General Assist Technical Reference
VRF External Input Controls
Functions, terminals, signal requirements and BMS integration
Reference for VRF outdoor units, central controllers, RB units and external control interfaces
External inputs allow compatible VRF equipment to receive commands from a Building Management System (BMS), external switch, energy-management device or other third-party control system. The available functions and electrical requirements vary depending on the equipment being connected.
Important: Do not assume all external input terminals use the same signal type. Confirm the applicable service or installation manual before wiring. Some inputs use dry contacts, while others use an applied DC voltage or pulse signal.
1. Available external input functions
Depending on the unit or controller, external inputs may be used for the following functions:
| Function | Purpose |
|---|---|
| Emergency Stop | Stops system operation through an external control input. |
| Low Noise Mode | Reduces outdoor unit operating noise using selectable low-noise levels. |
| Cooling / Heating Priority | Allows an external system to influence mode priority where the function is supported. |
| Outdoor Unit Operation Peak Control | Limits outdoor unit operation to a selected demand level for energy management. |
| Batch Stop | Provides a central external stop command for connected equipment. |
| Power Usage Information Input | Receives pulse information from a compatible electricity meter for energy monitoring. |
| All ON / All OFF | Allows centralised start/stop control from an external switch or BMS. |
2. Signal and electrical characteristics
The source reference identifies the following typical characteristics for edge/pulse external inputs:
| Signal Type | Terminal Voltage | External Supply | Allowable Current | Cable | Maximum Length |
|---|---|---|---|---|---|
| Edge / Pulse (+3) | DC 12-24 V | DC 12 V / DC 24 V | 5-10 mA or less | AWG22 twisted | 25-150 m |
Apply Voltage inputs: The source identifies PIN 1 as positive (+). For pulse signal operation, the source specifies DIP SW2-2 = ON.
3. Common connection terminals
| Terminal | Typical Function | Typical Application |
|---|---|---|
| CN131-CN135 (PIN 1-2) | Operation control / Batch stop | VRF outdoor units |
| CN6-CN12 | Remote / touch panel inputs | Central Remote Controller UTY-DGGY / Touch Panel Controller UTY-DTGY |
| CN401 / CN402 | Power meter / RB unit input | Energy monitoring interface |
| CNA01 / CNA02 | External control inputs | BMS or third-party interfaces |
Terminal numbering is product-specific. Always verify the terminal designation and signal type against the exact model's technical documentation before connecting an external device.
4. Applicable equipment referenced
| Outdoor Units | VR-II, V-II, J-II and J series |
| Controllers | UTY-DGGY Central Remote Controller; UTY-DTGY Touch Panel Controller |
| RB Units | UTP-RX01A(H/B), UTP-RX04A(H/B) |
5. Function settings referenced
Outdoor unit operation peak control
| Function Setting | Operation Level |
|---|---|
| 30-00 | Stop |
| 30-01 | 40% |
| 30-02 | 60% |
| 30-03 | 80-100% operation |
Low noise operation
The source identifies settings 42-00 to 42-02 for selectable low-noise Levels 0-2.
The meaning and availability of function numbers can differ between product generations. Confirm the applicable model documentation before changing any function setting.
6. External input wiring reference
The following existing Freshdesk attachment is retained as a visual reference from the source article.
7. Technician checklist
| 1 | Confirm the exact model and the external input function required. |
| 2 | Confirm whether the input requires dry contact, applied voltage, edge or pulse operation. |
| 3 | Verify terminal numbers, polarity and allowable voltage/current before connection. |
| 4 | Apply any required DIP-switch or function-setting changes. |
| 5 | Test the external command and confirm the VRF system responds as intended. |
Service note: This article is a general reference covering multiple VRF components. Model-specific service and installation documentation takes precedence where terminal assignments, signal types or function settings differ.