA-B149 Natural Gas and Propane Installation Codes in SCREEN...
  • Page 23 TABLE 9 Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For Winter Design Temperatures Two - Stage High Efficiency Furnace Winter Design Unit Input Size Vent Pipe Tempera- Diameter tures1 °F (°C) 2 in 32 to 21 (0 to -6) 2-1/2 in 3 in...
  • Page 24 ‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of two sides beneath the floor. Lennox recommends avoiding this location if possible. FIGURE 28...
  • Page 25 ‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of two sides beneath the floor. Lennox recommends avoiding this location if possible. FIGURE 29 Page 25...
  • Page 26 Details of Intake and Exhaust Piping Terminations for 6 - On field supplied terminations, a minimum distance Direct Vent Installations between the end of the exhaust pipe and the end of the intake pipe without a termination elbow is 8” and NOTE - In Direct Vent installations, combustion air is taken a minimum distance of 6”...
  • Page 27 7 - If intake and exhaust piping must be run up a side wall to position above snow accumulation or other obstructions, piping must be supported. At least EXHAUST 12” one bracket must be used within 6” from the top of (305mm) VENT the elbow and then every 24”...
  • Page 28 FIELD FABRICATED WALL TERMINATION NOTE − FIELD−PROVIDED REDUCER MAY BE 2” (51mm) 3” (76mm) REQUIRED TO ADAPT LARGER VENT PIPE SIZE Vent Pipe Vent Pipe TO TERMINATION A− Minimum clearance above grade or average 12” (305 mm) 12” (305 mm) snow accumulation B−...
  • Page 29 24 inches (610mm) Lennox provides a crawl space vent kit to install 2” or 3” PVC exhaust piping through the floor joists and into the When exhaust piping must be run up an outside wall, crawl space.
  • Page 30 Condensate Piping 1 - Determine which side condensate piping will exit the unit, location of trap, field-provided fittings and This unit is designed for either right- or left-side exit of condensate piping. Refer to FIGURE 42 and FIGURE 43 length of PVC pipe required to reach available drain. for condensate trap locations.
  • Page 31 Heat cable kit Drain Connection is available from Lennox in various lengths; 6 ft. (1.8m) - kit no. 26K68; 24 ft. (7.3m) - kit no. 26K69; and 50 ft.(15.2m) - kit no. 26K70.
  • Page 32 TRAP / DRAIN ASSEMBLY USING 1/2” PVC OR 3/4” PVC Optional Condensate Drain Connection Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) 90° Street Elbow 3/4 inch PVC (not furnished) Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) Condensate Drain Connection In Unit 1 (25 mm) Min.

  • Page 33: Gas Piping

    IMPORTANT Gas Piping CAUTION Compounds used on threaded joints of gas piping must be resistant to the actions of liquefied petroleum gases. If a flexible gas connector is required or allowed by the authority that has jurisdiction, black iron pipe shall be Leak Check installed at the gas valve and extend outside the furnace After gas piping is completed, carefully check all piping...
  • Page 34 Left Side Piping AUTOMATIC MANUAL (Standard) GAS VALVE MAIN SHUT-OFF MANUAL (with manual VALVE AUTOMATIC MAIN SHUT-OFF shut-off valve) (1/8 in. NPT GAS VALVE VALVE plugged tap (with manual (1/8 in. NPT shown) shut-off valve) plugged tap shown) GROUND JOINT UNION GROUND JOINT...

  • Page 35: Electrical

    CAUTION Electrical Failure to use properly sized wiring and circuit breaker ELECTROSTATIC DISCHARGE (ESD) may result in property damage. Size wiring and circuit Precautions and Procedures CAUTION breaker(s) per Product Specifications bulletin (EHB) and unit rating plate. Electrostatic discharge can affect electronic The power supply wiring must meet Class I restrictions.
  • Page 36 One line voltage “HUM” 1/4” spade terminal is provided on • The furnace integrated control requires both correct polarity and proper ground. Both polarity and proper the furnace integrated control. Any humidifier rated up to grounding should be checked before attempting to one amp can be connected to this terminal with the neutral operate the furnace on either permanent or tempo- leg of the circuit being connected to one of the provided...
  • Page 37 Active Dehumidification Automatic Heat Staging To achieve additional dehumidification, clip the jumper wire located below the DEHUM terminal on the integrat- ed ignition/ blower control board and connect a humidity control that opens on humidity rise to the DEHUM and R terminals.

  • Page 38: Blower Motor Performance

    First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position. Lennox HarmonyIII™ Zoning System Applications - Minimum blower speed is 300 cfm. B LO WER DATA...
  • Page 39 First stage COOL (two-stage air conditioning units only) is approximately 70% of the same second stage COOL speed position. Continuous Fan Only speed is approximately 38% of the same second stage COOL speed position. Lennox HarmonyIII Zoning System Applications - Minimum blower speed is 460 cfm.
  • Page 40 FIGURE 54 Page 40...

  • Page 41: Integrated Control

    Troubleshooting Integrated Control Make the following visual checks before troubleshooting: 1 - Check to see that the power to the furnace and the integrated ignition/blower control is ON. 2 - The manual shutoff valves in the gas line to the furnace must be open.

  • Page 42: Unit Start-Up

    6 - Adjust the thermostat to deactivate the heating Unit Start-Up demand and wait for the combustion air inducer to FOR YOUR SAFETY READ BEFORE OPERATING stop. At this point, the trap should be primed with sufficient water to ensure proper condensate drain WARNING operation.

  • Page 43: Gas Pressure Measurement

    NOTE - Pressure test adapter kit (10L34) is available from 3 - After a 15-second prepurge, the hot surface ignitor energizes. Lennox to facilitate manifold pressure measurement. 1 - Connect the test gauge positive side “+“ to manifold 4 - After a 20-second ignitor warm-up period, the gas valve solenoid opens.

  • Page 44: Proper Combustion

    Proper Combustion High Altitude Information Furnace should operate minimum 15 minutes with correct NOTE - In Canada, certification for installations at eleva- manifold pressure and gas flow rate before checking com- tions over 4500 feet (1372 m) is the jurisdiction of local bustion.
  • Page 45 8 - If improper venting is observed during any of the Testing of Non-Direct Vent Applications for Proper above tests, the venting system must be corrected Venting and Sufficient Combustion Air or sufficient combustion/make-up air must be provided. The venting system should be re-sized WARNING to approach the minimum size as determined by using the appropriate tables in appendix G in the...

  • Page 46: Sequence Of Operation

    Cooling Heating Sequence of Operation The unit is set up at the factory for single stage cooling. On a call for heat from the room thermostat, the control For two stage cooling operation, clip the jumper wire lo- board performs a 1 second self check. Upon confirma- cated between the Y to Y2 terminals on the integrated ig- tion that the pressure switch contacts are in an open posi- nition/ blower control board.

  • Page 47: Service

    13- Perform a complete combustion analysis during the At the beginning of each heating season, and to comply furnace inspection to ensure proper combustion with the Lennox Limited Warranty, your system should be and operation. Consult Service Literature for proper checked as follows: combustion values.

  • Page 48: Repair Parts List

    3 - Clock gas meter to ensure that the unit is operating at 11 - Reconnect plug to gas valve. the specified firing rate for each stage of operation. 12 - Replace the blower compartment access panel. Check the supply pressure and the manifold pressure 13 - Refer to instruction on verifying gas and electrical on both low fire and high fire.
  • Page 49 4 - INSPECTION. The state or local gas inspector of the Requirements for Commonwealth of Massachusetts side wall, horizontally vented, gas-fueled equipment Modifications to NFPA-54, Chapter 10 shall not approve the installation unless, upon Revise NFPA-54 section 10.8.3 to add the following inspection, the inspector observes carbon monoxide requirements: detectors and signage installed in accordance with...
  • Page 50 For The Province Of Ontario, Horizontal Sidevent Applications Only See FIGURE 57 for venting for all province of Canada. Lennox approves the following termination for use in all For exterior horizontal venting applications, the 2” X 1.5” provinces of Canada.

  • Page 51: Start-Up And Performance Check List

    Start-Up & Performance Check List UNIT SET UP (typical) Furnace: Model Number_______________ Serial Number_________________ SUPPLY Line Voltage GAS SUPPLY LP Propane Gas Natural Gas Piping Connections Tight Leak Tested Flter Supply Line Pressure “W.C.________ RETURN AIR Gas Supply Pressure DUCT SYSTEM SUPPLY AIR DUCT Sealed INTAKE / EXHAUST PIPE...
  • Page 52 UNIT OPERATION HEATING MODE COOLING MODE GAS MANIFOLD PRESSURE “W.C._____ INDOOR BLOWER AMPS______ COMBUSTION SAMPLE CO CO PPM_______ TEMPERATURE DROP ______ Return Duct Temperature _________ INDOOR BLOWER AMPS______ Supply Duct Temperature _______ Temperature Drop = _________ TEMPERATURE RISE TOTAL EXTERNAL STATIC (dry coil) Supply Duct Temperature ________ Supply External Static _______ Return Duct Temperature...

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