1. Series Configuration (Left Side of Diagram)
Description
The motion sensor and time clock are connected in series.
Both must be activated (closed circuit) for the air conditioning system to turn ON.
If either one deactivates, the circuit opens and the unit turns OFF.
Application
This setup is used when you want both conditions to be met before operation is allowed — for example:
Office applications: System operates only during scheduled hours and when motion is detected.
Energy-saving logic: Prevents after-hours operation unless occupancy is confirmed.
Logic Summary
| Condition | Unit State |
|---|---|
| Motion detected and Time Clock ON | ON |
| Motion not detected or Time Clock OFF | OFF |
Advantages
Saves energy by ensuring operation only when needed.
Ideal for strict energy-controlled environments.
2. Parallel Configuration (Right Side of Diagram)
Description
The motion sensor and time clock are connected in parallel.
If either device closes its contact, the circuit activates and the unit turns ON.
The system will remain ON as long as one of the two stays active.
Application
Used when either occupancy or schedule should enable the system:
Retail environments: Operate on schedule but also activate early if motion is detected.
Showrooms or corridors: Allow manual or automatic operation without full dependence on time scheduling.
Logic Summary
| Condition | Unit State |
|---|---|
| Motion detected or Time Clock ON | ON |
| Motion not detected and Time Clock OFF | OFF |
Advantages
More flexible operation.
Useful for comfort-first environments with extended or unpredictable usage.
3. Integration into VRF / Split Systems
In systems like Fujitsu AIRSTAGE VR-II, this type of external control is connected to the External Input Terminal on the indoor PCB or control board.
“External Input” can be configured (via DIP switch or controller setting) to respond to contact closure from devices like:
Motion sensors
Time clocks
Building management system (BMS) relays
Example Setup
Terminal 1: Common (COM)
Terminal 2: External ON/OFF signal (Dry Contact)
Terminal 3: Ground or additional input (varies by model)
When the external contacts close according to the series or parallel wiring method, the indoor unit interprets it as a run command.
4. Best Practice Notes
Always use dry contact (volt-free) inputs to avoid electrical interference.
Series wiring = logic “AND” (both must be active).
Parallel wiring = logic “OR” (either one can activate).
Verify polarity or signal type per manufacturer’s control schematic.
For Fujitsu VRF systems, refer to the indoor PCB CN16/CN17 terminals for motion sensor or time clock inputs.
