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Service Literature
WARNING
Improper installation, adjustment, alteration, 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.
IMPORTANT
This unit must be matched with an indoor coil as specified
with AHRI. For AHRI Certified system matchups and
expanded ratings, visit www.LennoxPros.com. Coils
previously charged with HCFC-22 must be flushed.
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
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.
CAUTION
Servicing shall be performed only as recommended by
the manufacturer.
UNIT INFORMATION
ML14KP1 (R-454B) SERIES OUTDOOR UNITS
100108
February 24, 2025
Table of Contents
Installation Clearances ...................................................6
Model Number Identification ...........................................7
Dimensions .....................................................................8
Specifications .................................................................9
Typical Unit Parts Arrangement .................................... 11
Operating Gauge Set and Service Valves .................... 11
Unit Placement ............................................................13
Removing and Installing Louvered Panels ...................14
New or Replacement Line Set ......................................15
Brazing Connections ...................................................17
Flushing Line Set and Indoor Coil ................................20
Installing Indoor Metering Device .................................21
Leak Test Line Set and Indoor Coil ..............................22
Evacuating Line Set and Indoor Coil ...........................23
Electrical .......................................................................24
System Operation .......................................................25
Charging ......................................................................26
System Configuration ...................................................26
Defrost System ...........................................................29
Maintenance ...............................................................32
Servicing Units Void of Charge ...................................36
Start-Up ......................................................................36
Decommissioning ........................................................37
General Information
These instructions are intended as a general guide and do
not supersede national or local codes in any way. Consult
authorities having jurisdiction before installation.
The Merit® ML14KP1 model is designed for use with
R-454B refrigerant only. This unit must be installed with
an approved indoor air handler or coil. For AHRI Certified
system matchups and expanded ratings, visit www.Len-
noxPros.com.
This outdoor unit is designed for use in systems that use
the following refrigerant metering device:
• Check thermal expansion valve (CTXV)
IMPORTANT: Special procedures are required for clean-
ing the all-aluminum coil in this unit. See page 30 in this
instruction for information.
NOTE - This unit ML14KP1 is a PARTIAL UNIT AIR CON-
DITIONER, complying with PARTIAL UNIT requirements
of this Standard, and must only be connected to other
units that have been confirmed as complying to corre-
sponding PARTIAL UNIT requirements of this Standard,
UL 60335-2-40/CSA C22.2 No. 60335-2-40, or UL 1995/
CSA C22.2 No 236.
Page 1
ML14KP1
...........................34
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Summary of Contents for Lennox ML14KP1-018
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Page 1: Table Of Contents
ML14KP1 UNIT INFORMATION 100108 February 24, 2025 Service Literature ML14KP1 (R-454B) SERIES OUTDOOR UNITS Table of Contents Installation Clearances ...........6 Model Number Identification ...........7 Dimensions ..............8 Specifications ..............9 Typical Unit Parts Arrangement ........11 Operating Gauge Set and Service Valves ....11 Unit Placement ............13 Removing and Installing Louvered Panels ....14 New or Replacement Line Set ........15... - Page 2 WARNING CAUTION • Do not use means to accelerate the defrosting pro- Under no circumstances shall potential sources of cess or to clean, other than those recommended by ignition be used in the searching for or detection of the manufacturer. refrigerant leaks.
- Page 3 CAUTION IMPORTANT Repair and maintenance to electrical components shall Where electrical components are being changed, they include initial safety checks and component inspection shall be fit for the purpose and to the correct specification. procedures such as that capacitors are discharged At all times the manufacturer’s maintenance and service in a safe manner to avoid possibility of sparking, that guidelines shall be followed.
- Page 4 IMPORTANT IMPORTANT When breaking into the refrigerant circuit to make Prior to beginning work on systems containing flammable repairs – or for any other purpose – conventional refrigerants, safety checks are necessary to ensure that procedures shall be used. However, for flammable the risk of ignition is minimised.
- Page 5 IMPORTANT IMPORTANT Before carrying out work on systems containing When removing refrigerant from a system, either for refrigerant, it is essential that the technician is servicing or decommissioning, it is recommended good completely familiar with the equipment and all its detail. practice that all refrigerants are removed safely.
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Page 6: Installation Clearances
NOTE – R-454B is an A2L refrigerant. The system installation must meet the following parameters based upon total refrigerant charge (line set included). TAmin (Total minimum conditioned area) is the minimum allowable conditioned area based upon the total system charge at sea level. Values must be multiplied by altitude adjustment factor at installed altitude. Qmin table refers to minimum airflow requirements during refrigerant leak mitigation by the refrigerant detection system, based upon total system charge. -
Page 7: Model Number Identification
Model Number Identification ML 14 K P 1 - 036 - 230 A 01 Product Tier Minor Revision Number ML = Merit ® Series Ratings Revision Number Nominal SEER2 14 = 14.0 to 16.0 Voltage 230 = 208/230V-1ph-60Hz Refrigerant Nominal Cooling Capacity K = R-454B 018 = 1.5 tons 024 = 2 tons... -
Page 8: Dimensions
Dimensions 4-3/8 4-3/8 (111) (111) INLET 4-3/8 4-3/8 (111 111) OPTIONAL UNIT INLET INLET STAND-OFF KIT (4) COMPRESSOR (Field Installed) COIL DRAIN OUTLETS (Around perimeter of base) 6-3/8 SUCTION LINE 4-3/8 (162) CONNECTION (111) LIQUID LINE INLET 6-3/8 4-3/8 CONNECTION (162) (111) TOP VIEW... -
Page 9: Specifications
Specifications Size Nominal Tonnage Sound Rating Number Connections Liquid line (OD) - in. (sweat) Vapor line (OD) - in. Refrigerant R-454B charge furnished 4 lbs. 7 oz. 5 lbs. 3 oz. 6 lbs. 7 oz. 7 lbs. 2 oz. Indoor Unit Expansion Valve (TXV) 26Z70 26Z70 26Z70... -
Page 10: Electrical Data
SPEC I FI CATI ON S Size Nominal Tonnage Sound Rating Number Connections Liquid line (OD) - in. (sweat) Vapor line (OD) - in. 1-1/8 Refrigerant R-454B charge furnished 8 lbs. 5 oz. 8 lbs. 6 oz. 9 lbs. 6 oz. Indoor Unit Expansion Valve (TXV) 26Z71 26Z71... -
Page 11: Typical Unit Parts Arrangement
Gauge hoses must be rated for use at up to 800 psig of recess. pressure with a 4000 psig burst rating. See the Lennox Service and Application Notes #C-08-1 OPERATING SERVICE VALVES for further details and information. The liquid and vapor line service valves are used for re-... -
Page 12: Service Valves
SERVICE VALVES ANGLE AND BALL Operating Angle Type Service Valve: 1. Remove stem cap with an appropriately sized wrench. 2. Use a service wrench with a hex-head extension (3/16” for liquid line valve sizes and 5/16” for vapor line valve sizes) to back the stem out counterclockwise as far as it will go. -
Page 13: Unit Placement
DETAIL B DETAIL A INSTALL UNIT LEVEL OR, IF ON A SLOPE, MAINTAIN SLOPE TOLERANCE INSTALL UNIT AWAY OF 2 DEGREES (OR 2 INCHES PER 5 FEET [50 MM PER 1.5 M]) AWAY FROM WINDOWS FROM BUILDING STRUCTURE. DISCHARGE AIR BUILDING STRUCTURE MOUNTING... -
Page 14: Removing And Installing Louvered Panels
Removing and Installing Louvered Panels WARNING To prevent personal injury, or damage to panels, unit or structure, be sure to observe the following: While installing or servicing this unit, carefully stow all removed panels out of the way, so that the panels will not cause injury to personnel, nor cause damage to objects or structures nearby, nor will the panels be subjected to damage (e.g., being bent or scratched). -
Page 15: New Or Replacement Line Set
Perform operations only in well-ventilated areas. from the outdoor unit (braze connections) to the indoor Wear gloves and protective goggles or face shield to unit coil (flare or braze connections). Use Lennox L15 protect against burns. (braze, non-flare) series line set, or use field-fabricated refrigerant lines as listed in table 2. -
Page 16: Installation
LINE SET IMPORTANT — Refrigerant lines must not contact structure. INSTALLATION REFRIGERANT LINE SET — INSTALLING Line Set Isolation — The following illustrations are VERTICAL RUNS (NEW CONSTRUCTION SHOWN) examples of proper refrigerant line set isolation: NOTE — Insulate liquid line when it is routed through areas where the surrounding ambient temperature could become higher than the REFRIGERANT LINE SET —... -
Page 17: Brazing Connections
IMPORTANT Brazing Connections Use the procedures outlined in figures 6 and 7 for brazing Allow braze joint to cool before removing the wet rag line set connections to service valves. from the service valve. Temperatures above 250ºF can damage valve seals. WARNING IMPORTANT Danger of fire. - Page 18 CAP AND CORE REMOVAL CUT AND DEBUR Cut ends of the refrigerant lines square (free from nicks or dents) Remove service cap and core from and debur the ends. The pipe must remain round. Do not crimp end both the suction / vapor and liquid line of the line.
- Page 19 WRAP SERVICE VALVES To help protect service valve seals during brazing, wrap water saturated cloths around service valve bodies and copper tube stubs. Use additional water saturated cloths underneath the valve body to protect the base paint. FLOW NITROGEN Flow regulated nitrogen (at 1 to 2 psig) through the refrigeration gauge set into the valve stem port connection on the liquid service valve and out of the suction / vapor valve stem port.
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Page 20: Flushing Line Set And Indoor Coil
Flushing Line Set and Indoor Coil TYPICAL EXISTING EXPANSION VALVE REMOVAL CONNECT GAUGES AND EQUIPMENT FOR PROCEDURE (UNCASED COIL SHOWN) FLUSHING PROCEDURE STUB END INVERTED CYLINDER GAUGE TWO PIECE PATCH PLATE LIQUID LINE CHECK CONTAINS CLEAN MANIFOLD (UNCASED COIL ONLY) ORIFICE EXPANSION HCFC22* TO BE USED... -
Page 21: Installing Indoor Metering Device
See the Lennox ML14KP1 Product Specification bulletin expansion valve. Refer to below illustration for reference for approved expansion valve kit match-ups. The expan- during installation of expansion valve unit. -
Page 22: Leak Test Line Set And Indoor Coil
Take care WARNING to empty all existing traps. Polyol ester (POE) oils are used in Lennox units charged with R-454B refrigerant. Refrigerant can be harmful if it is inhaled. Refrigerant Residual mineral oil can act as an insulator, preventing must be used and recovered responsibly. -
Page 23: Evacuating Line Set And Indoor Coil
Evacuating Line Set and Indoor Coil CONNECT GAUGE SET HIGH NOTE — Remove cores from service valves (if not already done). Connect low side of manifold gauge set with 1/4 SAE in-line tee to vapor line service valve Connect high side of manifold gauge set to liquid line service valve OUTDOOR MANIFOLD... -
Page 24: Electrical
IMPORTANT Electrical In the U.S.A., wiring must conform with current local codes Use a thermocouple or thermistor electronic vacuum and the current National Electric Code (NEC). In Canada, gauge that is calibrated in microns. Use an instrument wiring must conform with current local codes and the cur- capable of accurately measuring down to 50 microns. -
Page 25: System Operation
Single-Stage Heat Pump with Air Handler RDS Sensor Thermostat Air Handler SENSOR #1 RDS Blower Control Board – 24 Volt Cat # (27A02) OPTIONAL TSTAT INDOOR N.C. CONDENSATE ZONING ALARM FLOAT SWITCH NO COM NC NO COM NC Thermostat / Outdoor Unit Terminal Block (BLACK) Indoor Unit Terminal Block (BLUE) Single-Stage Heat Pump Class II Voltage field wiring... -
Page 26: Charging
ML14KP1 unit is factory-charged with enough R454B re- Charging frigerant to accommodate a 15-foot length of refrigerant piping. For line lengths over 15 feet, add 3 oz of refrigerant Verify the unit is electrically grounded before charging the for every 5 feet of piping beyond 15 feet. system. - Page 27 TEST PINS (P1) NOMINAL DEFROST SELECTION TIME (P3) DEFROST TERMINATION PIN SETTINGS (P1) SENSOR CONNECTION (COIL AND AMBIENT SENSORS) (P4) DIAGNOSTIC LEDS (DS1 AND DS2) DELAY PINS (P5) 24V TERMINAL STRIP REVERSING VALVE CONNECTIONS (O OUT) (P2) Demand Defrost PRESSURE Control (A108) SWITCH CIRCUIT CONNECTIONS...
- Page 28 Service Light Output 24VAC service light output. 24VAC typically used to supply power to the Lennox System Operation 24 Volt output Monitor (LSOM). Not used in this system. Page 28...
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Page 29: Defrost System
The unit will run in the defrost mode until the coil tempera- Defrost System ture reaches the defrost termination temperature setpoint. The maximum length of defrost cycle is 14 minutes and This section addresses: the defrost cycle will automatically be terminated if the de- •... - Page 30 Test Pins (P1) Function Compressor Delay Mode (P5) Placing the jumper on the field test pins (P1) allows the The demand defrost control has a field-selectable function technician to: to reduce occasional sounds that may occur while the unit is cycling in and out of the defrost mode. When a jumper •...
- Page 31 TABLE 4 DEMAND DEFROST CONTROL (A108) DIAGNOSTIC LEDS DS1 and DS2 System Status, Fault and Lockout Codes Condition/Code Possible Cause(s) Solution Type Green Check control transformer power (24V). No power (24V) to demand defrost If power is available to demand defrost control and Status Power problem control terminals R and C or demand...
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Page 32: Maintenance
NOTICE ! 1. Clean or change filters. Failure to follow instructions will cause damage to 2. Lennox blower motors are prelubricated and perma- the unit. nently sealed. No more lubrication is needed. This unit is equipped with an aluminum coil. -
Page 33: Outdoor Coil
Extended Power Outage 1 - Air Filter – Ask your Lennox dealer to show you The heat pump is equipped with a compressor crankcase where your indoor unit's filter is located. It will be... -
Page 34: Wiring And Sequence Of Operation
Wiring and Sequence of Operation CUT SIZE: 6" WIDE x 10" TALL CMC1 COIL DISCH DUAL GREEN CAPACITOR THERMOSTAT BLACK W1 O O OUT OUTDOOR LO-PS YELLOW BLACK COMPRESSOR COMPRESSOR Y1-OUT S173 CONTACTOR HI-PS 60/ 1 208-230/ GROUND CRANKCASE GROUND CMC1 HEATER COIL... - Page 35 FIGURE 15. Typical Factory Wiring Page 35...
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Page 36: Servicing Units Void Of Charge
ML14KP1 OPERATING SEQUENCE Servicing Units Void of Charge This is the sequence of operation for ML14KP1 series If the outdoor unit is void of refrigerant, clean the system units. The sequence is outlined by numbered steps which using the procedure described below. correspond to circled numbers on the adjacent diagram. -
Page 37: Decommissioning
d) Pump down refrigerant system, if possible. Decommissioning e) If a vacuum is not possible, make a manifold so that Before carrying out this procedure, it is essential that the refrigerant can be removed from various parts of the technician is completely familiar with the equipment and system. - Page 38 Table 2 may be used to help perform maintenance checks. This table is not a procedure Table 2 lists all the Lennox recommended indoor unit matchups along with the charge levels for charging the system and any minor variations in the pressures may be expected due to for the various sizes of outdoor units.
- Page 39 R‐454B Refrigerant Pressure‐Temperature Chart Saturated Saturated Saturated Saturated Saturated Saturated Saturated Saturated Pressure Pressure Pressure Pressure Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor (psig) (psig) (psig) (psig) Temp (°F) Temp (°F) Temp (°F) Temp (°F) Temp (°F) Temp (°F) Temp (°F) Temp (°F) ‐58.9 ‐57.1 58.9 61.3 93.0 95.4 113.4 115.6 ‐19.2 ‐17.2...
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Page 40: Start-Up And Performance Checklist
Start-Up and Performance Checklist Job Name Job no. Date Job Location City State Installer City State Unit Model No. Serial No. Service Technician Nameplate Voltage Rated Load Ampacity Compressor Outdoor Fan Maximum Fuse or Circuit Breaker Electrical Connections Tight? Indoor Filter clean? Supply Voltage (Unit Off) Indoor Blower RPM S.P.
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