Lennox ML296UHVK Series Unit Information

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S e r v i c e L i t e r a t u r e

ML296UHVK(X) series units are 90% efficiency gas fur-

naces used for downflow applications only, manufactured

with Lennox Duralok heat exchangers formed of alumi-

nized steel. ML296UHVK(X) units are available in heating

capacities of 44,000 to 110,000 Btuh and cooling appli-

cations 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-

HVK(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

WARNING

This furnace is equipped with an ignition control

factory enabled for use with Lennox A2L refrigerant

systems.

Disabling

functionality on A2L system is prohibited by safety

codes. Refer to furnace installation instructions for

non-A2L and non-Lennox refrigerant system setup.

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 2

Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 4

I Unit Components . . . . . . . . . . . . . . . . . . . . . . . . Page 7

II Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 21

III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 43

IV Heating System Service Checks

V Typical Operating Characteristics

VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . Page 47

VII Low GWP Application . . . . . . . . . . . . . . . . . . . . . Page 50

VIII Diagram and DIP Switch Settings. . . . . . . . . . .Page 53

UNIT INFORMATION

ML296UHVK(X) With R-454B SERIES UNITS

the

refrigerant

detection

. . . . . . . . . Page 44

. . . . . . . . . Page 47

100179

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.

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.

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

Electrostatic discharge can affect electronic

components. Take precautions to neutralize

electrostatic charge by touching your hand

and tools to metal prior to handling the

control.

Page 1

ML296UHVK(X)

C C C C

I I I I

WARNING

adjustment,

CAUTION

alteration,

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Summary of Contents for Lennox ML296UHVK Series

Page 1: Table Of Contents
ML296UHVK(X) series units are 90% efficiency gas fur- naces used for downflow applications only, manufactured with Lennox Duralok heat exchangers formed of alumi- nized steel. ML296UHVK(X) units are available in heating capacities of 44,000 to 110,000 Btuh and cooling appli- cations up to 5 tons.
Page 2: Specifications
SP ECIFI CAT IONS Model No. ML296UH045XV36BK ML296UH070XV36BK 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 Accessories
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. ML296UH070XV36BK BLOWER PERFORMANCE (less filter) BOTTOM RETURN AIR, SINGLE SIDE RETURN AIR OR SIDE RETURN AIR WITH OPTIONAL RETURN AIR BASE 0 through 0.8 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 380 cfm. ML296UH110XV60CK BLOWER PERFORMANCE (less filter)
Page 6: Parts Identification
PARTS IDENTIFICATION Burner Box Assembly Field Make Up Box Heat Exchanger Gas Valve Primary Limit 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 6...
Page 7: I Unit Components
I-UNIT COMPONENTS 3. Ignition 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 8 Two Stage, Variable Speed, Non-Communicating 107629-XX FIGURE 3 Page 8...
Page 9 TABLE 4 Low GWP Test Page 9...
Page 10: Integrated Control
Integrated Control Switch Settings Bank Of Eight DIP Switches SW2 Conventional Thermostat Switches 1 and 2 - Cooling Mode Blower Speed - The unit is shipped from the factory with the dip switches po- ML296UHVK units are equipped with a two-stage, vari- sitioned for high speed (4) indoor blower motor operation able speed integrated control.
Page 11 TABLE 9 Heat Speed DIP Switch 7 DIP Switch 8 Medium High (Default) High Medium Low TABLE 10 Allowable Heating Speeds ML296UHVK Speed Adjust Setting “D” Setting “C” Setting “B” Setting “A” Model +10% Allowed 045XV36B Norm Factory Setting Allowed -10% Allowed +10%...
Page 12 Accessory Terminals On-Board Links One line voltage “ACC” 1/4” spade terminal is provided on WARNING the furnace integrated control. Refer to FIGURE 60 for integrated control configuration. This terminal is energized when the indoor blower is operating.Any accessory rated Carefully review all configuration information provided. up to one amp can be connected to this terminal with the Failure to properly set DIP switches, jumpers and on- neutral leg of the circuit being connected to one of the pro-...
Page 13 B- Blower Compartment GenTeq BLOWER MOTOR B3 MOTOR CONTROLLER FIGURE 5 NIDEC BLOWER MOTOR B3 Power Choke Blower Motor (5 Ton Only) (B3) MOTOR 16X4 Pin Wire Box (May be located To Remove Blower From Unit: Remove Bolts and on the blower Wiring Jackplugs.
Page 14: Motor Start-Up
TABLE 11 Nidec 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 15 2. 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...
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
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 10 Page 17...
Page 18 Ignitor Check Test 1 Check ignitor circuit for correct resistance. Remove HSI/CAI 5-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
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 13 and use the provided fittings and tubing to follow the steps a. Take one reading immediately after start-up. below.
Page 21: Ii-Placement And Installation
II-PLACEMENT AND INSTALLATION TABLE 17 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: Danger Of Explosion
TABLE 18 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: 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 24: Vent Piping Guidelines
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 16 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 20 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 21 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 ML296UHVK 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 22 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 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 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. locally adopted installation codes.
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 38 piping through the floor joists and into the crawl space. See FIGURE 38.
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 24 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: Furnace Status
I- Proper Ground and Voltage 2 - In addition, measure the AC voltage from Line Hot to Line Neutral (spade terminals) on the integrated NOTE - Terminal locations will varie between controls. control. See FIGURE 50. This voltage should be in Use figure 51 as a reference.
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: Low Gwp Application
VII-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 51 FURNACE CONTROL BOARD LOW GWP MODES OF 2. The furnace control board activates the blower (high OPERATION speed). The blower purges refrigerant from the cabinet, plenum, and ductwork. The modes of operation for the furnace control board are Initializing, Normal, Leak Detected, and Fault. 3.
Page 52: Start-Up Procedure
LGWP TEST BUTTON FUNCTIONALITY External Alarm (For applications with external alarms wired directly to the The furnace control board is equipped with a Test/Reset furnace control board) push button. The Test button can be used to perform sev- The furnace control board triggers the external alarm sys- eral functions, depending on the mode of operation of the tem when it enters Leak Detected mode.
Page 53: Diagram And Dip Switch Settings
VIII- Unit Diagram and DIP Switch Settings Page 53...
Page 54: Sequence Of Operation
SEQUENCE OF OPERATION WARNING Heating The system must not be in either the passive or active On a call for heat from the room thermostat, the control dehumidification mode when charging a cooling system. board performs a 1 second self check. Upon confirma- tion that the pressure switch contacts are in an open posi- Cooling tion, the control energizes the combustion blower on high...
Page 55: Dip Switch Settings
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 TERM. STRIP UNIT NOTE - Use DIP switch 2 to set second-stage heat ON delay.
Page 56 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 (M30 T-stat) T'STAT TERM. STRIP UNIT CUT ON-BOARD LINK W915 2 STAGE COMPR...
Page 57 DIP Switch Settings and On-Board Links DIP Switch 1 Wiring Connections Thermostat On Board Links Must Be Cut To Select Thermostat Heating System Options Stages Dual Fuel FURNACE HEAT PUMP T'STAT TERM. STRIP Single Stage Heat Pump CUT ON-BOARD LINK (M30 T-stat) W951 67M41*...
Page 58 DIP Switch Settings and On-Board Links DIP Switch 1 Wiring Connections Thermostat On Board Links Must Be Cut To Select Thermostat Heating System Options Stages Dual Fuel FURNACE HEAT PUMP T'STAT TERM. STRIP Single Stage Heat Pump CUT ON-BOARD LINK (M30 T-stat) W951 67M41*...

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