Lennox ML14KP1 (R-454B) Series Outdoor Units - Unit Information

General Information & Safety

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 by 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 the blower, remove the 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.

This document provides general guidance and does not supersede national or local codes. Consult authorities having jurisdiction before installation.

The Merit® ML14KP1 model is designed for use with R-454B refrigerant only. It must be installed with an approved indoor air handler or coil. The unit is designed for systems using a thermal expansion valve (TXV) as the refrigerant metering device.

IMPORTANT: Special procedures are required for cleaning the all-aluminum coil in this unit. See page 30 for details.

NOTE: This unit ML14KP1 is a PARTIAL UNIT AIR CONDITIONER, complying with PARTIAL UNIT requirements of UL 60335-2-40/CSA C22.2 No. 60335-2-40, or UL 1995/CSA C22.2 No 236.

Table of Contents

• Installation Clearances
• Model Number Identification
• Dimensions
• Specifications
• Typical Unit Parts Arrangement
• Operating Gauge Set and Service Valves
• Unit Placement
• Removing and Installing Louvered Panels
• New or Replacement Line Set
• Brazing Connections
• Flushing Line Set and Indoor Coil
• Installing Indoor Metering Device
• Leak Test Line Set and Indoor Coil
• Evacuating Line Set and Indoor Coil
• Electrical
• System Operation
• Charging
• System Configuration
• Defrost System
• Maintenance
• Wiring and Sequence of Operation
• Servicing Units Void of Charge
• Start-Up
• Decommissioning

Safety Warnings & Precautions

WARNING: Do not use means to accelerate the defrosting process or to clean, other than those recommended by the manufacturer.

WARNING: The appliance shall be stored in a room without continuously operating ignition sources (e.g., open flames, an operating gas appliance, or an operating electric heater).

WARNING: Do not pierce or burn. Be aware that refrigerants may not contain an odor.

WARNING: Ducts connected to an appliance shall not contain a potential ignition source.

WARNING: Every working procedure that affects safety means shall only be carried out by competent persons. This appliance is not to be used by persons (including children) with reduced physical, sensory or mental capabilities, or lack of experience and knowledge, unless they have been given supervision or instruction concerning use of the appliance by a person responsible for their safety. Children should be supervised to ensure they do not play with the appliance.

IMPORTANT: 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.

IMPORTANT: Verify cabling will not be subject to wear, corrosion, excessive pressure, vibration, sharp edges, or any other adverse environmental effects.

IMPORTANT: Pipe work, including piping material, pipe routing, and installation shall include protection from physical damage in operation and service, and be in compliance with national and local codes and standards, such as ASHRAE 15, ASHRAE 15.2, IAPMO Uniform Mechanical Code, ICC International Mechanical Code, or CSA B52. All field joints shall be accessible for inspection prior to being covered or enclosed.

CAUTION: Under no circumstances shall potential sources of ignition be used in the searching for or detection of refrigerant leaks. A halide torch (or any other detector using a naked flame) shall not be used.

Acceptable leak detection methods include electronic leak detectors (ensure calibration and suitability for R-454B) and leak detection fluids (avoid chlorine-based detergents). If a leak is suspected, extinguish all naked flames.

WARNING: Auxiliary devices which may be a potential ignition source shall not be installed in the duct work.

WARNING: For appliances using A2L refrigerants connected via an air duct system, only use auxiliary devices approved by the manufacturer or declared suitable.

WARNING: For duct-connected appliances, false ceilings or drop ceilings may be used as a return air plenum if a REFRIGERANT DETECTION SYSTEM is provided.

CAUTION: Repair and maintenance to electrical components require initial safety checks, including capacitor discharge and earth bonding continuity. If a fault exists that could compromise safety, do not connect electrical supply until it is satisfactorily dealt with.

IMPORTANT: Work shall be undertaken under a controlled procedure to minimize the risk of flammable gas or vapor. All maintenance staff must be instructed on the work being carried out, and work in confined spaces should be avoided.

IMPORTANT: The area shall be checked with an appropriate refrigerant detector prior to and during work. Ensure leak detection equipment is suitable for all applicable refrigerants (non-sparking, sealed, or intrinsically safe).

IMPORTANT: If any hot work is to be conducted, appropriate fire extinguishing equipment must be available.

CAUTION: No person carrying out work on a refrigerating system involving pipe work shall use any sources of ignition that may lead to fire or explosion. Keep all possible ignition sources, including cigarette smoking, far away from the work site.

IMPORTANT: When changing electrical components, ensure they are fit for purpose and to the correct specification. Follow manufacturer’s maintenance and service guidelines. Check installations using FLAMMABLE REFRIGERANTS for actual charge, ventilation, secondary circuit refrigerant presence, legible markings, and component material suitability.

CAUTION: Sealed electrical components shall be replaced, not repaired.

CAUTION: Intrinsically safe components must be replaced, not repaired.

CAUTION: Some leak detection soaps are corrosive. Rinse piping thoroughly after leak test. Do not use matches, candles, or flame for leak checks.

WARNING: PARTIAL UNITS shall only be connected to an appliance suitable for the same refrigerant.

IMPORTANT: When breaking into the refrigerant circuit, use conventional procedures. For flammable refrigerants, follow best practices such as safe refrigerant removal, purging with inert gas, evacuation, and opening the circuit by cutting or brazing. Recover refrigerant into correct cylinders if venting is not allowed. Purge systems containing flammable refrigerants with oxygen-free nitrogen. Repeat this process until no refrigerant is within the system. Vent down to atmospheric pressure. Ensure vacuum pump outlet is not near ignition sources and ventilation is available.

IMPORTANT: In addition to conventional charging procedures, ensure no contamination of refrigerants occurs. Use short hoses. Keep cylinders in appropriate positions. Earth the refrigerating system before charging. Label the system when charging is complete. Do not overfill. Pressure-test with purging gas and leak-test after charging, before commissioning. Conduct a follow-up leak test before leaving the site.

IMPORTANT: Prior to beginning work on systems containing flammable refrigerants, perform safety checks to minimize ignition risk.

IMPORTANT: During repairs to sealed components, disconnect all electrical supplies before removing covers. If electrical supply is necessary during servicing, use permanently operating leak detection.

IMPORTANT: Ensure casing is not altered in a way that affects the level of protection when working on electrical components. Check for damage to cables, excessive connections, incorrect terminals, damaged seals, or improper glands. Ensure apparatus is mounted securely. Ensure seals have not degraded. Use manufacturer’s specified replacement parts.

IMPORTANT: Before carrying out work on systems containing refrigerant, technicians must be familiar with the equipment. Recover refrigerants safely. Take oil and refrigerant samples if analysis is required for re-use. Ensure electrical power is available. Steps include: familiarization, electrical isolation, mechanical handling equipment availability, PPE, competent supervision, and conforming recovery equipment.

IMPORTANT: After field piping for split systems, pressure test with inert gas and vacuum test prior to refrigerant charging. Field-made joints must be tightness tested with a sensitivity of .2 oz. per year or better.

IMPORTANT: When removing refrigerant for servicing or decommissioning, remove refrigerants safely. Use appropriate recovery cylinders. Ensure correct number of cylinders are available and labeled. Cylinders must have pressure-relief valves and shut-off valves. Evacuate and cool empty cylinders. Recovery equipment must be in good working order with instructions. Calibrated weighing scales and leak-free hoses are required. Check equipment before use. Return recovered refrigerant to the supplier. Do not mix refrigerants. Evacuate compressors and oils to remove flammable refrigerant before returning them.

WARNING: If this appliance is conditioning a space smaller than TAmin, the space must be without continuously operating open flames or other potential ignition sources.

R-454B Refrigerant Information

R-454B is an A2L refrigerant. System installation must meet parameters based on total refrigerant charge and line set length. TAmin (Total minimum conditioned area) is the minimum allowable conditioned area based on total system charge at sea level, adjusted by altitude.

Qmin table refers to minimum airflow requirements for refrigerant leak mitigation.

TAmin Table

NOTE: Multiply TAmin values by the Altitude Adjustment Factors to correct for installed altitude.

Altitude Adjustment Factor Table

Qmin Table

Installation Clearances

NOTES: Service clearance of 30 in. (762 mm) must be maintained on one of the sides adjacent to the control box. Clearance to one of the other three sides must be 36 in. (914 mm). Clearance to one of the remaining two sides may be 12 in. (305 mm) and the final side may be 6 in. (152 mm). A clearance of 24 in. must be maintained between two units. 48 in. (1219 mm) clearance required on top of unit.

Diagram Description: The diagram illustrates the required clearances around the outdoor unit for proper service access and airflow. It shows the control box side requiring 30 inches, other sides requiring 36, 12, and 6 inches respectively, and a 24-inch clearance between units. Top clearance is 48 inches.

Model Number Identification

The model number ML14KP1-036-230A01 breaks down as follows:

• ML: Merit® Series
• 14: Nominal SEER2 rating (14.0 to 16.0)
• K: Refrigerant type (R-454B)
• P: Unit Type (Heat Pump)
• 1: Cooling Stages (Single-Stage Compressor)
• 036: Nominal Cooling Capacity (3 tons)
• 230: Voltage (208/230V-1ph-60Hz)
• A01: Minor Revision Number

Dimensions

Diagram Description: The diagrams show the top and side views of the outdoor unit, indicating inlet and outlet air flow, connections (suction, liquid, electrical), and the compressor location. Dimensions are provided in inches and millimeters.

Specifications

ELECTRICAL DATA

CONTROLS - ORDER SEPARATELY

OPTIONAL ACCESSORIES - ORDER SEPARATELY

NOTE: Extremes of operating range are plus 10% and minus 5% of line voltage. Refrigerant charge is sufficient for 15 ft. of refrigerant lines. For longer line set requirements, see Installation Instructions for information about line set length and additional refrigerant charge.

NOTE: HACR type breaker or fuse. Refer to National or Canadian Electrical Code manual for wire, fuse, and disconnect size requirements. Crankcase Heater and Freezestat are recommended with Low Ambient Kit.

Typical Unit Parts Arrangement

Diagram Description: The diagram illustrates the typical plumbing arrangement of the outdoor unit, showing components such as the defrost coil sensor, check/expansion valve, reversing valve, bi-flow filter drier, pressure switches (low and high), and service valves (liquid and vapor line).

Torque Requirements

Using Manifold Gauge Set

Use a manifold gauge set with low loss anti-blow back fittings, rated for the higher operating pressures of R-454B systems (0-800 psig high side, 30" vacuum to 250 psig low side). Gauge hoses must be rated for up to 800 psig with a 4000 psig burst rating.

Operating Service Valves

Service valves (liquid and vapor line) are used for refrigerant removal, flushing, leak testing, evacuation, checking charge, and charging. Each valve has a service port with a factory-installed valve stem.

Service Valves: Angle and Ball Types

Diagram Description: The diagrams illustrate the operation of angle-type and ball-type service valves, including how to open and close them, and how to access the service port. It also details the procedure for reinstalling stem caps.

Operating Angle Type Service Valve: Remove stem cap, back stem out counterclockwise. When OPEN, service port is open to line set, indoor, and outdoor unit. When CLOSED, service port is open to line set and indoor unit.

Operating Ball Type Service Valve: Remove stem cap. To open, rotate stem counterclockwise 90°. To close, rotate stem clockwise 90°.

To Access Service Port: Remove service port cap, connect gauge set, and replace cap after testing. Finger tighten and torque cap per Table 3, or finger tighten and turn an additional 1/6 turn clockwise without a torque wrench.

Reinstall Stem Cap: Finger tighten and torque cap per Table 3 with a torque wrench, or finger tighten and turn an additional 1/12 turn clockwise without a torque wrench.

Unit Placement

Diagram Description: Figure 3 shows placement guidelines. Detail A illustrates installing the unit away from windows. Detail B shows installing the unit level or with a slope tolerance away from the building structure.

Positioning Considerations:

• Install the unit as far as possible from property lines to comply with local sound ordinances.
• Avoid installing the unit directly outside a window due to high sound transmission through glass.

Placing Unit on Slab: The slab should be high enough above grade to prevent water collection. It should have a slope tolerance as described in Detail B.

Roof Mounting: Install the unit a minimum of 6 inches (152 mm) above the roof surface to avoid ice build-up. Locate above a load-bearing wall. Consult local codes for rooftop applications. A wind barrier may be needed if the unit cannot be placed away from prevailing winter winds.

NOTICE: Protect the roof surface from refrigerant and oil during service and installation, as some roofing materials may absorb oil, causing swelling and leaks.

Removing and Installing Louvered Panels

WARNING: Stow removed panels carefully to prevent injury or damage.

Diagram Description: Figure 4 shows the steps for removing and installing louvered panels. Removal involves unscrewing the panel, lifting it to clear side lips, and tilting it out. Installation involves inserting the panel under the top cap lip, aligning side lips with grooves, and securing with screws.

Removal Steps:

1. Remove mounting screws securing the panel.
2. Slightly lift the panel to clear the side lips from the base.
3. Tilt the panel out slightly and pull downward to remove.

Installation Steps:

1. Insert the panel under the unit top cap lip and lift slightly to clear the side lip from the base.
2. Move the panel towards the unit, aligning side lips with grooves.
3. Secure the panel with mounting screws.

New or Replacement Line Set

This section covers line set installation and replacement. If routing lines through a wall, seal and isolate the opening to prevent vibration transmission.

Field refrigerant piping consists of liquid and suction lines. Use Lennox L15 series line set or field-fabricated lines.

TABLE 2: REFRIGERANT LINE SET – INCHES (MM)

L15 Line Sets: L15-41 (15 ft. - 50 ft.), L15-65 (15 ft. - 50 ft.).

NOTE: Some applications may require a field-provided 7/8" to 1-1/8" adapter.

NOTE: For lines longer than 50 feet, contact Lennox Technical Support. Provide model, size, line set diameters, total length, and number of elbows/rise/drop.

IMPORTANT: Mineral oils are not compatible with R-454B. Use Polyol ester oil. The compressor is charged with POE oil for up to 50 ft. of piping. Add 1 oz of oil for every 5 lbs of refrigerant for systems over 20 lbs.

LINE SET ISOLATION:

Diagram Description: Figure 5 shows methods for isolating refrigerant lines to prevent vibration transmission. It illustrates vertical runs (using wire ties, hangers, sleeves) and horizontal runs (using strapping, wire ties, sleeves).

CAUTION: Brazing alloys and flux are hazardous. Avoid breathing fumes, work in ventilated areas, and wear protective gear.

IMPORTANT: The Clean Air Act of 1990 bans intentional venting of refrigerants. Follow approved recovery, recycling, or reclaiming methods.

IMPORTANT: If matching with older units or coils charged with mineral oil, flush the coil and line set to remove residual mineral oil, which can impede heat transfer and clog the expansion device.

Brazing Connections

Follow procedures in Figures 6 and 7 for brazing line set connections to service valves.

WARNING: Danger of fire. Bleeding the refrigerant charge from only the high side may pressurize the low side. Applying a torch to a pressurized system can ignite the refrigerant/oil mixture.

WARNING: Use nitrogen to pressurize or purge systems. Use a regulator that controls pressure down to 1 or 2 psig.

CAUTION: Brazing alloys and flux are hazardous. Avoid breathing vapors or fumes, perform in well-ventilated areas, and wear protective gear.

IMPORTANT: Allow braze joints to cool before removing wet rags. Temperatures above 250°F can damage valve seals.

IMPORTANT: Use silver alloy brazing rods: 5% minimum silver for copper-to-copper, 45% minimum for copper-to-brass and copper-to-steel.

WARNING: Fire, Explosion, and Personal Safety hazard. Never use oxygen to pressurize or purge refrigeration lines.

Brazing Procedures (Figure 6 & 7)

1. Cut and Debur: Cut refrigerant lines square, debur ends, ensure pipe remains round. Do not crimp.
2. Cap and Core Removal: Remove service caps and cores from suction/vapor and liquid line service ports.
3. Attach Manifold Gauge Set: Connect gauge set low pressure side to liquid line service valve. Connect center port to nitrogen cylinder. Remove core from suction/vapor line service port to allow nitrogen escape. Flow nitrogen (1-2 psig) through the liquid line service port and out the suction/vapor line service port.
4. Wrap Service Valves: Use water-saturated cloths around service valve bodies and copper tube stubs to protect seals. Use additional cloths under the valve body.
5. Flow Nitrogen: Continue flowing nitrogen as described in step 3.
6. Braze Line Set: Wrap service valves with water-saturated cloths. Braze line set connections, pointing flame away from service valves. Keep cloths saturated throughout brazing and cool-down.
7. IMPORTANT: Allow braze joint to cool. Apply additional water-saturated cloths. Do not remove cloths until piping has cooled. Temperatures above 250°F will damage valve seals.
8. WARNING: Fire, injury, or property damage may result if water-saturated cloths are not used. Quench with water after brazing. Do not open service valves until lines and coil are leak-tested and evacuated.
9. Preparation for Next Step: After brazing, disconnect manifold gauge set. Apply water-saturated cloths to cool piping. Remove cloths once cool.

Flushing Line Set and Indoor Coil

Diagram Description: Figure 8 illustrates the procedure for removing the metering device and flushing the system. It shows connecting gauges and equipment, and the flow of refrigerant for flushing.

Typical Existing Expansion Valve Removal Procedure:

1. Remove patch plate, distributor tubes, equalizer line, vapor line sensing bulb, liquid line assembly, and check expansion valve.
2. Disconnect equalizer line from vapor line.
3. Disconnect liquid line from check expansion valve.
4. Remove and discard check expansion valve and Teflon® rings.
5. Temporarily reconnect liquid line to indoor unit's orifice housing.

Connect Gauges and Equipment for Flushing:

1. Connect inverted HCFC-22 cylinder to vapor service valve.
2. Connect HCFC-22 gauge set (low side) to liquid line valve.
3. Connect gauge set center port to recovery machine inlet with an empty recovery tank.
4. Connect recovery tank to recovery machine per instructions.

Flushing Line Set:

Flush the line set and indoor coil with the same amount of clean refrigerant as the system's original charge. Check flushing cylinder charge before proceeding.

1. Set recovery machine for liquid recovery and start it. Open gauge set valves to pull a vacuum on the line set and indoor coil.
2. Invert the clean HCFC-22 cylinder and open its valve to allow liquid refrigerant to flow through the system and into the recovery machine.
3. After liquid recovery, switch to vapor recovery. Allow the machine to pull the system down to 0.
4. Close valves on HCFC-22 drum and gauge set. Pump remaining refrigerant from the machine and turn it off.

IMPORTANT: Use only clean refrigerant (no compressor burnout). If burnout occurred, replace line set and indoor coil.

Installing Indoor Metering Device

This unit uses a check/expansion valve metering device at the indoor coil. The valve can be installed internally or externally. For field-provided plenums, ensure service access.

Indoor Expansion Valve Installation:

1. Remove temporary fitting reconnecting the liquid line.
2. Install Teflon® ring around the expansion valve stub end, lubricate threads and ring surface with refrigerant oil.
3. Attach valve stub end to liquid line orifice housing. Finger tighten, then turn an additional 1/2 turn clockwise (or to 20 ft-lb).
4. Place remaining Teflon® washer on the other end of the valve. Lubricate threads and ring surface.
5. Attach liquid line assembly to the expansion valve. Finger tighten, then turn an additional 1/2 turn clockwise (or to 20 ft-lb).

Sensing Bulb Installation:

Attach the vapor line sensing bulb in the proper orientation using the provided clamp and screws. Ensure proper thermal contact before insulating. For lines smaller than 7/8", mount bulb at 3 or 9 o'clock. For 7/8" and larger lines, mount at 4 or 8 o'clock. Never mount on the bottom of the line.

Equalizer Line Installation:

1. Remove flare seal cap or flare nut/bonnet from the equalizer line port on the vapor line.
2. Connect the equalizer line from the expansion valve to the equalizer vapor port on the vapor line. Finger tighten the flare nut plus 1/8 turn (7 ft-lbs).

Leak Test Line Set and Indoor Coil

IMPORTANT: Follow Clean Air Act regulations regarding refrigerant venting.

IMPORTANT: If matching with older units, flush the system to remove residual mineral oil.

Connect Gauge Set:

1. Connect R-454B manifold gauge set high pressure hose to the vapor valve service port (for pressure protection).
2. Connect R-454B cylinder to the center port of the manifold gauge set.

Test for Leaks:

1. With manifold valves closed, connect R-454B cylinder to the center port. Open R-454B cylinder valve.
2. Open high pressure side of manifold to allow R-454B into the system. Weigh in a trace amount (max 2 oz or 3 lbs pressure). Close R-454B cylinder valve and high pressure manifold valve. Disconnect R-454B cylinder.
3. Connect dry nitrogen cylinder with regulator to the center port.
4. Adjust nitrogen pressure to 160 psig (1103 kPa). Open high side manifold valve to pressurize the system.
5. After a few minutes, open a service valve port to verify refrigerant is measurable by leak detector. Leak check the entire system (joints and line set) to a sensitivity of 5 grams/year.
6. Disconnect gauges from service ports.

WARNING: Use a regulator that can control pressure down to 1 or 2 psig when using nitrogen.

IMPORTANT: Leak detector must be capable of sensing HFC refrigerant.

WARNING: Refrigerant can be harmful if inhaled. Use and recover responsibly.

Evacuating Line Set and Indoor Coil

Diagram Description: Figure 11 shows the setup for evacuating the system using a manifold gauge set, vacuum pump, and nitrogen. It details connecting components and the evacuation process.

Connect Gauge Set:

1. Remove cores from service valves (if not done).
2. Connect low side of manifold gauge set with 1/4 SAE in-line tee to vapor line service valve.
3. Connect high side of manifold gauge set to liquid line service valve.
4. Connect micron gauge to the 1/4 SAE in-line tee.
5. Connect vacuum pump (with gauge) to the center port of the manifold gauge set.

Evacuate the System:

1. Open both manifold valves and start the vacuum pump.
2. Evacuate to an absolute pressure of 23,000 microns (29.01 in. Hg). A rapid pressure rise indicates a large leak; repeat leak testing if necessary.
3. When 23,000 microns is reached, close manifold gauge valves, close vacuum pump valve, turn off pump, and disconnect pump hose.
4. Attach nitrogen cylinder hose to center port, set regulator to 150 psig (1034 kPa), and purge hose. Open manifold gauge valves to break vacuum.
5. Close manifold gauge valves. Shut off nitrogen cylinder, remove hose, and release nitrogen from line set/indoor unit.
6. Reconnect manifold gauge to vacuum pump. Evacuate until absolute pressure does not rise above 500 microns within 20 minutes after pump shutdown.
7. Once requirement is met, disconnect hose from vacuum pump and connect to R-454B cylinder. Open manifold gauge valve 1-2 psig to release vacuum.
8. Close manifold gauge valves. Shut off R-454B cylinder.
9. Reinstall service valve cores quickly with core tool while maintaining positive system pressure.
10. Replace stem caps, finger tighten, then tighten an additional 1/6 turn.

IMPORTANT: Use an electronic vacuum gauge calibrated in microns (down to 50 microns).

WARNING: Avoid deep vacuum operation; do not use compressors for evacuation, as it can cause internal arcing and compressor failure, voiding the warranty.

Evacuating non-condensables is critical for proper operation. Non-condensables and water can corrode copper piping and compressor parts.

Electrical

Wiring must conform to current local codes and the National Electric Code (NEC) in the U.S.A., or Canadian Electrical Code (CEC) in Canada.

Refer to furnace/air handler installation instructions for wiring diagrams and unit nameplate for circuit ampacity and overcurrent protection.

24VAC TRANSFORMER: Use the transformer provided with the furnace or air handler for low-voltage control power (24VAC - 40 VA minimum).

WARNING: Electric Shock Hazard. Ensure unit is properly grounded. Line voltage is present at all components when the unit is not in operation on units with single-pole contactors. Disconnect all remote electric power supplies before opening access panels.

Size Circuit and Install Service Disconnect Switch

Refer to the unit nameplate for minimum circuit ampacity and maximum fuse/breaker (HACR per NEC). Install power wiring and a properly sized disconnect switch.

Diagram Description: A simple diagram shows the main fuse box/breaker panel connected to a service disconnect switch, which then connects to the unit.

Install Thermostat:

Install room thermostat (ordered separately) on an inside wall, approximately in the center of the conditioned area, 5 feet (1.5m) from the floor. Avoid outside walls or areas affected by sunlight or drafts.

Diagram Description: A diagram shows a thermostat mounted on an interior wall, 5 feet from the floor.

System Operation

UNIT COMPONENTS:

IMPORTANT: Some scroll compressors have an internal vacuum protector that unloads scrolls when suction pressure drops below 20 psig. A hissing sound may be heard. The protector resets when low pressure rises above 40 psig. DO NOT REPLACE COMPRESSOR.

The outdoor unit and indoor blower cycle on demand from the room thermostat. If the thermostat blower switch is set to ON, the indoor blower operates continuously.

Bi-Flow Liquid Line Filter Drier: The unit is equipped with a large-capacity bi-flow filter drier for system cleanliness and dryness. Order replacements of the same design and capacity, suitable for R-454B refrigerant.

Low Pressure Switch (S87): Auto-reset switch on the vapor line. Shuts off compressor when vapor pressure falls below factory setting. Ignored during defrost. Closes at 40 ± 5 psig, opens at 25 ± 5 psig. Not adjustable.

High Pressure Switch (S4): Auto-reset switch on the liquid line. Shuts off compressor when discharge pressure rises above factory setting. Normally closed, trips (opens) at 590 ± 15 psig.

Crankcase Heater (HR1): Belly band type heater prevents liquid from accumulating in the compressor. Controlled by an integrated thermostat switch. On when compressor is not operating. Closes at 45°F, opens at 65°F.

Diagram Description: Figure 12 shows the Field Wiring Diagram for a Single-Stage Heat Pump with Air Handler, illustrating connections between the thermostat, RDS sensor, outdoor unit terminal block (black), and indoor unit terminal block (blue) for various control signals (W1, W2, G, O/B, R, C, Y1, Y2, DS, etc.).

Charging

Verify unit is electrically grounded before charging. Do not overfill the refrigerating system.

Charge should be checked and adjusted using information in this section and on the unit’s charging label. R454B is a zeotropic blend with two saturation temperatures at any given pressure.

Units must be charged with liquid refrigerant. Follow conventional procedures. Mark the total charge (factory + additional) on the unit nameplate.

R454B cylinders have a 1/4" LH flare connection; a 1/4" LH female flare adapter is required. Connect manifold gauges and position cylinder to deliver liquid refrigerant.

The ML14KP1 is factory-charged for a 15-foot refrigerant piping length. For lines over 15 feet, add 3 oz of refrigerant for every 5 feet of piping beyond 15 feet.

Initiate cooling demand and allow pressures/temperatures to stabilize. Adjust charge using the subcooling method. Subcooling = Saturated Liquid Temperature – Liquid Line Temperature. Compare results with the unit charging label.

NOTE: Nameplate shown is for illustration only.

System Configuration: Demand Defrost Control (A108)

The demand defrost control monitors ambient temperature, outdoor coil temperature, and run time to detect frost build-up. It self-calibrates and adjusts frost accumulation time based on previous defrost cycle history.

Control Connections, Jumpers, Settings, and Features:

• P1 (Defrost Termination Jumper): Selections: 50, 70, 90, 100°F (10, 21, 32, 38°C). Factory default is 50°F (10°C) if shunt is not installed, default is 90°F (32°C).
• P3 (Nominal Defrost Time Selection): Options: 165, 140, 100, 60 seconds. Factory default is 140 seconds.
• P5 (Compressor Delay Mode): Jumper on DELAY pins cycles compressor off for 30 seconds during defrost mode entry/exit. Shipped with jumper installed.
• Diagnostic LEDs (DS1/DS2): Indicate system status, faults, and lockouts.

Diagram Description: Figure 13 shows the Demand Defrost Control (A108) board, highlighting test pins (P1), defrost termination settings (P1), sensor connections (P4), delay pins (P5), reversing valve (O OUT), pressure switch connections, nominal defrost time selection (P3), diagnostic LEDs (DS1/DS2), 24V terminal strip connections (P2), and fan connections.

TABLE 3: DEMAND DEFROST CONTROL (A108) INPUTS, OUTPUTS AND CONFIGURABLE SETTINGS

TABLE 4: DEMAND DEFROST CONTROL (A108) DIAGNOSTIC LEDS

Defrost System

The defrost system prevents frost build-up on the outdoor coil during heating mode.

Emergency Heat (Amber Light):

Some thermostats have an emergency heat function. This isolates the outdoor unit and bypasses outdoor thermostats. An amber light indicates emergency heat mode. Use during outdoor unit shutdown or after a power outage if outdoor temperature is below 50°F (10°C).

Defrost System Overview:

The control monitors ambient temperature, outdoor coil temperature, and total run time to determine when a defrost cycle is needed. The coil temperature probe is mounted between the TXV outlet and the distributor.

NOTE: The demand defrost control measures frost accumulation, leading to longer run times between defrost cycles.

Demand Defrost Operation:

The control uses a time-dependent frost accumulation algorithm. It monitors ambient temperature, outdoor coil temperature, and compressor run time. When the outdoor coil temperature is below 37°F, it accumulates frost time. Once met, a defrost cycle is initiated.

The unit runs in defrost mode until the coil temperature reaches the termination setpoint. Maximum defrost cycle is 14 minutes. It can also be terminated by room thermostat demand or if the cycle exceeds 14 minutes.

Two consecutive low pressure switch trips in heating mode can also initiate defrost.

Frost Accumulation Time:

This is the time the heat pump runs in heating mode below 37°F. Initial target is 90 minutes, adjusted based on previous defrost cycle history. If defrost cycle time is short (≤70%), accumulation time increases by 30 min. If long (≥130%), it decreases by 30 min. If significantly longer (≥200%) or terminates at max time, accumulation time is set to 30 min. No change if within 70%-130% of target.

Cold Climate Defrost:

Below 10°F, frost accumulation time is set to 360 minutes to reduce defrost frequency and increase efficiency. Normal operation resumes above 15°F, resetting accumulation time to 90 minutes.

NOTE: Colder climates may require higher defrost termination temperatures to ensure the coil is cleared of frost.

Maintenance

Maintenance and service must be performed by a qualified installer or service agency.

Outdoor Unit:

1. Clean and inspect outdoor coil (flush with water hose). Ensure power is off.
2. Outdoor unit fan motor is pre-lubricated and sealed; no further lubrication is needed.
3. Visually inspect connecting lines, joints, and coils for oil leaks.
4. Check all wiring for loose connections.
5. Check for correct voltage at unit (operating).
6. Check amp draw on outdoor fan motor.
7. Inspect and clean drain holes in coil compartment base.

NOTE: If insufficient heating/cooling occurs, check refrigerant charge.

Outdoor Coil Maintenance:

Flush outdoor coil more frequently if exposed to corrosive substances or airflow-blocking debris (e.g., pet urine, cottonwood seeds, salts). Use a water hose for flushing. Coastal areas require frequent cleaning due to salt corrosion.

Indoor Unit:

1. Clean or change filters.
2. Lennox blower motors are pre-lubricated and sealed.
3. Adjust blower speed for cooling. Measure pressure drop over the coil to determine correct blower CFM.
4. Belt Drive Blowers: Check belt for wear and tension.
5. Check all wiring for loose connections.
6. Check for correct voltage at unit (blower operating).
7. Check amp draw on blower motor.
8. Indoor Coil: Clean coil if necessary. Check connecting lines, joints, and coil for oil leaks. Check condensate line and clean if necessary.

Homeowner Maintenance:

Cleaning of the outdoor unit's coil should be performed by a trained service technician. Contact your dealer for a schedule (preferably twice a year, at least once a year). Homeowners can assist with basic checks.

IMPORTANT: Sprinklers and soaker hoses should not expose the outdoor unit to treated water, as it can corrode parts and affect performance.

Routine Maintenance: Clogged filters and blocked airflow reduce efficiency. Check air filters monthly and clean or replace as needed. Use disposable filters of the same type/size. Reusable foam filters can be cleaned with mild soap and water.

Thermostat Operation: Refer to the thermostat homeowner manual.

Heat Pump Operation:

Heat pumps deliver large volumes of warm air. Frost may develop on the outdoor coil in winter below 45°F (7°C). An electronic control activates a defrost cycle (5-15 min) at intervals to clear frost. Steam may be seen rising from the unit during defrost. Auxiliary heat may engage to satisfy demand.

Extended Power Outage:

The heat pump has a crankcase heater. For outages of several hours or more, set the thermostat to EMERGENCY HEAT to protect the heat pump. Auxiliary heat satisfies demand; heat pump operation is locked out.

Preservice Check:

Before calling for service, verify thermostat settings, ensure disconnect switches are ON, check for blown fuses/tripped breakers, confirm unit access panels are in place, and verify the air filter is clean.

Accessories: Refer to Lennox ML14KP1 Product Specification bulletin, Lennox Product Catalog, and Lennox Price Book for current information.

Wiring and Sequence of Operation

Diagram Description: Figure 14 shows the Typical Unit Wiring diagram, illustrating the electrical connections between the thermostat, outdoor fan, compressor, compressor contactor, crankcase heater, reversing valve, and various switches (high pressure, low pressure, defrost, thermal protection) via the defrost control board (CMC1). Figure 15 shows Typical Factory Wiring.

Operating Sequence:

COOLING: Thermostat energizes terminal O, activating the reversing valve (L1). Demand at Y1 energizes compressor contactor K1. K1-1 closes, energizing compressor (B1) and outdoor fan motor (B4).

END OF COOLING DEMAND: Y1 de-energized, K1 de-energized, compressor and fan stop.

FIRST STAGE HEAT: Thermostat de-energizes terminal O, de-energizing the reversing valve (L1). Sequence is similar to cooling.

DEFROST MODE: Control energizes reversing valve solenoid and turns off condenser fan. 24VAC is applied to W1 (auxiliary heat). Unit stays in defrost until coil sensor temp reaches termination setpoint, 14 min defrost time is completed, or thermostat demand is satisfied.

Servicing Units Void of Charge:

1. Leak check system.
2. Evacuate system.
3. Use nitrogen to break vacuum and install new filter drier.
4. Evacuate system again.
5. Weigh in refrigerant.

Start-Up:

IMPORTANT: If unit has a crankcase heater, energize it 24 hours before start-up to prevent compressor damage.

1. Rotate fan to check for binding.
2. Inspect all wiring for loose connections.
3. After evacuation, open liquid and suction line service valves to release refrigerant charge.
4. Replace stem caps and tighten as specified.
5. Check voltage supply at disconnect switch; ensure it is within nameplate range.
6. Set thermostat for cooling demand. Turn on indoor unit power and close outdoor unit disconnect switch.
7. Check system for sufficient refrigerant using start-up/charging procedures.
8. Recheck voltage while running.

Decommissioning

Technicians must be familiar with the equipment. Recover refrigerants safely. Take oil/refrigerant samples if needed. Ensure electrical power is available.

1. Familiarize with equipment operation.
2. Isolate system electrically.
3. Ensure mechanical handling equipment, PPE, competent supervision, and conforming recovery equipment are available.
4. Pump down refrigerant system if possible.
5. If vacuum is not possible, use a manifold to remove refrigerant from various parts.
6. Ensure cylinder is on scales before recovery.
7. Start recovery machine per instructions.
8. Do not overfill cylinders (max 80% liquid charge).
9. Do not exceed cylinder maximum working pressure.
10. When cylinders are filled, remove equipment promptly and close isolation valves.
11. Recovered refrigerant shall not be charged into another system unless cleaned and checked.

IMPORTANT: Label equipment as decommissioned and emptied of refrigerant, signed and dated. Ensure labels state refrigerant flammability.

R-454B Refrigerant Charging Information

Use Table 1 for normal operating pressures and Table 2 for indoor unit matches and subcooling charge levels. Charge levels on the nameplate are for 15ft. line sets; add 3 oz. refrigerant for every 5 ft. longer than 15 ft.

Cooling Mode (≥60°F ambient): Adjust charge using subcooling method (target values based on 70-80°F indoor return air).

Heating Mode (<60°F ambient): Adjust charge using subcooling method (target values based on 65-75°F indoor return air).

Weigh-in Method: If system is void, repair leaks, evacuate, then weigh in charge, adjusting for matchup and line set length. If weighing facilities are unavailable, use subcooling method.

TABLE 1: Normal Operating Pressures (Liquid & Suction ±5 psig)

*Temperature of air entering the outdoor coil.

TABLE 2: Indoor Unit Matches and Subcooling Charge Levels and Additional Charge**

**Amount of charge required in addition to charge shown on unit nameplate.

R-454B Refrigerant Pressure-Temperature Chart

Notes:

• R-454B is a zeotropic blend and must be charged with liquid refrigerant only.
• Saturated liquid temperature is used to calculate liquid subcooling.
• Saturated vapor temperature is used to calculate suction superheat.
• See unit charging label for subcooling values and additional charging information.

Start-Up and Performance Checklist

This section provides a checklist for installers to complete after installation and before final system operation. It covers checks for job details, unit information, electrical connections, indoor filter, airflow, pressures, refrigerant charge, service valves, and thermostat settings.