Lennox ML193UHE Series Manual
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Lennox ML193UHE Series Manual

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Service Literature
ML193UHE series units are high-efficiency gas fur­
naces manufactured with Lennox DuralokPlust alumi­
nized steel clamshell-type heat exchangers, with a stainless
steel condensing coil. ML193UHE units are available in
heating input capacities of 30,000 to 110,000 Btuh (8.8 to
32.2 kW) and cooling applications from 2 through 5 tons (7.0
through 17.6 kW). Refer to Engineering Handbook for proper
sizing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LPG operation. All ML193UHE
units are equipped with a hot surface ignition system. The
Gas Valve is redundant to assure safety shut-off as re­
quired by C.S.A.
The heat exchanger, burners and manifold assembly can be
removed for inspection and service. The maintenance section
gives a detailed description on how this is done.
The ML193UHE can be "twinned" with a second unit. See
twinning kit 16W72 for information for two units to operate
as one, in a shared duct system controlled by a single ther­
mostat.
All specifications are subject to change. Procedures outlined
in this manual are presented as a recommendation only
and do not supersede or replace local or state codes.
WARNING
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon­
nect switch(es). Unit may have multiple
power supplies.

Table of Contents

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. . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Performance Data
I-Unit Components
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
II Placement and Installation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV-Heating System Service Checks
V-Typical Operating Conditions
VI-Maintenance
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VII-Sequence of Operation and Flow Charts
Corp. 1905
ML193UHE SERIES UNITS
. . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .
. . . . . .
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person­
al injury or loss of life. Installation and service must
2
be performed by a licensed professional HVAC in­
4
staller (or equivalent), service agency or the gas sup­
5
plier.
7
20
39
40
As with any mechanical equipment, contact with
44
sharp sheet metal edges can result in personal in­
45
jury. Take care while handling this equipment and
wear gloves and protective clothing.
48
Page 1
ML193UHE
WARNING
CAUTION
© 2019 Lennox Industries Inc.
Litho U.S.A.

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  • Page 1 ML193UHE Corp. 1905 Service Literature ML193UHE SERIES UNITS ML193UHE series units are high-efficiency gas fur­ naces manufactured with Lennox DuralokPlust alumi­ nized steel clamshell-type heat exchangers, with a stainless steel condensing coil. ML193UHE units are available in heating input capacities of 30,000 to 110,000 Btuh (8.8 to 32.2 kW) and cooling applications from 2 through 5 tons (7.0...
  • Page 2 SPECIFICATIONS Model No. ML193UH030XE36B ML193UH045XE36B ML193UH070XE36B ML193UH090XE36C Heating AHRI Reference No. 20256877 20256878 20256879 20256880 Performance AFUE Input - Btuh 30,000 44,000 66,000 88,000 Output - Btuh 29,000 42,000 63,000 84,000 Temperature rise range - °F 25 - 55 30 - 60 40 - 70 50 - 80 Gas Manifold Pressure (in.
  • Page 3 OPTIONAL ACCESSORIES “B” Width Models “C” Width 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 Condensate Drain Heat Cable 6 ft.
  • Page 4 BLOWER DATA ML193UH030XE36B PERFORMANCE (Less Filter) External Air Volume / Watts at Various Blower Speeds Static High Medium-High Medium Medium-Low Pressure Watts Watts Watts Watts Watts in. w.g. 0.00 1435 1170 1000 0.10 1400 1130 0.20 1360 1085 0.30 1325 1055 0.40 1300...
  • Page 5 BLOWER DATA ML193UH090XE48C PERFORMANCE (Less Filter) External Air Volume / Watts at Various Blower Speeds Static High Medium-High Medium Medium-Low Pressure Watts Watts Watts Watts Watts in. w.g. 0.00 1710 1500 1395 1315 1205 0.10 1675 1475 1365 1275 1160 0.20 1655 1460...
  • Page 6 ML193UHE PARTS IDENTIFICATION FLEXIBLE NO-HUB EXHAUST COLLAR BURNER BOX ASSEMBLY TOP CAP GAS VALVE DuralokPlus HEAT EXCHANGER ASSEMBLY COMBUSTION AIR INDUCER BURNER­ ACCESS PANEL BAG ASSEMBLIES (shipping location) PRIMARY LIMIT COLD END BLOWER­ HEADER BOX ACCESS BLOWER PANEL COMBUSTION ASSEMBLY AIR PRESSURE SWITCH CONTROL BOX...
  • Page 7 I-UNIT COMPONENTS 3. Circuit Breaker (CB8) A 24V circuit breaker is also located in the control box. The switch provides overcurrent protection to the transformer ELECTROSTATIC DISCHARGE (ESD) (T1). The breaker is rated at 3A at 32V. If the current ex­ ceeds this limit the breaker will trip and all unit operation will Precautions and Procedures shutdown.
  • Page 8 TABLE 3 1/4” QUICK CONNECT TERMINALS 120HUM Humidifier 120VAC LINE 120VAC XFMR Transformer 120VAC CIRC Indoor blower 120VAC Indoor air quality accessory 120VAC NEUTRALS Common 120VAC HUM24 Humidifier 24VAC 3/16” QUICK CONNECT TERMINALS COOL Cooling tap 24VAC HEAT Heating tap 24VAC Continuous blower 24 VAC PARK (no power) Park terminal for unused speed taps...
  • Page 9 Heating Fan Off Time INTEGRATED CONTROL Fan off time (time that the blower operates after the heat (Automatic Hot Surface Ignition System) demand has been satisfied) can be adjusted by moving the jumper to a different setting. The unit is shipped with a fac­ tory fan off setting of 90 seconds.
  • Page 10 ML193UHE Burner Box Assembly Burner Assembly Rollout Switch(s) Flame Sensor Ignitor Gas Valve Burner Box Front FIGURE 5 B-Heating Components 2. Heat Exchanger (Figure 6) ML193UHE units use an aluminized steel primary and Combustion air inducer (B6), primary limit control (S10), ig­ stainless steel secondary heat exchanger assembly.
  • Page 11 5. Flame Sensor (Figure 5) Primary Limit Location and Heat Exchanger A flame sensor is located on the left side of the burner sup­ port. The sensor is mounted on the front burner box plate and the tip protrudes into the flame envelope of the left- most burner.
  • Page 12 Measuring Flame Signal (Furnace and Control Used For Reference) Flame Signal In Microamps Normal Drop Out  1.5  0.4 0.5 - 1.4 Flame Sensor Wire Remove sensor from integrated control and connect alligator clip (−) to flame sensor lead. Multi−Meter Intergrated Control...
  • Page 13 Test 1 Check ignitor circuit for correct resistance. Remove 4-pin plug from control. Check ohms reading across terminals 2 and 4. 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 14 0 - 4500 4501 - 7500 7501 - 10000 Unit Set Point “w.c. Set Point “w.c Set Point “w.c. ML193UHE series units are equipped with a differential pressure switch located on the cold end header box. The -030 -0.65 -0.60 -0.55...
  • Page 15 Measuring Pressure Differential Red and Black Tubing or Red Tubing (negative −) Black Tubing (positive +) To Cold End Header Box To Cold End Header Box Field Provided Tubing To Pressure Switch “+” High “−” Low 1 - Remove thermostat demand and allow unit to 4 - Operate unit and observe manometer reading.
  • Page 16 TABLE 7 Pressure Switch Troubleshooting Guide Problem Corrective Action Check that the pressure switch is open without the combustion air inducer operat­ Pressure switch stuck closed ing. Replace if defective. Pressure switch does not close due to Check for restricted vent. Remove all blockage. obstruction in vent pipe.
  • Page 17 C- Blower Compartment BLOWER WHEEL REPLACEMENT IMPORTANT Center Blower Wheel in Blower Housing Each blower is statically and dynamically balanced as an assembly before installation in the unit. EL196UHE units are equipped with a constant torque ECM motor. It has a DC motor coupled to an electronic control module both contained in the same motor housing.
  • Page 18 Multi−Meter (set to VAC) Multi−Meter (set to VAC) Test 1 Test 3 (if necessary) Turn on power to unit. Check for 120 volts across terminals Check for 120 volts across terminals “CIRC” and “Neutrals” “L” and “N” on input plug P48. If voltage is present continue on the integrated control.
  • Page 19 Replacing the Motor Module Motor Test 1. Disconnect electrical power to unit. 2. Remove unit access panel. 3. Unplug the two harnesses from the motor control mod­ ule. See figure 16. Unplug the Two Harness Connection TWO HARNESS FIGURE 18 CONNECTIONS TABLE 8 MOTOR...
  • Page 20 II-PLACEMENT AND INSTALLATION TABLE 9 PIPING AND FITTINGS SPECIFICATIONS Schedule 40 PVC (Pipe) D1785 Pipe & Fittings Specifications Schedule 40 PVC (Cellular Core Pipe) F891 All pipe, fittings, primer and solvent cement must conform Schedule 40 PVC (Fittings) D2466 with American National Standard Institute and the Ameri­ Schedule 40 CPVC (Pipe) F441 can Society for Testing and Materials (ANSI/ASTM) stan­...
  • Page 21 TABLE 10 OUTDOOR TERMINATION USAGE* STANDARD CONCENTRIC Flush­ Wall Kit Wall Ring Kit Mount 1-1/2 inch 2 inch 3 inch Vent 2 inch 3 inch 2 inch Pipe Input Size Field Dia. in. 51W11 71M80 69M29 Fabricated 44J40 (US) 22G44 (US) (US) (US) 60L46 (US)
  • Page 22 6. In areas where piping penetrates joists or interior walls, hole must be large enough to allow clearance on ® NOTE - Lennox has approved the use of DuraVent and Cen­ all sides of pipe through center of hole using a hanger.
  • Page 23 In some applications which permit the use of several differ­ ent sizes of vent pipe, a combination vent pipe may be Which needs used. Contact Lennox' Application Department for assis­ most elbows? tance in sizing vent pipe in these applications.
  • Page 24 TABLE 12 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 25 TYPICAL EXHAUSTAND INTAKE PIPE CONNECTIONS IN UPFLOW DIRECT OR NON-DIRECT VENT APPLICATIONS 2” 2” EXHAUST EXHAUST INTAKE INTAKE 2” 2” 2” 2” 3” 3” 030/045/070 Only 1−1/2” TRANSITION Exhaust 2” Exhaust DO NOT transition from larger to smaller DO NOT transition Exhaust pipe in horizontal runs from smaller to larger...
  • Page 26 Intake Piping TYPICAL AIR INTAKE PIPE CONNECTIONS The ML193UHE 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 27 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 and the flue gases are discharged to the out­ combustion air coming in from a space serviced by doors.
  • Page 28 TABLE 14 Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For Winter Design Temperatures Single - Stage High Efficiency Furnace Unit Input Size Winter Design Vent Pipe Temperatures °F (°C) Diameter 1-1/2 in. 32 to 21 2 in.
  • Page 29 VENT TERMINATION CLEARANCES FOR NON-DIRECT VENT INSTALLATIONS IN THE USA AND CANADA INSIDE CORNER DETAIL Fixed Operable Fixed Closed Closed Operable AREA WHERE TERMINAL AIR SUPPLY INLET VENT TERMINAL IS NOT PERMITTED US Installations Canadian Installations Clearance above grade, veranda, 12 inches (305mm) or 12 in.
  • Page 30 VENT TERMINATION CLEARANCES FOR DIRECT VENT INSTALLATIONS IN THE USA AND CANADA INSIDE CORNER DETAIL Fixed Operable Fixed Closed Closed Operable AREA WHERE TERMINAL AIR SUPPLY INLET VENT TERMINAL IS NOT PERMITTED US Installations Canadian Installations Clearance above grade, veranda, 12 inches (305mm) or 12 in.
  • Page 31 Details of Intake and Exhaust Piping Terminations for TABLE 15 EXHAUST PIPE TERMINATION SIZE REDUCTION Direct Vent Installations ML193UHE Termination NOTE - In Direct Vent installations, combustion air is tak­ MODEL Pipe Size en from outdoors and flue gases are discharged to out­ 1-1/2”...
  • Page 32 7. If intake and exhaust piping must be run up a side wall to position above snow accumulation or other ob­ structions, piping must be supported. At least one 12” EXHAUST (305mm) bracket must be used within 6” from the top of the el­ VENT 5-1/2”...
  • Page 33 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 34 3. If exhaust piping must be run up a side wall to position ML193UHE DIRECT VENT APPLICATION above snow accumulation or other obstructions, pip­ USING EXISTING CHIMNEY ing must be supported every 24 inches (610mm). STRAIGHT-CUT OR When exhaust piping must be run up an outside wall, ANGLE-CUT IN DIRECTION 3”-8”...
  • Page 35 Heating cable kit is drain together. See figures 48, 50 and 51. available from Lennox in various lengths; 6 ft. (1.8m) - kit no. 26K68 and 24 ft. (7.3m) - kit no. 26K69. Page 35...
  • Page 36 CONDENSATE TRAP LOCATIONS Condensate Trap With Optional Overflow Switch (Unit shown in upflow position with remote trap) From Evaporator Coil Horizontal Furnace4” Min. to 5” Max. above Field ProvidedVent condensate drain connection) Min. 1” Above Condensate Drain Connection 1” Min. 2”...
  • Page 37 ML193UHE with Evaporator Coil Using a Separate Drain (Unit shown in horizontal left-hand discharge position) Field Provided Vent Evaporator (4” min. to 5” max. above Coil condensate connection) 4”min 5”max 5’ max. PVC Pipe Only Condensate Drain Connection (Trap at coil is optional) *Piping from furnace and evaporator coil must Drain Pan slope down a minimum 1/4”...
  • Page 38 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 39 III-START‐UP 2 - Set the thermostat to the lowest setting. 3 - Turn off all electrical power to the unit. A-Preliminary and Seasonal Checks 4 - This furnace is equipped with an ignition device which 1 - Inspect electrical wiring, both field and factory installed automatically lights the burners.
  • Page 40 Take care to re­ Gas Leak Detector is strongly recommended. It is available place pressure tap plug. through Lennox under part number 31B2001. See Corp. 8411-L10, for further details. 6 - Start unit and perform leak check. Seal leaks if found.
  • Page 41 Negative Barbed Fitting (remove for manifold adjustment) (−) 2” Long Square Tubing (remove for manifold adjustment) Manifold Pressure Outlet Gas Valve Regulator Vent Hose (to burner box) Barbed Fitting 10” Long Square Tubing Measuring Device FIGURE 55 Page 41...
  • Page 42 E-Proper Combustion F-High Altitude NOTE - In Canada, certification for installations at eleva­ Furnace should operate minimum 15 minutes with correct tions over 4500 feet (1372 m) is the jurisdiction of local au­ manifold pressure and gas flow rate before checking com­ thorities.
  • Page 43 G- Proper Ground and Voltage 2 - In addition, measure the AC voltage from Line Hot to Line Neutral (spade terminals) on the integrated con­ WARNING trol. See figure 56. This voltage should be in the range of 97 to 132 Vac Electric Shock Hazard.
  • Page 44 V-TYPICAL OPERATING CHARACTERISTICS C-External Static Pressure 1 - Tap locations shown in figure 58.. A-Blower Operation and Adjustment1 2 - Punch a 1/4” diameter hole in supply and return air NOTE- The following is a generalized procedure and plenums. Insert manometer hose flush with inside does not apply to all thermostat controls.
  • Page 45 2 - Remove hoses from cold end header box. Twist and specifications provided by the filter manufacturer pull screens to remove. against the data given in the appropriate Lennox Product Specifications bulletin. Additional informa­ 3 - Inspect screens and rinse with tap water if needed.
  • Page 46 18 - Mark and disconnect any remaining wiring to heating Condensate Hose Screens compartment components. Disengage strain relief bushing and pull wiring and bushing through the hole in the blower deck. 19 - Remove the primary limit from the vestibule panel. 20 - Remove top cap screws to allow top cap to be tilted up­...
  • Page 47 44 - Reconnect wires to gas valve. note not to allow ignitor plate to dislodge from the as­ sembly. 45 - Replace the blower compartment access panel. 9 - Gently clean the face of the burners using the soft 46 - Refer to instruction on verifying gas and electrical con­ brush attachment on a vacuum cleaner.
  • Page 48 VII-WIRING DIAGRAM AND SEQUENCE OF OPERATION 1 - When there is a call for heat, W1 of the thermostat en­ 5 - Gas valve opens for a 4-second trial for ignition ergizes W of the furnace control with 24VAC. 6 - Flame is sensed, gas valve remains open for the heat 2 - S10 primary limit switch and S47 rollout switch are call.
  • Page 49 Sequence of Operation Flow Chart Troubleshooting: Heating Sequence of Operation HEATING SEQUENCE OF OPERATION ABNORMAL HEATING MODE NORMAL HEATING MODE POWER ON GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER DELAY OFF. CONTROL SELF-CHECK OKAY? LED SLOW FLASH (RESET CONTROL BY TURNING MAIN POWER OFF.) LED FLASHES CODE 1 - POLARITY IS POLARITY CORRECT? REVERSED.
  • Page 50 Troubleshooting: Heating Sequence of Operation (Continued) HEATING SEQUENCE CONTINUED NORMAL HEATING MODE ABNORMAL HEATING MODE 15‐SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. LED FLASHES CODE 13 - LOW LINE VOLTAGE. ONCE VOLTAGE IS ABOVE IGNITOR WARM‐UP -- 20 SECONDS. IS VOLTAGE ABOVE 70 VOLTS? 75 VOLTS, HEATING SEQUENCE RESTARTS.
  • Page 51 Troubleshooting: Cooling Sequence of Operation COOLING SEQUENCE OF OPERATION NORMAL COOLING MODE ABNORMAL COOLING MODE POWER ON IGNITION CONTROL MAIN POWER ON. LED FLASHES STEADY - CIRCUIT BOARD FAILURE CONTROL SELF DIAGNOSTIC CHECK. GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. IS CONTROL OPERATING NORMALLY? INDOOR BLOWER OFF WITH NORMAL DELAY.
  • Page 52 Troubleshooting: Continuous Fan / Accessories Sequence of Operation CONTINUOUS FAN / ACCESSORIES SEQUENCE OF OPERATION LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT FAN SPEED. EAC TERMINAL IS ENERGIZED. THERMOSTAT CALLS FOR HEAT (W).

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