General Assist Technical Reference
VRF External Input & Output
Outdoor units, indoor units, RB units and system controllers
Technical reference for V-series and J-series VRF applications covered by the External Input & Output manual
External input and output terminals allow a VRF system to interface with BMS, relays, time clocks, fire systems, ventilation equipment, energy management systems and status indicators. The exact terminals available depend on the unit series and PCB fitted.
Important: Do not apply mains voltage to low-voltage input or output terminals. Confirm the model-specific service documentation before wiring. External input wiring must be electrically isolated from power wiring and installed using the specified cable type and length.
1. Outdoor Unit External Input
The outdoor unit can accept several control inputs. Availability varies by VRF series. The manual identifies the following functions and connectors.
| Connector | Function | Signal / Behaviour |
|---|---|---|
| CN131 | Low noise mode | Dry contact. ON = low noise mode operation. |
| CN132 | Cooling / heating priority | Dry contact. Used to select cooling or heating priority where supported. |
| CN133 | Outdoor unit operation peak control | Dry contact. Used for demand / energy-saving control. Requires the corresponding outdoor unit function setting. |
| CN134 | Batch stop / Emergency stop | Dry contact. Function is selected by outdoor unit function setting. |
| CN135 | Electricity meter pulse | Pulse input. Pulse width and interval must each be 50 ms or greater. |
Wiring specification: The outdoor unit external inputs are low-voltage / ground-level inputs. The manual specifies twisted-pair cable, typically 22 AWG, with a maximum cable length of 150 m. Do not apply voltage to the input terminal unless the model-specific circuit explicitly requires it.
Batch stop versus Emergency stop
| Mode | What happens |
|---|---|
| Batch stop | All indoor units in the same refrigerant system stop. After the batch-stop input is released, operation by remote controller is possible. |
| Emergency stop | All indoor units in the same refrigerant system stop. While Emergency stop is active, indoor-unit stop and Start/Stop operation from a remote controller are restricted. |
2. Outdoor Unit External Output
| Connector | Output | Electrical detail |
|---|---|---|
| CN136 | Error status | External DC supply required. Output indicates Normal / Error status. |
| CN137 | Operation status | External DC supply required. Output indicates Operation / Stop status. |
| CN115 | Base heater | Output for base-heater control where supported. Manual identifies an allowable current of 1 A or less. |
Output supply: For CN136 and CN137, provide an external DC 12-24 V power supply. The manual specifies a maximum allowable current of 30 mA or less and requires a protective resistor if necessary so the current remains within this limit.
3. Indoor Unit External Input
Indoor units can be controlled by either apply-voltage inputs or dry-contact inputs. The terminal type must be selected to suit the external device.
| Terminal | Type | Typical functions |
|---|---|---|
| CNA01 | Apply voltage | Operation / Stop, Emergency stop or Forced stop. |
| CNA02 | Dry contact | Operation / Stop, Emergency stop or Forced stop. |
| CNA03 | Apply voltage | Forced thermostat OFF. |
| CNA04 | Dry contact | Forced thermostat OFF. |
Apply-voltage input
For CNA01 / CNA03, provide an external DC 12-24 V supply. The manual requires a current of approximately DC 1 mA or less at the input device and specifies that polarity must be observed.
Dry-contact input
For CNA02 / CNA04, use a low-current contact suitable for approximately DC 12 V, DC 1 mA or less. Dry-contact wiring should be separated from power wiring.
Multiple indoor units: When one external device is required to control multiple indoor units, do not directly parallel the indoor-unit dry-contact inputs. The manual shows each indoor unit being isolated by its own relay contact.
Input signal type - Edge or Pulse
The input signal can be configured as Edge or Pulse using indoor-unit DIP switch SET 2-2. The manual identifies OFF as Edge and ON as Pulse. Forced thermostat OFF remains Edge only.
| Control function | Function setting | Notes |
|---|---|---|
| Operation / Stop | 46-00 | Allows external start / stop control. |
| Emergency stop | 46-01 | Stops indoor units and restricts normal operation while active. |
| Forced stop | 46-02 | Forces indoor unit OFF while input is active. |
| Forced thermostat OFF - fan follows remote-controller setting | 49-00 | Cooling-only application example shown in manual. |
| Forced thermostat OFF - fan stops | 49-01 | Cooling-only application example shown in manual. |
4. Indoor Unit External Output
The indoor-unit output connector is CNB01. The manual identifies four outputs:
| CNB01 pins | Output | Output state |
|---|---|---|
| 1-2 | Operation status | DC 12 V when indoor unit is operating; 0 V when stopped. |
| 1-3 | Error status | DC 12 V when an indoor-unit error is generated; 0 V when normal. |
| 1-4 | Indoor unit fan status | DC 12 V when indoor-unit fan is operating; 0 V when stopped. |
| 1-5 | Auxiliary heater output | DC 12 V output for auxiliary-heater control where supported. |
CNB01 electrical limit: Output voltage is DC 12 V with an allowable current of approximately 50 mA or less. Where the connected load requires more current, use the output to drive a suitable relay / interface rather than powering the load directly.
5. RB Unit External Input
RB units can accept an external cooling / heating priority command.
| Connector | Type | Command |
|---|---|---|
| CNA01 | Dry contact | OFF = Cooling priority; ON = Heating priority. |
| CNA02 | Apply voltage | OFF = Cooling priority; ON = Heating priority. |
The RB-unit input method is selected by changing the RB PCB DIP switch setting. The manual specifies twisted-pair cable, typically 22 AWG, with a maximum cable length of 150 m.
6. Touch Panel Controller
The Touch Panel Controller can receive an external command to perform Emergency stop or All On / All Off, and can provide Operation and Error status outputs.
| Terminal / Connector | Function | Details |
|---|---|---|
| TM201 - CN411 | Dry-contact input | External Emergency stop or All On / All Off. |
| TM201 - CN412 | Apply-voltage input | DC 12-24 V external input. |
| CN410 pins 1-2 | Operation status output | DC 12 V output when at least one indoor unit is operating. |
| CN410 pins 3-4 | Error status output | DC 12 V output when an indoor unit, outdoor unit or Touch Panel Controller error is present. |
Input operation can be configured for Edge or Pulse. The manual notes that the external input function is disabled from the factory and must be enabled and configured by the installer.
7. Central Remote Controller
| Connector | Function | Notes |
|---|---|---|
| CN6 / CN7 | Dry-contact external input | Emergency stop or All On / All Off. Supports Edge or Pulse operation. |
| CN11 / CN12 | Apply-voltage external input | External DC 24 V supply. Supports Edge or Pulse operation. |
| CN9 pins 3-4 | Operation status output | DC 12 V output when at least one indoor unit is operating. |
| CN9 pins 1-2 | Error status output | DC 12 V output when an indoor unit, outdoor unit or Central Remote Controller error is present. |
Controller cable length: The Touch Panel Controller and Central Remote Controller sections specify twisted-pair cable, typically 22 AWG, with a maximum external input/output cable length of 25 m.
8. Quick Reference - Common Connections
| Requirement | Where to connect | Key point |
|---|---|---|
| Start / stop one indoor unit | CNA01 or CNA02 | Set Function 46 to 00. |
| Emergency stop indoor unit / group | CNA01 or CNA02 | Set Function 46 to 01. |
| Forced stop indoor unit / group | CNA01 or CNA02 | Set Function 46 to 02. |
| Thermostat OFF from BMS / ventilation interlock | CNA03 or CNA04 | Forced thermostat OFF is Edge input only. Function 49 determines fan behaviour. |
| Indoor unit running indication | CNB01 pins 1-2 | DC 12 V output while operating. |
| Indoor unit fault indication | CNB01 pins 1-3 | DC 12 V output during indoor-unit error. |
| Outdoor unit system fault indication | CN136 | External DC supply required. |
| Outdoor unit operation indication | CN137 | External DC supply required. |
| System-wide emergency stop from central controller | Touch Panel TM201 or Central Remote CN6/CN7 or CN11/CN12 | Configure controller external-input function before use. |
9. Optional External Connect Kits
The manual lists dedicated external-connect harnesses for different input/output functions. The required harness depends on the terminal and unit type.
| Application | Manual-listed kit examples |
|---|---|
| Outdoor unit low-noise / priority / peak-control input | UTY-XWZXZ6 |
| Outdoor unit Emergency stop / electricity-meter pulse | UTY-XWZXZF |
| Outdoor unit error / operation display output | UTY-XWZXZ6 |
| Outdoor unit base-heater output | UTY-XWZXZ9 |
| Indoor unit external output | UTY-XWZXZC |
| Indoor unit control input - apply voltage | UTY-XWZXZB |
| Indoor unit control input - dry contact | UTY-XWZXZD |
| Indoor unit forced thermostat OFF - apply voltage | UTY-XWZXZ7 |
| Indoor unit forced thermostat OFF - dry contact | UTY-XWZXZE |
Before ordering a harness: Confirm the exact indoor, outdoor, RB or controller model and the connector present on its PCB. Not every connector or function is available on every VRF series.
This article is a technician reference derived from the AIRSTAGE VRF External Input & Output documentation. Always confirm model-specific service documentation, PCB terminal identification and applicable electrical requirements before installation.