There are two control strategies for fan coil applications:
- Serial fan operation: The air volume is only increased if the valve's or reheater's positioning signal is fully open and the room temperature exceeds or breaches an additional offset.
- Parallel fan operation: The fan speed is increased in parallel to the valve's or reheater's positioning signal.
The two strategies are illustrated in the following examples using a modulating fan and one heating and cooling valve. Both strategies can be used in the same manner for staged fans.
Serial
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Y | Output signal |
| TR | Room temperature |
SpH | Effective heating setpoint |
| SpC | Effective cooling setpoint |
YH | Heating valve |
| YC | Cooling valve |
FanSpMaxH | Max. fan speed heating |
| FanSpMaxC | Max. fan speed cooling |
FanSpMinH | Min. fan speed heating |
| FanSpMinC | Min. fan speed cooling |
OfsFanSttH | Offset for fan start heating |
| OfsFanSttC | Offset for fan start cooling |
Q | Fan signal |
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Figure: Example of a serial control strategy using a modulating fan
Parallel
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Y | Output signal |
| TR | Room temperature |
SpH | Effective heating setpoint |
| SpC | Effective cooling setpoint |
YH | Heating valve |
| YC | Cooling valve |
FanEndSpdPrlH | Fan end speed for parallel heating |
| FanEndSpdPrlC | Fan end speed for parallel cooling |
FanSpMinH | Min. fan speed heating |
| FanSpMinC | Min. fan speed cooling |
CoilVlVEndPrlH | Valve end position for parallel heating |
| CoilVlVEndPrlC | Valve end position for parallel cooling |
CoilVlVSttPrlH | Valve position start fan heating |
| CoilVlVSttPrlC | Valve position start fan cooling |
Q | Fan signal |
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Figure: Example of a parallel control strategy using a modulating fan
The control strategy can be configured in the application using the following parameters for the cooling sequence and heating sequence.
Description | Name | Default value |
|---|---|---|
Fan operation for cooling 0:Serial | FanOp | 1:Parallel |
Fan operation for heating 0:Serial | FanOp | 1:Parallel |