Lennox LGM Series Unit Information
Lennox LGM Series Unit Information

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
Ultra High Efficiency LGM036U through 074U with R-454B
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.
False ceilings or drop ceiling may be used as a return air
plenum only if the unit being installed has a Refrigerant
Detection System installed.
All maintenance staff and others working in the local area
shall be instructed on the nature of work being carried out
with work in confined spaces being avoided.
Ensure that the area is in the open or that it is adequately
ventilated before breaking into the system or conducting
any hot work. A degree of ventilation shall continue during
the period that the work is carried out. The ventilation
should safely disperse any released refrigerant and pref-
erably expel it externally into the atmosphere.
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
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.
UNIT INFORMATION
UNIT INFORMATION
adjustment,
alteration,
100126
01/2025
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 4
Specifications . . . . . . . . . . . . . . . . . . . . Page 7
High Altitude . . . . . . . . . . . . . . . . . . . . . Page 8
Blower Data . . . . . . . . . . . . . . . . . . . . . Page 9
Electrical Data . . . . . . . . . . . . . . . . . . . Page 13
I-Unit Components . . . . . . . . . . . . . . . . Page 17
- RDS Sensors . . . . . . . . . . . . . . . . . Page 23
II-Placement and Installation . . . . . . . . . . Page 36
III-Start Up Operation . . . . . . . . . . . . . . . Page 36
IV-Charging . . . . . . . . . . . . . . . . . . . . Page 37
V-System Service Checks . . . . . . . . . . . . Page 46
VI-Maintenance . . . . . . . . . . . . . . . . . . Page 48
VII-Accessories . . . . . . . . . . . . . . . . . . Page 51
VIII-Decommissioning . . . . . . . . . . . . . . Page 60
IX-Diagrams . . . . . . . . . . . . . . . . . . . . Page 61
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 100126 S e r v i c e L i t e r a t u r e 01/2025 Ultra High Efficiency LGM036U through 074U with R-454B LGM036U, 048U, 060U, and 074U are ultra high efficien-...
  • Page 2 WARNING WARNING Only manufacturer approved auxiliary devices are •This appliance must be installed in accordance with permitted to be installed in this unit. local and national wiring regulations. •If the appliance is not fitted with an option for full WARNING disconnection from power, a means of disconnection must be incorporated in the fixed wiring in accordance If this appliance is conditioning a space with an area...
  • Page 3 A2L Refrigerant Considerations When breaking into the refrigerant circuit to make repairs – or for any other purpose – conventional procedures shall Ensure that the work area is adequately ventilated before be used. However, for flammable refrigerants it is important breaking into the system or conducting any hot work.
  • Page 4: Options

    DirectPlus™ Direct Drive ECM Blower System with VAV Factory CABINET Combination Coil/Hail Guards 13T03 Corrosion Protection (indoor coil / outdoor coil) Factory CONTROLS 54W27 Commercial Controls Lennox CORE Control System - LonTalk Module ® ® CPC Einstein Integration Factory Novar Factory ®...
  • Page 5 O PTIONS / AC C ESSORIES Size Order 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 6: Indoor Air Quality

    O PTIONS / AC C ESSORIES Size Order Item Number INDOOR AIR QUALITY Air Filters 54W21 Healthy Climate High Efficiency Air Filters MERV 8 (Order 4) ® 20 x 20 x 2 in. 52W39 MERV 13 (Order 4) MERV 16 (Order 4) 21U40 Replaceable Media Filter With Metal Mesh Frame (Order 4)
  • Page 7: Specifications

    SP ECIF ICATIONS U NIT Model LGM036U5E LGM048U5E LGM060U5E LGM074U5E Blower Type DirectPlus™ DirectPlus™ DirectPlus™ DirectPlus™ ECM Direct Drive ECM Direct Drive ECM Direct Drive ECM Direct Drive with SZVAV with SZVAV with SZVAV with SZVAV Model Number LGM036U5P LGM048U5P LGM060U5P LGM074U5P Blower Type...
  • Page 8: High Altitude

    SP ECIF ICATIONS GA S HEAT Model 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 Output 1st Stage...
  • Page 11: Blower Data

    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 BLO WER DATA CEILING DIFFUSERS AIR RESISTANCE (in. w.g.) RTD9-65S Step–Down Diffuser RTD11-95S Step–Down Diffuser FD9-65S FD11-95S Air Volume Flush Flush 2 Ends 1 Side & All Ends & 2 Ends 1 Side & All Ends & Diffuser Diffuser Open 2 Ends Open Sides Open Open...
  • Page 13: Electrical Data

    ELECTRIC AL DATA 3 TO N Model LGM036U5E / LGM036U5P Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph Compressor Rated Load Amps (Inverter) Locked Rotor Amps Outdoor Fan Full Load Amps (1 ECM) Motor Power Exhaust Full Load Amps (1) 0.33 HP Service Outlet 115V GFI (amps) Indoor Blower Horsepower...
  • Page 14 ELECTRIC AL DATA 5 TO N Model LGM060U5E / LGM060U5P Voltage - 60Hz 208/230V-3ph 460V-3ph 575V-3ph Compressor Rated Load Amps 14.6 (Inverter) Locked Rotor Amps Outdoor Fan Full Load Amps (1 ECM) Motor Power Exhaust Full Load Amps (1) 0.33 HP Service Outlet 115V GFI (amps) Indoor Blower Horsepower...
  • Page 15 FIELD WIRING NOTES • For use with copper wiring only • Field wiring not furnished • All wiring must conform to NEC or CEC and local electrical codes • For specific wiring information, please refer to the installation instructions Minimum R454B Space and CFM Requirements Minimum Airflow¹...
  • Page 16: Parts Arrangement

    PARTS ARRANGEMENT REHEAT COIL BLOWER EVAPORATOR CONDENSER (OPTIONAL) (DIRECT DRIVE) COIL FILTERS (4) 20 X 20 X 2” COIL GUARDS (OPTIONAL) ECONOMIZER (OPTIONAL) INDOOR RDS SENSOR (BEHIND EVAPORATOR COIL) CONDENSATE DRAIN CONDENSER COMBUSTION COIL BURNERS AIR INDUCER GAS VALVE COMPRESSOR RDS SENSOR UNIT (BEHIND CABINET) COMPRESSOR...
  • Page 17: 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 P2 Expansion 4−Character Seven Segment LED Card Connection White Push Button (C4) J380 MODBUS J413 Black Push 24VAC 24VAC J379...
  • Page 18 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 evaporator service app. Follow the prompts to pair the coil. See FIGURE 5. All units use one draw-through type condenser fan and a single direct drive blower.
  • Page 19 PLUMBING AND COMPRESSOR PROTECTION COMPONENTS EVAPORATOR COIL CONDENSER COIL EXPANSION VALVE DRIER 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 Units are equipped with four factory-installed thermistors proper locations.
  • Page 20 LGM/LCM/LGT/LCT/SGH/SCH036, 048, 060, 072/074 EVAPORATOR COIL RT42, 46 22J07 22J06 YELLOW YELLOW RT42 RT46 CLAMP THERMISTOR TO BARE COPPER. DETAILS NOT TO SCALE FIGURE 6 Page 20...
  • Page 21 LGM/LCM036, 048, 060, 074U5 CONDENSER COIL (RT44) 22J09 YELLOW RT44 CLAMP THERMISTOR TO BARE COPPER. DETAILS NOT TO SCALE FIGURE 7 Page 21...
  • Page 22 LCM/LGM036, 048, 060, 074 CONDENSER COIL RT48 22J08 YELLOW RT48 CLAMP THERMISTOR TO BARE COPPER CLOSE TO CENTER OF BACK MANIFOLD OF COIL. DETA T T ILS NOT TO SCALE FIGURE 8 Page 22...
  • Page 23: Rds Sensors

    5-RDS Sensors TABLE 2 Units are equipped with factory-installed RDS Sensors RDS Sensor Figures located on different points on the unit. The RDS sensors Model Qty. Type Figure provide the Unit Controller with continuous readings for INDOOR SENSOR FIGURE 9 leaked refrigerant concentration levels and sensor health LGM036-074 2 sensors...
  • Page 24 COMPRESSOR RDS SENSOR LOCATION SCREW RDS SENSOR FIGURE 10 Page 24...
  • Page 25 6-Variable Speed Compressor B1 WARNING All units use one variable speed scroll compressor. See Electrical shock hazard. Compressor must be “SPECIFICATIONS” and “ELECTRICAL DATA” (table of grounded. Do not operate without protective cover contents) or compressor nameplate for compressor spec- over terminals.
  • Page 26 7-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 27: Event Action

    TABLE 3 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 28: Top View

    INVERTER WIRE ROUTING TRANSFORMER A192 INVERTER 208/230V INVERTER BOARD SHOWN FILTER BOARD W V U R S T High voltage enters the filter board here. High voltage enters the compressor here. COMPRESSOR FIGURE 14 INVERTER HEAT SINK TOP VIEW CONDENSER SECTION HEAT SINK DIVISION PANEL BETWEEN COMPRESSOR...
  • Page 29 C-GAS HEAT COMPONENTS At the start of the ignition sequence, the adjustable 40 sec- ond (default) indoor blower delay period begins. Sparking LGM units are available with two stages of gas heat. See stops immediately after flame is sensed or at the end of SPECIFICATION - GAS HEAT the 8 second trial for ignition.
  • Page 30 3-Heat Exchanger FIGURE 17 Burners All units use inshot burners. Burners are factory set and The LGM units use aluminized steel inshot burners with do not require adjustment. A peep hole with cover is fur- tubular aluminized (stainless is optional) steel heat ex- nished in the heating access panel for flame viewing.
  • Page 31 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 20. 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 32 prove switch closes, proving that the combustion air in- TABLE 5 ducer is operating before allowing the ignition sequence to Operating Pressure (outlet) Factory Setting “W.C continue. When the combustion air prove switch is closed Natural and the delay is over, the A3 ignition control activates the appropriate stage operator of the gas valve, the spark and High High...
  • Page 33 11-Flame Sensor IMPORTANT The flame sensor (FIGURE 23) is mounted through a hole Three phase scroll compressors must be phased in the burner support and the tip protrudes into the flame sequentially for correct compressor and blower envelope of the appropriate burner. See FIGURE 19 for rotation.
  • Page 34 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 35 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 36: Ii-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 roof mounting frame (T1CURB-AN or C1CURB-AN).
  • Page 37: Iv-Charging

    Turning Off Gas to Unit E-Refrigerant Leak Detection System 1 - If using an electromechanical thermostat, set to the The Refrigerant Leak Detection System can be tested by lowest setting. using the following mobile service app menu path: 2 - Before performing any service, turn off all electrical RTU MENU >...
  • Page 38 shall be vented down to atmospheric pressure to enable • If compressors or compressor oils are to be re- work to take place. Ensure that the outlet for the vacuum moved, ensure that they have been evacuated to pump is not close to any potential ignition sources and an acceptable level to make certain that flamma- that ventilation is available.
  • Page 39 B-Subcooling Method - Ultra High Efficiency Units 4 - The subcooling temperature should be as shown in TABLE 7. A subcooling temperature greater than 1 - Attach gauge manifold to the liquid line. With the this value indicates an overcharge. A subcooling economizer disabled, operate the unit in cooling temperature less than this value indicates an mode at high speed using the following mobile...
  • Page 40 TABLE 9 048 Normal Operating Pressures - No Reheat - All-Aluminum Coil - 581224-01 Outdoor Coil Entering Air Temperature 75°F 85°F 95°F 105°F 115°F 65°F Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc (psig) (psig) (psig) (psig) (psig) (psig)
  • Page 41 TABLE 10 060 Normal Operating Pressures - No Reheat - All-Aluminum Coil - 581225-01 Outdoor Coil Entering Air Temperature 75°F 85°F 95°F 105°F 115°F 65°F Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc (psig) (psig) (psig) (psig) (psig) (psig)
  • Page 42 TABLE 11 074 Normal Operating Pressures - No Reheat - All-Aluminum Coil - 581226-01 Outdoor Coil Entering Air Temperature 75°F 85°F 95°F 105°F 115°F 65°F Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc (psig) (psig) (psig) (psig) (psig) (psig)
  • Page 43 TABLE 12 036 Normal Operating Pressures - Reheat - All-Aluminum Coil - 581267-01 Outdoor Coil Entering Air Temperature 75°F 85°F 95°F 105°F 115°F 65°F Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc (psig) (psig) (psig) (psig) (psig) (psig) (psig)
  • Page 44 TABLE 13 048 Normal Operating Pressures - Reheat - All-Aluminum Coil - 581268-01 Outdoor Coil Entering Air Temperature 75°F 85°F 95°F 105°F 115°F 65°F Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc (psig) (psig) (psig) (psig) (psig) (psig) (psig)
  • Page 45 TABLE 14 060 Normal Operating Pressures - Reheat - All-Aluminum Coil - 581269-01 Outdoor Coil Entering Air Temperature 75°F 85°F 95°F 105°F 115°F 65°F Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc (psig) (psig) (psig) (psig) (psig) (psig) (psig)
  • Page 46: V-System Service Checks

    TABLE 17 074 Normal Operating Pressures - Reheat - All-Aluminum Coil - 581270-01 Outdoor Coil Entering Air Temperature 75°F 85°F 95°F 105°F 115°F 65°F Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc Suct Disc (psig) (psig) (psig) (psig) (psig) (psig) (psig)
  • Page 47: Gas Valve

    2-Testing Gas Piping 4-Check and Adjust Manifold Pressure After line pressure has been checked and adjusted, check NOTE- In case shutdown is required, turn off the main manifold pressure. Move test gauge to the outlet pressure manual shut-off valve and disconnect the main power to tap located on unit gas valve GV1.
  • Page 48: Vi-Maintenance

    B-Cooling System Service Checks TABLE 15 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 49 • Where electrical components are being changed, ser- refrigerants but the use of detergents containing chlorine vice technicians shall be fit for the purpose and to the cor- shall be avoided as the chlorine may react with the refrig- rect specification. At all times the manufacturer’s mainte- erant and corrode the copper pipe-work.
  • Page 50 A-Filters Clean combustion air inducer as follows: 1 - Shut off power supply and gas to unit. Units are equipped with temporary filters which must be 2 - Remove the mullion on the right side of the heat replaced prior to building occupation. See FIGURE 29. All section.
  • Page 51: Vii-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 52 Sensors MOTORIZED OUTDOOR AIR DAMPER 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 35 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 53: Sensor Location

    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 34 SENSOR LOCATION RT17 OUTDOOR AIR SENSOR (SECURED TO INSIDE OF CORNER MULLION) RT16 RETURN AIR SENSOR...
  • Page 54: Horizontal Airflow

    HORIZONTAL AIRFLOW DUCT TRANSITION DUCT BACK INLET OF UNIT SUPPLY DO NOT ATTACH RETURN AIR DUCTWORK HERE OPTIONAL GED RETURN DAMPER AND HOOD FIGURE 36 TABLE 16 ECONOMIZER MODES AND SETPOINT Free| Free Field- Dampers will modulate to 55°F discharge air (RT6) when Permitted Cooling Cooling...
  • Page 55 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 56 I-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 57 J-Optional Cold Weather Kit N-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 58 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 sec- Compressor modulates based on zone relative humidity, tion.
  • Page 59 REHEAT MODE REFRIGERANT ROUTING RETURN OUTDOOR EVAPORATOR EXPANSION COIL VALVE REHEAT COIL SUPPLY COMPRESSOR CONDENSER COIL CHECK VALVE REHEAT VALVE FIGURE 40 COOLING MODE REFRIGERANT ROUTING RETURN OUTDOOR EVAPORATOR EXPANSION COIL VALVE REHEAT COIL SUPPLY COMPRESSOR CONDENSER COIL CHECK VALVE REHEAT VALVE FIGURE 41...
  • Page 60: Viii-Decommissioning

    VIII-Decommissioning Ensure that the detector is not a potential source of igni- tion and is suitable for the refrigerant used. Leak detec- Before carrying out this procedure, it is essential that the tion equipment shall be set at a percentage of the LFL of technician is completely familiar with the equipment and the refrigerant and shall be calibrated to the refrigerant all its detail.
  • Page 61: Ix-Diagrams

    IX-Wiring Diagrams and Sequence of Operation LGM036-074 J VOLT DIAGRAM TO A3 ON SHIELDED GAS UNITS. CABLE REF A-SECT 538166-02 LOC CC01-02 RED-BLK 24VAC RT17 SHIELDED HPSW1 CABLE 24VAC RED-BLK RED-BLK HTSW1 RT48 24VAC RED-BLK 5VDC RT46 LPSW1 RT42 RED-BLK RED-BLK RT44 MAIN CTRL...
  • Page 62 LGM036-074 G VOLT DIAGRAM TO A3 ON SHIELDED GAS UNITS. CABLE REF A-SECT 538107-04 LOC CC01-02 RED-BLK 24VAC RT17 SHIELDED HPSW1 CABLE 24VAC RED-BLK RED-BLK RT48 HTSW1 24VAC RED-BLK 5VDC RT46 LPSW1 RT42 RED-BLK RT44 RED-BLK MAIN CTRL J394 J378 J390 J390 J389...
  • Page 63 LGM036-074 Y VOLT DIAGRAM TO A3 ON SHIELDED GAS UNITS. CABLE REF A-SECT 538110-03 LOC CC01-02 RED-BLK SHIELDED 24VAC RT17 CABLE HPSW1 24VAC RED-BLK RED-BLK RT48 HTSW1 ODF1 24VAC RED-BLK RT46 LPSW1 RT42 RED-BLK RT44 RED-BLK MAIN CTRL J389 J390 J392 J395 J394...
  • Page 64 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 65 LGM036-074 GAS HEAT DIAGRAM 538237-02 LOW TEMP VEST HTR MODBUS BURNER 1 MAIN CTRL J393 J413 P393 P413 P229 MODBUS CABLE P229 P406 P411 P229 J406 J411 A G B DSI CTRL 1 MODBUS-1 J407 J410 P407 P410 P229 MODBUS CABLE J408 J374 J408...
  • Page 66 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 67 THERMOSTAT 538078-02 A173 CTRL SMOKE DETECT J250 P250 P251 J251 J252 P252 P253 J253 FIRE ALARM CONTACT SUPPLIED BY OTHERS FROM IAQ WIRING DIAGRAM DI-1 P299 P387 J299 J387 MAIN CTRL J297 J298 P297 P298 IAQ+ WB-044 WB-045 IAQ+ WB-046 TO B5-SECT LOC CC03 APPLIES ONLY...
  • Page 68 ECONOMIZER 538072-01 MS7110K RANGE 2-10 VDC NF24-SR AF24-SR RANGE 2-10 VDC P104 P105 RT16 J104 J105 P384 J384 MAIN CTRL Model: LC,LG,LH,LD,SC,SG Series ACCS ACCS Economizer & Motorized OAD WIRING DIAGRAM FLOW Voltage: All Voltages 538072-01 Supersedes: N/A Form No: Rev: 2 REV EC NO.
  • Page 69 RDS SENSOR REFR. LEAK REFR. LEAK SENSOR 1 SENSOR 2 MAIN CNTRL A+ B- A+ B- J386 P386 DENOTES OPTIONAL COMPONENTS AND WIRING MODEL: Units w/CORE Contr. Refr. Leak Detection VOLT: 538440-01 SUPSDS: N/A REV EC NO. DATE APVD REVISION NOTE 3 x 7 --- CN-012295C 04-03-2024...

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