Lennox LGM Series Unit Information
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S e r v i c e L i t e r a t u r e
LGM036U, 048U, 060U, and 074U are ultra high efficien-
cy gas packaged units equipped with variable speed di-
rect drive blowers, an inverter-driven variable speed com-
pressor, and a variable speed outdoor fan.
LGM036 units are available in 65,000 to 108,000 Btuh
(19 to 31 kW) heating inputs. LGM048, 060 and 074 units
are available in 65,000 to 150,000 Btuh (19 to 43.9 kW)
heating inputs. Gas heat sections are designed with alu-
minized (stainless optional) steel tube heat exchangers.
Cooling capacities range from 3 to 6 tons (7 to 21kW).
Information contained in this manual is intended for use
by qualified service technicians only. All specifications are
subject to change. Procedures outlined in this manual are
presented as a recommendation only and do not super-
sede or replace local or state codes.
If the unit must be lifted for service, rig unit by attaching
four cables to the holes located in the unit base rail (two
holes at each corner). Refer to the installation instructions
for the proper rigging technique.
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.
WARNING
installation,
Improper
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.
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 disconnect
switch(es). Unit may have multiple power
supplies.
UNIT INFORMATION
UNIT INFORMATION
Ultra High Efficiency LGM036U through 074U
adjustment,
alteration,
100038
02/2022
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
Electrostatic
electronic components. Take precautions
to neutralize electrostatic charge by
touching your hand and tools to metal
prior to handling the control.
Options . . . . . . . . . . . . . . . . . . . . . . . Page 2
Specifications . . . . . . . . . . . . . . . . . . Page 5
High Altitude . . . . . . . . . . . . . . . . . . . Page 6
Blower Data . . . . . . . . . . . . . . . . . . . Page 7
Electrical Data . . . . . . . . . . . . . . . . Page 12
I Unit Components . . . . . . . . . . . . . Page 15
III Start Up Operation . . . . . . . . . . . Page 32
IV Charging . . . . . . . . . . . . . . . . . . . Page 33
V System Service Checks . . . . . . . Page 34
VI Maintenance . . . . . . . . . . . . . . . . Page 36
VII Accessories . . . . . . . . . . . . . . . . Page 38
VIII Diagrams . . . . . . . . . . . . . . . . . . Page 47
Page 1
LGM SERIES
3 to 6 ton
CAUTION
discharge

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Summary of Contents for Lennox LGM Series

  • Page 1: Table Of Contents

    UNIT INFORMATION UNIT INFORMATION LGM SERIES 3 to 6 ton 100038 S e r v i c e L i t e r a t u r e 02/2022 Ultra High Efficiency LGM036U through 074U LGM036U, 048U, 060U, and 074U are ultra high efficien-...
  • Page 2: Options

    DirectPlus™ Direct Drive ECM Blower System with VAV Factory CABINET 13T03 Combination Coil/Hail Guards Corrosion Protection (indoor coil / outdoor coil) Factory CONTROLS Commercial Controls 54W27 Lennox CORE Control System - LonTalk Module ® ® CPC Einstein Integration Factory Novar Factory ®...
  • Page 3 O PTIONS / AC C ESSORIES Unit Model Number Catalog Item Number ECONOMIZER High Performance Economizer With Outdoor Air Hood (Sensible Control) (Approved for California Title 24 Building Standards / AMCA Class 1A Certified) High Performance Economizer - Includes Barometric Relief Dampers and Combination Hood 20H48 High Performance Economizer - No Exhaust Option Factory...
  • Page 4 O PTIONS / AC C ESSORIES Unit Model Number Catalog Item Number INDOOR AIR QUALITY Air Filters Healthy Climate High Efficiency Air Filters MERV 8 (Order 4) 54W21 ® 20 x 20 x 2 in. MERV 13 (Order 4) 52W39 MERV 16 (Order 4) 21U40 44N60...
  • Page 5: Specifications

    SP ECIF ICATIONS U NIT General Data Nominal Tonnage 3 Ton 4 Ton 5 Ton 6 Ton Efficiency Type Ultra-High Ultra-High Ultra-High Ultra-High Model Number LGM036U4E LGM048U4E LGM060U4E LGM074U4E Blower Type DirectPlus™ DirectPlus™ DirectPlus™ DirectPlus™ ECM Direct Drive ECM Direct Drive ECM Direct Drive ECM Direct Drive with MSAV...
  • Page 6: High Altitude

    SP ECIF ICATIONS G A S HEAT Model No. 036, 048 036, 048 060, 074 060, 074 060, 074 Heat Input Type Standard (2 Stage) Medium (2 Stage) High (2 Stage) Input 1st Stage 53,000 81,000 113,000 Btuh 2nd Stage 65,000 108,000 150,000...
  • Page 7: Blower Data

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  • Page 11 BLO WER DATA FACTORY INSTALLED OPTIONS/FIELD INSTALLED ACCESSORY AIR RESISTANCE - in. w.g. Wet Indoor Coil Gas Heating Filters Humiditrol ™ Volume Economizer Medium Reheat Coil 036, 048 060, 074 High Heat MERV 8 MERV 13 MERV 16 Heat 0.01 - - - - - - 0.02...
  • Page 12: Electrical Data

    ELECTRIC AL DATA 3 TO N Model No. LGM036U4E / LGM036U4P Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph Compressor Rated Load Amps Outdoor Fan Full Load Amps Motor Power Exhaust Full Load Amps (1) 0.33 HP Service Outlet 115V GFI (amps) Indoor Blower Horsepower Motor...
  • Page 13 ELECTRIC AL DATA 5 TO N Model No. LGM060U4E / LGM060U4P Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph Compressor Rated Load Amps 14.6 Outdoor Fan Full Load Amps Motor Power Exhaust Full Load Amps (1) 0.33 HP Service Outlet 115V GFI (amps) Indoor Blower Horsepower Motor...
  • Page 14 LGM PARTS ARRANGEMENT BLOWER REHEAT COIL EVAPORATOR (DIRECT DRIVE) (OPTIONAL) COIL CONDENSER FILTERS (4) 20 X 20 X 2” COIL GUARDS (OPTIONAL) ECONOMIZER (OPTIONAL) 8.8.8.8 CONDENSER COIL CONDENSATE DRAIN COMBUSTION AIR INDUCER UNIT BURNERS GAS VALVE IGNITON CONTROL CONTROLLER COMPRESSOR FIGURE 1 LGM HINGED CONTROL PANEL K191...
  • Page 15: I Unit Components

    CORE Unit Controller (A55) Wireless Control (W4) J384 J385 J386 J387 J388 J389 J390 J391 J392 J393 J394 J383 J395 J382 J381 J358 4−Character Seven P2 Expansion Segment LED Card Connection White Push (C4) Button J380 MODBUS J413 Black Push 24VAC 24VAC J379...
  • Page 16 B-Cooling Components Attention! All units use a single cooling circuit consisting of a variable Use this QR code to download the mobile speed compressor, fin/tube condenser coil and evapora- service app. Follow the prompts to pair the tor coil. See figure 5. All units use one draw-through type condenser fan and a single direct drive blower.
  • Page 17 PLUMBING AND COMPRESSOR PROTECTION COMPONENTS CONDENSER COIL EVAPORATOR COIL EXPANSION DRIER VALVE INDOOR BLOWER SECTION RETURN AIR SECTION HEAT SECTION COMPRESSOR FIGURE 5 4-Thermistors Each thermistor must be specifically placed for proper unit operation and to initiate valid alarms. See table 1 for prop- Units are equipped with four factory-installed thermistors er locations.
  • Page 18 THERMISTOR LOCATION RT42 & 46 036 & 048 THREE-ROW EVAPORATOR COIL (VIEW FROM FRONT SIDE OF UNIT) RT46 CLAMP THERMISTOR TO BARE COPPER; TOR SLEEVE TOR TUBE DETAILS NOT TO SCALE TXV BULB RT42 SUCTION LINE FIGURE 6 Page 18...
  • Page 19 THERMISTOR LOCATION RT42 & 46 060U & 074 FOUR-ROW EVAPORATOR COIL (VIEW FROM FRONT SIDE OF UNIT) RT46 CLAMP THERMISTOR TO BARE COPPER; NOT THE DISTRIBUTOR SLEEVE DISTRIBUTOR TUBE DETAILS NOT TO SCALE TXV BULB RT42 SUCTION LINE FIGURE 7 Page 19...
  • Page 20 WARNING THERMISTOR LOCATION RT44 & RT48 036-048 CONDENSER COIL Electrical shock hazard. Compressor must be (VIEW FROM FRONT SIDE OF UNIT) grounded. Do not operate without protective cover RT48 over terminals. Disconnect power before removing protective cover. Discharge capacitors before servicing unit.
  • Page 21 COMPRESSOR DIAGNOSTICS Motor Winding Resistance at 77°F (+/-7%) Unit Size 0.64 0.63 0.63 0.70 0.70 0.70 060/074 0.62 0.62 0.62 FIGURE 10 Page 21...
  • Page 22 6-Compressor Inverter A192 a MODBUS protocol. Inverter status and diagnostics are continuously monitored and reported to the Unit Controller WARNING such as: -Improper Unit Controller input voltage compared to unit Electrical Hazard model number High Voltage -High input voltage Wait 7 Minutes -Low input voltage Electrical components may hold charge.
  • Page 23 TABLE 2 INVERTER-RELATED ALARMS ALARM DISPLAY MESSAGE EVENT ACTION CODE Possible alarming values for Prodigy Alarm 187 are: 12 - High compressor input current 13 - High heat sink temperature 14 - High PFC input current Alarm might be caused by outdoor fan abnormal operation, high ambient conditions, dirty outdoor coil, INVERTER LOW LEVEL refrigerant overcharge, or a blocked heat sink.
  • Page 24 INVERTER WIRE ROUTING TRANSFORMER A192 INVERTER 208/230V INVERTER BOARD SHOWN FILTER BOARD W V U High voltage enters the filter board here. High voltage enters the compressor here. COMPRESSOR REACTOR FIGURE 12 INVERTER HEAT SINK TOP VIEW CONDENSER SECTION HEAT SINK DIVISION PANEL BETWEEN COMPRESSOR CONTROLS /...
  • Page 25 C-GAS HEAT COMPONENTS At the start of the ignition sequence, the adjustable 40 sec- ond (default) indoor blower delay period begins. Sparking LGM048U, 060U, and 074U are available with two stages stops immediately after flame is sensed or at the end of of gas heat.
  • Page 26 3-Heat Exchanger Figure 15 Burners The LGM units use aluminized steel inshot burners with All units use inshot burners. Burners are factory set and tubular aluminized (stainless is optional) steel heat ex- do not require adjustment. A peep hole with cover is fur- changers and redundant gas valve.
  • Page 27 6-Combustion Air Prove Switch S18 BURNER ORIENTATION Prove switch S18 is a SPST N.O. switch located to the right of the induced draft assembly. See figure 18. S18 150,000 BTUH - 7 BURNERS monitors combustion air inducer operation. Switch S18 is wired to A3 ignition controller which checks its status upon a call for heating.
  • Page 28 8-Combustion Air Inducer B6 TABLE 4 Combustion air inducers provide air to the corresponding Operating Pressure (outlet) Factory Setting “W.C burners while clearing the combustion chamber of ex- Natural haust gases. The inducer begins operating immediately High High upon receiving a thermostat demand and is de-energized when thermostat demand is satisfied.
  • Page 29 11-Flame Sensor Figure 20 IMPORTANT The flame sensor is mounted through a hole in the burn- Three phase scroll compressors must be phased er support and the tip protrudes into the flame envelope sequentially for correct compressor and blower of the appropriate burner. See figure 17 for location. The rotation.
  • Page 30 LOCATION OF STATIC PRESSURE READINGS INSTALLATIONS WITH DUCTWORK INSTALLATIONS WITH CEILING DIFFUSERS ROOFTOP UNIT ROOFTOP UNIT RETURN AIR READING LOCATION RETURN AIR READING LOCATION SUPPLY SUPPLY TURN TURN FIRST BRANCH OFF OF MAIN RUN MAIN DUCT RUN SUPPLY AIR SUPPLY AIR READING READING DIFFUSER...
  • Page 31 C-Adjusting Unit CFM Blower calibration is required only on units that are newly installed or if there is a change in the duct work or air filters The supply CFM can be adjusted by changing Unit Con- after installation. Use the mobile service app to navigate troller settings.
  • Page 32: Placement And Installation

    II-PLACEMENT AND INSTALLATION CAUTION Make sure the unit is installed in accordance with the in- SMOKE POTENTIAL stallation instructions and all applicable codes. See acces- The heat exchanger in this unit could be a source sories section for conditions requiring use of the optional of smoke on initial firing.
  • Page 33: Charging

    Turning Off Gas to Unit If weighing facilities are not available, or to check the charge, use the following procedure: 1 - If using an electromechanical thermostat, set to the 1 - Attach gauge manifolds and operate unit in cooling lowest setting.
  • Page 34: System Service Checks

    TABLE 6 TABLE 10 581009-01 SUBCOOLING TEMPERATURE LG/LC 036SU NORMAL OPERATING PRESSURES Unit Liquid Saturated Temp. Minus Outdoor Coil Discharge Suction + 5 Liquid Temperature Entering Air Temp +10 psig psig 036U 11°F + 1 (6.0°C + 0.5) 048U 11.5°F + 1 (6.4°C + 0.5) 060U 13.5°F + 1 (7.5°C + 0.5) 074U...
  • Page 35 When checking piping connection for gas leaks, use the The manifold pressure is factory set and should not re- preferred means. Common kitchen detergents can cause quire adjustment. See table 4. If manifold pressure is in- harmful corrosion on various metals used in gas piping. correct and no other source of improper manifold pressure The use of specialty Gas Leak Detector is strongly rec- can be found, the valve must be replaced.
  • Page 36: Maintenance

    B-Cooling System Service Checks TABLE 11 LGM units are factory charged and require no further ad- Input Rate Seconds Natuarl Seconds LP/Propane justment; 65,000 however, charge should be checked periodically using the 105,000 approach method. The approach method compares actual 150,000 liquid temperature with the outdoor ambient temperature.
  • Page 37 C-Burners 5 - Clean inducer wheel blades with a small brush and wipe off any dust from housing. Take care not to Periodically examine burner flames for proper appearance damage exposed fan blades. Clean accumulated during the heating season. Before each heating season dust from front of flue box cover.
  • Page 38: Accessories

    VII-ACCESSORIES ASSEMBLED ROOF MOUNTING FRAME The accessories section describes the application of most of the optional accessories which can be factory- or field-installed to the LGM units. A-C1/T1CURB When installing the LGM units on a combustible surface for downflow discharge applications, the C1/T1CURB 8 inch, 14-inch, 18 inch or 24-inch height roof mounting frame is used.
  • Page 39 MOTORIZED OUTDOOR AIR DAMPER Sensors Units are equipped with the following factory-installed, EC Title 24 approved sensors: RT17 - Outside Air Temperature RT16 - Return Air Temperature RT6 - Discharge Air Temperature See figure 33 for sensor location. Optional field-provided sensors may be used instead of unit sensors to determine whether outdoor air is suitable for free cooling.
  • Page 40 ECONOMIZER ECONOMIZER (STANDARD ECONOMIZER SHOWN) DAMPER MOTOR UNIT SMOKE DETECTOR (WHEN EQUIPPED) A2 SENSOR (REMOTE FOR USE WITH DDC CONTROLLED UNITS) RT16 SENSOR RETURN AIR OPENING FIGURE 32 SENSOR LOCATION RT17 OUTDOOR AIR SENSOR (SECURED TO INSIDE OF CORNER MULLION) RT16 RETURN AIR SENSOR...
  • Page 41 HORIZONTAL AIRFLOW DUCT TRANSITION DUCT BACK INLET OF UNIT SUPPLY DO NOT ATTACH RETURN AIR DUCTWORK HERE OPTIONAL GED RETURN DAMPER AND HOOD FIGURE 34 TABLE 12 ECONOMIZER MODES AND SETPOINT Free| Free Field- Dampers will modulate to 55°F discharge air (RT6) when Permitted Cooling Cooling...
  • Page 42 Outdoor Air Damper and Economizer Operation F-Power Exhaust Relay K65 (power exhaust units) DIRECT DRIVE DRIVE SYSTEM OPERATION: Power exhaust relay K65 is a DPDT relay with a 24VAC coil. K65 is used in all LGM units equipped with the op- Note: Direct drive units feature ECM condenser fans that tional power exhaust dampers.
  • Page 43 J-Needlepoint Bipolar Ionizer (Optional) REMOVE IONIZER The optional, brush-type ionizer produces positive and RETAIN THE SCREW TO SECURE THE negative ions to clean air and reduce airborne contami- BACK SIDE OF THE IONIZER BRACKET nants. The ionizer was designed to be low maintenance. The device should be checked semi-annually to confirm REMOVE THE TOP RIGHT SCREW SECURING THE BACK OF THE...
  • Page 44 I-Optional Cold Weather Kit M-Drain Pan Overflow Switch S149 (optional) An electric heater is available to automatically con- The overflow switch is used to interrupt cooling operation trol the minimum temperature in the gas burner com- when excessive condensate collects in the drain pan. partment.
  • Page 45 Check-Out B-Thermostat Mode With Zone RH Sensor Test reheat operation using the following procedure. No Y1 demand but a call for dehumidification. 1 - Make sure reheat is wired as shown in wiring Compressor modulates based on zone relative humidity, section.
  • Page 46 REHEAT MODE REFRIGERANT ROUTING RETURN OUTDOOR EVAPORATOR EXPANSION COIL VALVE REHEAT COIL SUPPLY COMPRESSOR CONDENSER COIL CHECK VALVE REHEAT VALVE FIGURE 38 COOLING MODE REFRIGERANT ROUTING RETURN OUTDOOR EVAPORATOR EXPANSION COIL VALVE REHEAT COIL SUPPLY COMPRESSOR CONDENSER COIL CHECK VALVE REHEAT VALVE FIGURE 39...
  • Page 47: Diagrams

    VIII-Wiring Diagrams and Sequence of Operation LGM/LCM036/074 J Voltage TO A3 ON SHIELDED GAS UNITS. CABLE REF A−SECT LOC CC01−02 RED−BLK 24VAC RT17 SHIELDED HPSW1 CABLE RED−BLK RED−BLK 24VAC RT48 HTSW1 24VAC RED−BLK 5VDC RT46 LPSW1 RED−BLK RT42 RED−BLK RT44 MAIN CTRL J389 J390...
  • Page 48 LGM/LCM036/074 G Voltage TO A3 ON SHIELDED GAS UNITS. CABLE REF A−SECT LOC CC01−02 RED−BLK 24VAC RT17 SHIELDED HPSW1 CABLE RED−BLK RED−BLK 24VAC RT48 HTSW1 24VAC RED−BLK 5VDC RT46 LPSW1 RED−BLK RT42 RED−BLK RT44 MAIN CTRL J394 J378 J390 J390 J389 J390 J392...
  • Page 49 LGM/LCM036/074 Y Voltage SHIELDED TO A3 ON CABLE GAS UNITS. REF A−SECT RED−BLK LOC CC01−02 24VAC RT17 SHIELDED HPSW1 CABLE RED−BLK RED−BLK 24VAC HTSW1 RT48 ODF1 24VAC RED−BLK RT46 LPSW1 RT42 RED−BLK RED−BLK RT44 MAIN CTRL J389 J390 J392 J395 J394 J378 J390...
  • Page 50 Cooling Sequence of Operation Power: 1 - Line voltage energizes transformer T1. T1 provides 24VAC power to the A55 Unit Controller. A55 provides 24VAC to the unit cooling, heating and blower controls. 2 - Line voltage provides voltage to compressor crankcase heater relay K191-1 N.C. contacts, compressor contactor K1, blower motor B3, and outdoor fan motor B4 (on G volt units line voltage is supplied to two fuses F27, transformer T4, blower motor B3, and outdoor fan motor B4).
  • Page 51 TO K1−L2 BURNER TO K1−L1 OR F10 T1 LOAD P228 P228 LP CONVERSION Model: LGM Series RTU − Gas Heat HEATI N G COOLI N G COOLI N G ACCS ACCS Input Heat Capacity 70k − 150k Btuh SECTI O N...
  • Page 52 TWO-STAGE GAS HEAT SEQUENCE OF OPERATION First Stage Heat: 1 - The thermostat initiates W1 heating demand. 2 - 24VAC is routed to controller A3. A3 proves N.C. primary limit S10.. 3 - Control board A3 energizes combustion air inducer B6. After B6 has reached full speed, the combustion air blower proving switch S18 contacts close.
  • Page 53 TO PROVIDE SUPERMARKET REHEAT SCHEME USE S86 DEHUMIDISTAT AND K55 SUPERMARKET REHEAT DENOTES OPTIONAL COMPONENTS AND WIRING CLASS II FIELD WIRING Model: LCM, LGM Series RTU HEATI N G COOLI N G COOLI N G ACCS ACCS Thermostat SECTI O N...
  • Page 54 RANGE 2−10 VDC NF24−SR AF24−SR RANGE 2−10 VDC P104 P105 RT16 J104 J105 P384 J384 MAIN CTRL Model: LCM, LGM Series RTU ACCS ACCS Economizer & Motorized OAD WIRING DIAGRAM FLOW Voltage: All Voltages 538072−01 Supersedes: N/A Form No: Rev:0 Page 54...

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