LENNOX ML18XC2 Outdoor Air Conditioner Installation Guide

LENNOX ML18XC2 Outdoor Air Conditioner

Product Information

Specifications

• Model Numbers:
  • ML18XC2-024-230A
  • ML18XC2-036-230A
  • ML18XC2-048-230A
  • ML18XC2-060-230A
• All-aluminum coil
• Designed for use with HFC-410A refrigerant

Installation Instructions
This ML18XC2 outdoor air conditioner must be installed with an approved indoor air handler or coil. Please consult authorities having jurisdiction before installation, as these instructions are intended as a general guide and do not supersede local codes.

Warnings and Cautions

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, or service agency.

CAUTION: Take care while handling the equipment to avoid contact with sharp sheet metal edges that may result in personal injury. Wear gloves and protective clothing.

Cleaning Instructions
Special procedures are required for cleaning the all-aluminum coil in this unit. Please refer to page 16 of the instruction manual for detailed information.

Clearance Requirements
The following clearance requirements must be maintained for proper installation:

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

NOTICE: Specific applications may require adjustment of the listed installation clearances to provide protection for the unit from physical damage or to avoid conditions that limit operating efficiency. Additional clearances may be required to prevent snow or ice from falling on the top of the unit or to prevent air recirculation when installed in a tight space.

Unit Dimensions
Refer to Figure 1 and Table 1 for unit dimensions:

Product Usage Instructions

• Step 1: Ensure the electrical power to the unit is turned OFF at the disconnect switch before performing any service or maintenance.
• Step 2: Follow the installation instructions provided in the manual to properly install the ML18XC2 outdoor air conditioner with an approved indoor air handler or coil.
• Step 3: Maintain the required clearance around the unit for optimal performance. Refer to the clearance requirements section for specific measurements.
• Step 4: If cleaning of the all-aluminum coil is required, follow the special procedures mentioned on page 16 of the instruction manual.
• Step 5: For charging information, refer to the charging procedure sticker on the unit access panel. For more in-depth information, consult the Installation and Service Procedures manual on LennoxPros.com or contact the Technical Support department at 800-453-6669.

FAQ

• Q: What refrigerant is compatible with this air conditioner?
• A: This air conditioner is designed for use with HFC-410A refrigerant only.
• Q: Can I perform the installation and service myself?
• A: No, installation and service must be performed by a licensed professional HVAC installer or equivalent, or service agency.
• Q: How should I handle the removed panels during installation or service?
• A: Carefully stow all removed panels to prevent injury to personnel, objects, or nearby structures. Consider weather conditions, especially wind, that may cause panels to be blown around and damaged.

General

This ML18XC2 outdoor air conditioner with an all-aluminum coil is designed for use with HFC-410A refrigerant only. This unit must be installed with an approved indoor air handler or coil. For AHRI Certified system match-ups and expanded ratings, visit www.LennoxPros.com. These instructions are intended as a general guide and do not supersede local codes in any way. Consult authorities having jurisdiction before installation.

NOTICE!
Charging information is given on the charging procedure sticker on the unit access panel. For more in-depth information, consult the Installation and Service Procedures manual on LennoxPros.com or through the Technical Support department at 800-453-6669.

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, or service agency.

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.

IMPORTANT :
Special procedures are required for cleaning the all-aluminum coil in this unit. See page 16 in this instruction for information.

STEP 1 SETTING THE UNIT 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 is required on top of the unit.

NOTICE : Specific applications may require adjustment of the listed installation clearances to provide protection for the unit from physical damage or to avoid conditions that limit operating efficiency. (Example: Clearances may have to be increased to prevent snow or ice from falling on the top of the unit. Additional clearances may also be required to prevent air recirculation when the unit is installed under a deck or in another tight space.)

TABLE 1
UNIT DIMENSIONS

CAUTION
Before attempting to perform any service or maintenance, turn the electrical power to the unit OFF at the disconnect switch.

WARNING
To prevent personal injury, as well as damage to panels, units, or structures, observe the following: While installing or servicing this unit, carefully stow all removed panels so that the panels will not cause injury to personnel, objects, or nearby structures. Also, take care to store panels where they will not be subject to damage (e.g., being bent or scratched). While handling or stowing the panels, consider any weather conditions (especially wind) that may cause panels to be blown around and damaged.

NOTICE!
Roof Damage! This system contains both refrigerant and oil. Some rubber roofing material may absorb oil, causing the rubber to degrade. Failure to follow this notice could result in damage to the roof surface.

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.

IMPORTANT
Exhaust vents from dryers, water heaters, and furnaces should be directed away from the outdoor unit. Prolonged exposure to exhaust gases and the chemicals contained within them may cause condensation to form on the steel cabinet and other metal components of the outdoor unit. This will diminish unit performance and longevity.

STEP 2 REFRIGERANT PIPING Flushing Existing Line Set & Indoor Coil

WARNING
Refrigerant can be harmful if it is inhaled. Refrigerant must be used and recovered responsibly. Failure to follow this warning may result in personal injury or death.

IMPORTANT
If this unit is being matched with an approved line set or indoor unit coil that was previously charged with mineral oil, or if it is being matched with a coil that was manufactured before January 1999, the coil and line set must be flushed before installation. Take care to empty all existing traps. Polyvinyl ether (PVE) oils are used in Lennox variable-capacity units charged with HFC- 410A refrigerant. Residual mineral oil can act as an insulator, preventing proper heat transfer. It can also clog the expansion device and reduce system performance and capacity. Failure to properly flush the system per this instruction and the detailed Installation and Service Procedures manual will void the warranty.

Flush the existing line set per the following instructions. For more information, refer to the Installation and ServiceProcedures manual available on LennoxPros.com.

CAUTION
DO NOT attempt to flush and re-use existing line sets or indoor coil when the system contains contaminants (i.e., compressor burnout).

If a new line set is being installed, size the piping per table 2.

WARNING
When using a high-pressure gas such as nitrogen to pressurize a refrigeration or air conditioning system, use a regulator that can control the pressure down to 1 or 2 psig (6.9 to 13.8 kPa).

WARNING
Polyol ester (POE) oils used with HFC-410A refrigerant absorb moisture very quickly. The refrigerant system must be kept closed as much as possible. DO NOT remove line set caps or service valve stub caps until you are ready to make connections.

WARNING
Fire, Explosion, and Personal Safety hazard. Failure to follow this warning could result in damage, personal injury, or death. Never use oxygen to pressurize or purge refrigeration lines. Oxygen, when exposed to a spark or open flame, can cause fire and/ or an explosion, that could result in property damage, personal injury, or death.

LIQUID LINE FILTER DRIER INSTALLATION
The provided filter drier must be field installed in the liquid line between the outdoor unit’s liquid line service valve and the indoor coil’s metering device (fixed orifice or TXV) as illustrated in Figure 5. This filter drier must be installed to ensure a clean, moisture-free system. Failure to install the filter drier will void the warranty. A replacement filter drier is available from Lennox. See Brazing Connections page 6 for special procedures on brazing filter drier connections to the liquid line.

TABLE 2
REFRIGERANT LINE SET – INCHES (MM)

Model Number

| Valve Size Connections| Recommended Line Sets
---|---|---
Liquid Line| Suction Line| L15 Line Set Model| Line Set Length| Catalog Number

ML18XC2-024-230

| ****

3/8” (10 mm)

| ****

3/4” (19 mm)

| L15-41-20| 20 feet (6.1 m)| 89J56
L15-41-30| 30 feet (9.1 m)| 89J57
L15-41-40| 40 feet (12.2 m)| 89J58
L15-41-50| 50 feet (15.2 m)| 89J59

ML18XC2-036-230 ML18XC2-048-230

| ****

3/8” (10 mm)

| ****

7/8” (22 mm)

| L15-65-30| 30 feet (9.1 m)| 89J60
L15-65-40| 40 feet (12.2 m)| 89J61
L15-65-50| 50 feet (15.2 m)| 89J62
ML18XC2-060-230| 3/8” (10 mm)| 1-1/8” (29 mm) *| Field-fabricated| N/A| N/A

• Some applications may require a field-provided 1-1/8” to 7/8” adapter.

NOTE
When installing refrigerant lines longer than 50 feet, refer to the Refrigerant Piping Design and Fabrication Guidelines manual available on LennoxPros.com (Corp. 9351-L9), or contact the Technical Support Department Product Application group for assistance.

NOTE
 For new or replacement line set installation, refer to Service and Application Note – Corp. 9112-L4 (C-91-4).

LINE SET
IMPORTANT — Refrigerant lines must not contact structure.

INSTALLATION

Line Set Isolation
The following illustrations are examples of proper refrigerant line set isolation:

REFRIGERANT LINE SET TRANSITION FROM VERTICAL TO HORIZONTAL

REFRIGERANT LINE SET INSTALLING HORIZONTAL RUNS
To hang the line set from a joist or rafter, use either metal strapping material or anchored heavy nylon wire ties.

REFRIGERANT LINE SET INSTALLING VERTICAL RUNS
(NEW CONSTRUCTION SHOWN)

IMPORTANT
Refrigerant lines must not contact the wall

NOTE
Insulate liquid line when it is routed through areas where the surrounding ambient temperature could become higher than the temperature of the liquid line or when pressure drop is equal to or greater than 20 psig.

IMPORTANT
Refrigerant lines must not contact the wall

NOTE
Similar installation practices should be used if the line set is to be installed on the exterior of outside wall

TYPICAL EXISTING FIXED ORIFICE REMOVAL PROCEDURE
(UNCASED COIL SHOWN)

• A – On fully cased coils, remove the coil access and plumbing panels.
• B – Remove any shipping clamps from the liquid line and distributor assembly.
• C – Using two wrenches, disconnect the liquid line from the liquid line orifice housing. Take care not to twist or damage distributor tubes during this process.
• D – Remove and discard the fixed orifice, valve stem assembly (if present), and Teflon® washer as illustrated above.
• E – Use a field-provided fitting to temporarily reconnect the liquid line to the indoor unit’s liquid line orifice housing.

CONNECT GAUGES AND EQUIPMENT FOR FLUSHING PROCEDURE

• A – HCFC-22 cylinder with clean refrigerant (positioned to deliver liquid refrigerant) to the vapor service valve.
• B – HCFC-22 gauge set (low side) to the liquid line valve.
• C – HCFC-22 gauge set center port to inlet on the recovery machine with an empty recovery tank connected to the gauge set.
• D – Connect the recovery tank to the recovery machine per machine instructions.

TYPICAL EXISTING EXPANSION VALVE REMOVAL PROCEDURE
(UNCASED COIL SHOWN)

• A – On fully cased coils, remove the coil access and plumbing panels.
• B – Remove any shipping clamps from the liquid line and distributor assembly.
• C – Disconnect the equalizer line from the check expansion valve equalizer line fitting on the vapor line.
• D – Remove the vapor line sensing bulb.
• E – Disconnect the liquid line from the check expansion valve at the liquid line assembly.
• F – Disconnect the check expansion valve from the liquid line orifice housing. Take care not to twist or damage distributor tubes during this process.
• G – Remove and discard the check expansion valve and the two Teflon® rings.
• H – Use a field-provided fitting to temporarily reconnect the liquid line to the indoor unit’s liquid line orifice housing.

FLUSHING LINE SET

The line set and indoor unit coil must be flushed with at least the same amount of clean refrigerant that previously charged the system. Check the charge in the flushing cylinder before proceeding.

• A – Set the recovery machine for liquid recovery and start the recovery machine. Open the gauge set valves to allow the recovery machine to pull a vacuum on the existing system line set and indoor unit coil.
• B – Position the cylinder of clean HCFC-22 for delivery of liquid refrigerant and open its valve to allow liquid refrigerant to flow into the system through the vapor line valve. Allow the refrigerant to pass from the cylinder and through the line set and the indoor unit coil before it enters the recovery machine.
• C – After all of the liquid refrigerant has been recovered, switch the recovery machine to vapor recovery so that all of the HCFC-22 vapor is recovered. Allow the recovery machine to pull the system down to 0.
• D – Close the valve on the inverted HCFC-22 drum and the gauge set valves. Pump the remaining refrigerant out of the recovery machine and turn the machine off.

REFRIGERANT PIPING

Brazing Procedures

1. CUT AND DEBURR
   Cut the ends of the refrigerant lines square (free from nicks or dents) and debur the ends. The pipe must remain round. Do not crimp the end of the line .

2. CAP AND CORE REMOVAL
   Remove the service cap and core from both the vapor and liquid line service ports.

3. ATTACH THE MANIFOLD GAUGE SET FOR BRAZING LIQUID AND VAPOR LINE SERVICE VALVES
   Flow regulated nitrogen (at 1 to 2 psig) through the low-side refrigeration gauge set into the liquid line service port valve, and out of the vapor line service port valve.

   • A – Connect gauge set low-pressure side to liquid line service valve (service port).

   • B – Connect the gauge set center port to a bottle of nitrogen with the regulator.

   • C – Remove the core from the valve in the vapor line service port to allow nitrogen to escape.

   • CAUTION
     

   • Brazing alloys and flux contain materials that are hazardous to your health.

   • Avoid breathing vapors or fumes from brazing operations. Perform operations only in well-ventilated areas.

   • Wear gloves and protective goggles or face shields to protect against burns.

   • Wash hands with soap and water after handling brazing alloys and flux.

   • WARNING: Danger of fire. Bleeding the refrigerant charge from only the high side may result in pressurization of the low side shell and suction tubing. Application of a brazing torch to a pressurized system may result in the ignition of the refrigerant and oil mixture. Check the high and low pressures before applying heat.

4. 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.

5. 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 vapor, valve stem port. See steps 3A, 3B, and 3C on manifold gauge set connections.

6. BRAZE LINE SET
   Wrap both service valves with water-saturated cloths as illustrated here and as mentioned in step 4, before brazing to the line set. Clothes must remain water-saturated throughout the brazing and cool-down process.
   WARNING: FIRE, PERSONAL INJURY, OR PROPERTY DAMAGE may result if you do not wrap a water-saturated cloth around both liquid and suction line service valve bodies and copper tube stub while brazing the line set! The braze, when complete, must be quenched with water to absorb any residual heat. Do not open service valves until refrigerant lines and indoor coil have been leak-tested and evacuated. Refer to the Installation and Service Procedures manual found on LennoxPros.com.

7. PREPARATION FOR THE NEXT STEP
   After all connections have been brazed, disconnect the manifold gauge set from service ports. Apply additional water-saturated cloths to both service valves to cool the piping. Once the piping is cool, remove all water-saturated cloths.

Install Indoor Expansion Valve
This outdoor unit is designed for use in systems that use an expansion valve metering device (purchased separately) at the indoor coil. See the ML18XC2 Product Specifications bulletin (EHB) for approved expansion valve kit matchups. The expansion valve unit can be installed internal or external to the indoor coil. In applications where an uncased coil is being installed in a field-provided plenum, install the expansion valve in a manner that will provide access for field servicing of the expansion valve. Refer to the below illustration for reference during the installation of the expansion valve unit.

INDOOR EXPANSION VALVE INSTALLATION

EQUALIZER LINE INSTALLATION

1. Remove and discard either the flare seal cap or flare nut with copper flare seal bonnet from the equalizer line port on the vapor line as illustrated in the figure below.
2. Remove the field-provided fitting that temporarily reconnected the liquid line to the indoor unit’s distributor assembly.
3. Install one of the provided Teflon® rings around the stubbed end of the check expansion valve lightly lubricate the connector threads and expose the surface of the Teflon® ring with refrigerant oil.
4. Attach the stubbed end of the check expansion valve to the liquid line orifice housing. Finger tighten and use an appropriately sized wrench to turn an additional 1/2 turn clockwise as illustrated in the figure above, or tighten to 20 ft-lb.
5. Place the remaining Teflon® washer around the other end of the check expansion valve. Lightly lubricate connector threads and expose the surface of the Teflon® ring with refrigerant oil.
6. Attach the liquid line assembly to the check expansion valve. Finger tighten and use an appropriately sized wrench to turn an additional 1/2 turn clockwise as illustrated in the figure above or tighten to 20 ft-lb.

SENSING BULB INSTALLATION

1. Attach the vapor line sensing bulb in the proper orientation as illustrated below using provided.
   ON LINES SMALLER THAN 3/4″, MOUNT THE SENSING BULB AT EITHER THE 1 OR 11 O’CLOCK POSITION. ON 3/4″ AND LARGER LINES, MOUNT THE SENSING BULB AT EITHER THE 3 OR 9 O’CLOCK POSITION.

   • NOTE
     NEVER MOUNT THE SENSING BULB ON THE BOTTOM OF THE LINE.

   • NOTE
     Though it is preferred to have the sensing bulb installed on a horizontal run of the vapor line, installation on a vertical run of piping is acceptable if necessary. See figure to right for proper bulb orientation on a vertical run of piping.

   • NOTE
     Confirm proper thermal contact between the vapor line and check/expansion bulb before insulating the sensing bulb once installed.

2.  Connect the equalizer line from the check expansion valve to the equalizer vapor port on the vapor line. Finger tighten the flare nut plus 1/8 turn (7 ft-Ibs) as illustrated to the right.

LEAK TEST AND EVACUATION

1. CONNECT GAUGE SET
   

2. A – Connect the high-pressure hose of an HFC-410A manifold gauge set to the vapor valve service port.

  *  **NOTE:** Normally, the high-pressure hose is connected to the liquid line port. However, connecting it to the vapor port better protects the manifold gauge set from high-pressure damage.
2.  **B** – With both manifold valves closed, connect the cylinder of HFC-410A refrigerant to the center port of the manifold gauge set.
  *  **NOTE** – Later in the procedure, the HFC-410A container will be replaced by the nitrogen container.

2. TEST FOR LEAKS
   After the line set has been connected to the indoor and outdoor units, check the line set connections and indoor unit for leaks. Use the following procedure to test for leaks:

   • A – With both manifold valves closed, connect the cylinder of HFC-410A refrigerant to the center port of the manifold gauge set. Open the valve on the HFC-410A cylinder (vapor only).
   • B – Open the high-pressure side of the manifold to allow HFC-410A into the line set and indoor unit. Weigh in a trace amount of HFC-410A. [A trace amount is a maximum of two ounces (57 g) refrigerant or three pounds (31 kPa) pressure.] Close the valve on the HFC-410A cylinder and the valve on the high-pressure side of the manifold gauge set. Disconnect the HFC-410A cylinder.
   • C – Connect a cylinder of nitrogen with a pressure regulating valve to the center port of the manifold gauge set.
   • D – Adjust nitrogen pressure to 150 psig (1034 kPa). Open the valve on the high side of the manifold gauge set to pressurize the line set and the indoor unit.
   • E – After a few minutes, open one of the service valve ports and verify that the refrigerant added to the system earlier is measurable with a leak detector.
   • F – After leak testing, disconnect gauges from service ports.

3. CONNECT GAUGE SET
   NOTE Remove cores from service valves (if not already done).

   • A – Connect the low side of the manifold gauge set with 1/4 SAE in-line tee to the vapor line service valve
   • B – Connect the high side of the manifold gauge set to the liquid line service valve
   • C – Connect the available micron gauge connector on the 1/4 SAE in-line tee.
   • D – Connect the vacuum pump (with vacuum gauge) to the center port of the manifold gauge set. The center port line will be used later for both the HFC-410A and nitrogen containers.

4. EVACUATE THE SYSTEM

   • A – Open both manifold valves and start the vacuum pump.
   • B – Evacuate the line set and indoor unit to an absolute pressure of 23,000 microns (29.01 inches of mercury).
   • NOTE – During the early stages of evacuation, closing the manifold gauge valve at least once is desirable. A rapid rise in pressure indicates a relatively large leak. If this occurs, repeat the leak testing procedure.
   • NOTE – Absolute pressure means the total actual pressure above absolute zero within a given volume or system. Absolute pressure in a vacuum is equal to atmospheric pressure minus vacuum pressure.
   • WARNING! Possible equipment damage. Avoid deep vacuum operation. Do not use compressors to evacuate a system. Extremely low vacuum can cause internal arcing and compressor failure. Damage caused by deep vacuum operation will void the warranty.
   • C – When the absolute pressure reaches 23,000 microns (29.01 inches of mercury), perform the following:
   • Close manifold gauge valves.
   • Close the valve on the vacuum pump.
   • Turn off the vacuum pump.
   • Disconnect the manifold gauge center port hose from the vacuum pump.
   • Attach the manifold center port hose to a nitrogen cylinder with a pressure regulator set to 150 psig (1034 kPa) and purge the hose.
   • Open manifold gauge valves to break the vacuum in the line set and indoor unit.
   • Close manifold gauge valves.
   • D – Shut off the nitrogen cylinder and remove the manifold gauge hose from the cylinder. Open the manifold gauge valves to release the nitrogen from the line set and indoor unit.
   • E – Reconnect the manifold gauge to the vacuum pump, turn the pump on, and continue to evacuate the line set and indoor unit until the absolute pressure does not rise above 500 microns (29.9 inches of mercury) within 20 minutes after shutting off the vacuum pump and closing the manifold gauge valves.
   • F – When the absolute pressure requirement above has been met, disconnect the manifold hose from the vacuum pump and connect it to a cylinder of HFC-410A positioned to deliver liquid refrigerant. Open the manifold gauge valve 1 to 2 psig to release the vacuum in the line set and indoor unit.
   • G – Perform the following:
   • Close manifold gauge valves. 1/6
   • TURN Shut off the HFC-410A cylinder.
   • Reinstall service valve cores by removing the manifold hose from the service valve. Quickly install cores with the core tool while maintaining a positive system pressure.
   • Replace stem caps and finger-tighten them, then tighten an additional one-sixth (1/6) of a turn as illustrated.

ELECTRICAL

Circuit Sizing and Wire Routing
In the U.S.A., wiring must conform to current local codes and the current National Electric Code (NEC). In Canada, wiring must conform with current local codes and the current Canadian Electrical Code (CEC). Refer to the furnace or air handler installation instructions for additional wiring application diagrams and refer to the unit nameplate for minimum circuit ampacity and maximum overcurrent protection size.

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

WARNING
Electric Shock Hazard. Can cause injury or death. The unit must be properly grounded in national and local codes. Line voltage is present at all components when it is not in operation on units with single-pole contactors. Disconnect all remote electric power supplies before opening the access panel. The unit may have multiple power supplies.

IMPORTANT
If the unit is equipped with a crankcase heater, it should be energized 24 hours before unit start-up to prevent compressor damage as a result of slugging.

WARNING
Fire Hazard. Use of aluminum wire with this product may result in a fire, causing property damage, severe injury, or death. Use copper wire only with this product.

WARNING
Failure to use properly sized wiring and circuit breakers may result in property damage. Size wiring and circuit breaker(s) per Product Specifications bulletin (EHB) and unit rating plate.

WARNING
ELECTROSTATIC DISCHARGE(ESD)

Precautions and Procedures
Electrostatic discharge can affect electronic components. Take care during unit installation and service to protect the unit’s electronic controls. Precautions will help to avoid control exposure to electrostatic discharge by putting the unit, the control,l, and the technician at the same electrostatic potential. Touch your hand and all tools on an unpainted unit surface before performing any service procedure to neutralize electrostatic charge.

SIZE CIRCUIT AND INSTALL SERVICE DISCONNECT SWITCH
Refer to the unit nameplate for minimum circuit ampacity, and maximum fuse or circuit breaker (HACR per NEC). Install power wiring and properly sized disconnect switch.

NOTE
Units are approved for use only with copper conductors. Ground unit at the disconnect switch or connect to earth ground.

INSTALL THERMOSTAT
Install room thermostat (ordered separately) on an inside wall approximately in the center of the conditioned area and 5 feet (1.5m) from the floor. It should not be installed on an outside wall or where it can be affected by sunlight or drafts.

NOTE
24VAC, Class II circuit connections are made in the control panel.

UNIT LOW VOLTAGE CONNECTIONS

• A. Run 24VAC control wires through ca cutout with a grommet.
• B. Run 24VAC control wires through wa ire tie.
• C. Make 24VAC control wire connections using field-provided wire nuts.
• D. Tighten wire tie to security 24V control wiring.

NOTE
 FOR PROPER VOLTAGES, SELECT THE THERMOSTAT WIRE (CONTROL WIRES) GAUGE PER TABLE ABOVE.

NOTE
WIRE TIE PROVIDES LOW-VOLTAGE WIRE STRAIN RELIEF AND MAINTAINS SEPARATION OF FIELD-INSTALLED LIGH-VOLTAGE CIRCUITS.

NOTE
DO NOT BUNDLE ANY EXCESS 24VAC CONTROL WIRES INSIDE CONTROL BOX.

24VAC Control Wiring Diagrams (Field Installed)

1. Air handler shipped with jumpers installed between W1 and W2 and W2 and W3.
2. R connection is required for the air conditioner with LSOM. A resistor kit (CAT #47W97) is required when connecting ComfortSense 7000 with LSOM 2.
3. L connection wired on units with LSOM.
4. Remove the bumper for 2-stage cooling.
5. Clip onboard Y1 to Y2 for 2-stage cooling.

NOTE
Refer to the furnace, blower coil, and accessory instructions for additional wiring configurations with other optional controls.

NOTE

1. FOR USE WITH COPPER CONDUCTORS ONLY. REFER TO UTHE NIT RATING PLATE FOR MINIMUM CIRCUIT AMPACITY AND MAXIMUM OVERCURRENT PROTECTION SIZE
2. REFER TO THE COMPRESSOR IN THE UNIT FOR THE ACTUAL TERMINAL ARRANGEMENT
3. WARNING ELECTRIC SHOCK HAZARDS, AN CAUSE INJURY OR DEATH. UNIT MUST BE GROUNDED BY NATIONAL AND LOCAL CODES.
4. REMOVE JUMPER FOR TWO-STAGE COOL
5. ON A92 CUT ONBOARD W914 JUMPER FROM D5 TO R, WHEN HUMIDITY CONTROL IS USED
6. ON A92 DO NOT CUT OTHER NBOARD W951 JUMPER FROM R TO O. IT IS USED FOR APPLICATIONS FOR CONDENSING UNITS
7. FOR CONDENSING UNIT APPLICATIONS USE RTHE  TO O JUMPER. REMOVE IN HEAT PUMP APPLICATIONS
8. REMOVE DS TO Y1 JUMPER WHEN HUMIDITY CONTROL IS USED
9. WHEN TASTING THERMOSTAT IS USED, CONNECT THE SECOND STAGE HEAT BULB TO TERMINAL “W2”, AND REMOVE JTHE JUMPER BETWEEN “R” AND “W2”
10. L34 SOLENOID IS LOCATED IN CTHE OMPRESSOR. COIL IS 24VDC. DO NOT CONNECT 24VAC TO COIL TERMINALS
11. S11 IS OPTIONAL LOW AMBIENT SWITCH
12. AN OPTIONAL HARD START KIT MAY BE REQUIRED ON APPLICATIONS WHERE VOLTAGES ARE LESS THAN 230 VOLTS KIT INCLUDES SK31 AND C7 WITH ALL NECESSARY WIRING.
13. S40 AND HRI ARE USED ON 048 AND 060 UNITS ONLY

NOTE
IF ANY WIRE IN THIS APPLIANCE IS REPLACED,  IT MUST BE REPLACED WITH WIRE OF LIKE SIZE, RATING, INSULATION THICKNESS, AND TERMINATION.

NOTE
MINIMUM TRANSFORMER REQUIRED IN INDOOR UNIT-40 VA

UNIT START-UP

IMPORTANT
If the nit is equipped with a crankcase heater, it should be energized 24 hours before unit start-up to prevent compressor damage as a result of slugging.

1. Rotate the fan to check for binding.
2. Inspect all factory- and field-installed wiring for loose connections.
3. After evacuation is complete, open the liquid line and vapor line service valve stems to release the refrigerant charge (contained in the outdoor unit) into the system.
4. Replace the stem caps and tighten them to the value listed in Table 2.
5. Check the voltage supply at the disconnect switch. The voltage must be within the range listed on the unit’s nameplate. If not, do not start the equipment until you have consulted with the power company and the voltage condition has been corrected.
6. Connect manifold gauge set for testing and charging.
7. Set the thermostat for a cooling demand. Turn on the power to the indoor unit close the outdoor unit disconnect the switch to start the unit.
8. Recheck voltage while the unit is running. Power must be within the range shown on the unit nameplate.
9. Check the system for sufficient refrigerant using the procedures outlined under Checking Refrigerant Charge.

OPERATING MANIFOLD GAUGE SET AND SERVICE VALVES
The liquid and vapor line service valves are used for removing refrigerant, flushing, leak testing, evacuating, checking charge, and charging. Each valve is equipped with a service port which has a factory-installed valve stem. Figures 14 and 15 provide information on how to access and operate both angle- and ball-type service valves.

Torque Requirements
When servicing or repairing heating, ventilating, and air conditioning components, ensure the fasteners are appropriately tightened. Table 3 lists torque values for fasteners.

TABLE 3 – TORQUE REQUIREMENTS

IMPORTANT
To prevent stripping of the various caps used, the appropriately sized wrench should be used and fitted snugly over the cap before tightening.

Using Manifold Gauge Set
When checking the system charge, only use a manifold gauge set that features low-loss anti-blow back fittings. The manifold gauge assessed with the HFC- 410A refrigerant system must be capable of handling the higher system operating pressures. The gauges should be rated for use with pressures of 0 – 800 psig on the high side and a low side of 30″ vacuum to 250 psig with dampened speed to 500 psi. Gauge hoses must be rated for use at up to 800 psig of pressure with a 4000 psig burst rating.

OPERATING BALL-TYPE SERVICE VALVE

1. Remove the stem cap with an appropriately sized wrench.
2. Use an appropriately sized wrench to open it. To open the valve, rotate the stem counterclockwise 90°. To close, rotate the stem clockwise 90°.

OPERATING ANGLE-TYPE SERVICE VALVE

1. Remove the 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.

When the service valve is CLOSED, the service port is open to the line set and indoor unit.

NOTE
A label with specific torque requirements may be affixed to the stem cap. If the label is present, use the specified torque.

ACCESS SERVICE PORT
A service port cap protects the service port core from contamination and serves as the primary leak seal.

1. Remove the service port cap with an appropriately sized wrench.
2. Connect gauge set to service port.
3. When testing is completed, replace the service port cap and tighten it as follows:
   • With a torque wrench, finger tighten, and torque cap per table 2.
   • Without a torque wrench, finger tighten and use an appropriately sized wrench to turn an additional 1/6 turn clockwise.

Reinstall Stem Cap
The team cap protects the valve stem from damage and is the primary seal. Replace the stem cap and tighten it as follows:

• With a torque wrench, finger tighten and then torque cap per table
• Without a torque wrench, use an appropriately sized wrench to turn an additional 1/12 turn clockwise.

Checking and Adding System Charge
The ML18XC2 unit is factory-charged with enough HFC-410A refrigerant to accommodate a 15-foot length of refrigerant piping. For refrigerant piping greater than 15 feet, calculate the additional charge using the table below. Then add the additional charge specified for the specific indoor coil match-up listed on the unit charging sticker.

The charge should be checked and adjusted using the tables provided on the charging procedure sticker on the unit access panel. Detailed information is given in the ML18XC2 Installation and Service Procedures manual, which is available on LennoxPros.com.

Refrigerant Charge per Line Set Length

LIQUID LINE DIA.| OUNCES PER 5 FEET (G PER 1.5 M) ADJUST FROM 15 FEET (4.6 M) LINE SET*
---|---
3/8″ (9.5 MM)| 3 OUNCES PER 5′ (85 G PER 1.5 M)

High-Pressure Switch (S4)
This unit is equipped with a high-pressure switch which is located on the liquid line. The SPST, normally closed pres-sure switch opens when liquid line pressure rises above the factory setting of 590 ± 15 psig and automatically re-sets at 418 ± 15 psig.

Low Pressure Switch
This unit is equipped with a low-pressure switch which is located on the compressor suction line. The SPST, normally a closed pressure switch opens when the suction line pressure drops below the factory setting of 40 ± 5 psig and automatically resets at 95 ± 5 psig.

Homeowners Information

CAUTION
Before attempting to perform any service or maintenance, turn the electrical power to the unit OFF at the disconnect switch.

To ensure peak performance, your system must be properly maintained. Clogged filters and blocked airflow prevent your unit from operating at its most efficient level. The system should be inspected and serviced before each cooling and heating season by a licensed professional HVAC service technician (or equivalent).

Homeowner Maintenance
The following maintenance may be performed by the homeowner.

• Contact a licensed professional HVAC technician to schedule inspection and maintenance appointments for your equipment before each heating and cooling season.
• Check the indoor unit filter each month and replace the filter, if necessary.
• Have your Lennox dealer show you where your indoor unit filter is located. It will be either at the indoor unit (installed internally or externally to the cabinet) or behind a return air grille in the wall or ceiling. Check the filter monthly and clean or replace it as needed. Disposable filters should be replaced with a filter of the same type and size.
• Check the indoor unit drain line for obstructions monthly. The indoor coil is equipped with a drain pan to collect condensate formed as your system removes humidity from the inside air. Have your dealer show you the location of the drain line and how to check for obstructions. (This would also apply to an auxiliary drain if installed.)
• Check the area around the outdoor unit monthly and remove any obstructions that may restrict airflow to the outdoor unit. This would include grass clippings, leaves, or papers that may have settled around the unit.
• Trim shrubbery away from the unit and periodically check for debris that collects around the unit.
• During the winter months, keep the snow level below the louvered panels.

NOTE
The filter and all access panels must be in place any time the unit is in operation. If you are unsure about the filter required for your system, call your Lennox dealer for assistance.

IMPORTANT
Sprinklers and soaker hoses should not be installed where they could cause prolonged exposure to the outdoor unit by treated water. Prolonged exposure of the unit to treated water (i.e., sprinkler systems, soakers, wastewater, etc.) will corrode the surface of the steel and aluminum parts, diminish performance, and affect the longevity of the unit.

Thermostat Operation
See the thermostat homeowner manual for instructions on how to operate your thermostat.

Pre-Service Check
If your system fails to operate, check the following before calling for service:

• Verify room thermostat settings are correct.
• Verify that all electrical disconnect switches are ON.
• Check for any blown fuses or tripped circuit breakers.
• Verify unit access panels are in place.
• Verify air filter is clean.

If service is needed, locate and write down the unit model number and have it handy before calling.

Professional Maintenance

NOTICE
Failure to follow instructions will cause damage to the unit.

This unit is equipped with an aluminum coil. Aluminum coils may be damaged by exposure to solutions with a pH below 5 or above 9. The aluminum coil should be cleaned using potable water at moderate pressure (less than 50 psi). If the coil cannot be cleaned using water alone, Lennox recommends the use of a coil cleaner with a pH in the range of 5 to 9. The coil must be rinsed thoroughly after cleaning.

In coastal areas, the coil should be cleaned with potable water several times per year to avoid corrosive buildup (salt).

Your heating and air conditioning system should be inspected and maintained twice each year (before the start of the cooling and heating seasons) by a licensed professional HVAC technician. You can expect the technician to check the following items. These checks may only be conducted by a licensed professional HVAC technician.

Outdoor Unit

1. Inspect component wiring for loose, worn, or damaged connections. Also, check for any rubbing or pinching of wires. Confirm proper voltage plus amperage of the outdoor unit.
2. Check the cleanliness of the outdoor fan and blade condition (cracks) and clean or replace them, if necessary.
3. Inspect base pan drains for debris and clean as necessary.
4. Inspect the condition of refrigerant piping and confirm that pipes are not rubbing copper-to-copper. Also, check the condition of the insulation on the refrigerant lines. Repair, correct, or replace as necessary.
5. Test capacitor. Replace as necessary.
6. Inspect contactor contacts for pitting or burn marks. Replace as necessary.
7. Check the outdoor fan motor for worn bearings/ bushings. Replace as necessary.
8. Inspect and clean outdoor coils, if necessary, and note any damage to coils or signs of leakage.

Indoor Unit (Air Handler or Furnace)

1. Inspect component wiring for loose, worn, or damaged connections. Confirm proper voltage plus amperage of the indoor unit.
2. Inspect and clean or replace air filters in indoor units.
3. Check the cleanliness of the indoor blower and clean the blower, if necessary.
4. Inspect the indoor coil drain pans and condensate drains for rust, debris, obstructions, leaks, or cracks. Pour water in pans to confirm proper drainage from the pan through to the outlet of the pipe. Clean or replace as necessary.
5. Inspect and clean the indoor coil, if necessary.
6. Inspect the condition of the refrigerant lines and confirm that pipes are not rubbing copper-to-copper. Also, ensure that refrigerant pipes are not being affected by indoor air contamination. Check the condition of the insulation on the refrigerant lines. Repair, correct, or replace as necessary.
7. Inspect the duct system for leaks or other problems. Repair or replace as necessary.
8. Check for bearing/bushing wear on the indoor blower motor. Replace as necessary.
9. Indoor unit service will also include inspection and cleaning of the burners, and a full inspection of the gas valve, heat exchanger, and flue (exhaust) system.

General System Test with System Operating

1. Your technician should perform a general system test. They will turn on the air conditioner to check operating functions such as the startup and shutoff operation. They will also check for unusual noises or odors, and measure indoor/outdoor temperatures and system pressures as needed. They will check the refrigerant charge per the charging sticker information on the outdoor unit.
2. Verify that the system’s total static pressure and airflow settings are within specific operating parameters.
3. Verify the correct temperature drop across the indoor coil.

ML18XC2 Start-Up and Performance Checklist

ML18XC2 Start-Up and Performance Checklist

Customer Address
Indoor Unit Model Serial
Outdoor Unit Model Serial
Notes: __

START-UP CHECKS

Refrigerant Type:
Rated Load Amps:                      Actual Amps Rated Volts |

Actual Volts __

Condenser Fan Full Load Amps                      Actual Amps:
COOLING MODE
Suction Pressure: Liquid Pressure:
Supply Air Temperature: __ Ambient Temperature: Return Air: Temperature: __
System Refrigerant Charge (Refer to manufacturer’s information on unit or installation instructions for required subcooling and approach temperatures.)
Subcooling:

Saturated Condensing Temperature (A)

minus Liquid Line Temperature (B)

| A| —| B| =     SUBCOOLING
Approach:

Liquid Line Temperature (A)

minus Outdoor Air Temperature (B)

| A| —| B| =       APPROACH
Indoor Coil Temperature Drop (18 to 22°F)

Return Air Temperature (A)

minus Supply Air Temperature (B)

| A| —| B| = COIL TEMP DROP

References

• HVAC Supplier | LennoxPros

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