Lennox ML296UHV(X) Series Manual
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Lennox ML296UHV(X) Series Manual

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Service Literature
ML296UHV(X) series units are 90% efficiency gas fur­
naces used for upflow or horizontal applications only,
manufactured with Lennox Duralokt heat exchangers
formed of aluminized steel. ML296UHV(X) units are avail­
able in heating capacities of 44,000 to 132,000 Btuh and
Cooling applications up to 5 tons. Refer to Engineering
Handbook for proper sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. ML296UHV(X)
unit meets the California Nitrogen Oxides (NO
and California Seasonal Efficiency requirements. All units
use a redundant gas valve to assure safety shut-off as re­
quired by C.S.A.
All specifications in this manual are subject to change. Pro­
cedures outlined in this manual are presented as a recom­
mendation only and do not supersede or replace local or
state codes. In the absence of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommendations only and do not consti­
tute code.

TABLE OF CONTENTS

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II Installation
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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV Heating System Service Checks
V Typical Operating Characteristics
VI Maintenance
. . . . . . . . . . . . . . . . . . . . . . . . . .
VII Wiring and Sequence of Operation
Corp. 1903-L1
ML296UHV(X) SERIES UNITS
) Standards
x
Page 2
Page 3
Page 9
Page 21
Page 43
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Page 44
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Page 47
Page 47
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Page 50
Page 1
ML296UHV(X)
WARNING
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 HVAC in­
staller (or equivalent), service agency or the gas sup­
plier.
CAUTION
As with any mechanical equipment, contact with
sharp sheet metal edges can result in personal in­
jury. Take care while handling this equipment and
wear gloves and protective clothing.
© 2019 Lennox Industries Inc.

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  • Page 1 ML296UHV(X) Corp. 1903-L1 Service Literature ML296UHV(X) SERIES UNITS ML296UHV(X) series units are 90% efficiency gas fur­ naces used for upflow or horizontal applications only, manufactured with Lennox Duralokt heat exchangers formed of aluminized steel. ML296UHV(X) units are avail­ able in heating capacities of 44,000 to 132,000 Btuh and cooling applications up to 5 tons.

  • Page 2: Specifications

    SPECIFICATIONS Model No. ML296UH045XV36B ML296UH070XV36B Heating AHRI Reference No. Performance AFUE High Input - Btuh 44,000 66,000 Fire Output - Btuh 42,000 62,000 Temperature rise range - °F 35 - 65 50 - 80 Gas Manifold Pressure (in. w.g.) 3.5 / 10.0 3.5 / 10.0 Nat.

  • Page 3: Blower Data

    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 - minimum 500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm. BLOWER DATA...
  • Page 4 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 - minimum 500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm. BLOWER DATA...
  • Page 5 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 - minimum 500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm. BLOWER DATA...
  • Page 6 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 - minimum 500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 453 cfm. BLOWER DATA...
  • Page 7 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 - minimum 500 cfm. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 478 cfm. BLOWER DATA ML296UH110XV60C BLOWER PERFORMANCE (less filter) SINGLE SIDE RETURN AIR −...
  • Page 8 ML296UHV PARTS IDENTIFICATION Field Make Up Box Burner Box Assembly Heat Exchanger Gas Valve Combustion Pressure Air Inducer Switch Assembly Bag Assemblies (shipping location) Door Interlock Primary Limit Switch Variable Speed Motor Access Panel Two-Stage Integrated Control FIGURE 1 Page 8...

  • Page 9: I Unit Components

    I-UNIT COMPONENTS 3. Integrated Control (A92) Units are equipped with a two-stage, variable speed inte­ ML296UHV(X) unit components are shown in figure 1. The grated control. The system consists of a ignition / blower gas valve, combustion air inducer and burners can be ac­ cessed by removing the access panel.
  • Page 10 TABLE 1 TABLE 4 High Heat State Green LED 12 Pin Terminal Designation LED Status DESCRIPTION PIN # Function Gas Valve Second Stage LED Off No demand for high heat Second Stage Prove Switch LED On High heat demand, operating normally Rollout Switch In High heat demand, high pressure LED Flashing...
  • Page 11 INTEGRATED CONTROL Heat Stage Jumper (single stage shown) Air Flow Heat Jumper Taps Cool Taps TERMINAL DESIGNATIONS HUM -Humidifier (120VAC) Line - Input (120VAC) XFMR - Transformer (120VAC) Cont - Continuous blower EAC - Indoor Air Accessory (120VAC) Cool - Cool Speed (120VAC) Park 1 - Dead terminal for alternate speed tap Park 2 - Dead terminal for alternate speed tap HI Heat - High heat speed...
  • Page 12 B- Indoor Blower Motor NIDEC BLOWER MOTOR B3 MOTOR 16X4W CONTROLLER FIGURE 6 BLOWER MOTOR COMPONENTS STATOR (WINDINGS) Power Choke Blower Motor BEARING (5 Ton Only) (B3) OUTPUT To Remove Blower From Unit: Remove Bolts and SHAFT Wiring Jackplugs. Then Slide Out Front of Unit. FIGURE 4 ROTOR Blower Motor (B3)
  • Page 13 TABLE 5 Emerson Motor Only Motor Action Blower Blink Blink Normal Rotating Blink Blink Blink Rotating Normal. PW blink is 100cfm/blink Verify 16X4W and motor control hp match. Verify power to motor control. Blink Blink Rotating Turn off power for 1 minute then restart. If motor still does not rotate replace the controller.
  • Page 14 Power Choke (L13) GenTeq HARNESS CONNECTORS A choke coil is used on 5 ton 1 hp units. The choke is lo­ POWER CONTROL cated on the blower housing and is used to suppress transient CONNECTOR J48 CONNECTOR J49 current spikes. PIN 1 ‐...
  • Page 15 MOTOR SPEED CONTROL WITH D.C. PULSE‐WIDTH MODULATION Motor speed is determined by the size of the electrical pulse sent to the motor windings. The longer the pulse, the faster the motor. OUTPUT FROM CONTROLLER TO MOTOR WINDINGS WINDINGS TURNED OFF WINDINGS TURNED ON Ç...
  • Page 16 C- Heating Components LPG change over kits are available from Lennox. Kits include burner orifices and a gas valve. 1. Ignitor The ignitor is made of durable silicon nitride. Ignitor longev­ 4. Flame Rollout Switches (S47) ity is enhanced by controlling voltage to the ignitor. The in­...
  • Page 17 ML296UHV HEATING COMPONENTS Burner Assembly Intake Air Top Cap Sensor Rollout Switch Rollout Switch Ignitor Manifold And Gas Orifices Burner Box Cover Two-Stage Gas Valve FIGURE 11 Page 17...
  • Page 18 ML296UHV Ignitor Check Test 1 Check ignitor circuit for correct resistance. Remove 4-pin plug from control. Check ohms reading across terminals 1 and 5. Reading should be between 39 and 70 ohms. If value is correct, this is the only test needed. If the reading on the meter is not correct, (0 or infinity) then a second test is needed.
  • Page 19 0.45 0.75 Pressure Switch (S18) -090 0.50 0.85 ML296UHV(X) series units are equipped with a dual com­ -110 0.45 0.81 bustion air pressure switch (first and second stage) located on the combustion air inducer orifice bracket. See figure 13. TABLE 10 7501 - 10,000' The switch is connected to the combustion air inducer hous­...
  • Page 20 Pressure Switch Check 5 - Operate unit and observe manometer reading. Readings will change as heat exchanger warms. To check pressure switch differential, refer to figure 14 and a. Take one reading immediately after start‐up. use the provided fittings and tubing to follow the steps be­ low.
  • Page 21 II-PLACEMENT AND INSTALLATION TABLE 11 PIPING AND FITTINGS SPECIFICATIONS All pipe, fittings, primer and solvent cement must conform Schedule 40 PVC (Pipe) D1785 with American National Standard Institute and the Ameri­ Schedule 40 PVC (Cellular Core Pipe) F891 can Society for Testing and Materials (ANSI/ASTM) stan­ Schedule 40 PVC (Fittings) D2466 dards.

  • Page 22: Joint Cementing Procedure

    TABLE 12 OUTDOOR TERMINATION USAGE* STANDARD CONCENTRIC Flush­ Wall Kit Wall Ring Kit Mount 1-1/2 inch 2 inch 3 inch 2 inch 3 inch 2 inch Vent Pipe Input Size Field 51W11 Dia. in. 71M80 69M29 Fabricated 44J40 (US) 22G44 (US) (US) (US) 60L46 (US)
  • Page 23 Conduct the following test while each appliance is operat­ Venting Practices ing and the other appliances (which are not operating) re­ main connected to the common venting system. If the venting system has been installed improperly, you must correct the system as indicated in the general venting re­ quirements section.

  • Page 24: Vent Piping Guidelines

    NOTE - Exhaust pipe MUST be glued to furnace exhaust fittings. ® NOTE - Lennox has approved the use of DuraVent NOTE - Exhaust piping should be checked carefully to make sure there are no sags or low spots.
  • Page 25 TABLE 13 Use the following steps to correctly size vent pipe diameter. MINIMUM VENT PIPE LENGTHS ML296UHV MIN. VENT LENGTH* MODEL Piping Size Process 15 ft. or 5 ft. plus 2 elbows or 045, 070, 090, 110 10 ft. plus 1 elbow What is the *Any approved termination may be added to the minimum length listed.
  • Page 26 TABLE 14 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. 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 27 TABLE 14 Continued Maximum Allowable Intake or Exhaust Vent Length in Feet 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 2”...
  • Page 28 TABLE 15 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 29 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 30 Intake Piping TYPICAL AIR INTAKE PIPE CONNECTIONS The ML296UHV furnace may be installed in either direct HORIZONTAL NON−DIRECT VENT APPLICATIONS (Horizontal Right−Hand Air Discharge Application Shown) vent or non-direct vent applications. In non-direct vent applications, 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 PVC pipe...
  • Page 31 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 gases are discharged to the outdoors.
  • Page 32 TABLE 16 Maximum Allowable Exhaust Vent Pipe Length (in ft.)Without Insulation In Unconditioned Space For Winter Design Temperatures Two - Stage High Efficiency Furnace Unit Input Size Winter Design Vent Pipe Temperatures °F (°C) Diameter 2 in. 32 to 21 (0 to -6) 2-1/2 in.

  • Page 33: Vent Termination Clearances

    ‡ 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 26...
  • Page 34 ‡ 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 27 Page 34...
  • Page 35 Details of Intake and Exhaust Piping Terminations for 3”(76MM) MAX. Inches(MM) SIZE TERMINATION Direct Vent Installations PIPE PER TABLE 17. NOTE - In Direct Vent installations, combustion air is tak­ UNCONDITIONED en from outdoors and flue gases are discharged to out­ ATTIC SPACE 8”...
  • Page 36 7. If intake and exhaust piping must be run up a side wall FIELD-PROVIDED to position above snow accumulation or other ob­ REDUCER MAY BE REQUIRED structions, piping must be supported. At least one TO ADAPT LARGER VENT PIPE SIZE TO TERMINATION bracket must be used within 6”...
  • Page 37 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 38 4. Distance between exhaust pipe terminations on mul­ tiple furnaces must meet local codes. Crawl Space and Extended Horizontal Venting KIT 51W81 Lennox provides kit 51W18 to install 2” or 3” PVC exhaust (USA) piping through the floor joists and into the the crawl space. KIT 51W81 See figure 39.
  • Page 39 Condensate Piping CONDENSATE TRAP AND PLUG LOCATIONS This unit is designed for either right‐ or left‐side exit of con­ (Unit shown in upflow position) densate piping in upflow applications. In horizontal applica­ Trap tions, the condensate trap must extend below the unit. An (same on 8”...
  • Page 40 Heating cable kit is installation, prime trap per procedure outlined in Unit available from Lennox in various lengths; 6 ft. (1.8m) - Start-Up section. kit no. 26K68; 24 ft. (7.3m) - kit no. 26K69; and 50 ft.
  • Page 41 Condensate Trap With Optional Overflow Switch ML296UHV with Evaporator Coil Using a Common Drain From Evaporator Coil Evaporator drain Field Provided Vent line required 1” min. 2” max. above condensate drain. (Trap at coil is optional) (1” min. to 2” Max.above condensatedrain connection) FurnaceCondensate Drain Connection...
  • Page 42 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 43: Iii Start Up

    III-START‐UP 4 - This furnace is equipped with an ignition device which automatically lights the burners. Do not try to light the A-Preliminary and Seasonal Checks burners by hand. 1 - Inspect electrical wiring, both field and factory installed 5 - Remove the upper access panel. for loose connections.

  • Page 44: Iv Heating System Service Checks

    IV-HEATING SYSTEM SERVICE CHECKS through Lennox under part number 31B2001. See Corp. 8411-L10, for further details. A-CSA Certification All units are CSA design certified without modifications. Do not use matches, candles, flame or any other Refer to the ML296UHV(X) Installation Instruction.
  • Page 45 NOTE- To obtain accurate reading, shut off all other gas Furnace should operate minimum 15 minutes with correct appliances connected to meter. manifold pressure and gas flow rate before checking com­ bustion. See sections E- and F-. Take combustion sample TABLE 18 beyond the flue outlet.
  • Page 46 I- Proper Ground and Voltage 2 - In addition, measure the AC voltage from Line Hot to Line Neutral (spade terminals) on the integrated con­ A poorly grounded furnace can contribute to premature ig­ trol. See figure 51. This voltage should be in the range nitor failure.

  • Page 47: V Typical Operating Characteristics

    V-TYPICAL OPERATING CHARACTERISTICS 3 - With only the blower motor running and the evaporator coil dry, observe the manometer reading. Adjust blow­ A-Blower Operation and Adjustment er motor speed to deliver the air desired according to 1 - Blower operation is dependent on thermostat control the job requirements.
  • Page 48 3 - Disconnect the 2 wires from the gas valve. specifications provided by the filter manufacturer 4 - Remove gas supply line connected to gas valve. Re­ against the data given in the appropriate Lennox move the burner box cover (if equipped) and remove Product Specifications bulletin. Additional informa­...
  • Page 49 17 - Remove electrical junction box from the side of the fur­ 40 - Reinstall gas valve manifold assembly. Reconnect nace. gas supply line to gas valve. 41 - Reconnect the combustion air intake pipe. 18 - Mark and disconnect any remaining wiring to heating compartment components.

  • Page 50: Vii Wiring And Sequence Of Operation

    VII- Wiring and Sequence of Operation Page 50...
  • Page 51 On a call for heat from the room thermostat, the control Cooling board performs a 1 second self check. Upon confirmation The unit is set up at the factory for single stage cooling. For that the pressure switch contacts are in an open position, two stage cooling operation, clip the jumper wire located the control energizes the combustion blower on high speed.

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