General Assist Technical Reference
UTD-ECS5A External Control Set
External start/stop, operation status, fan-linked and auxiliary-heater interfaces
Installation manual reference: Part No. 9374983018-02
The UTD-ECS5A is an optional external control wiring set for compatible ducted and concealed indoor units. It provides field connections for remote start/stop, operation indication, fan-linked control and auxiliary electric-heater control.
Confirm the indoor PCB type before connection: The connector numbers differ between Type A and Type B indoor control boards. Connecting a harness to the wrong connector may damage the equipment or cause incorrect operation.
1. Available functions
| Function | Harness colour | Purpose |
|---|---|---|
| Preparation lead | Black | Required on Type A boards when using the external input/output functions |
| Start/stop input | White | Remote ON/OFF control from a dry contact |
| Operation-status output | White | Indicates whether the indoor unit is operating or stopped |
| Fan-linked output | Green | Controls a field-supplied secondary fan in synchronisation with the indoor fan |
| Auxiliary-heater output | Orange | Controls a field-supplied booster heater on compatible ducted indoor units |
The kit does not provide direct BMS communication, temperature adjustment, mode selection or detailed fault-code output. It provides discrete input/output functions only.
2. Indoor PCB types and connector locations
| Function | Type A PCB | Type B PCB |
|---|---|---|
| Preparation lead | CN106 to CN5 | Not used |
| Start/stop input | CN114 | CN102 |
| Operation-status output | CN115 | CN103 |
| Fan-linked output | CN14 | CN6 |
| Auxiliary-heater output | CN15 | CN10 |
Page 1 of the manual shows the visual PCB layouts for Type A and Type B. Confirm the physical board layout rather than relying only on the indoor-unit family name.
3. Start/stop input
| Specification | Requirement |
|---|---|
| Signal type | No-voltage contact |
| Contact capacity | DC 12 V, 10 mA |
| Type A connector | CN114 |
| Type B connector | CN102 |
Type A input selection
On Type A boards, DIP switch SW2-2 selects the input behaviour:
OFF = Edge signal
ON = Pulse signal
OFF = Edge signal
ON = Pulse signal
| Input mode | How it operates |
|---|---|
| Edge | A change in contact state commands the indoor unit ON or OFF. The external state and remote-controller operation interact as shown in the manual timing chart. |
| Pulse | A pulse of at least approximately 200 ms commands ON or OFF operation. The manual shows separate pulse transitions for start and stop. |
Type B input operation
Type B uses a continuous ON/OFF dry-contact signal at CN102. The input contact provides remote start/stop control without the Type A edge/pulse selection.
Do not apply voltage to the start/stop input. Use an isolated voltage-free contact. A powered BMS output must operate an interposing relay rather than connect directly to the indoor board.
Typical input applications
BMS relay Card-key relay Occupancy control External timer Remote wall switch
4. Operation-status and fan-linked outputs
Operation-status output
| Specification | Requirement |
|---|---|
| Output type | No-voltage contact |
| Contact capacity | Maximum DC 24 V, 10 mA to 1 A or less |
| Type A connector | CN115 |
| Type B connector | CN103 |
| Indoor unit operating | Contact short / closed |
| Indoor unit stopped | Contact open |
Fan-linked output
| Specification | Requirement |
|---|---|
| Output type | DC 12 V output synchronised with indoor-fan operation |
| Type A connector | CN14 |
| Type B connector | CN6 |
| Indoor fan operating | Approximately 12 V |
| Indoor fan stopped | 0 V |
Use a field-supplied relay, power supply and fuse suitable for the connected secondary fan or device. The indoor PCB output must not directly carry the external fan motor load.
5. Auxiliary-heater output
Ducted indoor units only: The auxiliary-heater output is intended for compatible ducted systems and must be engineered with appropriate heater safety controls, airflow proving and over-temperature protection.
| Item | Reference |
|---|---|
| Type A connector | CN15 |
| Type B connector | CN10 |
| Output when enabled | Approximately 12 V |
| Heater ON condition | Room temperature approximately 3°C to 10°C below setpoint |
| Heater OFF condition | Room temperature approximately 1°C below setpoint |
| Fan overrun option | Cut jumper JM3 to continue indoor-fan operation for approximately 1 minute after heating thermostat-off |
The manual requires the external heater to be installed between the indoor unit and the supply ductwork. The one-minute fan-delay control must be used to dissipate residual heater heat.
The auxiliary output is a control signal only. Use a correctly rated field contactor or relay, independent heater supply, fusing, thermal cut-outs and airflow interlocks. Do not connect an electric heater directly to the indoor PCB.
6. Installation procedure
| 1 | Isolate all electrical supplies. Confirm the indoor and outdoor units are safe before opening electrical covers. |
| 2 | Identify the indoor PCB type. Match the physical PCB layout to Type A or Type B. |
| 3 | Install the preparation lead where required. Type A uses the black CN106-to-CN5 lead; Type B does not. |
| 4 | Connect only the required harnesses. Use the correct connector numbers for the identified PCB type. |
| 5 | Connect the field device. Extend with suitable field wiring where required and fully insulate every joint. |
| 6 | Configure Type A input mode. Set SW2-2 to Edge or Pulse as required. |
| 7 | Commission each function. Test start/stop, operation output, fan-linked output and heater output separately. |
7. Functional summary
| Function | Supported? |
|---|---|
| Remote ON/OFF input | Yes |
| Edge input on Type A | Yes |
| Pulse input on Type A | Yes |
| Continuous input on Type B | Yes |
| Operation-status output | Yes |
| Fan-linked output | Yes |
| Auxiliary-heater output | Yes, compatible ducted units only |
| Detailed fault output | No |
| Mode or temperature control | No |
8. Compatibility information required
- Complete indoor-unit model and serial number
- Photo of the indoor control PCB
- Confirmation whether the PCB is Type A or Type B
- Required function: start/stop, status, fan-linked output or auxiliary heater
- Field-device contact or relay specifications
- Whether other optional controls or interface boards are already fitted
- For auxiliary heat: heater capacity, safety controls, airflow proving and electrical design
Terminology: UTD-ECS5A may be described as an External Control Set, external connector kit or I/O harness set. It is not the same product as UTY-XWZX or UTY-XWZXZ5.
Based on Fujitsu General UTD-ECS5A External Control Set Installation Manual, Part No. 9374983018-02. This simplified field reference does not replace the indoor-unit installation manual, electrical design requirements or current model-compatibility information.