VRF External Inputs and Outputs - Reference Guide
This article provides a consolidated reference for VRF external inputs and outputs used on indoor units, outdoor units, RB units, Central Remote Controllers and Touch Panel Controllers.
Quick Reference - Main Functions
| Device | External Input | External Output |
|---|---|---|
| Outdoor unit | CN131 Low noise, CN132 Cooling/Heating priority, CN133 Peak cut, CN134 Batch stop/Emergency stop | CN136 Normal/Error, CN137 Operation/Stop, CN115 Base heater |
| RB unit | CNA01 / CNA02 Cooling/Heating priority | - |
| Indoor unit | CNA01 / CNA02 Operation/Stop, Emergency stop, Forced stop; CNA03 / CNA04 Forced thermostat off | CNB01 Operation/Stop, Normal/Error, Indoor fan operation |
| Central Remote Controller | CN6 / CN7 / CN11 / CN12 Emergency stop and All On/Off | CN9 Operation/Stop and Normal/Error |
| Touch Panel Controller | CN411 / CN412 Emergency stop and Batch operation/stop | CN410 Operation state and Error state |
Voltage vs Dry Contact
External inputs may use either applied voltage or dry-contact / no-voltage methods depending on the terminal.
- Applied voltage: External equipment supplies the specified DC voltage to the input.
- Dry contact: The indoor/outdoor/control PCB supplies the sensing voltage and the external device provides a contact closure.
- Do not apply external voltage to a dry-contact input unless the applicable manual specifically allows it.
Indoor Unit Inputs and Outputs
| Terminal | Type | Function | Connector Part No. |
|---|---|---|---|
| CNA01 | Applied voltage | Operation/Stop, Emergency stop, Forced stop | 9368779016 |
| CNA02 | Dry contact | Operation/Stop, Emergency stop, Forced stop | 9368779023 |
| CNA03 | Applied voltage | Forced thermostat off | 9368778002 |
| CNA04 | Dry contact | Forced thermostat off | 9368778019 |
| CNB01 | Output | Operation/Stop, Normal/Error, Fan operation/stop | 9379529013 |
Forced Thermostat Off
When forced thermostat off is active, the indoor unit stops calling for cooling/heating regardless of room temperature. In cooling it can continue fan operation; during heating the fan may stop.
The source guide shows this function being used with a DDC and damper arrangement. CNA04 is shown as the dry-contact input example.
Operation / Stop
Operation/Stop can be used with occupancy sensors, BMS contacts or similar controls. The source example uses a human sensor to stop the indoor unit when the room is unoccupied.
Function setting 46 = 00 is shown for Start/Stop. Pulse input operation is enabled by setting DIP switch SET2-2 to ON.
Emergency Stop
Emergency Stop stops all units in the applicable refrigerant system and prevents normal operation from the remote controller until the emergency stop condition is cancelled.
The source guide shows indoor-unit field setting 49 = 01 for Emergency Stop.
Forced Stop
Forced Stop is typically used with card keys or occupancy controls. When active, the affected indoor unit is stopped and operation from the remote controller is prohibited.
The source guide shows indoor-unit field setting 49 = 02 for Forced Stop.
Operation / Error Output
CNB01 can be used to provide external indication of indoor-unit operation and error status.
- Output voltage: DC12 V
- Rated current: 50 mA or less
- Typical application: relay, lamp, BMS or status input
Indoor Fan Operation Output
CNB01 may also be used to interlock an external ventilator so that the ventilator runs when the indoor unit fan operates.
RB Unit - Cooling / Heating Priority
The RB unit can use an external input to force either Cooling Priority or Heating Priority.
- CNA01 - Dry-contact input
- CNA02 - Applied-voltage input
- Typical wiring: AWG22 twisted cable, 0.33 mm²
- Maximum cable length shown: 150 m
The source guide shows DIP switch SET2-1 = ON to enable the external Cooling/Heating Priority function on the RB unit.
Outdoor Unit Inputs
| Terminal | Function | Typical State |
|---|---|---|
| CN131 | Low noise mode | OFF = Normal, ON = Low noise |
| CN132 | Cooling / Heating priority | OFF = Cooling priority, ON = Heating priority |
| CN133 | Capacity save / peak cut | OFF = Normal, ON = Peak cut |
| CN134 | Batch stop / Emergency stop | OFF = Normal, ON = Stop function |
Low Noise Mode - CN131
Low noise mode reduces outdoor-unit sound level. The source guide shows approximately 5-6 dB reduction depending on model and operating condition.
- Mode 40: 00 Quiet priority / 01 Capacity priority
- Mode 42: 00 Level 1 / 01 Level 2
Priority Mode - CN132
Allows external selection between Cooling Priority and Heating Priority.
- Function 21 = 00: Priority to first command
- Function 21 = 01: Priority to external input of outdoor unit
- Function 21 = 02: Priority to administrative indoor unit
Capacity Save / Peak Cut - CN133
Peak cut limits the maximum operating capacity of the outdoor unit to reduce peak electrical demand.
| Setting | Capacity Level |
|---|---|
| 00 | Level 1 - Stop |
| 01 | Level 2 - 40% |
| 02 | Level 3 - 60% |
| 03 | Level 4 - 80% |
| 04 | Level 5 - 100% |
Batch Stop / Emergency Stop - CN134
- Function 20 = 00: Batch stop
- Function 20 = 01: Emergency stop
Outdoor Unit Outputs
| Terminal | Function | Output |
|---|---|---|
| CN136 | Normal / Error | 0 V = Normal, DC12-24 V = Error |
| CN137 | Operation / Stop | 0 V = Stop, DC12-24 V = Operation |
| CN115 | Base heater | 0 V = Heater OFF, AC220-240 V = Heater ON |
CN136/CN137 require an external DC12-24 V supply and are limited to 30 mA or less in the source guide.
Base Heater - CN115
The base heater output is used to prevent the outdoor-unit drain area from freezing.
- Output turns ON when outdoor temperature falls below approximately 2°C.
- Output turns OFF when outdoor temperature rises to approximately 4°C.
- Output voltage: AC220-240 V.
- Rated current: 1 A or less.
- Connector service part: 9708642000.
- Where the connected heater requires more than 1 A, use an external relay.
Central Remote Controller
| Terminal | Function |
|---|---|
| CN6 / CN7 | Dry-contact external input - Emergency stop / All On-Off |
| CN11 / CN12 | Voltage external input - Emergency stop / All On-Off |
| CN9 | Operation/Stop and Error/Normal output |
Touch Panel Controller
| Terminal | Function |
|---|---|
| CN411 | Dry-contact external input |
| CN412 | Voltage external input |
| CN410 | Operation state / Error state output |
Difference Between Start/Stop, Forced Stop and Emergency Stop
| Function | Effect | Remote Controller |
|---|---|---|
| Start/Stop | Starts or stops the indoor unit | Can still operate |
| Forced Stop | Forcibly stops the affected indoor unit | Operation prohibited while active |
| Emergency Stop | Stops all indoor units in the same refrigerant system | Operation prohibited until cancelled |
Typical Application Examples
- Forced thermostat off using a DDC and damper control.
- Occupancy sensor interlock using Operation/Stop.
- Emergency Stop of a complete refrigerant system.
- Hotel card-key control using Forced Stop.
- Indoor-unit Operation/Error status monitoring.
- Ventilator interlock with indoor fan operation.
- Cooling/Heating priority selection on RB groups.
- Outdoor-unit low noise operation at night.
- Peak-cut / demand limitation.
- Outdoor base heater control.
- Emergency Stop from a Central Remote Controller or building control system.
Cable and Wiring Limits
- Typical external input/output cable: AWG22 twisted pair, 0.33 mm².
- Outdoor unit external inputs: typically 150 m maximum.
- Indoor unit external inputs/outputs: typically 150 m maximum.
- Compact duct and compact wall-mounted external terminals: source guide shows 25 m maximum.
- Touch Panel Controller and Central Remote Controller external terminals: source guide shows 25 m maximum.
- CN115 base-heater wiring uses heavier cable; source material references AWG18 / 0.82 mm².