Lennox Merit Series Installation Instructions Manual
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Lennox Merit Series Installation Instructions Manual

Gas furnace upflow / horizontal air discharge
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© 2019 Lennox Industries Inc.
Dallas, Texas USA
Contents
Unit Dimensions - inches (mm) ......................................2
ML296UHV Gas Furnace ...............................................3
Shipping and Packing List ..............................................4
Safety .............................................................................3
General ...........................................................................5
Combustion, Dilution, Ventilation Air...............................5
Setting Equipment ..........................................................8
Filters ............................................................................13
Duct System ................................................................. 11
Pipe Fittings Specifications...........................................14
Joint Cementing Procedure ..........................................15
C C
I I
HI
INSTALLATION
INSTRUCTIONS
ML296UHV
MERIT
SERIES GAS FURNACE
®
UPFLOW / HORIZONTAL AIR DISCHARGE
507869-02
06/2019
Supersedes 507869-01
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 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.
Venting Practices ..........................................................16
Gas Piping ....................................................................36
Electrical .......................................................................39
Blower Motor Performance ...........................................42
Integrated Control .........................................................47
Unit Start-Up .................................................................48
Gas Pressure Measurement.........................................49
Proper Combustion.......................................................50
High Altitude .................................................................50
Repair Parts List ...........................................................51
Sequence of Operation.................................................52
Service..........................................................................53
Page 1
WARNING
CAUTION

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  • Page 1: Table Of Contents

    INSTALLATION INSTRUCTIONS ML296UHV © 2019 Lennox Industries Inc. Dallas, Texas USA MERIT SERIES GAS FURNACE ® UPFLOW / HORIZONTAL AIR DISCHARGE 507869-02 06/2019 Supersedes 507869-01 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) NOTE - 60C size units that require air volumes over 1800 cfm must have one of the following: 1. Single side return air and Optional Return Air Base EXHAUST AIR 3-3/8 OUTLET with transition that must accommodate required (86) 20 x 25 x 1 inch (508 x 635 x 25 mm) air filter to maintain proper velocity.

  • Page 3: Ml296Uhv Gas Furnace

    ML296UHV Gas Furnace Shipping and Packing List The ML296UHV Category IV gas furnace is shipped ready Package 1 of 1 contains for installation in the upflow or horizontal position. The fur- 1 - Assembled ML296UHV unit nace is shipped with the bottom panel in place. The bot- 1 - Bag assembly containing the following: tom panel must be removed if the unit is to be installed in horizontal or upflow applications with bottom return air.

  • Page 4: Use Of Furnace As A Construction Heater

    In order to ensure proper unit operation in non-direct vent applications, combustion and ventilation air supply must Heating Unit Installed Parallell to Air Handler Unit Dampers be provided according to the current National Fuel Gas (open during heating operation only) Code or CSA-B149 standard.

  • Page 5: General

    FAILURE TO FOLLOW THE ABOVE INSTALLATION IN- exposure to the following substances in the combustion STRUCTIONS VOIDS THE MANUFACTURER’S EQUIP- air supply: MENT LIMITED WARRANTY. LENNOX DISCLAIMS ALL LIABILITY IN CONNECTION WITH INSTALLER’S Permanent wave solutions FAILURE TO FOLLOW THE ABOVE INSTALLATION IN- Chlorinated waxes and cleaners 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 leg). See figure 10. The bolt and washer must be removed EQUIPMENT IN CONFINED SPACE - ALL AIR FROM OUTSIDE before the furnace is placed into operation. After the bolt (All Air Through Ventilated Attic) and washer have been removed, the rigid leg will not touch the blower housing.

  • Page 9: Setting Equipment

    SETTING EQUIPMENT Unit must be level side-to-side. Unit may be positioned from level to 1/2” toward the front to aid in draining. UPFLOW APPLICATION UNIT FRONT UNIT FRONT AIR FLOW 1/2” max. SIDE VIEW SIDE VIEW FRONT VIEW HORIZONTAL APPLICATION UNIT FRONT 1/2”...
  • Page 10 Return Air Guidelines WARNING Return air can be brought in through the bottom or either Improper installation of the furnace can result in side of the furnace installed in an upflow application. If the furnace is installed on a platform with bottom return, make personal injury or death.
  • Page 11 Optional Return Air Base CONDENSATE (Upflow Applications Only) TRAP FURNACE FRONT 23 (584) 3−1/4 IF BASE Overall (83) IS USED (Maximum) Minimum WITHOUT 11 (279) IAQ CABINET, Maximum 22−7/16 INDOOR AIR A SINGLE Unit side return air 14 (356) QUALITY (570) RETURN AIR Opening...
  • Page 12 18, or install the furnace on this outlet will be easily noticed by the homeowner. a platform, as shown in figure 19. A horizontal suspension kit (51W10) may be ordered from Lennox or use equiva- lent. Page 12...

  • Page 13: Filters

    If a gas appliance is operating in the data given in the appropriate Lennox Product a room with negative pressure, the flue products can be Specifications bulletin. Additional information is provided pulled back down the vent pipe and into the room.

  • Page 14: Pipe Fittings Specifications

    Return air can be brought in through the bottom or either TABLE 2 side of the furnace (return air brought into either side of PIPING AND FITTINGS SPECIFICATIONS furnace allowed only in upflow applications). If a furnace Schedule 40 PVC (Pipe) D1785 with bottom return air is installed on a platform, make an airtight seal between the bottom of the furnace and the...

  • Page 15: Joint Cementing Procedure

    TABLE 3 OUTDOOR TERMINATION USAGE* STANDARD CONCENTRIC Wall Ring Wall Kit 1-1.2 inch 2 inch 3 inch Flush Mount Kit Vent Pipe 2 inch 3 inch 2 inch Input Size Field 71M80 69M29 Dia. in. 51W11 22G44 44J40 Fabricated (US) (US) 60L46 (US) (US)

  • Page 16: Venting Practices

    8 - After assembly, wipe excess cement from pipe at Conduct the following test while each appliance is oper- end of fitting socket. A properly made joint will show ating and the other appliances (which are not operating) a bead around its entire perimeter. Any gaps may remain connected to the common venting system.
  • Page 17 Resize the common venting system to the minimum vent Vent Piping Guidelines pipe size determined by using the appropriate tables in NOTE - Lennox has approved the use of DuraVent® and Appendix G. (These are in the current standards of the Centrotherm manufactured vent pipe and terminations National Fuel Gas Code ANSI Z223.1.
  • Page 18 Includes all vent pipe and elbows inside and outside the house. FIGURE 24 NOTE - Lennox offers a glueless vent adapter kit 17H92 as an option for exhaust exiting at the furnace top cap coupling. Page 18...
  • Page 19 TABLE 5 Maximum Allowable Intake or Exhaust Vent Length in Feet NOTE - Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Both Intake and Exhaust must be same pipe size Standard Termination at Elevation 0 - 4500 ft Number 2”...
  • Page 20 TABLE 5 Continued Maximum Allowable Intake or Exhaust Vent Length in Feet NOTE - Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Both Intake and Exhaust must be same pipe size. Concentric Termination at Elevation 0 - 4500 ft Number 2”...
  • Page 21 TABLE 6 Maximum Allowable Exhaust Vent Lengths With Furnace Installed in a Closet or Basement Using Ventilated Attic or Crawl Space For Intake Air in Feet NOTE - Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Both Intake and Exhaust must be same pipe size.
  • Page 22 TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN UPFLOW DIRECT OR NON-DIRECT VENT APPLICATIONS EXHAUST INTAKE EXHAUST INTAKE 2” 2” 2” 2” 3” 3” TRANSITION TRANSITION 2” 2” *2” *2” DO NOT transition from smaller to larger pipe in horizontal runs of exhaust pipe.
  • Page 23 Intake Piping TYPICAL AIR INTAKE PIPE CONNECTIONS HORIZONTAL NON−DIRECT VENT APPLICATIONS The ML296UHV furnace may be installed in either direct (Horizontal Right−Hand Air Discharge Application Shown) vent or non-direct vent applications. In non-direct vent ap- plications, when intake air will be drawn into the furnace from the surrounding space, the indoor air quality must be considered and guidelines listed in Combustion, Dilution and Ventilation Air section must be followed.
  • Page 24 General Guidelines for Vent Terminations CAUTION In Non-Direct Vent applications, combustion air is taken If this unit is being installed in an application with from indoors or ventilated attic or crawlspace and the flue combustion air coming in from a space serviced by an gases are discharged to the outdoors.
  • Page 25 TABLE 7 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) 32 to 21 2 in (0 to -6) 2-1/2 in...
  • Page 26 ‡ 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 32...
  • Page 27 ‡ 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 33 Page 27...
  • Page 28 Details of Intake and Exhaust Piping Terminations for At least one bracket must be used within 6” from the Direct Vent Installations top of the elbow and then every 24” (610mm) as shown in figure 42, to prevent any movement in any direction. NOTE - In Direct Vent installations, combustion air is taken When exhaust and intake piping must be run up an from outdoors and flue gases are discharged to outdoors.
  • Page 29 TABLE 8 FIELD-PROVIDED EXHAUST PIPE TERMINATION SIZE REDUCTION QUIRED TO ADAPT LARGER VENT PIPE ML296UHV Model Termination Pipe Size SIZE TO TERMINATION. OUTSIDE *045 and 070 1-1/2” (38MM) INTAKE WALL *090 2” (51MM) EXHAUST EXHAUST 2” (51MM) *ML296UHV-045, -070 and -090 units with the flush mount termination must use the 1-1/2”accelerator supplied with the kit.
  • Page 30 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 31 KIT 15Z70 Crawl Space and Extended Horizontal Venting (CANADA) Lennox provides kit 51W18 to install 2” or 3” PVC exhaust piping through the floor joists and into the crawl space. See figure 45. This kit can also be used as a supplemental drain for in- stallations with condensate run back in the vent pipe (ie.
  • Page 32 Condensate Piping CONDENSATE TRAP AND PLUG LOCATIONS This unit is designed for either right- or left-side exit of (Unit shown in upflow position) condensate piping in upflow applications. In horizontal Trap applications, the condensate trap must extend below the (same on unit.
  • Page 33 (Unit shown in upflow position with remote trap) ble, a heat cable kit may be used on the condensate trap and line. Heating cable kit is available from Lennox in var- ious lengths; 6 ft. (1.8m) - kit no. 26K68; 24 ft. (7.3m) - kit FieldProvidedVent no.
  • Page 34 IMPORTANT Furnace with Evaporator Coil Using a Common Drain When combining the furnace and evaporator coil drains together, the A/C condensate drain outlet must Evaporator drain be vented to relieve pressure in order for the furnace line required pressure switch to operate properly. (Trap at coil is optional) Condensate Trap With Optional Overflow Switch (1”...
  • Page 35 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 36: Gas Piping

    IMPORTANT Gas Piping Gas supply piping should not allow more than 0.5”W.C. Compounds used on threaded joints of gas piping must drop in pressure between gas meter and unit. Supply gas be resistant to the actions of liquefied petroleum gases. pipe must not be smaller than unit gas connection.
  • Page 37 Upflow Application Upflow Application Left Side Piping Right Side Piping (Standard) (Alternate) 1/2” NPT 1/2” NPT MANUAL MAIN SHUT-OFF VALVE MANUAL MAIN SHUT-OFF VALVE GROUND GROUND JOINT JOINT UNION UNION DRIP LEG FIELD PROVIDED AND INSTALLED DRIP LEG NOTE - BLACK IRON PIPE ONLY TO BE ROUTED INSIDE OF CABINET FIGURE 56 Horizontal Applications Possible Gas Piping Configurations...
  • Page 38 TABLE 9 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 39: Electrical

    The power supply wiring must meet Class I restrictions. Electrical Protected by either a fuse or circuit breaker, select circuit protection and wire size according to unit nameplate. ELECTROSTATIC DISCHARGE (ESD) Precautions and Procedures CAUTION CAUTION Failure to use properly sized wiring and circuit breaker Electrostatic discharge can affect electronic may result in property damage.

  • Page 40: Integrated Control

    One line voltage “HUM” 1/4” spade terminal is provided on • The furnace integrated control requires both correct the furnace integrated control. Any humidifier rated up to polarity and proper ground. Both polarity and prop- one amp can be connected to this terminal with the neutral er grounding should be checked before attempting leg of the circuit being connected to one of the provided to operate the furnace on either permanent or tem-...
  • Page 41 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 42 BLOWER DATA ML296UH045XV36B BLOWER PERFORMANCE (less filter) BOTTOM RETURN AIR 0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range Speed Switch Positions “ADJUST” Switch Second Stage “HEAT” Speed - cfm Second Stage “COOL” Speed - cfm Positions 1005 1075...
  • Page 43 BLOWER DATA ML296UH090XV48C BLOWER PERFORMANCE (less filter) BOTTOM RETURN AIR, RETURN AIR FROM BOTH SIDES OR RETURN AIR FROM BOTTOM AND ONE SIDE 0 through 0.8 in. w.g. (Heating) and 0 through 1.0 in. w.g. (Cooling) External Static Pressure Range Speed Switch Positions “ADJUST”...
  • Page 44 Allowable Heating Speeds ML296UHV Speed Adjust Setting “D” Setting “C” Setting “B” Setting “A” Model +10% Allowed 045XV36B Norm Factory Setting Allowed -10% Allowed +10% 070XV36B Norm Factory Setting -10% Allowed Allowed Allowed Not Allowed +10% 090XV48C Norm Factory Setting -10% Allowed +10%...
  • Page 45 ML296UHV Schematic Wiring Diagram FIGURE 61 Page 45...
  • Page 46 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 47: 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 48 2 - Combustion air pressure switch proves blower NOTE - Pressure test adapter kit (10L34) is available from operation. Switch is factory set and requires no Lennox to facilitate manifold pressure measurement. adjustment. A manifold pressure post located on the gas valve pro- 3 - After a 15-second prepurge, the hot surface ignitor vides access to the manifold pressure.

  • Page 49: 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 50: Repair Parts List

    Repair Parts List The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model number listed on the CSA nameplate -- Example: ML296UH045XV36B. All service must be performed by a licensed professional installer (or equivalent), service agency, or gas supplier.

  • Page 51: Sequence Of Operation

    The circulating blower ramps up to 50% of 1st stage heat Other Unit Adjustments speed and operates at that speed for one minute (includ- Primary Limit. ing ramp up time), then at 75% of 1st stage heat speed for an additional minute. After that, the circulating blower op- The primary limit is located on the heating compartment erates at full 1st stage heat speed until either the heat call vestibule panel.

  • Page 52: Service

    At the beginning of each heating season, and to comply For heat pump operation, clip the jumper wire located bel- with the Lennox Limited Warranty, your system should low the O terminal on the integrated ignition/blower control be checked as follows: board.
  • Page 53 8- Evaluate the heat exchanger integrity by inspecting Winterizing and Condensate Trap Care the heat exchanger per the AHRI heat exchanger 1 - Turn off power to the furnace. inspection procedure. This procedure can be viewed 2 - Have a shallow pan ready to empty condensate at www.ahrinet.org water.
  • Page 54 Requirements for Commonwealth of Massachusetts Modifications to NFPA-54, Chapter 10 4 - INSPECTION. The state or local gas inspector of the side wall, horizontally vented, gas-fueled equipment Revise NFPA-54 section 10.8.3 to add the following shall not approve the installation unless, upon requirements: inspection, the inspector observes carbon monoxide For all side wall, horizontally vented, gas-fueled equip-...
  • Page 55 ADDENDUM FOR THE PROVINCE OF SASKATCHEWAN See below for venting in the province of Saskatchewan. Lennox approves the following termination for use in Saskatchewan Canada. 12” 2” (51MM) 3” (76MM)

This manual is also suitable for:

Merit ml296uhv seriesMerit ml296uh045xv36bMerit ml296uh070xv36bMerit ml296uh090xv48cMerit ml296uh110xv60c

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