MANUFACTURED FOR:
MITSUBISHI ELECTRIC US, INC.
Thermostat Interface 2
PAC-US445CN-1
INSTALLATION/INSTRUCTION MANUAL
Before using the device, carefully read this installation/instruction manual to ensure
proper operation.
Contents
1. Supplied parts .....................................................................................................1
2. Safety precautions ..............................................................................................1
3. System conguration ........................................................................................... 3
4. How to install .......................................................................................................5
5. Usage ..................................................................................................................9
6. Usage with PAA unit ............................................................................................9
1. Supplied parts
Check that the box includes the following parts in addition to this installation manual:
• 1 x Thermostat Interface 2 (PAC-US445CN-1)
• 1 x PAA unit accessory cable
2. Safety precautions
• Thoroughly read the following safety precautions before use.
• Hazards that can occur from incorrect handling are classied by the symbols
below:
WARNING Incorrect handling can result in death, serious injury, etc.
CAUTION
• After reading this manual, keep it for future reference. When the device is
reinstalled or repaired, give this manual to those who provide these services.
When the user changes, make sure the new user receives this manual.
WARNING
• Only a dealer or qualied technician
should install, relocate, reinstall or
repair the device.
Improper installation or repair may
result in electrical shock or re.
Incorrect handling can result in bodily injury and/or
structure damage.
• Properly install the device on a
stable, load-bearing surface.
Device installed on an unstable surface
may fall and cause injury.
FOR INSTALLER
• Only use the specied cables;
securely connect each so that
the terminals do not bear any
cable weight.
Improperly connected or short-circuited
cables may produce heat and cause a
re.
• Do not make any modications or
alternations to the device.
Modications or improper repair may
result in electric shock or re. Consult
your dealer for repair.
CAUTION
• Do not install the device in a
location where a ammable gas leak
may occur.
Gas may leak, collect around the
device, ignite and/or explode.
• Do not install the device in
environments where large
amounts of oil (including machine),
suldizing gas, or acidic, alkaline,
chemical sprays are present.
These types of substances may
damage internal parts, cause device
performance to be reduced, and cause
electrical shock.
• Do not install the device in a
bathroom, kitchen or any room
where steam could form.
Condensation may develop and cause
electrical shock, and/or the device to
malfunction.
• Use standard wires with the
proper current capacity to avoid the
possibility of current leak, excessive
heat, and/or re.
• Do not touch the main circuit board;
also, make sure dust does not
accumulate on the circuit board.
• All electrical work should be
performed by an authorized
electrician according to local
regulations and instructions
outlined in this manual.
Shorting the power supply circuit or
improper installation may result in
electrical shock or re.
• Properly install the device
according to the instructions in this
Installation/Instruction Manual.
Improper installation may result in
electric shock or re.
• When installing the device in a
hospital, communication facility,
etc., provide sucient protection
against frequency noise.
Power generators and inverters,
high-frequency medical or radio
communication equipment may
interfere with the normal operation of
this device. Subsequently, the device
may also aect medical treatment,
image broadcasting, etc., by creating
frequency noise.
• Include some slack in the power
supply wires.
Tension on the wires may cause them
to excessively heat up and/or break,
resulting in a re.
• Do not install the device in a
location where there is direct
sunlight or where the temperature
may become greater than 40° C
(104° F) or less than 0° C (32° F).
If the device is installed in such
place, it may result in deformation or
malfunctions.
• Do not immerse the device in water.
Doing so may lead to electric shock or
malfunctions.
3. System conguration
WARNING
Thermostat should be congured for use with a conventional system (not heat
pump).
Thermostat Interface terminals
Terminal Purpose
TC C: common (in)
C C: common (out)
TR R: 24 VAC (in)
R R: 24 VAC (out)
G3 High fan speed
G2 Medium fan speed
G1 Low fan speed
Y2 Stage 2 cooling
Y1 Stage 1 cooling
W2 Stage 2 heating
W1 Stage 1 heating
G Fan
1. All wiring shown should be performed with 18 AWG thermostat wire.
2. Terminals on the PAC-US445CN-1 support 20-30 VAC.
3. High/medium/low fan signals are optional and may not be available on all
thermostat models.
4. W2 and Y2 signals are optional and may be omitted for single-stage thermostats.
5. The PAC-US445CN-1 runs in two modes: heating/cooling or o/fan.
Upon receiving the initial request from the thermostat for the heating/cooling
mode, the Thermostat Interface switches to the heating/cooling mode.
For indoor units that support Mode 25 and Mode 27 initial settings, the G signal
at the time of entering the heating/cooling mode determines the fan state during
thermal o. If the G signal was on, the thermal o fan is on. If the G signal was
o, SW1-2 and SW 2-5 settings determine the thermal o fan speed.
Once there is no longer a request from the thermostat for heating or cooling, the
Thermostat Interface switches the indoor unit to either o or fan mode depending
upon whether the G signal is o or on. If SW1-1 has enabled delay time, the
unit remains in heating or cooling mode for 2 hours before switching to o or fan
mode.
Example 1: Two-stage cooling and heating
IDU
PAC-US445CN-1
Example 2: Single-stage cooling and heating
IDU
PAC-US445CN-1
Example 3: Single-stage cooling and heating with dedicated fan speed relays
IDU
PAC-US445CN-1
Example 4: Single-stage cooling with alternate primary heating source
Note: For this conguration, it is recommended to set SW2-6 to the ON position.
Follow the wiring from Example 2 with the following adjustments:
1. Connect thermostat W1 to the alternate heat source.
2. Connect the thermostat W2 terminal to the PAC-US445CN-1 W1 terminal.
4. How to install
4.1. Device conguration
Initial settings can be congured via the two banks of DIP switches on the circuit
board, SW1 and SW2. The circuit board can be accessed by unfastening the four
screws on the back of the case.
Note: Factory default is OFF for all switches.
4.2. Functions of DIP switch
Zero delay timer
SW1-1: Chooses the fan/o delay mode following heating or cooling mode.
SW1-1 Delay timer
OFF Stay in heating or cooling mode for 2 hours once W1 or Y1 is no longer
active, which provides more ecient operation but does not respond to
fan request changes (G) during the 2 hours. This setting allows more
time for defrost timers in the outdoor unit to run (default).
ON Once heat or cool request W1 or Y1 is no longer active, the system
turns o or goes into fan mode immediately depending on the G signal.
This is less ecient operation but responds more quickly to fan request
changes. This setting operates most like the previous Thermostat
Interface with zero hold time after achieving set point.
Fan speed during cooling thermal o if G is o
SW1-2: Chooses the cooling mode thermal o fan speed when G is not energized.
This setting depends upon whether it is more important to stop the fan when not
cooling or to keep the air moving when not cooling.
SW1-2 Mode 27 / Fan speed
OFF 2 (default) / O
ON 3 / Extra low
SW1-3/4: The indoor unit fan speed can be adjusted via the following settings:
SW1-3 SW1-4 Result
OFF OFF Custom Auto (default)
ON OFF Medium
OFF ON High
ON ON Auto
Note: Custom Auto (default) provides higher fan speeds for more comfortable fan
speed operation vs. the more ecient Auto.
Specications are subject to change without notice.
1
© 2022 Mitsubishi Electric US, Inc.
Specications are subject to change without notice.
2
© 2022 Mitsubishi Electric US, Inc.
Specications are subject to change without notice.
3 © 2022 Mitsubishi Electric US, Inc.
Specications are subject to change without notice.
4 © 2022 Mitsubishi Electric US, Inc.
Specications are subject to change without notice.
5 © 2022 Mitsubishi Electric US, Inc.
Specications are subject to change without notice.
6 © 2022 Mitsubishi Electric US, Inc.
SW01
Two-stage thermostat operation
SW2-6: Adjusts indoor unit operation during stage 1 heating (W1) and stage 1
cooling (Y1) according to the following table:
SW2-6 Operation during stage 1
OFF The capacity is adjusted so that the room temperature is
adjusted (heated or cooled) at a xed rate (default).
ON Full capacity
Note: When either Y2 or W2 is left unconnected, it is recommended to set SW2-6
to the ON position. When both Y2 and W2 are connected, it is recommended to set
SW2-6 to the OFF position.
Static pressure settings
SW2-1, SW2-2, SW2-3: Adjust the static pressure function settings of the indoor unit
according to the following table:
DIP switch position on
Indoor unit settings
PAC-US445CN-1
SW2-1 SW2-2 SW2-3 Mode 8 Mode 10 Mode 23 Mode 11
OFF OFF OFF Not set Not set Not set Not set
OFF OFF ON Not set Not set Not set Not set
OFF ON OFF 2 1 Set by SW2-4 2
OFF ON ON 2 2 Set by SW2-4 2
ON OFF OFF 1 1 Set by SW2-4 2
ON OFF ON 1 2 Set by SW2-4 2
ON ON OFF 3 1 Set by SW2-4 2
ON ON ON 3 2 Set by SW2-4 2
Refer to the appropriate indoor unit installation manual for Mode 8 and Mode 10
function setting denitions.
SW2-4: Adjusts Mode 23 function settings according to the following table:
SW2-4 Mode 23
OFF 1 (default)
ON 2
Refer to the appropriate indoor unit installation manual for Mode 23 function setting
denitions. For Mode 23 function settings for the PAA unit, refer to the “Usage with
PAA unit” section in this manual.
Specications are subject to change without notice.
7
© 2022 Mitsubishi Electric US, Inc.
Fan speed during heating mode, thermal o
SW2-5: Adjusts Mode 25 initial setting according to the following table.This setting
depends upon whether it is more important to stop the fan or to keep the air moving
when not heating.
SW2-5 Mode 25 / Fan speed
OFF 2 (default) / O
ON 1 / Extra low
Thermostat Interface non-changeable function settings
In addition, the thermostat interface also aects the following function settings of the
connected indoor unit.
Mode When using the thermostat interface
Mode 1 (auto recovery after power
Always enabled
failure)
Mode 2 (room temperature detection
location)
Unused (room temperature detected
by the connected thermostat)
Mode 24 (heat oset for height) Unused
Additional function settings not addressed by the Thermostat Interface may be
congured by temporarily connecting an MA remote controller. Indoor unit Mode
settings only work for M-Series indoor units that begin with an “S” and P-Series
units.
4.3. Installing the Thermostat Interface
Make sure power supply to the indoor unit is o. We also recommend
conguring the DIP switch settings (see “Device conguration” section) before
installing the Thermostat Interface.
1. Choose a place to install the PAC-US445CN-1. The device provides two
mounting holes that can be used to mechanically ax the case to a solid surface.
Double-sided tape may be used to ax the device. When using tape, ensure the
tape is approved for use within the anticipated operating temperature ranges.
2. Install the transformer, as necessary, per building code and manufacturer’s
installation instructions.
3. Make sure the power supply to the indoor unit is o. Connect the
PAC-US445CN-1 cable to the connector CN105 on the indoor unit control board.
4. Connect PAC-US445CN-1 terminals using 18 AWG wire.
4.4. Grouping
The connection of more than one PAC-US445CN-1 to a single set of thermostat
dry-contacts is not supported.
4.5. Temperature sensing
The PAC-US445CN-1 relies upon both the 24 VAC thermostat and the indoor unit’s
thermistors in order to monitor room temperature. The thermostat’s temperature
sensing is used to set the room temperature. The indoor unit thermistor is used
when calculating cooling and heating rates of change.
Specications are subject to change without notice.
8 © 2022 Mitsubishi Electric US, Inc.
5. Usage
Operate the third-party thermostat per the manufacturer’s instructions. During
normal operation, the connection of Mitsubishi Electric remote controllers (e.g.
MA/ME) is not supported as they will interfere with the correct operation of the
PAC-US445CN-1.
Notes:
1. The indoor unit will limit the internal temperature control set point based on the
indoor unit specication.
2. Fan signals G1,G2 and G3, when energized, take precedence over SW1-3 & 4.
3. Only fan speeds available on the IDU can be set by the Thermostat Interface.
4. When all cooling and heating signals are disabled and the 2-hour period (if
enabled) has expired, energizing G will place the IDU into fan mode.
5. When used with the PAA unit, it is recommended to set SW1-2 and SW2-5 to
remain in default setting of OFF.
6. Usage with PAA unit
The PAC-US445CN-1 Thermostat Interface 2 must be installed in the PAA unit
control box if a third-party 24 VAC thermostat is used to control the PAA unit.
Previous Thermostat Interface PAC-US444CN-1 is not compatible with the PAA unit.
6.1. How to install Thermostat Interface in PAA unit control box
Make sure power supply is o.
1. Use M3-0.5 x 12 mm metric socket cap head screws and 3 mm nuts, or
equivalent (eld supplied), to attach the Thermostat Interface 2 to the top of
the protruding metal bracket in the control box (see image below). Ensure the
Thermostat Interface is securely attached to the bracket.
①
②
③
④
Thermostat Interface Third-party thermostat
Thermostat control signals
(R, C, W1, W2, Y1, Y2, G)
2. Connect the Thermostat Interface to the CN105 connector on the control board.
3. Connect the PAA unit accessory cable included with the PAC-US445CN-1 to the
CNH02 connection on the relay board in the PAA control box.
4. Connect the opposite end of the PAA unit accessory cable to the corresponding
connections on the Thermostat Interface 2.
Specications are subject to change without notice.
PAA unit control box
9 © 2022 Mitsubishi Electric US, Inc.
Cable assembly connections to the Thermostat Interface 2
Wire color Signal
Green G: fan
White W1: rst stage of heating
Brown W2: second stage of heating
Yellow Y1: rst stage of cooling
Blue Y2: second stage of cooling
Light blue C: 24 VAC return
Red R: 24 VAC hot
5. Connect the thermostat to the pins/signals (13A to 19A) on the terminal block in
the control box as shown in the following image.
DIP switch SW01 on the relay board
is located as indicated in the image
and has 4 switches that change the
conguration.
Specications are subject to change without notice.
10 © 2022 Mitsubishi Electric US, Inc.
Thermostat power supply
The thermostat may receive power from the furnace transformer or may have a
separate power supply. An example of when it might have it’s own power supply is
when using a damper control system as dampers typically require more power than
the furnace transformer can supply.
SW01-1: Determines whether to allow the thermostat to provide its own power
or allow the furnace to supply power to the thermostat in Emergency and Normal
operation modes according to the following table:
SW01-1 Result
OFF Electronically disconnects the R line from the furnace to the auxiliary
control equipment and allows the auxiliary equipment to provide its
own power.
ON Electronically routes the R line from the furnace through the PAA
unit control box to the thermostat terminals if connections within the
PAA unit control box provide operating power to the thermostat in
Emergency and Normal operation modes (default).
SW01-1= ON SW01-1= OFF
R
AC
①
C R
③
①
C R
② ②
③
R
AC
C
C
R
AC
C
Signals from thermostat
PAA unit control box
Control signals to furnace (See terminal block image in “How to install
Thermostat Interface in PAA unit control box” section.)
Specications are subject to change without notice.
11 © 2022 Mitsubishi Electric US, Inc .
SW01-4: Determines Emergency and Test mode operations according to the
following table:
SW01-4 Result
OFF Thermostat (or non-adjustable thermostat, if used) controls the heat
and fan signals applied to the furnace during Emergency operation
modes (default).
ON Test mode operation
For information about the non-adjustable thermostat and Test mode operation, refer
to the PAA unit installation manual.
Thermostat Interface DIP switch settings for PAA unit only
SW2-4: Adjusts PAA unit Mode 23 function settings according to the following table.
Note: This DIP switch is on the Thermostat Interface, not the relay board of the PAA
unit.
If the furnace does not support two fan speeds via Y1 and Y2, set Mode 23 to 1 for
G and Y.
If the furnace supports two fan speeds via Y1 and Y2, to allow that to be used when
cooling or heating using the heat pump, set Mode 23 to 2. For Mode 23 setting 2,
the recommended DIP switch SW1-3/4 setting is Auto to vary fan speed, not Custom
Auto.
SW2-4 Mode 23
OFF 1 (default)
ON 2
Refer to the PAA unit Installation Manual for connections to furnace based upon the
setting of Mode 23.
After changing Mode 23 setting, you need to power cycle the system for the change
to reliably take eect.
This device is designed and intended for use in the residential environment.
MEUS DOC# MD-1622-K001 Ver. 2, April 2022 PA79G664H02
Specications are subject to change without notice.
12 © 2022 Mitsubishi Electric US, Inc.
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