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© 2024 Lennox Industries Inc.
Dallas, Texas USA
Contents
Unit Dimensions - inches (mm) ......................................2
ML296DFVK Gas Furnace .............................................3
Shipping and Packing List ..............................................3
Safety .............................................................................3
Use of Furnace as a Construction Heater ......................4
General ...........................................................................5
Combustion, Dilution, Ventilation Air...............................5
Setting Equipment ..........................................................8
Filters ............................................................................12
Duct System .................................................................12
Pipe Fittings Specifications...........................................12
Joint Cementing Procedure ..........................................15
Venting Practices ..........................................................15
Gas Piping ....................................................................33
INSTALLATION
INSTRUCTIONS
ML296DFVK
MERIT
SERIES
®
DOWNFLOW AIR DISCHARGE
508521-01
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.
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
This furnace is equipped with an ignition control
factory enabled for use with Lennox A2L refrigerant
systems.
functionality on A2L system is prohibited by safety
codes. Refer to furnace installation instructions for
non-A2L and non-Lennox refrigerant system setup.
Electrical .......................................................................35
Ignition Control .............................................................38
Low GWP Application ...................................................47
Unit Start-Up .................................................................50
Gas Pressure Measurement.........................................51
Proper Combustion.......................................................52
High Altitude .................................................................52
Other Units Adjustments ...............................................53
Sequence of Operation.................................................54
Service..........................................................................55
Repair Parts Lits ...........................................................56
Blower Datra .................................................................59
Start-Up and Performance Check list ...........................61
Page 1
WARNING
CAUTION
WARNING
Disabling
the
refrigerant
detection
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Summary of Contents for Lennox MERIT ML296DFVK
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Page 1: Table Of Contents
WARNING C C C C I I I I 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)
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: Ml296Dfvk Gas Furnace
ML296DFVK Gas Furnace Shipping and Packing List The ML296DFVK Category IV gas furnace is shipped Package 1 of 1 contains ready for installation in the downflow position. 1 - Assembled ML296DFVK unit The furnace is equipped for installation in natural gas 1 - Bag assembly containing the following: applications. -
Page 4: Building Codes
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 ALL LIABILITY IN CONNECTION WITH INSTALLER’S Water softening chemicals FAILURE TO FOLLOW THE ABOVE INSTALLATION IN- De-icing salts or chemicals STRUCTIONS. -
Page 6: Confined Space
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”...
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Page 8: Installation - 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: Setting Equipment
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.
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Page 11: Outside Cabinet
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: Specification
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 (Fittings) D2466 pipe. When using ABS vent pipe, use transitional solvent cement to make connections to the PVC fittings in the Schedule 40 CPVC (Pipe) F441... - Page 14 TABLE 5 OUTDOOR TERMINATION USAGE* STANDARD CONCENTRIC Flush Mount Wall Kit 1-1/2 inch 2 inch 3 inch Vent Pipe Dia. Input Size Field 2 inch 3 inch Fabricated 51W11 (US) 71M80 (US) 69M29 (US) 60L46 (US) 22G44 (US) 44J40 (US) 51W12 (CA) 444W92 (CA) 444W92 (CA)
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Page 15: Joint Cementing Procedure
Joint Cementing Procedure Venting Practices All cementing of joints should be done according to the NOTE - For any Low GWP refrigerant systems with ex- specifications outlined in ASTM D 2855. posed line set joints installed in the same space, each non-direct vent furnace system must have a refrigerant NOTE - A sheet metal screw may be used to secure the detection sensor installed below the level of the burners... - Page 16 1 - In areas where piping penetrates joists or interior 4 - Follow the lighting instructions. Turn on the appliance walls, hole must be large enough to allow clearance that is being inspected. Adjust the thermostat so that on all sides of pipe through center of hole using a the appliance operates continuously.
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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 as 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.
- 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 1-1/2”...
- Page 20 TYPICAL EXHAUST PIPE CONNECTIONS 045/070 Only 2” 1−1/2” 2” 2” 2” TRANSITION 2” 2” Exhaust Exhaust 3” DO NOT transition from larger to smaller pipe in horizontal runs of exhaust pipe. TRANSITION INTAKE EXHAUST DO NOT transition from smaller *2” to larger pipe size in horizontal TOP VIEW runs of exhaust pipe.
- Page 21 Intake Piping FIGURE 23 EQUIPMENT IN CONFINED SPACE (Inlet Air from Ventilated Crawlspace and Outlet Air to Outside) The ML296DFVK 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) 1-1/2 32 to 21 2 in (0 to -6) 2-1/2 in...
- Page 24 ‡ Permitted only if veranda, porch, deck or balcony is fully open NOTE - This figure is intended to illustrate clearance on a minimum of two sides beneath the floor. Lennox recommends requirement and does not serve as a substitute for avoiding this location if possible.
- Page 25 ‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of locally adopted installation codes. 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 Vent Pipe Vent Pipe LARGER VENT PIPE SIZE 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.
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Page 30: Condensate Piping
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.
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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 field-in-... - 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...
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Page 35: Electrical
IMPORTANT Electrical When matching this gas furnace with zoning, ELECTROSTATIC DISCHARGE (ESD) defrost tempering stat or other 24V accessories, Precautions and Procedures CAUTION It is recommended to replace the factory installed transformer with kit 27J32. Electrostatic discharge can affect electronic Kit 27J32 contains a 75VA transformer, so you do components. - Page 36 Electrical Wiring CAUTION The furnace must be grounded and wired in accordance Failure to use properly sized wiring and circuit breaker with local codes or, in the absence of local codes, with the may result in property damage. Size wiring and circuit National Electrical Code ANSI/NFPA No.
- Page 37 FIGURE 52 Page 37...
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Page 38: Ignition Control
Bank Of Eight DIP Switches SW2 IGNITION CONTROL Switches 1 and 2 - Cooling Mode Blower Speed - The Integrated Control Switch Settings unit is shipped from the factory with the dip switches po- Conventional Thermostat sitioned for high speed (4) indoor blower motor operation during the cooling mode. - Page 39 TABLE 17 Heat Speed DIP Switch 7 DIP Switch 8 Medium High High Medium Low TABLE 18 Allowable Heating Speeds ML296DFVK Speed Adjust Setting “D” Setting “C” Setting “B” Setting “A” Model +10% Allowed 045XV36BK Norm Factory Setting Allowed -10% Allowed +10% 070XV48BK...
- Page 40 Two Stage, Variable Speed, Non-Communicating 107629-01 FIGURE 53 TABLE 19 TABLE 20 1/4” QUICK CONNECT TERMINALS THERMOSTAT INPUT TERMINALS LOW STAGE HEAT LINE 120VAC INPUT TO THE CONTROL HIGH STAGE HEAT XFMR 120VAC OUTPUT TO THE TRANSFORMER CIRC 120VAC OUTPUT TO THE INDOOR BLOWER BLOWER LOW STAGE COOL (when W915 is clipped) UNPOWERED NORMALLY OPEN (DRY)
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Page 41: Ignition Control Diagnostic Codes
IGNITION CONTROL DIAGNOSTIC CODES Low GWP Test Page 41... - Page 42 Any accessory rated up to one amp can be connected to On-Board Links this terminal with the neutral leg of the circuit being con- nected to one of the provided neutral terminals. If an ac- WARNING cessory rated at greater than one amp is connected to this terminal, it is necessary to use an external relay.
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Page 43: Wiring Connections
Field Wiring Applications With Conventional Thermostat (see Ignition Control section for DIP switch settings) DIP Switch Settings and On-Board Links DIP Switch 1 On Board Links Must Be Cut To Select Thermostat Thermostat Wiring Connections System Options Heating Stages 1 Heat / 1 Cool FURNACE OUTDOOR T'STAT... - Page 44 Field Wiring Applications With Conventional Thermostat (see Ignition Control section for DIP switch settings) DIP Switch Settings and On-Board Links DIP Switch 1 On Board Links Must Be Cut To Select Thermostat Thermostat Wiring Connections System Options Heating Stages 2 Heat / 2 Cool FURNACE OUTDOOR T'STAT...
- Page 45 Field Wiring Applications With Conventional Thermostat (see Ignition Control section for DIP switch settings) DIP Switch Settings and On-Board Links DIP Switch 1 Thermostat On Board Links Must Be Cut To Select Wiring Connections Thermostat Heating System Options Stages FURNACE Dual Fuel HEAT PUMP T'STAT...
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Page 46: System Options
Field Wiring Applications With Conventional Thermostat (see Ignition Control section for DIP switch settings) DIP Switch Settings and On-Board Links DIP Switch 1 On Board Links Must Be Cut To Select Wiring Connections Thermostat Thermostat Heating System Options Stages FURNACE Dual Fuel HEAT PUMP T'STAT... -
Page 47: Low Gwp Application
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 56 and follow steps below: 1 - Route sensor wire #1 through provided grommet. - Page 48 TABLE 23 lists the functions of the Test button during each Leak Detected When the furnace control board detects a refrigerant leak: mode of operation. 1. The furnace control board shuts off the (R) input TABLE 23 (24VAC power) to the thermostat, which de- LGWP Test Button Function energizes the outdoor unit compressor and heat Mode of Operation...
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Page 49: Start-Up Procedure
Cooling Demand External Alarm (For applications with external alarms wired directly to the 1. Prompt a cooling demand at the thermostat. furnace control board) 2. Press the LGWP Test button on the furnace control The furnace control board triggers the external alarm sys- board. -
Page 50: 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 51: Supply Pressure Measurement
NOTE - Pressure test adapter kit (10L34) is available from Lennox to facilitate manifold pressure measurement. 1 - Connect the test gauge positive side “+“ to manifold Gas Pressure Adjustment pressure tap on gas valve as noted above. -
Page 52: 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 53: Other Units Adjustments
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 54: 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 55: 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 56: Repair Parts Lits
Winterizing and Condensate Trap Care Repair Parts List 1 - Turn off power to the furnace. Cabinet Parts 2 - Have a shallow pan ready to empty condensate Outer access panel water. Blower access panel 3 - Remove the clean out cap from the condensate trap and empty water. -
Page 57: Manufacturer Requirements - Gas Equip- Ment Venting System Provided
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 58 For The Province Of Ontario, Horizontal Sidevent Applications Only See FIGURE 58 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.
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Page 59: Blower Datra
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 60 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.
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Page 61: 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 62: Unit Operation
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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