Lennox ML296UHV Series Unit Information
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Lennox ML296UHV Series Unit Information

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Table of Contents

S e r v i c e L i t e r a t u r e
ML296UHV(X) series units are 90% efficiency gas furnac-
es used for downflow applications only, manufactured with
Lennox Duralok heat exchangers formed of aluminized
steel. ML296UHV(X) units are available in heating capac-
ities of 44,000 to 110,000 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. ML296U-
HV(X) unit meets the California Nitrogen Oxides (NOx)
Standards and California Seasonal Efficiency require-
ments. All units use a redundant gas valve to assure safe-
ty shut-off as required by C.S.A.
All specifications in this manual are subject to change.
Procedures outlined in this manual are presented as a
recommendation only and do not supersede or replace lo-
cal or state codes. In the absence of local or state codes,
the guidelines and procedures outlined in this manual (ex-
cept where noted) are recommendations only and do not
constitute code

TABLE OF CONTENTS

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2
Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 3
I Unit Components . . . . . . . . . . . . . . . . . . . . . . . . Page 9
II Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 21
III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 43
VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 47
UNIT INFORMATION
UNIT INFORMATION
Corp 1903-L1
Revised 01/2022
ML296UHV(X) SERIES UNITS
Page 1
WARNING
Improper
installation,
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.
CAUTION
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.
ML296UHV(X)
C C C C
I I I I
HI
HI
adjustment,
alteration,
©2016 Lennox Industries, Inc.

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Summary of Contents for Lennox ML296UHV Series

  • Page 1: Table Of Contents

    ML296UHV(X) series units are 90% efficiency gas furnac- es used for downflow applications only, manufactured with Lennox Duralok heat exchangers formed of aluminized steel. ML296UHV(X) units are available in heating capac- ities of 44,000 to 110,000 Btuh and cooling applications up to 5 tons.

  • Page 2: Specifications

    SP ECIF ICATIONS Model No. ML296UH045XV36B ML296UH070XV36B Heating AFUE Performance 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 OPTIONAL A C C ESSORIES NOTE - FURNACES CANNOT BE TWINNED! “B” Width “C” Width Models Models CABINET ACCESSORIES Horizontal Suspension Kit - Horizontal only 51W10 51W10 Return Air Base - Upflow only 50W98 50W99 High Performance Economizer (Commercial Only) 10U53 10U53 CONDENSATE DRAIN KITS...

  • Page 4: 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. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 300 cfm. ML296UH045XV36B BLOWER MOTOR WATTS (COOLING) Motor Watts @ Various External Static Pressures - in.
  • 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. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 300 cfm. ML296UH070XV36B BLOWER MOTOR WATTS (COOLING) Motor Watts @ Various External Static Pressures - in.
  • 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. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 380 cfm. ML296UH090XV48C BLOWER MOTOR WATTS (COOLING) Motor Watts @ Various External Static Pressures - in.
  • 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. Lennox Harmony III™ Zoning System Applications - Minimum blower speed is 460 cfm. ML296UH110XV60C BLOWER MOTOR WATTS (COOLING) Motor Watts @ Various External Static Pressures - in.
  • Page 8 ML296UHV PARTS IDENTIFICATION Burner Box Assembly Field Make Up Box Heat Exchanger Primary Limit Gas Valve Combustion Air Inducer Access Panel Pressure Switch Assembly Bag Assemblies Door (shipping location) Interlock Switch Variable Speed Motor 16X4W Box (some models) Access Panel Two-Stage Integrated Control FIGURE 1 Page 8...

  • Page 9: I Unit Components

    I-UNIT COMPONENTS 3. Integrated Control (A92) Unit components are shown in FIGURE 1. The gas valve, Units are equipped with a two-stage, variable speed inte- combustion air inducer and burners can be accessed by grated control. The system consists of a ignition / blower removing the access panel.
  • Page 10 TABLE 2 TABLE 4 Diagnostic Codes Red LED 12 Pin Terminal Designation LED Status Description Pin # Function No power to control or control har- Gas Valve Second Stage LED Off ware fault detected. Second Stage Prove Switch LED On Normal operation.
  • Page 11 INTEGRATED CONTROL Heat Stage Jumper (single stage shown) Fan O Delay Air Flow Heat Jumper Taps Cool Taps TERMINAL DESIGNATIONS HUM -Humidifier (120VAC) Line - Input (120VAC) XFMR - Transformer (120VAC) 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 FIGURE 3...
  • Page 12 GenTeq BLOWER MOTOR B3 MOTOR CONTROLLER FIGURE 6 NIDEC BLOWER MOTOR B3 Power Choke Blower Motor (5 Ton Only) (B3) MOTOR 16X4W (May located To Remove Blower From Unit: Remove Bolts and on the blower Wiring Jackplugs. Then Slide Out Front of Unit. housing) FIGURE 4 Blower Motor (B3)
  • Page 13 TABLE 5 Nidec / Emerson Motor Only PW LED RX LED TX LED Motor Blower Action Blink Blink Not Rotating Normal Blink Blink Blink Rotating Normal. PW blink is 100cfm/blink Verify 16X4W and motor control hp match. Verify power to motor control. Blink Blink Not Rotating...
  • Page 14 Power Choke (L13) GenTeq HARNESS CONNECTORS A choke coil is used on 5 ton 1 hp units. The choke is POWER CONTROL located on the blower housing and is used to suppress CONNECTOR J48 CONNECTOR J49 transient current spikes. PIN 1 C1 PIN 2 W / W1 Precautions PIN 3 C2...
  • 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 ON PULSE OFF PULSE...
  • Page 16 Inlet and outlet pressure taps are located on the valve. A regulator adjustment screw is located on the valve LPG change over kits are available from Lennox. Kits in- clude burner orifices and a gas valve. Page 16...
  • Page 17 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 12 Page 17...
  • Page 18 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 COMBUSTION AIR PRESSURE SWITCH NOTE - Each furnace model uses a unique CAI. Refer to Lennox Repair Parts listing for correct inducer for replace- ment. The combustion air inducer is installed on the cold end header box. The cold end header box is a single piece made of hard plastic.
  • 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 15 and use the provided fittings and tubing to follow the steps a. Take one reading immediately after start-up. below.

  • Page 21: Installation

    II-PLACEMENT AND INSTALLATION TABLE 11 Pipe & Fittings Specifications 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)
  • Page 22 TABLE 12 OUTDOOR TERMINATION USAGE* STANDARD CONCENTRIC Wall Kit 1-1.2 inch 2 inch 3 inch Flush Mount Vent Pipe Dia. 2 inch 3 inch Input Size Field 71M80 (US) 69M29 (US) 60L46 (US) 51W11 (US) Fabricated 22G44 (US) 44J40 (US) 444W92 (CA) 444W92 (CA) 444W93 (CA)
  • Page 23 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 24 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 25 Intake or exhaust? FIGURE 18 NOTE - Lennox offers a glueless vent adapter kit 17H92 How many elbows? as an option for exhaust exiting at the furnace top cap Count all elbows inside coupling.
  • 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 Standard Termination at Elevation 0 - 4500 ft No Of 1-1/2”...
  • Page 27 TABLE 14 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 No Of 1-1/2”...
  • 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 2” EXHAUST EXHAUST INTAKE INTAKE 2” 2” 2” 2” 2” 3” 3” 045/070 Only 1−1/2” TRANSITION Exhaust 2” 6” Min Exhaust DO NOT transition from larger to smaller DO NOT transition pipe in horizontal runs from smaller to larger...
  • Page 30 Intake Piping Follow the next two steps when installing the unit in Non- Direct Vent applications where combustion air is taken The ML296UHV furnace may be installed in either direct from indoors or ventilated attic or crawlspace and flue vent or non-direct vent applications. In non-direct vent ap- gases are discharged outdoors.
  • 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 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 33 ‡ 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 ‡ 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 34...
  • Page 35 Details of Intake and Exhaust Piping Terminations for 3”(76mm) MAX. Inches(mm) Direct Vent Installations NOTE - In Direct Vent installations, combustion air is taken UNCONDITIONED from outdoors and flue gases are discharged to outdoors. ATTIC SPACE 8” (203mm) MIN NOTE - Flue gas may be slightly acidic and may adverse- 12”...
  • Page 36 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 FIELD-PROVIDED Accelerator not required REDUCER MAY BE one bracket must be used within 6” from the top of for 3”...
  • Page 37 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 38 KIT 15Z70 multiple furnaces must meet local codes. (CANADA) Crawl Space and Extended Horizontal Venting Lennox provides kit 51W18 to install 2” or 3” PVC exhaust FIGURE 40 piping through the floor joists and into the crawl space. See FIGURE 40.
  • Page 39 Condensate Piping CONDENSATE TRAP AND PLUG LOCATIONS This unit is designed for either right- or left-side exit of (Unit shown in upflow position) Trap condensate piping in upflow applications. In horizontal (same on applications, the condensate trap must extend below the right side) unit.
  • Page 40 Heating cable kit is avail- (Unit shown in upflow position with remote trap) able 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.
  • Page 41 IMPORTANT Furnace with Evaporator Coil Using a Common Drain When combining the furnace and evaporator coil drains together, the A/C condensate drain outlet Evaporator drain must be vented to relieve pressure in order for the line required furnace pressure switch to operate properly. (Trap at coil is optional) Condensate Trap With Optional Overflow Switch From Evaporator Coil...
  • 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: Start Up

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

  • Page 44: Heating System Service Checks

    IV-HEATING SYSTEM SERVICE CHECKS It is available through Lennox under part number 31B2001. See Corp. 8411-L10, for further details. A-CSA Certification Do not use matches, candles, flame or any other source of ignition to check for gas leaks. All units are CSA design certified without modifications.
  • Page 45 NOTE- To obtain accurate reading, shut off all other gas G- Proper Combustion appliances connected to meter. Furnace should operate minimum 15 minutes with correct TABLE 18 manifold pressure and gas flow rate before checking com- bustion. See sections E- and F-. Take combustion sam- GAS METER CLOCKING CHART ple 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 A poorly grounded furnace can contribute to premature control. See FIGURE 52. This voltage should be in ignitor failure.

  • Page 47: Typical Operating Characteristics

    V-TYPICAL OPERATING CHARACTERISTICS For heating speed (second stage heat speed) external static pressure drop must not be more than A-Blower Operation and Adjustment 0.8” W.C. For cooling speed (second stage cool speed) external static pressure drop must not be 1 - Blower operation is dependent on thermostat control more than 1.0”...
  • Page 48 1 when disas- specifications provided by the filter manufacturer sembling unit. Use papers or protective covering in front of against the data given in the appropriate Lennox furnace while removing heat exchanger assembly. Product Specifications bulletin.
  • Page 49 15 - Disconnect the condensate drain line. 40 - Reinstall gas valve manifold assembly. Reconnect gas supply line to gas valve. 16 - Remove cold end header box. 41 - Reconnect the combustion air intake pipe. 17 - Remove electrical junction box from the side of the furnace.

  • Page 50: Wiring And Sequence Of Operation

    VII- Wiring and Sequence of Operation ML296UHV Schematic Wiring Diagram Page 50...
  • Page 51 Heating Cooling On a call for heat from the room thermostat, the control The unit is set up at the factory for single stage cooling. board performs a 1 second self check. Upon confirma- For two stage cooling operation, clip the jumper wire lo- tion that the pressure switch contacts are in an open posi- cated between the Y to Y2 terminals on the integrated ig- tion, the control energizes the combustion blower on high...

This manual is also suitable for:

Ml296uhvx seriesMl296uh045xv36bMl296uh070xv36bMl296uh090xv48cMl296uh110xv60cMl296dfv(x) series

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