INSTALLATION
INSTRUCTIONS
©
2016 Lennox Industries Inc. 
Dallas, Texas, USA
MLA/MPA/MPB and 
M22A/M33A/M33B Series
SINGLE-ZONE MINI-SPLIT SYSTEMS  
(208/230V) --  
Cassette-Mounted Indoor Unit 
507546-06 
10/2017 
Supersedes 10/2016
WARNING
Improper installation, adjustment, alteration, ser vice or 
maintenance can cause property damage, personal 
injury or loss of life.
Installation and service must be performed by a li censed 
professional HVAC installer (or equivalent) or a service 
agency.
WARNING
The clean Air Act of 1990 bans the intentional venting of 
refrigerant (CFCs, HCFCs, and HFCs) as of July, 1992. 
Approved methods of recovery, recycling or reclaiming 
must be followed. Fines and/or incarceration may be 
levied for non-compliance.
WARNING
This product contains a chemical known to the State 
of California to cause cancer, birth defects, or other 
reproductive harm.
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.
General
Refer to the Product Specications bulletin (EHB) for more 
product information.
These instructions are intended as a general guide and 
do not supersede local or national codes in any way. 
Authorities having jurisdiction should be consulted before 
installation.
The M22A, M33A and M33B ceiling cassette indoor units 
are matched with an outdoor heat pump unit to create a 
mini-split system that uses HFC-410A refrigerant.
Table of Contents
General ...........................................................................1
Included Parts.................................................................2
Model Number Identication ...........................................3
Indoor / Outdoor Unit Match-Ups....................................4
Typical System Components ..........................................5
System Dimensions ........................................................6
Outdoor Units................................................................6
Indoor Units ..................................................................7
System Clearances ........................................................9
Outdoor Unit .................................................................9
Indoor Unit ....................................................................9
Torque Requirements for Caps and Fasteners.............10
Indoor Unit Installation ..................................................10
Unit Placement Considerations ..................................10
Installation of Cassette Base ......................................10
Installation of M33 Cassette Cover Panel...................11
Indoor Unit Condensate Piping Connections ..............13
Outdoor Unit Installation ...............................................13
Placement Considerations ..........................................13
Direct Sunlight, Rain, Snow and Ice Protection ..........14
Prevailing Winds .........................................................15
Buried Refrigerant Pipe Protection .............................15
Outdoor Unit Condensate Piping ................................15
Securing the Outdoor Unit ..........................................16
Refrigerant Piping Connections ....................................17
Leak Test and Evacuation ............................................18
Leak Test ....................................................................18
Triple Evacuation Procedure .......................................18
Wiring Connections ......................................................19
Outdoor Unit  ..............................................................19
Indoor Unit ..................................................................19
Unit Start-Up .................................................................27
Adding Refrigerant for Longer Line Set ........................27
Troubleshooting ............................................................28
Test Run .......................................................................28
Pre-Checks .................................................................28
Procedure ...................................................................28
Dry Mode Operation (Dehumidication) .......................28
Procedure ...................................................................28
Sequence of Operation ...............................................28
THIS MANUAL MUST BE LEFT WITH THE OWNER 
FOR FUTURE REFERENCE