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S e r v i c e L i t e r a t u r e
The LHT302 is a configured to order unit (CTO) with a
wide selection of factory installed options.
Optional electric heat is factory- or field-installed. Electric
heat operates in single or multiple stages depending on
the kW input size. 30kW to 90 kW heat sections are avail-
able.
The unit has a 25 ton cooling capacity and utilizes two
compressors and six condenser fans.
Multi-Stage Air Volume MSAV
The VFD-driven blower will operate at lower speeds when
demand is low and increase to higher speeds when de-
mand is high.
All LHT units are designed to accept any of several differ-
ent energy management thermostat control systems with
minimum field wiring. Factory- or field-provided control op-
tions connect to the unit through Smartwire connectors.
When "plugged in" the controls become an integral part of
the unit wiring.
False ceilings or drop ceiling may be used as a return air
plenum only if the unit being installed has a Refrigerant
Detection System
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.
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
LHT302 with R454B
blower option is available.
®
adjustment,
alteration,
100183
02/2025
To prevent serious injury or death:
1- Lock-out/tag-out before performing maintenance.
2- If system power is required (e.g., smoke detector
maintenance), disable power to blower, remove
fan belt where applicable, and ensure all
controllers and thermostats are set to the "OFF"
position before performing maintenance.
3- Always keep hands, hair, clothing, jewelry, tools,
etc., away from moving parts.
OOptions / Accessories
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LHT SERIES
WARNING
Table of Contents
25 ton
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Summary of Contents for Lennox LHT Series
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Page 1: Table Of Contents
LHT SERIES UNIT INFORMATION UNIT INFORMATION 25 ton 100183 S e r v i c e L i t e r a t u r e 02/2025 LHT302 with R454B The LHT302 is a configured to order unit (CTO) with a wide selection of factory installed options. - Page 2 CAUTION WARNING As with any mechanical equipment, contact with sharp •This appliance must be installed in accordance with sheet metal edges can result in personal in jury. Take local and national wiring regulations. care while handling this equipment and wear gloves and •If the appliance is not fitted with an option for full protective clothing.
- 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.
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Page 4: Options & Accessories
OPT IONS / A C C ESSORIES Size Order Item Description Number COOLING SYSTEM 22H54 Condensate Drain Trap 76W27 Copper 21Z07 Drain Pan Overflow Switch Stainless Steel Condensate Drain Pan 83W42 BLOWER - SUPPLY AIR Motors Belt Drive (standard efficiency) - 5 hp Factory Belt Drive (standard efficiency) - 7.5 hp Factory... -
Page 5: Indoor Air Quality
OPT IONS / A C C ESSORIES Size Order Item Description Number INDOOR AIR QUALITY Air Filters Healthy Climate High Efficiency Air Filters MERV 8 54W21 ® 20 x 20 x 2 - order 12 per unit MERV 13 52W39 21U40 MERV 16 Replaceable Media Filter with Metal Mesh Frame (includes Non-Pleated... -
Page 6: Outdoor Air
OPT IONS / A C C ESSORIES Size Order Item Description Number ECONOMIZER High Performance Economizer (Approved for California Title 24 Building Standards / AMCA Class 1A Certified) 18X87 High Performance Economizer (Downflow or Horizontal) Includes Economizer Dampers with Outdoor Air Hood Downflow Applications - Use furnished Outdoor Air Hood - Order Downflow Barometric Relief Dampers with Exhaust Hood separately Horizontal Applications - Use furnished Outdoor Air Hood - Order... -
Page 7: Roof Curbs
OPT IONS / A C C ESSORIES Size Order Item Description Number ROOF CURBS Hybrid Roof Curbs, Downflow 11F62 14 in. height 11F63 18 in. height 24 in. height 11F64 Standard Roof Curbs, Horizontal - Requires Horizontal Return Air Panel Kit 30 in. -
Page 8: Specifications
SP ECIF ICATIONS Model LHT302H5M Nominal Tonnage 25 Ton Efficiency Type High Blower Type MSAV® Multi-Stage Air Volume Cooling Gross Cooling Capacity - Btuh 285,000 Performance Net Cooling Capacity (Btuh) 274,000 AHRI Rated Air Flow (cfm) 8500 Total Unit Power - kW 25.9 IEER (Btuh/Watt) 14.8... -
Page 10: Blower Data
BLO WER DATA DRIVE KIT SPECIFICATIONS Motor Efficiency Nominal Maximum Drive Kit Number RPM Range Standard 5.75 660 - 810 Standard 5.75 770 - 965 Standard 5.75 570 - 720 Standard 5.75 480 - 630 Standard 5.75 410 - 535 Standard 8.63 715 - 880... - Page 11 BLO WER DATA POWER EXHAUST PERFORMANCE - STANDARD STATIC Return Duct Negative Static Pressure Air Volume Exhausted in. w.g. 0.00 12,800 0.05 12,200 0.10 11,500 0.15 10,800 0.20 9900 0.25 9000 0.30 7900 0.35 6750 0.40 5450 0.45 4150 0.50 2900 POWER EXHAUST - HIGH STATIC Return Duct Negative Static Pressure - In.
- Page 12 BLO WER DATA CEILING DIFFUSER AIR RESISTANCE - in. w.g. Step-Down Diffuser Flush Diffuser Volume LARTD30/36S LAFD30/36S 2 Ends Open 1 Side/2 Ends Open All Ends & Sides Open 7500 0.37 0.31 0.25 0.29 8000 0.42 0.36 0.29 0.34 8500 0.48 0.41 0.34...
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Page 13: Electrical / Electric Heat Data
ELECT RICA L DATA Model LHT302H5M Voltage - 60Hz 208/230V - 3 Ph 460V - 3 Ph 575V - 3 Ph Compressor 1 Rated Load Amps 46.5 21.2 16.9 Locked Rotor Amps 335.5 Compressor 2 Rated Load Amps 31.8 11.9 Locked Rotor Amps 93.7 Outdoor Fan... - Page 14 ELECTRIC H EAT D ATA Model LHT302H5M Voltage - 60Hz 208/230V - 3 Ph 460V - 3 Ph 575V - 3 Ph Indoor Blower Motor - HP Electric Heat Voltage 208V 240V 208V 240V 208V 240V 480V 480V 480V 600V 600V 600V Maximum...
- Page 15 ELECTRIC H EAT C APACITIES 30 kW 45 kW 60 kW 90 kW Volts Btuh Btuh Btuh Btuh Input kW Input Stages kW Input Stages kW Input Stages kW Input Stages Output Output Output Output 22.5 76,800 33.8 115,300 45.0 153,600 67.6 230,700...
- Page 16 Minimum R454B Space and CFM Requirements Minimum Airflow¹ Refrigerant Charge R-454B Unit (CFM) (m³h) Unit (lbs) (kg) LHT302 1302 LHT302 Stage 1 29.00 13.15 LHT302 Stage 2 28.00 12.70 ¹ NOTE - The minimum airflow is the lowest CFM allowed during venting operation (leak mitigation).
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Page 17: Unit Parts Arrangement
Parts Arrangement INDOOR FILTERS COIL (SIX - 24 X 24 X 2”) BLOWERS ECONOMIZER OUTDOOR DAMPERS FANS (OPTIONAL) BLOWER MOTOR BLOWER INVERTER INDOOR COIL RDS SENSOR (BEHIND COIL) CONDENSATE DRAIN UNIT OUTDOOR CONTROLLER COILS COMPRESSORS COMPRESSOR DISCONNECT RDS SENSOR (FACTORY-INSTALLED (BEHIND COMPRESSORS) OPTION) ELECTRIC... -
Page 18: Control Box Components
CONTROL BOX COMPONENTS A178 K203 TB13 K202 K231 TB25 A173 FIGURE 3 Control Box Components K150 K152 K153 K149 FIGURE 4 Page 18... - Page 19 4-Terminal Block TB13 9-Power Exhaust Relay K65 & K231 (PED units) TB13 terminal block distributes line voltage power to the Power exhaust relays K65 and K231 are N.O. DPDT line voltage items in the unit. relays with a 24VAC coil. The relay are used in units equipped with the optional power exhaust dampers.
- Page 20 Relative Humidity Sensor - Optional Economizer Differential Pressure Sensor - Optional Rooftop units installed with Smart Airflow™ will have a The indoor relative humidity sensor (A91) is an analog Pressure Transducer (PT5) present in the economizer. sensor with a 0-10VDC output over a relative humidity PT5 requires 5VDC power supply (P266-5 and {P266- range of 0-100% relative humidity.
- Page 21 15-Second-Stage Power Exhaust Relay K231 15-Fuse F61 (Higher SCCR units only) (Staged-Blower units equipped with power exhaust) Fuse F61 is used on units with higher SCCR rating. F61 The second power exhaust fan is controlled by K231. provides overcurrent protection to compressor and other A133 will enable K231 only when the blower reaches 70% cooling components.
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Page 22: Compressor Components
SIEMENS OVERLOAD RELAY BLUE RESET BUTTON IN FACTORY SET AUTO MODE (Turn clockwise to H for manual reset) GREEN TRIP INDICATOR (Flush with surface -- not tripped; Above surface -- tripped) AMP ADJUSTMENT DIAL Adjust relay amp setting according to value given on the blower motor nameplate. Proper relay amp setting equals motor nameplate FLA X service factor of 1.15 X .95. -
Page 23: Refrigerant Circuits
REFRIGERANT CIRCUITS INDOOR COIL CIRCUIT 1 & 2 ARE INTERLACED CIRCUIT 1 OUTDOOR COIL CIRUIT 2 OUTDOOR COIL FIGURE 8 B-Cooling Components WARNING Units use independent cooling circuits consisting of one Electrical shock hazard. Compressor must be compressor, one condenser coil, and one evaporator coil grounded. - Page 24 2-Crankcase Heaters HR1 and HR2 5-Defrost Control All LHT units use insertion type heaters. Heater HR1 is The defrost control ensures that the heat pump outdoor installed around compressor B1 and HR2 compressor B2. coil does not ice excessively during the heating mode. The defrost control uses input from the coil and ambient sen- 3-High Pressure Switches S4 and S7 sor to initiate demand defrost cycles from the M4 Board.
- Page 25 LHT302 INDOOR COIL RT46, RT47 22J06 Blue RT47 22J06 Yellow RT46 FIGURE 9 Page 25...
- Page 26 LHT302 OUTDOOR COIL RT48, RT49 22J08 22J08 BLUE YELLOW RT49 RT48 FIGURE 10 Page 26...
- Page 27 10-RDS Sensors TABLE 4 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 11 leaked refrigerant concentration levels and sensor health LHT302 2 sensors...
- Page 28 LHT 302 COMPRESSOR RDS SENSOR SCREW RDS SENSOR USE WIRE TIES TO KEEP HARNESS WIRES AWAY FROM HOT OR SHARP SURFACES. FIGURE 12 Page 28...
- Page 29 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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Page 30: Operation / Adjustment
C-Blower Compartment IMPORTANT The blower compartment is located between the evapora- Three Phase Scroll Compressor Voltage tor coil and the compressor / control section on the oppo- Phasing site side of the condenser coil. The blower assembly is ac- cessed by disconnecting the blower motor wiring (and all Three phase scroll compressors must be phased other plugs) and removing the screws on either side of the sequentially to ensure correct compressor and... - Page 31 B-Blower Access 2 - With all access panels in place, measure static pressure external to unit (from supply to return). 1 - Disconnect jack/plug connector to blower motor. Blower performance data is based on static pressure Also disconnect jack/plug connector heating limit readings taken in locations shown in FIGURE 14.
- Page 32 BLOWER ASSEMBLY - NO TENSIONER TO INCREASE CFM LOOSEN ALLEN SCREW & TO INCREASE BELT TENSION TURN PULLEY CLOCKWISE 1-Loosen four screws securing blower motor to TO DECREASE CFM sliding base. TURN PULLEY COUNTERCLOCKWISE clockwise, to move the motor downward and tighten the belt.
- Page 33 3 - Measure belt deflection force. For a used belt, the deflection force should be 5 lbs. A new belt PULLEY ALIGNMENT - WITH TENSIONER deflection force should be 7 lbs ALIGNED A force below these values indicates and under ten- TENSIONER sioned belt.
- Page 34 D-OPTIONAL ELECTRIC HEAT 3-High Temperature Limits S15 and S107 (Primary) See ELECTRICAL / ELECTRIC HEAT DATA and ELEC- S15 and S107 are SPST N.C. auto-reset thermostats lo- TRIC HEAT CAPACITIES (table of contents) for LHT to cated on the back panel of the electric heat section below EHA match-ups and electrical ratings.
- Page 35 FIGURE 20 EHA 15, 30, 45, 60 and 90 KW ELECTRIC HEAT SECTION PARTS ARRANGEMENT HEATING ELEMENTS HE1 - HE14 ELECTRIC HEAT VESTIBULE CONTROL WIRE HARNESS TRIC HEAT LIMIT S15(1 SECTION) S107(2 SECTION) FIGURE 21 Page 35...
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Page 36: Ii-Placement And Installation
TABLE 7 LHT ELECTRIC HEAT SECTION FUSE RATING FUSE (3 each) EHA QUANTITY VOLTAGES & SIZE F3 - 1 F3 - 2 F3 - 3 F3 - 4 F3 - 5 F3 - 6 F3 - 7 F3 - 8 60 Amp 60 Amp 208/230V... - Page 37 shall be vented down to atmospheric pressure to enable and the relevant waste transfer note arranged. Do work to take place. Ensure that the outlet for the vacuum not mix refrigerants in recovery units and especially not in cylinders. pump is not close to any potential ignition sources and that ventilation is available.
- Page 38 pressures obtained from the gauges. Check unit 7 - Add or remove charge in increments. Allow the sys- components if there are significant differences. tem to stabilize each time refrigerant is added or re- moved. 5 - Measure the outdoor ambient temperature and the suction pressure.
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Page 39: Start Up - Operation
IV- START-UP OPERATION V- SYSTEMS SERVICE CHECKS A-Cooling System Service Checks A-Preliminary and Seasonal Checks 1 - Make sure the unit is installed in accordance with LHT units are factory charged and require no further ad- the installation instructions and applicable codes. justment;... - Page 40 surveyed to make sure that there are no flammable potential sources of ignition be used in the searching for or detection of refrigerant leaks. A halide torch hazards or ignition risks. “No Smoking” signs shall (or any other detector using a naked flame) shall be displayed.
- Page 41 A-Filters E-Condenser Coil LHT units use six 24 X 24 X 2” fiberglass throw-away type Clean condenser coil annually with detergent or commer- filters. Filters may be accessed through the economizer / cial coil cleaner and inspect monthly during the cooling filter access door.
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Page 42: Vii-Accessories
Optional supply/return transitions C1DIFF33C-1 and frames are recommended in all other applications but C1DIFF34C-1 are available for use with LHT series units not required. If the LHT units are not mounted on a flat utilizing optional C1CURB roof curbs. Transition must be... - Page 43 NOTE - Gravity exhaust dampers are required with power C1DAMP10 MANUAL OUTDOOR AIR DAMPER exhaust. The economizer is controlled by the A55 Unit Controller. DAMPER COVER PLATE BLADES OPENING The economizer will operate in one of four modes. Each mode requires a different A55 Unit Controller DIP switch setting.
- Page 44 (A173) is located below the control pan- LHT series units. An exhaust hood is furnished with the el. Wiring for the smoke detectors are shown on the tem- gravity exhaust damper.
- Page 45 N-Drain Pan Overflow Switch S149 (optional) Location of both The overflow switch is used to interrupt cooling operation the Supply and Return IAQ Sensors when excessive condensate collects in the drain pan. The N.C. overflow switch is connected to the M2 Unit Control- ler (A55) through DI-3.
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Page 46: Viii-Multi-Staged Blower
VIII--Multi-Staged Blower Blwr Low” when blower CFM is BELOW a “midpoint” CFM. The Unit Controller will calculate the “midpoint” CFM. A-Design Specifications *Available blower speeds vary by unit and thermostat Use the TABLE 11 to fill in test and balance values when stages. -
Page 47: Electrical Shock Hazard
F-Unit Operation 5 - Restore power to unit. Blower will operate in constant air volume (CAV) mode. Use the mobile app to check unit mechanical operation. Note - The indoor blower motor will start as soon as See the Service - Test section of the Unit Controller man- the main unit power is restored. - Page 48 TABLE 12 HEATING, VENTILATION & SMOKE MINIMUM AND MAXIMUM CFM Unit Heating CFM (ECTO 0.04) Vent CFM Smoke CFM Heat Heat Model Tonnage Default Default Default Option Code Medium S, M 5925 LDT302H High 7125 10500 12000 10500 3750 12000 10500 3750 12000...
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Page 49: Ix-Wiring And Operation Sequence
IX-Wiring Diagrams and Sequence of Operation THERMOSTAT 5 3 8 0 7 8 -0 2 A173 CT RL S M OKE DE T E CT J 250 P250 P251 J 251 YE L YE L YE L YE L YE L YE L RE D RE D... - Page 50 ECONOMIZER 5 3 8 0 7 2 -0 1 M S 7110K RANGE 2- 10 VDC NF 24- S R AF 24- S R RANGE 2- 10 VDC 1, 2 P104 P105 RT 16 J 104 J 105 P384 J 384 M AI N CT RL Model: LC,LG,LH,LD,SC,SG Series...
- Page 51 EHA-15/90 G VOLTAGE Page 51...
- Page 52 EHA-15/90 Y VOLTAGE Page 52...
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Page 53: Heating Elements
SEQUENCE OF OPERATION 4 - N.O. contact K15-1 closes allowing the first bank of elements in heat section one (left side) to be HEAT PUMP energized. 1 - A55 Unit Controller receives W1 heating demand 5 - At the same time, N.O. contacts K9-1 close. A N.O. contact in A55 closes, energizing electric heat relay 2 - A55 energizes outdoor fans B4, B5 &... - Page 54 SEQUENCE OF OPERATION - MSAV MULTI-STAGE AIR VOLUME ® Objective: Outline the unit functions as a result of room thermostat or zone sensor demands Given: When economizer is present, it will function as an integral part of the unit cooling system When not present, unit will function as if economizer is present but outdoor ambient is high and sensed as not suitable UNIT OPERATION WITH 2-STAGE THERMOSTAT (2 COOL AND 2 HEAT STAGES, Y1, Y2, W1, W2) SUPPLY AIR BLOWER SPEED...
- Page 55 All compressors operate and supply air blower operates at high cooling speed DEFROST Coil Sensors (RT48 - Circuit 1 and RT49 - Circuit 2) and Ambient Sensor (RT17) provides input to the Lennox ® CORE Unit Controller to initiate a defrost cycle if needed...
- Page 56 SEQUENCE OF OPERATION - MSAV MULTI-STAGE AIR VOLUME ® HEATING Thermostat or Zone Sensor W1/H1 Demand: A first-stage heating demand (W1/H1) will energize compressors 1 and 2 and the outdoor fans. NOTE – L1 & L2 reversing valves are de-energized in the heating mode. Units With Optional Electric Heat: An increased heating demand (W2/H2) will energize electric heat NOTE –...
- Page 57 LHT/LDT302 G & J VOLT COOLING DIAGRAM MSAV - NO BYPASS RED-BLK 538353-01 MAIN CTRL RED-BLK RED-BLK RT17 24VAC CONTROL BOARD ARRANGEMENT HPSW1 RED-BLK RED-BLK RT48 RT46 24VAC HPSW2 RED-BLK RED-BLK RT49 RT47 24VAC LPSW1 DEFROST CONTROL EVAPORATOR COIL 24VAC FREEZE PROTECTION RT48-SENSOR, RT46-SENSOR,...
- Page 58 LHT/LDT302 Y VOLT COOLING DIAGRAM MSAV - NO BYPASS RED-BLK 538354-01 MAIN CTRL RED-BLK RED-BLK RT17 24VAC CONTROL BOARD ARRANGEMENT HPSW1 RED-BLK RED-BLK RT48 RT46 24VAC HPSW2 RED-BLK RED-BLK RT49 RT47 24VAC LPSW1 DEFROST CONTROL EVAPORATOR COIL 24VAC FREEZE PROTECTION RT48-SENSOR, LPSW2 COND COIL 1...
- Page 59 LHT/LDT302 G & J VOLT COOLING DIAGRAM MSAV - WITH BYPASS RED-BLK 538355-01 MAIN CTRL RED-BLK RED-BLK RT17 24VAC CONTROL BOARD ARRANGEMENT HPSW1 RED-BLK RED-BLK RT48 RT46 DENOTES OPTIONAL COMPONENTS 24VAC AND WIRING HPSW2 RED-BLK RED-BLK RT49 RT47 24VAC LPSW1 DEFROST CONTROL EVAPORATOR COIL 24VAC...
- Page 60 LHT/LDT302 Y VOLT COOLING DIAGRAM MSAV - WITH BYPASS RED-BLK 538356-01 MAIN CTRL RED-BLK RED-BLK RT17 24VAC CONTROL BOARD ARRANGEMENT HPSW1 RED-BLK RED-BLK RT48 RT46 24VAC HPSW2 RED-BLK RED-BLK RT49 RT47 24VAC DENOTES OPTIONAL COMPONENTS AND WIRING LPSW1 DEFROST CONTROL EVAPORATOR COIL 24VAC FREEZE PROTECTION...
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Page 61: X-Decommissioning
X-Decommissioning f) Make sure that cylinder is situated on the scales before recovery takes place. Before carrying out this procedure, it is essential that g) Start the recovery machine and operate in accordance the technician is completely familiar with the equipment with instructions.
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