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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.
IMPORTANT
This unit must be matched with an indoor coil as specied
with AHRI. For AHRI Certied system match-ups and
expanded ratings, visit www.LennoxPros.com. Coils
previously charged with HCFC-22 must be ushed.
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.
ML18XC2
Table of Contents
Installation Clearances ...................................................2
Model Number Identication ...........................................2
Dimensions .....................................................................3
Specications .................................................................4
Typical Unit Parts Arrangement ...................................... 5
Operating Gauge Set and Service Valves ......................5
Unit Placement ..............................................................7
Removing and Installing Louvered Panels .....................8
New or Replacement Line Set ........................................9
Brazing Connections ................................................... 11
Flushing Line Set and Indoor Coil ................................14
Installing Indoor Metering Device .................................15
Leak Test Line Set and Indoor Coil ..............................16
Evacuating Line Set and Indoor Coil ...........................17
Electrical .......................................................................18
System Operation .......................................................20
Maintenance ...............................................................20
Servicing Units Void of Charge ...................................22
Start-Up ......................................................................22
Service Literature
UNIT INFORMATION
100051
June 10, 2022
ML18XC2 (HFC-410A) SERIES OUTDOOR UNITS
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 Certied
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.
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