Mitsubishi Electric PAA-A18AA1 User manual

MANUFACTURED FOR:
MITSUBISHI ELECTRIC US, INC.
Air Conditioners
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
SERVICE MANUAL

Table of Contents
1. SAFETY PRECAUTIONS ........................................................................................................ 3
1.1. Before service and electric work .................................................................................... 3
1.2. Devices that use R410A refrigerant .............................................................................. 10
1.3. Before getting started .................................................................................................. 11
1.4. Before servicing or moving the PAA unit - electrical work ............................................... 16
1.5. Before starting the test run ........................................................................................... 18
1.6. To dispose of the PAA unit ........................................................................................... 19
2. INSTALLATION POSITIONS AND CORRESPONDING AIRFLOW DIRECTION ........................ 20
3. SPECIFICATIONS ................................................................................................................. 21
4. INTERNAL PRESSURE DROP ............................................................................................... 22
5. OUTLINES AND DIMENSIONS .............................................................................................. 25
6. WIRING DIAGRAM ................................................................................................................ 28
7. REFRIGERANT SYSTEM DIAGRAM ...................................................................................... 30
8. TEST MODE AND EMERGENCY MODE ................................................................................ 31
9. HUMIDIFIER CONTROL SPECIFICATIONS ............................................................................ 36
9.1. Humidifier ................................................................................................................... 36
9.2. Installation .................................................................................................................. 38
10. ERV (ENERGY RECOVERY VENTILATION) CONTROL ........................................................ 39
10.1. Energy recovery ventilation (ERV) .............................................................................. 39
10.2. Installation ................................................................................................................ 40
10.3. HRV/ERV heating operation for MXZ system ............................................................... 40
11. TROUBLESHOOTING .......................................................................................................... 41
11.1. Cautions on troubleshooting ....................................................................................... 41
11.2. Self-check function, Function Table ............................................................................. 42
11.3. Self-diagnosis action table .......................................................................................... 44
11.4. Troubleshooting by inferior phenomena ....................................................................... 49
11.5. Test point diagram ..................................................................................................... 50
11.5.1. Power supply board ........................................................................................ 50
11.5.2. Indoor controller board .................................................................................... 51
11.6. Trouble criterion of main parts .................................................................................... 52
11.7. Thermistor ................................................................................................................. 53
12. FUNCTIONS OF DIP SWITCH AND JUMPER WIRE ............................................................. 54
13. DISASSEMBLY PROCEDURE .............................................................................................. 55
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 2 © 2022 Mitsubishi Electric US, Inc.

1. SAFETY PRECAUTIONS
• Before servicing the unit, make sure you read all the safety precautions.
• Ensure all the equipment is properly installed per the installation manual.
• Ensure all precautions are followed.
• Carefully read the labels affixed to the main unit.
Symbols used in text:
WARNING
Describes precautions that should be observed to prevent the danger of injury or death to
the user.
CAUTION
Describes precautions that should be observed to prevent damage to the unit.
1.1. Before service and electric work
IMPORTANT
The Environmental Protection Agency of the United States (EPA) and Canadian Provincial
environmental agencies have issued various regulations regarding the introduction and
disposal of refrigerants. Failure to follow these regulations may harm the environment and
can lead to the imposition of substantial fines.
NOTE
The service of the unit is regulated by the mechanical code adopted by the authority
having jurisdiction.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 3 © 2022 Mitsubishi Electric US, Inc.

WARNING
Risks related to PAA unit servicing
• PAA unit must be serviced by a dealer, contractor, or technician with certifications
required by laws and codes.
– Improper service by the user may result in injury or damage to the unit such as water
leakage, electric shock, or fire.
• Be sure the unit is installed in a place that can withstand its weight before servicing.
– Inadequate strength may cause the unit to fall, resulting in injuries.
• In order to prevent the PAA unit from falling during typhoons, hurricanes, earthquakes
etc., be sure the unit is properly secured.
– Improper service may cause the unit to topple and result in injury.
• Prohibit anyone without the proper qualifications from doing repairs. If the air conditioner
must be repaired, consult a dealer, contractor or technician with certifications required by
laws and codes.
– If the PAA unit is repaired improperly, water leakage, electric shock, or fire may result.
• Service the air conditioner according to this service manual.
– If the unit is serviced improperly, water leakage, electric shock, or fire may result.
• Ensure the outdoor unit cover panel is installed correctly. Please refer to the outdoor
unit’s manual for proper installation.
– If the terminal cover panel is not installed correctly, dust or water may enter the
outdoor unit, which could result in fire or electric shock to the user.
• Ensure that the stop valves are opened immediately after connecting, vacuuming and
pressure testing the refrigerant lines when connecting the PAA unit to the outdoor unit.
– Failure to due so may cause the PAA unit or refrigerant lines to rupture because of
high-pressure refrigerant during the furnace's heating operation.
• If the PAA unit is not installed according to the installation manual, which requires a float
switch, condensed water from the PAA heat exchanger will deviate from the specified
path and may cause water to leak on to the heat exchanger of the gas furnace. This
may cause gas, oil, and water leakage from the furnace due to corrosion over time.
Furthermore, this can lead to poisoning, fire, explosion, water leakage, and bodily harm
and damage to property.
• When PAA unit (this product) is supported from the ceiling in a garage or an occupied
area, the product may fall due to insufficient strength of the suspension or support,
or deterioration over time, etc., causing bodily harm and damage to property. In some
cases, it can lead to death. Properly support the PAA unit in these situations.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 4 © 2022 Mitsubishi Electric US, Inc.

WARNING
Electrical risks
• When sizing wire and completing electrical connections during installation, please follow
local codes and standards.
– Inadequate connections and fastening may generate heat and cause a fire.
• Have all electric work performed by a properly qualified electrician in the state where the
electric work is being performed, according to the “National Electrical Code" and local
electrical codes, “Interior Wire Regulations” and the instructions provided in this service
manual, and always use a dedicated circuit.
– If the power source capacity is inadequate or electric work is performed improperly,
electric shock or fire may result.
• Keep the electric parts away from water.
– It might result in electric shock, fire, or smoke.
• Do not reconstruct or change the settings of the protection devices.
– If the pressure switch, thermal switch, float switch or other protection devices are
shorted and operated forcibly, or parts other than those specified by Mitsubishi Electric
are used, fire or explosion may result.
• If the supply cord is damaged, it must be replaced by the manufacturer service
personnel or licensed person.
• Be sure to ground the outdoor unit in accordance with local code. Do not connect the
earth cable to any gas pipe, water pipe, lightning rod, or telephone earth cable.
WARNING
Refrigerant leak risks
• If refrigerant gas leaks during service work, ventilate the room and do not use the
furnace until a technician considers that it is safe to use the furnace.
– If the refrigerant gas comes into contact with a flame, poisonous gases will be
released. When the odor is detected, contact a dealer, contractor or technician
regarding the appropriate measures to prevent the safety limit from being exceeded.
• After completing service work, make sure that refrigerant gas is not leaking.
– If the refrigerant gas leaks and is exposed to a fan heater, stove, oven, or another
heat source, it may generate noxious gases.
• Do not use refrigerant other than R410A.
– Doing so may cause the unit or pipes to burst, or result in an explosion during use,
repair, or at the time of disposal of the unit.
– Doing so may also be in violation of applicable laws.
– The manufacturer, Mitsubishi Electric Corporation, its affiliates and suppliers, cannot
be held responsible for malfunctions or accidents resulting from the wrong type of
refrigerant used.
• When the outdoor unit service valve is left closed after installation/service, or when
the outdoor unit service valve is closed due to operation stop, the volume of the
liquid refrigerant in the A-Coil and refrigerant piping will expand due to the the heating
operation in the gas furnace. This may cause the A-Coil or refrigerant piping to rupture.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 5 © 2022 Mitsubishi Electric US, Inc.

WARNING
Fuel leak risks
• Fuel and combustion gas may flow into the room if the exhaust duct is leaking, there
is a gap due to insufficient fixing of the connection part, or if regular maintenance is
neglected. As a result, fatal hazards such as poisoning and fire explosion may occur, so
regular maintenance is recommended to check for the following:
– Cracked ducts
– Clogged ducts
– Insufficient exhaust capacity or abnormal stop of the exhaust fan of gas furnace
– Gas leak due to gas furnace heat exchanger failure (including corrosion due to poor
installation environment)
– Incomplete combustion due to gas furnace equipment failure (malfunction / parts *
failure)
* Parts refer to piping, valves, electrical wiring, electrical / electronic parts, sensors,
circuit breakers, etc.
– Short-circuit or ground fault due to ignition, tracking or insufficient insulation of gas
furnace parts
– Damage to internal and external wiring of gas furnace
– Deterioration of heat resistance, strength, corrosion resistance, insulation, etc. of gas
furnace peripheral components
– Gas furnace protection circuit malfunction
– Electrical components for electromagnetic noise interference due to normal use over
time, parts failure, and/or installation of nearby electrical devices
– Inadequate confirmation of recalled products from the design / manufacturing year of
gas furnace
– Maintaining an abnormal installation state by overlooking a gas furnace installation
error or a red tag
• If our equipment is not installed, used, serviced, or maintained as described in the
PAA unit installation/operation/service manual, the following problems may occur. In this
case, stop the operation immediately by turning off the power, etc., and ask the dealer or
contractor for an inspection. Otherwise, gas leaks can cause poisoning, fire, explosions,
water leaks, etc., which can cause serious bodily harm and damage to property.
– If the installation or operating environment is out of the warranty range, the control box
may malfunction, and the gas furnace protection functions may also fail and disable.
The effect of the excessive heat generated by the gas furnace can cause cracks in
the A-Coil section resulting in refrigerant and oil leaks. Furthermore, poisoning, fire,
and explosions may occur from this, doing so can cause bodily harm and damage to
property.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 6 © 2022 Mitsubishi Electric US, Inc.

WARNING
Safety guidelines
• Follow all safety codes specified in the region where the service work is to take place.
Wear appropriate protective equipment such as safety glasses, protective clothing, and
gloves during service work such as refrigerant filling, torque wrench use, and unit
transportation. Use a quenching cloth and have a fire extinguisher available during
brazing operations.
– Failure to follow safety requirements can result in injury or death or building damage.
• Do not touch the heat exchanger fins.
– Improper handling may result in injury.
• Never substitute parts or components from other manufacturers when repairing or
replacing components in the PAA unit. Never service or operate the PAA unit if any
parts or components are damaged.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 7 © 2022 Mitsubishi Electric US, Inc.

WARNING
Service guidelines
• Read this manual carefully and follow all warnings and cautions provided with this unit.
Refer to your local building code and the latest National Electrical Code (NEC) NFPA70.
In Canada, be sure to refer to the latest Canadian Electrical Code CSA C22.1. Also,
follow all codes specified by your region.
We recommend installing a CO sensor and ventilation system.
– Failure to follow safety requirements can result in injury, death or building damage.
• When moving and reinstalling the PAA unit, consult the dealer, contractor or technician
with certifications required by laws and codes.
– If the air conditioner is serviced improperly, water leakage, electric shock, or fire may
result.
• Ask a dealer, contractor or technician with certifications as required by laws and codes
to service the accessories.
– Improper service by the user may result in water leakage, electric shock, or fire.
• Pay attention to the unit service location. Refrigerant is heavier than air and locations
such as basements or crawl spaces where refrigerant can accumulate can become
dangerous.
– Inadequate ventilation can lead to poisoning.
• The appliance is not intended for use by persons with reduced physical, sensory or
mental capabilities, or lack of experience and knowledge (including children) unless they
have been given supervision or instruction concerning the use of the appliance by a
person responsible for their safety.
•Do not add UV Lights into the PAA unit cabinet or to the attached ductwork.
•–UV Lights can cause degradation to plastic and insulation parts. Water leakage,
electric shock, or fire may result.
• If the gas furnace is not certified to safety standards (ANSI Z21.47/CSA2.3) by a
nationally recognized third-party certification organization (AGA, UL, CSA, ETL/Intertek,
etc.), or if the gas furnace does not comply with ACCA (Air Conditioning Contractors
Association) Standards and Guidelines (Code), NFPA54 (National Fuel Gas Code),
NFPA70 (NEC: National Electrical Code), and if the equipment is not properly installed,
used, serviced, and maintained in accordance with the building code for each district
(state, county, city, town, etc.), the following hazards may occur even if our equipment is
properly designed, installed, and operated, and serviced.
– If a leak sensor is not installed in the room, there is a risk of poisoning symptoms and
death without noticing a toxic gas leak.
– Gas fuel has an odor, but if you do not notice it, there is a risk that it can cause
poisoning symptoms or an accident, such as a fire or explosion.
– If the safety of gas furnace, gas supply piping, and exhaust duct worsen due to
improper ventilation of the system [ventilation must be in accordance with Law,
Standard or Guideline (Code)], or due to aging deterioration or the influence of the
usage environment, there is a risk of poisoning symptoms due to combustion gas or
igniting fuel gas and causing a fire or explosion.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 8 © 2022 Mitsubishi Electric US, Inc.

CAUTION
Risks related to PAA unit servicing
• When servicing and relocating the PAA unit, do not charge it with a refrigerant different
from the refrigerant specified on the unit.
– If a different refrigerant or air is mixed with the original refrigerant, the refrigerant cycle
may malfunction and the unit may be damaged. Use only recommended refrigerant
specified in ODU manual for system operation (ONLY R410A).
• The PAA unit is designed for indoor installation only.
• The PAA unit must be installed downstream (discharge air) side of the furnace.
• Do not alter the cabinet or braze inside the cabinet. Quench all brazed joints with water
or a wet rag to avoid overheating after brazing.
– It may affect the performance of the PAA unit.
• Do not use leak detection additive.
– ODU and PAA unit parts may be damaged by the refrigerant/additive mixture.
Refrigerant leak risks
• The service (technician) shall ensure there is no refrigerant leakage according to local
regulations and standards.
– Refrigerant leakage will affect the performance of the heat pump.
Service guidelines
• For PAA unit piping connections, use flare connection as the equipment was designed
for. Mitsubishi Electric US, Inc. is not responsible for improper brazing connection done
by the service technician.
– For pipe flaring, use an R410A flaring tool.
– Improper brazing connections may cause damage to the PAA unit.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 9 © 2022 Mitsubishi Electric US, Inc.

1.2. Devices that use R410A refrigerant
CAUTION
Service guidelines
• Use refrigerant piping made of C12200 (Cu-DHP) phosphorus deoxidized copper as
specified in the ASTM B280 Standard Specification for Seamless Copper Tube for Air
Conditioning and Refrigeration Field Service. Ensure that the inner and outer surfaces of
the pipes are clean and free of hazardous Sulphur, oxides, dust/dirt, shaving particles,
oils, moisture or any other contaminants.
– Contaminants on the inside of the refrigerant piping may cause the refrigerant residual
oil to deteriorate.
• Store the piping to be used during service indoors and keep both ends of the piping
sealed until just before brazing. (Store elbows and other joints in a plastic bag.)
– If dust, dirt, or water enters the refrigerant cycle, deterioration of the oil will result in
malfunction of the compressor.
• Do not use a refrigerant other than R410A.
– If any other refrigerant is used, the chlorine in that refrigerant may cause the
refrigerant oil to deteriorate.
– Since R410A does not contain any chlorine, gas leak detectors for conventional
refrigerant will not react to it.
• Use a vacuum pump with a reverse flow check valve.
– The vacuum pump oil may flow back into the refrigerant cycle and cause the
refrigerator oil to deteriorate.
• Do not use the following tools that are used with refrigerants other than R410A:
– Gauge manifold, charge hose, gas leak detector, reverse flow check valve, refrigerant
charge base, vacuum gauge, refrigerant recovery equipment.
• Do not use a charging cylinder.
– It may cause the refrigerant to deteriorate.
• Use liquid refrigerant to fill the system.
– If gas refrigerant is used to seal the system, the composition of the refrigerant in the
cylinder will change and performance may drop.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 10 © 2022 Mitsubishi Electric US, Inc.

1.3. Before getting started
PAA unit is compatible with P-Series and M/Nv-Series systems and is available in the following model
combinations.
PAA unit and ODU compatibility table
P-Series
ODU
IDU
PAA-A18AA1
PAA-A18BA1
PAA-A24AA1
PAA-A24BA1
PAA-A30AA1
PAA-A30BA1
PAA-A36BA1
PAA-A36CA1
PAA-A42BA1
PAA-A42CA1
Comment
PUY-A18NKA7 No connection allowed
PUY-A24NHA7 ✓ ✓
PUY-A30NHA7 ✓
PUY-A36NKA7 ✓
PUY-A42NKA7 ✓
PUZ-A18NKA7 No connection allowed
PUZ-A24NHA7 ✓ ✓
PUZ-A30NHA7 ✓
PUZ-A36NKA7 ✓
PUZ-A42NKA7 ✓
PUZ-HA24NHA1 ✓
PUZ-HA30NKA ✓
PUZ-HA36NKA ✓
PUZ-HA42NKA1 No connection allowed
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 11 © 2022 Mitsubishi Electric US, Inc.

M-Series/Nv-Series
IDU
PAA-
A18AA1
PAA-
A18BA1
PAA-
A24AA1
PAA-
A24BA1
PAA-
A30AA1
PAA-
A30BA1
PAA-
A36BA1
PAA-
A36CA1
PAA-
A42BA1
PAA-
A42CA1
Comment
ODU
MXZ-3C24NA3 ✔
MXZ-3C30NA3 ✔ ✔
MXZ-4C36NA3 ✔ ✔
MXZ-5C42NA3 ✔ ✔
MXZ-SM36NAM ✔ ✔ ✔ ✔
MXZ-SM48NAM ✔ ✔ ✔ ✔
MXZ-SM60NAM ✔ ✔ ✔ ✔
MXZ-3C24NAHZ3 ✔
MXZ-3C30NAHZ3 ✔ ✔
MXZ-
SM36NAMHZ
✔ ✔ ✔ ✔
MXZ-
SM42NAMHZ
✔ ✔ ✔ ✔
MXZ-
SM48NAMHZ
✔ ✔ ✔ ✔
PAA-series (Cased A-Coil) Connection
Maximum piping length Maximum total piping with PAA connection depends on the number of PAA indoor
units connected. Please refer to the table below for the appropriate total maximum piping length the system
can be designed to.
Minimum piping length For branch box systems where PAA is the only unit(s) connected, the minimum
piping length to each PAA unit from the outdoor unit should be 33 ft.
Number of PAA units connected
Model Total
Connected
Indoor
Capacity
(kBtu/h)
No PAA
Connected
1 2 3 or more
MXZ-SM36/48NAM
MXZ-
SM36/42/48NAMHZ
<27 492 ft
(150 m)
492 ft
(150 m)
(N/A,
*above 27
kBtu/h)
(N/A,
*above 27
kBtu/h)
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 12 © 2022 Mitsubishi Electric US, Inc.

Number of PAA units connected
Model Total
Connected
Indoor
Capacity
(kBtu/h)
No PAA
Connected
1 2 3 or more
28-54 492 ft
(150 m)
341 ft
(104 m)
276 ft
(84 m)
276 ft
(84 m)
>55 492 ft
(150 m)
308 ft
(94 m)
243 ft
(74 m)
243 ft
(74 m)
MXZ-SM60NAM
<27 492 ft
(150 m)
492 ft
(150 m)
(N/A,
*above 27
kBtu/h)
(N/A,
*above 27
kBtu/h)
28-54 492 ft
(150 m)
408 ft
(124 m)
361 ft
(110 m)
337 ft
(103 m)
>55 492 ft
(150 m)
384 ft
(117 m)
337 ft
(103 m)
314 ft
(96 m)
NOTE
For extended piping lengths, please refer to Diamond System Builder (DSB).
NOTE
The above chart is for M-Series/Nv-Series. For P-Series follow guidelines in the P-
Series installation manual.
PAA unit airflow restriction table
IDU
PAA-
A18AA1
PAA-
A18BA1
PAA-
A24AA1
PAA-
A24BA1
PAA-
A30AA1
PAA-
A30BA1
PAA-
A36BA1
PAA-
A36CA1
PAA-
A42BA1
PAA-
A42CA1
Airflow
Maximum CMM 23.0 23.5 29.0 34.0 47.0
CFM 812 830 1024 1201 1660
Minimum CMM 12.0 15.6 19.8 22.7 26.5
CFM 424 551 700 800 936
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 13 © 2022 Mitsubishi Electric US, Inc.

NOTE
The above airflow restriction is limited to the heat pump operation only.
WARNING
• Ensure the gas furnace complies with ANSI-Z21.47/CSA2.3 standards by NRTL 3rd
party lab such as AGA, CSA, UL, or ETL/Intertek. Mitsubishi Electric US, Inc. air
conditioner/heat pump system must only be connected with ANSI-Z21.47/CSA2.3
certificated gas furnace.
– Improper connection may result in poisonous gas, fire, explosion, electric shock or
water leak.
• Do not install the PAA unit onto any OIL or DRUM type furnaces.
– Failure to follow this warning could result in personal injury or death.
• Do NOT install the PAA unit on any furnaces or applications where supply air
temperature could exceed 200 ºF.
– Failure to follow this warning could result in personal injury or death.
• The PAA unit should only be installed on a furnace with an output capacity no greater
than 300% of the rated PAA unit cooling capacity.
– Failure to follow this warning could result in personal injury or death.
IMPORTANT
The furnace fan should be configured such that the airflow is greater than or equal to
350 CFM per ton and less than or equal to 400 CFM per ton of nominal PAA unit cooling
capacity.
In downflow orientation, the furnace fan should be configured to maintain an airflow face
velocity below 350 ft/min to prevent water blow-off.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 14 © 2022 Mitsubishi Electric US, Inc.

CAUTION
• Do not use the PAA unit in special environments.
– Oil, steam, sulfuric smoke, etc. can significantly reduce the performance of the PAA
unit or damage its parts.
• Always lock the furnace disconnect switch, if present, in the open position prior to
servicing the PAA unit.
• When servicing the unit in a hospital, communication station, or similar place, provide
sufficient protection against electromagnetic noise.
– The INVERTER equipment, private power generator, high-frequency medical
equipment, or radio communication equipment may cause the PAA unit to operate
erroneously, or fail to operate. On the other hand, the PAA unit may affect such
equipment by creating electromagnetic noise that disturbs medical treatment of image
broadcasting.
• Make sure an auxiliary drain pan is installed to prevent occasional condensation from
damaging the building.
• When the room humidity exceeds 80% or when the drain pipe is clogged, condensation
may drip from the indoor unit. Perform collective drainage work together with the outdoor
unit, as required.
• When the ambient dew point temperature exceeds 73° F (23° C), dew condensation
may occur on the unit surface. Perform appropriate treatment, such as duct wrap
insulation, to avoid dew condensation.
NOTE
Keep this service manual with the unit. Carefully read all instructions for the service prior
to servicing the product. Make sure each step or procedure is understood and any special
considerations are taken into account before starting service.
Gather all tools, hardware, and supplies needed to complete the installation. Refer to
the "System introduction" and "Indoor unit accessories" sections of the PAA installation
manual for items that are not included with the PAA unit. Make sure everything needed to
service the product is on hand before starting. If the power source capacity is inadequate
or electric work is performed improperly, electric shock and fire may result.
WARNING
• Failure to follow this warning could result in property damage, severe personal injury,
or death: verify the furnace is properly installed according to the gas furnace service
manual and local building codes.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 15 © 2022 Mitsubishi Electric US, Inc.

1.4. Before servicing or moving the PAA unit - electrical work
NOTE
Ensure the wiring is not pinched or damaged when fitting the control box cover.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 16 © 2022 Mitsubishi Electric US, Inc.

WARNING
• Be sure to ground the PAA unit and outdoor unit.
– Do not connect the earth cable to any gas pipe, water pipe, lightning rod, or telephone
earth cable. Incomplete grounding may cause a risk of electric shock. If the supply
cord is damaged, it must be replaced by a dealer, contractor or technician with
certifications as required by laws and codes, in order to avoid a hazard.
• Service the power cable so that tension is not applied to the cable.
– Tension may cause the cable to break and generate heat and cause a fire.
• Install a circuit breaker as required by all applicable codes and regulations and be sure
to use a qualified electrician/installer.
• Use power line cables of sufficient current carrying capacity and rating.
– Cables that are too small may leak, generate heat, and cause a fire.
• When sizing wire and completing electrical connections during service, please follow
local codes and standards.
– Fuse or circuit breaker of a larger capacity or a steel or copper wire may result in a
general unit failure or fire.
• Do not wash the PAA unit.
– Washing the PAA unit may cause an electric shock.
• Ensure that the installation base is not damaged.
– If damaged, the unit may fall and cause personal injury or property damage.
• Service the drain piping according to the PAA unit installation manual to ensure proper
drainage. Wrap thermal insulation around the pipes to prevent condensation.
– Improper drain piping may cause water leakage and damage to furniture and other
possessions.
• Be very careful about product transportation.
– If the product weighs more than 20 kg [44 lb], more than one person should carry the
product.
– Some products use polypropylene band (PP) bands for packaging. Do not use any PP
bands for a means of transportation; it is dangerous.
– Do not touch the heat exchanger fins. Doing so may cut your fingers.
• Safely dispose of the packing materials.
– Packing materials, such as nails and other metal or wooden parts, may cause stabs or
other injuries.
– Tear apart and throw away plastic packaging bags so that children will not play with
them. If children play with a plastic bag which was not torn apart, they face the risk of
suffocation.
• Before installing or servicing system, always turn off main power to system. There may
be more than one disconnect switch. Tag disconnect switch with a warning label.
– Failure to follow this warning could result in personal injury or death.
• Always disconnect power to the furnace before removing the blower door.
– Failure to disconnect power may result in electric shock or injury.
• Label all wires prior to disconnection when servicing controls. Verify proper operation
after servicing.
– Wiring errors can cause improper and dangerous operation.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 17 © 2022 Mitsubishi Electric US, Inc.

1.5. Before starting the test run
CAUTION
• Open the stop valves isolating the PAA unit from the outdoor unit before starting
operation to avoid refrigerant pipe bursting during furnace operation.
• Turn on the power at least 12 hours before starting operation.
– Starting operation immediately after turning on the main power switch can result
in severe damage to internal parts. Keep the power switch turned on during the
operational season.
• Do not turn off the power immediately after stopping operation. Wait at least five minutes
before turning off the power.
– Turning off the power immediately may cause a water to leak.
WARNING
• Do not touch the switches with wet fingers.
– Touching a switch with wet fingers can cause electric shock.
• Do not touch the refrigerant pipes during and immediately after operation.
– During and immediately after operation, the refrigerant pipes may be extremely hot
or cold, depending on the condition of the refrigerant flowing through the refrigerant
piping, compressor, and other refrigerant cycle parts. Your hands may suffer burns or
frostbite if you touch the refrigerant pipes.
• Read the chapters from the "Selecting an installation site" chapter to the "Electrical
wiring" chapter in the installation manual carefully before operating the equipment. Do
not operate the furnace, PAA unit or outdoor unit with the panel or guard removed.
– Injury may occur if you touch the rotating fan of the furnace or outdoor unit, high-
temperature parts such as compressors and pipes, or high-voltage parts such as
terminal blocks.
• Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this
or any other appliance. What to do you if you smell natural gas or gasoline:
– Do not touch any electrical switch.
– Do not use any phone in your building.
– Immediately call your gas supplier from a neighboring location.
– Follow the gas supplier's instructions.
– If you cannot reach your gas supplier, call the fire department.
– Do not try to light any appliance.
• Never use an open flame to detect refrigerant leaks. Explosive conditions may occur.
Use a leak test sensor or other approved methods for leak testing. Should furnace
discharge air supply overheating occur and the gas supply fails to shut off, follow the
furnace installation manual to disable the gas and electric supply to the furnace.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 18 © 2022 Mitsubishi Electric US, Inc.

1.6. To dispose of the PAA unit
CAUTION
To dispose of the PAA unit, consult a dealer, contractor, or technician with certifications
required by laws and codes.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 19 © 2022 Mitsubishi Electric US, Inc.

2. INSTALLATION POSITIONS AND CORRESPONDING
AIRFLOW DIRECTION
Indoor Unit
Vertical
Air Outlet
Air Inlet
Horizontal Right
Air Outlet
Air Inlet
Horizontal Left
Air Outlet Air Inlet
Downflow
Air Outlet
Air Inlet
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
Specifications are subject to change without notice. 20 © 2022 Mitsubishi Electric US, Inc.