Lennox Commercial ML18XC2 Merit Series Small Split Systems Instruction Manual

Lennox Commercial ML18XC2 Merit Series Small Split Systems

Specifications

• Model: ML18XC2
• Phase: 3-phase
• Refrigerant: HFC-410A
• Cooling Capacity: 3-5 tons
• Voltage: 208/230V or 460V
• Compressor Stages: Two-stage

Product Usage Instructions

Installation Guidelines
Follow the installation clearances provided in the manual.
Maintain appropriate service clearance of 30 in. next to the control box and other specified clearances around the unit. Ensure a 24 in. clearance between two units and a 48 in. clearance on top of the unit.

Maintenance and Safety
Before performing maintenance, always lock-out/tag-out the unit.
Disable power to the blower, remove fan belt if applicable, and set all controllers and thermostats to the OFF position. Keep hands, hair, clothing, jewelry, and tools away from moving parts to prevent injury.

Cleaning Instructions
This unit requires special procedures for cleaning the all-aluminum coil. Refer to page 21 of the instruction manual for detailed cleaning information.

FAQ

Q: What refrigerant type does this unit use?
A: The unit uses HFC-410A refrigerant.

Q: What voltage options are available for this unit?
A: The unit is available in 208/230V or 460V options for 3-phase operation.

ML18XC2 (HFC-410A) SERIES OUTDOOR UNITS (3-PHASE)

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

• The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFCs, HCFCs and HFCs) as of July 1, 1992. Approved methods of recovery, recycling or reclaiming must be followed. Fines and/or incarceration may be levied for noncompliance.
• This unit must be matched with an indoor coil as specified with AHRI. For AHRI Certified system match-ups 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
Electric Shock Hazard. Can cause injury or death. Unit must be properly grounded in accordance with national and local codes.
Line voltage is present at all components when unit is not in operation on units with single-pole contactors. Disconnect all remote electric power supplies before opening access panel. Unit may have multiple power supplies.

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® ML18XC2 model 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.Len- noxPros.com.

This outdoor unit is designed for use in systems that use the following refrigerant metering device:

• Thermal expansion valve (TXV)

IMPORTANT: Special procedures are required for clean-ing the all-aluminum coil in this unit. See page 21 in this instruction for information.

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.

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 A clearance of 24 in. must be maintained between two units. 48 in. (1219 mm) clearance required on top of unit.

Model Number Identification

Dimensions

Specifications

Model – 208/230V- 3ph|  | ML18XC2-036-233| ML18XC2-048-233| ML18XC2-060-233
---|---|---|---|---
Model – 460V-3ph|  | ML18XC2-036-463| ML18XC2-048-463| ML18XC2-060-463
Nominal Tonnage|  | 3| 4| 5
Sound Rating Number| dBA| 76| 77| 76
Connections| Liquid line (OD) – in.| 3/8| 3/8| 3/8
(sweat)| Suction line (OD) – in.| 7/8| 7/8| 1-1/8
Compressor Type|  | Two-Stage Scroll| Two-Stage Scroll| Two-Stage Scroll
Refrigerant| 1 R-410A charge furnished| 8 lbs. 0 oz.| 11 lbs.1 oz.| 12 lbs. 0 oz.
Indoor Unit Expansion Valve (TXV)|  | 12J19| 12J20| 12J20
Outdoor ** Net face area – ft.²         Outer coil               18.67 22.17                           29.09
Coil| Inner coil| 17.96|  | 21.23|  | 27.87|
 | Tube diameter – in.| 5/16|  | 5/16|  | 5/16|
 | Rows| 2|  | 2|  | 2|
 | Fins per in.| 22|  | 22|  | 22|
Fan Motor| HP| 1/6|  | 1/4|  | 1/3|
 | Diameter – in.| 22|  | 26|  | 26|
 | Blades| 3|  | 3|  | 3|
 | Cfm| 3160|  | 4100|  | 3900|
 | Rpm| 825|  | 825|  | 825|
 | Watts| 190|  | 275|  | 190|
Shipping Data – lbs.|  | 187|  | 231|  | 283|
ELECTRICAL DATA|  |  |  |  |  |  |
Line voltage data – 60 Hz – 3ph|  | 208/230V| 460V| 208/230V| 460V| 208/230V| 460V
² Maximum Overcurrent Protection| (MOCP) amps| 20| 15| 30| 15| 40| 15
³ Minimum circuit ampacity (MCA)|  | 13.6| 6.5| 17.6| 9.9| 23.4| 11.5
Compressor| Rated load amps| 10.1| 4.7| 12.9| 7.1| 16.7| 7.1
 | Locked rotor amps| 88| 44.3| 105| 62| 110| 54.7
 | Power factor| 0.94| 0.94| 0.93| 0.93| 0.92| 0.92
Outdoor Fan Motor| Full load amps| 1| 0.6| 1.4| 1.1| 2.6| 2.6
 | Locked Rotor amps| 1.9| 1.1| 3.2| 2.5| – – –| – – –
OPTIONAL ACCESSORIES – ORDER SEPARA**

45F08

Compressor Crankcase Heater                                    93M04

Compressor Sound Cover                                            18J42 47J27

Freezestat ** 3/8 in. tubing              93G35 5/8 in. tubing 50A93 58M81**

Indoor Blower Speed Relay Kit                                     40K58

Loss of Charge Switch Kit 84M23

⁴ Low Ambient Kit (Fan Cycling) (30°F)                       34M72

⁴ Low Ambient Speed Control              X5867

Control (0°F) Weatherproof Kit             56N41 208/230V only

Refrigerant ** 3/8 x 7/8 | 3/8 | 30 ft.               89J60**

Line Sets 3/8 x 7/8 | 3/8 | 40 ft.              89J61 Liquid x Suction OD |  3/8 x 7/8 | 3/8 | 50 ft.            89J62 Insulation Thickness | 3/8 x 1-1/8 | 3/8 | 30 ft. X0570 Length                           3/8 x 1-1/8 | 3/8 | 50 ft. 73P91

94J45

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NOTE – Extremes of operating range are plus 10% and minus 5% of line voltage.

1. Refrigerant charge sufficient for 15 ft. length of refrigerant lines. For longer line set requirements see the Installation Instructions for information about line set length and
   additional refrigerant charge required.

2. HACR type breaker or fuse.

3. Refer to National or Canadian Electrical Code manual to determine wire, fuse and disconnect size requirements.

4. Freezestat is recommended with Low Ambient Control.

Typical Unit Parts Arrangement

Operating Gauge Set and Service Valves

TORQUE REQUIREMENTS
When servicing or repairing HVAC components, ensure the fasteners are appropriately tightened. Table 1 provides torque values for fasteners.

IMPORTANT

• Only use Allen wrenches of sufficient hardness (50Rc – Rockwell Harness Scale minimum). Fully insert the wrench into the valve stem recess.
  Service valve stems are factory-torqued (from 9 ft-lbs for small valves, to 25 ft-lbs for large valves) to prevent refrigerant loss during shipping and handling. Using an Allen wrench rated at less than 50Rc risks rounding or breaking off the wrench, or stripping the valve stem recess.
  See the Lennox Service and Application Notes #C-08-1 for further details and information.

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

TABLE 1. Torque Requirements

USING MANIFOLD GAUGE SET
When checking the system charge, only use a manifold gauge set that features low-loss anti-blow back fittings.
Manifold gauge set used with HFC-410A refrigerant systems must be capable of handling the higher system oper-ating 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 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. Figure 2 provides information on how to access and operating both angle and ball 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.

WHEN SERVICE VALVE IS CLOSED, THE SERVICE PORT IS OPEN TO THE LINE SET AND INDOOR UNIT.

Operating Ball Type Service Valve:

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

To Access Service Port:
A service port cap protects the service port core from contamination and serves as the primary leak seal.

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

Reinstall Stem Cap:

Stem cap protects the valve stem from damage and serves as the primary seal. Replace the stem cap and tighten as follows:

• With Torque Wrench: Finger tighten and then torque cap per table 3.
• Without Torque Wrench: Finger-tighten and use an appropriately sized wrench to turn an additional 1/12 turn clockwise.

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

FIGURE 2. Angle and Ball Service Valves

Unit Placement
See Unit Dimensions on page 3 for sizing mounting slab, platforms or supports. Refer to page 2 for mandatory installation clearance requirements.

CAUTION
In order to avoid injury, take proper precaution when lifting heavy objects..

POSITIONING CONSIDERATIONS
Consider the following when positioning the unit:

• Some localities are adopting sound ordinances based on the unit’s sound level registered from the adjacent property, not from the installation property. Install the unit as far as possible from the property line.
• When possible, do not install the unit directly outside a window. Glass has a very high level of sound transmission.
  For proper placement of unit in relation to a window see the provided illustration in figure 3, detail A.

PLACING UNIT ON SLAB
When installing unit at grade level, the top of the slab should be high enough above grade so that water from higher ground will not collect around the unit. The slab should have a slope tolerance as described in figure 3, detail B.

ROOF MOUNTING
Install the unit a minimum of 6 inches (152 mm) above the roof surface to avoid ice build-up around the unit. Locate the unit above a load bearing wall or area of the roof that can adequately support the unit. Consult local codes for rooftop applications.
If unit coil cannot be mounted away from prevailing winter winds, a wind barrier should be constructed. Size barrier at least the same height and width as outdoor unit. Mount barrier 24 inches (610 mm) from the sides of the unit in the direction of prevailing winds.

NOTICE

Roof Damage!
This system contains both refrigerant and oil. Some rubber roofing material may absorb oil, causing the rubber to swell. Bubbles in the rubber roofing material can cause leaks. Protect the roof surface to avoid exposure to refrigerant and oil during service and installation. Failure to follow this notice could result in damage to roof surface.

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).
While handling or stowing the panels, consider any weather conditions, especially windy conditions, that may cause panels to be blown around and battered.

New or Replacement Line Set
This section provides information on new installation or replacement of existing line set. If a new or replacement line set is not required, then proceed to Brazing Connections on page 11.
If refrigerant lines are routed through a wall, seal and isolate the opening so vibration is not transmitted to the building. Pay close attention to line set isolation during installation of any HVAC system. When properly isolated from building structures (walls, ceilings. floors), the refrigerant lines will not create unnecessary vibration and subsequent sounds.

REFRIGERANT LINE SET
Field refrigerant piping consists of liquid and suction lines from the outdoor unit (braze connections) to the indoor unit coil (flare or braze connections). Use Lennox L15 (braze, non-flare) series line set, or use field-fabricated refrigerant lines as listed in table 2.

TABLE 2. Refrigerant Line Set – in. (mm)

Model

| Field Connections| Recommended Line Set
---|---|---
Liquid Line| Suction Line| Liquid Line| Suction Line| L15 Line Set
-036| 3/8”

(10mm)

| 7/8”

(22mm)

| 3/8”

(10 mm)

| 7/8”

(22 mm)

| L15-65: 15 ft.– 50 ft.

(4.6 m–15 m)

-048
-060| 3/8”

(10mm)

| 1-1/8”

(29 mm)

| 3/8”

(10 mm)

| 1-1/8”

(29 mm)

| Field-Fabricated
NOTE – Some applications may require a field-provided 7/8” to 1-1/8” adapter.

NOTE – When installing refrigerant lines longer than 50 feet, contact Lennox Technical Support Product Applications for assistance or Lennox piping manual. To obtain the correct information from Lennox, be sure to communicate the following points:

• Model (ML18XC2) and size of unit (e.g. -060).
• Line set diameters for the unit being installed as listed in table 4 and total length of installation.
• Number of elbows and if there is a rise or drop of the piping.

IMPORTANT
Mineral oils are not compatible with HFC-410A. If oil must be added, it must be a Polyol ester oil.
The compressor is charged with sufficient Polyol ester oil for line set lengths up to 50 feet. Recommend adding oil to system based on the amount of refrigerant charge in the system. No need to add oil in system with 20 pounds of refrigerant or less. For systems over 20 pounds – add one ounce for every five pounds of refrigerant.
Recommended topping-off POE oils are Mobil EAL ARCTIC 22 CC or ICI EMKARATE RL32CF.

MATCHING WITH NEW OR EXISTING INDOOR COIL AND LINE SET
The RFC1-metering line consisted of a small bore copper line that ran from condenser to evaporator coil. Refrigerant was metered into the evaporator by utilizing temperature/pressure evaporation effects on refrigerant in the small RFC line. The length and bore of the RFC line corresponded to the size of cooling unit. If the ML18XC2 is being used with either a new or existing indoor coil which is equipped with a liquid line which served as a metering device (RFCI), the liquid line must be replaced prior to the installation of the ML18XC2 unit. Typically a liquid line used to meter flow is 1/4” in diameter and copper.
LINE SET ISOLATION

CAUTION
Brazing alloys and flux contain materials which 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 shield to protect against burns.
Wash hands with soap and water after handling brazing alloys and flux.

IMPORTANT

• The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFC’s and HCFC’s) as of July 1, 1992.
  Approved methods of recovery, recycling or reclaiming must be followed. Fines and/or incarceration may be levied for non-compliance.

• 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 which was manufactured before January of 1999, the coil and line set must be flushed prior to installation. Take care to empty all existing traps. Polyol ester (POE) oils are used in Lennox 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.

LINE SET

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 line set from joist or rafter, use either metal strapping material or anchored heavy nylon wire ties.

REFRIGERANT LINE SET — INSTALLING VERTICAL RUNS (NEW CONSTRUCTION SHOWN)

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 wall

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

WARNING — Polyol ester (POE) oils used with HFC-410A refrigerant absorb moisture very quickly. It is very important that the refrigerant system 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.

Brazing Connections

Use the procedures outlined 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 result in pressurization of the low side shell and suction tubing. Application of a brazing torch to a pressurized system may result in ignition of the refrigerant and oil mixture. Check the high and low pressures before applying heat.
• 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).

CAUTION

• Brazing alloys and flux contain materials which 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 shield to protect against burns.
  Wash hands with soap and water after handling brazing alloys and flux.

IMPORTANT

• Allow braze joint to cool before removing the wet rag from the service valve. Temperatures above 250ºF can damage valve seals.
• Use silver alloy brazing rods with 5% minimum silver alloy for copper-to-copper brazing. Use 45% minimum alloy for copper-to-brass and copper-to-steel brazing.

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.

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

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

3. ATTACH THE MANIFOLD GAUGE SET FOR BRAZING LIQUID AND SUCTION / 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 suction /vapor line service port valve.

   • Connect gauge set low pressure side to liquid line service valve (service port).
   • Connect gauge set center port to bottle of nitrogen with regulator.
   • Remove core from valve in suction / vapor line service port to allow nitrogen to escape.

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 suction / 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 line set. Water saturated cloths must remain water saturated throughout the brazing and cool-down process .
   IMPORTANT — Allow braze joint to cool. Apply additional water saturated cloths to help cool brazed joint. Do not remove water saturated cloths until piping has cooled. Temperatures above 250ºF will damage valve seals.
   WARNING

7. 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 in the line set! The braze, when complete, must be quenched with water to absorb any residual heat.

8. Do not open service valves until refrigerant lines and indoor coil have been leak-tested and evacuated. Refer to procedures provided in this supplement.

9. PREPARATION FOR NEXT STEP
   After all connections have been brazed, disconnect manifold gauge set from service ports. Apply additional water saturated cloths to both services valves to cool piping. Once piping is cool, remove all water saturated cloths. Refer to the unit installation instructions for the next step in preparing the unit.

Flushing Line Set and Indoor Coil

TYPICAL EXISTING FIXED ORIFICE REMOVAL PROCEDURE (UNCASED COIL SHOWN)

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

TYPICAL EXISTING EXPANSION VALVE REMOVAL PROCEDURE (UNCASED COIL SHOWN)

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

CONNECT GAUGES AND EQUIPMENT FOR FLUSHING PROCEDURE

• Inverted HCFC-22 cylinder with clean refrigerant* to the vapor service valve.
• HCFC-22 gauge set (low side) to the liquid line valve.
• HCFC-22 gauge set center port to inlet on the recovery machine with an empty recovery tank to the gauge set.
• Connect recovery tank to recovery machines per machine instructions.

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.

• 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.
• Invert the cylinder of clean HCFC-22* 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.
• 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.
• 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.

IMPORTANT – Clean refrigerant is any refrigerant in a system that has not had compressor burn out. If the system has experienced burn out, it is recommended that the existing line set and indoor coil be replaced.

FIGURE 8. Removing Metering Device and Flushing

Installing Indoor Metering Device

This outdoor unit is designed for use in systems that use a check expansion valve metering device at the indoor coil.
See the Lennox ML18XC2 Product Specification bulletin for approved expansion valve kit match-ups. 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 below illustration for reference during installation of expansion valve unit.

INDOOR EXPANSION VALVE INSTALLATION

• Remove the field-provided fitting that temporary reconnected the liquid line to the indoor unit’s distributor assembly.
• Install one of the provided Teflon® rings around the stubbed end of the expansion valve and lightly lubricate the connector threads and expose surface of the Teflon® ring with refrigerant oil.
• Attach the stubbed end of the 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 20 ft-lb.
• Place the remaining Teflon® washer around the other end of the expansion valve. Lightly lubricate connector threads and expose surface of the Teflon® ring with refrigerant oil.
• Attach the liquid line assembly to the 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 20 ft-lb.

EQUALIZER LINE INSTALLATION

• 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 to the right.
• 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 to the right.

SENSING BULB INSTALLATION

• Attach the vapor line sensing bulb in the proper orientation as illustrated to the right using the clamp and screws provided.
  NOTE — Confirm proper thermal contact between vapor line and expansion bulb before insulating the sensing bulb once installed.

• 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) as illustrated below.

FIGURE 9. Installing Indoor Expansion Valve

IMPORTANT

• The Clean Air Act of 1990 bans the intentional venting of refrigerant (CFC’s and HCFC’s) as of July 1, 1992.
  Approved methods of recovery, recycling or reclaiming must be followed. Fines and/or incarceration may be levied for non-compliance.

• 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 which was manufactured before January of 1999, the coil and line set must be flushed prior to installation. Take care to empty all existing traps. Polyol ester (POE) oils are used in Lennox 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.

Leak Test Line Set and Indoor Coil

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).

IMPORTANT
Leak detector must be capable of sensing HFC refrigerant.

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.

1. CONNECT GAUGE SET

2. Connect an HFC-410A manifold gauge set high pressure hose 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.

3. 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.

4. 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:

5. 1. 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).

6. 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.

7. Connect a cylinder of dry nitrogen with a pressure regulating valve to the center port of the manifold gauge set.

8. Adjust dry nitrogen pressure to 150 psig (1034 kPa). Open the valve on the high side of the manifold gauge set in order to pressurize the line set and the indoor unit.

9. 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.

10. After leak testing disconnect gauges from service ports.

Evacuating Line Set and Indoor Coil

CONNECT GAUGE SET

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
• Connect micron gauge available connector on the 1/4 SAE in-line tee.
• 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.

EVACUATE THE SYSTEM

• Open both manifold valves and start the vacuum pump.

• 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, it is desirable to close the manifold gauge valve at least once. A rapid rise in pressure indicates a relatively large leak. If this occurs, repeat the leak testing procedure.
  NOTE — The term absolute pressure means the total actual pressure within a given volume or system, above the absolute zero of pressure. Absolute pressure in a vacuum is equal to atmospheric pressure minus vacuum pressure.

• When the absolute pressure reaches 23,000 microns (29.01 inches of mercury), perform the following:

  • Close manifold gauge valves
  • Close valve on vacuum pump
  • Turn off vacuum pump
  • Disconnect manifold gauge center port hose from vacuum pump
  • Attach manifold center port hose to a dry nitrogen cylinder with 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.

• Shut off the dry nitrogen cylinder and remove the manifold gauge hose from the cylinder. Open the manifold gauge valves to release the dry nitrogen from the line set and indoor unit.

• 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 a 20-minute period after shutting off the vacuum pump and closing the manifold gauge valves.

• When the absolute pressure requirement above has been met, disconnect the manifold hose from the vacuum pump and connect it to an upright cylinder of HFC-410A refrigerant. Open the manifold gauge valve 1 to 2 psig in order to release the vacuum in the line set and indoor unit.

• Perform the following:

  • Close manifold gauge valves.
  • Shut off HFC-410A cylinder.
  • Reinstall service valve cores by removing manifold hose from service valve. Quickly install cores with core tool while maintaining a positive system pressure.
  • Replace stem caps and secure finger tight, then tighten an additional one-sixth (1/6) of a turn as illustrated.

FIGURE 11. Evacuating the System

IMPORTANT
Use a thermocouple or thermistor electronic vacuum gauge that is calibrated in microns. Use an instrument capable of accurately measuring down to 50 microns.

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 warranty.
Evacuating the system of non-condensables is critical for proper operation of the unit. Non-condensables are defined as any gas that will not condense under temperatures and pressures present during operation of an air conditioning system. Non-condensables and water suction combine with refrigerant to produce substances that corrode copper piping and compressor parts.

Electrical
In the U.S.A., wiring must conform with 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 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 minimum).

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

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 disconnect switch or to an 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.

System Operation

UNIT COMPONENTS

IMPORTANT

Some scroll compressors have an internal vacuum protector that will unload scrolls when suction pressure goes below 20 psig. A hissing sound will be heard when the compressor is running unloaded. Protector will reset when low pressure in system 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 in the ON position, the indoor blower operates continuously.

Liquid line Filter Drier
The unit is equipped with a large-capacity filter drier which keeps the system clean and dry. If replacement is neces-sary, order another of the same design and capacity. The replacement filter drier must be suitable for use with HFC- 410A refrigerant.

Low Pressure Switch (S87)
The ML18XC2 is equipped with an auto-reset low pres-sure switch which is located on the vapor line. The switch shuts off the compressor when the vapor pressure falls below the factory setting. This switch, which is ignored during defrost operation, closes at pressures at or above 40 ± 5 psig (276 ± 34 kPa) and opens at 25 ± 5 psig (172 ± 34 kPa). It is not adjustable.

High Pressure Switch (S4)
The ML18XC2 is equipped with an auto-reset high pres-sure switch (single-pole, single-throw) which is located on the liquid line. The switch shuts off the compressor when discharge pressure rises above the factory setting. The switch is normally closed and is permanently adjusted to trip (open) at 590 ± 15 psig (4068 ± 103 kPa).

NOTE – A Schrader core is under the pressure switches.
Crankcase Heater (HR1) and Thermostat Switch (S40)
All models sizes are equipped with a belly band type crankcase heater. HR1 prevents liquid from accumulating in the compressor. The HR1 is controlled by a single pole, single throw thermostat switch (S40) located on the liquid line. On all units, the heater is on when there is no compressor operation.
Thermal Protection Switch (S173) – Compressor Mounted
Some ML18XC2 units are equipped with a compressor mounted normally closed temperature switch that prevents compressor damage due to overheating caused by internal friction. The switch is located on top of the compressor casing (see figure 1). This switch senses the compressor casing temperature and opens at 239-257°F (115°C-125°C) to shut off compressor operation. The auto-reset switch closes when the compressor cas-ing temperature falls to 151-187°F (66°C-86°C), and the compressor is re-energized. This single-pole, single- throw (SPST) bi-metallic switch is wired in series with the 24V Y input signal to control compressor operation.

Maintenance

DEALER

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

• 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.

Maintenance and service must be performed by a qualified installer or service agency. At the beginning of each cooling season, the system should be checked as follows:

Outdoor Unit

1. Clean and inspect outdoor coil (may be flushed with a water hose). Ensure power is off before cleaning.

2. Outdoor unit fan motor is pre-lubricated and sealed.
   No further lubrication is needed.

3. Visually inspect all connecting lines, joints and coils for evidence of oil leaks.

4. Check all wiring for loose connections.

5. Check for correct voltage at unit (unit operating).

6. Check amp draw on outdoor fan motor.
   Motor Nameplate:_____ Actual:__.

7. Inspect drain holes in coil compartment base and clean if necessary.
   NOTE – If insufficient cooling occurs, the unit should be gauged and refrigerant charge should be checked.

Outdoor Coil
It may be necessary to flush the outdoor coil more frequently if it is exposed to substances which are corrosive or which block airflow across the coil (e.g., pet urine, cot-tonwood seeds, fertilizers, fluids that may contain high levels of corrosive chemicals such as salts)

• Outdoor Coil – The outdoor coil may be flushed with a water hose.
• Outdoor Coil (Sea Coast) – Moist air in ocean locations can carry salt, which is corrosive to most metal. Units that are located near the ocean require frequent inspections and maintenance. These inspections will determine the necessary need to wash the unit including the outdoor coil. Consult your installing contractor for proper intervals/procedures for your geographic area or service contract.

NOTICE !

Failure to follow instructions will cause damage to the unit.
This unit is equipped with an aluminum coil. Alu-minum 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 a moderate pressure (less than 50psi). If the coil cannot be cleaned using water alone, Lennox recommends 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).

Indoor Unit

1. Clean or change filters.

2. Lennox blower motors are prelubricated and permanently sealed. No more lubrication is needed.

3. Adjust blower speed for cooling. Measure the pressure drop over the coil to determine the correct blower CFM. Refer to the unit information service manual for pressure drop tables and procedure.

4. Belt Drive Blowers – Check belt for wear and proper tension.

5. Check all wiring for loose connections.

6. Check for correct voltage at unit. (blower operating)

7. Check amp draw on blower motor.
   Motor Nameplate:_____ Actual:__. Indoor Coil

8. Clean coil if necessary.

9. Check connecting lines, joints and coil for evidence of oil leaks.

10. Check condensate line and clean if necessary.

HOMEOWNER
Cleaning of the outdoor unit’s coil should be performed by a trained service technician. Contact your dealer and set up a schedule (preferably twice a year, but at least once a year) to inspect and service your outdoor unit. The following maintenance may be performed by the homeowner.

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, waste water, etc.) will corrode the surface of the steel and aluminum parts, diminish performance and affect longevity of the unit.

Outdoor Coil
The outdoor unit must be properly maintained to ensure its proper operation.

•  Please contact your dealer to schedule proper inspection and maintenance for your equipment.
• Make sure no obstructions restrict airflow to the outdoor unit.
• Grass clippings, leaves, or shrubs crowding the unit can cause the unit to work harder and use more energy.
• Keep shrubbery trimmed away from the unit and periodically check for debris which collects around the unit.

Routine Maintenance
In order 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.

1. Air Filter – Ask your Lennox dealer to show you where your indoor unit’s filter is located. It will be either at the indoor unit (installed internal or external 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.

2. Disposable Filter – Disposable filters should be replaced with a filter of the same type and size.
   NOTE – If you are unsure about the filter required for your system, call your Lennox dealer for assistance.

3. Reusable Filter – Many indoor units are equipped with reusable foam filters. Clean foam filters with a mild soap and water solution; rinse thoroughly; allow filter to dry completely before returning it to the unit or grille.
   NOTE – The filter and all access panels must be in place any time the unit is in operation.

4. Electronic Air Cleaner – Some systems are equipped with an electronic air cleaner, designed to remove airborne particles from the air passing through the cleaner. If your system is so equipped, ask your dealer for maintenance instructions.

5. Indoor Unit – The indoor unit’s evaporator 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.)

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

Preservice Check
I f 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.

Accessories

For update-to-date information, see any of the following Mpublications:

• Lennox ML18XC2 3-Phase Product Specification bulletin
• Lennox Product Catalog
• Lennox Price Book

Servicing Units Void of Charge

If the outdoor unit is void of refrigerant, clean the system using the procedure described below.

1. Leak check system using procedure outlined on page 15.
2. Evacuate the system using procedure outlined on page 16.
3. Use nitrogen to break the vacuum and install a new filter drier in the system.
4. Evacuate the system again using procedure outlined on page 16.
5. Weigh in refrigerant.

Start-Up

IMPORTANT
If 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.

1. Rotate 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 suction line service valves to release the refrigerant charge (contained in outdoor unit) into the system.
4. Replace the stem caps and tighten as specified in Operating Service Valves on page 7.
5. Check 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. Set the thermostat for a cooling demand. Turn on power to the indoor indoor unit and close the outdoor unit disconnect switch to start the unit.
7. Recheck voltage while the unit is running. Power must be within range shown on the nameplate.
8. Check system for sufficient refrigerant by using the procedures listed under Start-Up and Charging Procedures.
9. Recheck voltage while the unit is running. Power must be within range shown on the nameplate.

ML18XC2 Start-Up and Performance Checklist

Documents / Resources

| Lennox Commercial ML18XC2 Merit Series Small Split Systems [pdf] Instruction Manual
ML18XC2 Merit Series Small Split Systems, ML18XC2, Merit Series Small Split Systems, Series Small Split Systems, Small Split Systems, Split Systems
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