MITSUBISHI ELECTRIC PAC-US444CN-1 Thermostat
Confirming the Supplied Parts
Check that the box includes the following part(s) in addition to this installation manual:
- PAC-US444CN-1 Thermostat Interface (1)
2. Safety Precautions
- Thoroughly read the following safety precautions before use.
- Hazards that can occur from incorrect handling are classified by the symbols below
- Warning Incorrect handling can result in death, serious injury, etc.
- Caution Incorrect handling can result in bodily injury and/or structure damage
Warning
- Only a dealer or qualified technician should install, relocate, reinstall, or repair the device.
- Improper installation or repair may result in electrical shock or fire Properly install the device on a stable, load-bearing surface.
- Device installed on an unstable surface may fall and cause injury Only use the specified 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 fire.
- Do not make any modifications or alternations to the device. Modifications or improper repair may result in electric shock or fire.
- Consult your dealer for repair All electrical work should be performed by an authorized electrician according to local regulations and instructions outlined in this manual.
- Capacity shortage to the power supply circuit or improper installation may result in electrical shock or fire.
- Properly install the device according to the instructions in this Installation/Instruction Manual. Improper installation may result in electric shock or fire
Caution
- Do not install the device in a location where a flammable 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), sulfidizing 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 fire.
- Do not touch the main circuit board; also, make sure that dust does not accumulate on the circuit board When installing the device in a hospital, communication facility, etc., provide sufficient 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 affect 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 fire.
- 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.
System Configuration
- All wiring shown should be performed with 18 AWG thermostat wire.
- Terminals on the PAC-US444CN-1 support 20-30VAC.
- High/medium/low fan signals are optional, and may not be available on all thermostat models.
- W2 and Y2 signals are optional, and may be omitted for single-stage thermostats
Two-stage Cooling and Heating
Single-stage Cooling and Heating
Single-stage Cooling and Heating with Dedicated Fan Speed Relays
Single-stage Cooling with Alternate Primary Heating Source
| Connector | Purpose | Purpose |
| TC | Common (In) | C |
| C | Common (Out) | C |
| TR | 24VAC (In) | R |
| R | 24VAC (Out) | R |
| G3 | Fan High | High Fan Speed |
| G2 | Fan Medium | Medium Fan Speed |
| G1 | Fan Low | Low Fan Speed |
| Y2 | Y2 | Stage 2 Cooling |
| Y1 | Y1 | Stage 1 Cooling |
| W2 | W2 | Stage 2 Heating |
| W1 | W1 | Stage 1 Heating |
| G | G | Fan |
Follow the wiring from example 2, with the following adjustments:
- Connect thermostat W1 to the alternate heat source.
- Connect the thermostat W2 terminal to the PAC-US444CN-1 W1 terminal.
How to Install
- Choose a place where to install the PAC-US444CN-1. The device provides two mounting holes that can be used to mechanically affix the case to a solid surface.
- Double-sided tape may be used to affix the device. When using tape, ensure that the tape is approved for use within the anticipated operating temperature ranges.
- Install the transformer, as necessary, per building code and manufacturer’s installation instructions.
- Connect the PAC-US444CN-1 cable to the connector CN105 on the indoor unit control board.
- Connect PAC-US444CN-1 terminals using 18 AWG wire.
Device Configuration
Initial settings can be configured 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
Delayed Off
SW1-1/2: After reaching thermostat set point, the unit will continue to run for a set period of time in order to improve efficiency. The period of time is set by adjusting SW1-1 and SW1-2 according to the following table:
| SW1-1 | SW1-2 | Result |
| OFF | OFF | 5 minutes (Default) |
| ON | OFF | 10 minutes |
| OFF | ON | 30 minutes |
| ON | ON | 0 minutes |
| SW1-3 | SW1-4 | Result |
| OFF | OFF | Auto (Default) |
| ON | OFF | Medium |
| OFF | ON | High |
| ON | ON | Custom Auto |
Two-Stage Thermostat Operation
SW2-6: Adjusts indoor unit operation during stage 1 heating and stage 1 cooling
according to the following table:
Static Pressure Settings
SW2-1, SW2-2, SW2-3: These adjust the static pressure function settings of the indoor unit according to the following table:
| DIP switch position on PAC-US444CN-1 | Indoor Unit Settings | |||||
| 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 |
CN24 Operation During Defrost
SW2-4: Adjusts Mode 23 function settings according to the following table:
| SW2-4 | Result | Fan and CN24 |
| OFF | Setting 2 (Default) | ON |
| ON | Setting 1 | OFF |
Fan Speed During Heating Mode, Thermal Off
SW2-5: Adjusts Mode 25 initial setting (fan speed in thermal off for heating) according to the following table:
| SW2-5 | Result |
| OFF | Extra low (Default) |
| ON | Set by Thermostat Interface |
In addition, the adapter also affects the following function settings of the connected indoor unit
| Mode | When using the adapter |
| Mode 1 (auto recovery after power failure) | Always enabled |
| Mode 2 (room temperature detection location) | Unused (room temperature detected by the connected thermostat) |
| Mode 24 (heat offset for height) | Unused |
Grouping
The connection of more than one PAC-US444CN-1 to a single set of thermostat dry-contacts is not supported.
Temperature Sensing
The PAC-US444CN-1 relies upon both the dry-contact 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
Usage
Operate the third-party thermostat per the manufacturer’s instructions. During normal operation, the connection of Mitsubishi remote controllers (e.g. MA/ME) is not supported, as they will interfere with the correct operation of the PAC‑US444CN‑1.
Notes:
- The indoor unit will limit the internal temperature control set point based on the indoor unit specification.
- Fan signals G1,G2,G3, when energized, take precedence over SW1-3&4.
- Only fan speeds available on the IDU can be set by the Thermostat Interface.
- The G signal is used only for operating the IDU in ventilation mode when all cooling and heating signals are disabled.
- When all cooling and signals are disabled, energizing G will place the IDU into ventilation mode
REFERENCE
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MITSUBISHI ELECTRIC PAC-US444CN-1 Thermostat Installation
