Fan coil applications in the DXR2 include one to three-stage automatic fan control. The fan stages are switched on or off with potential free relay contacts.
Sequences
|
| |||
Y | Output signal |
| TR | Room temperature |
SpH | Effective heating setpoint |
| SpC | Effective cooling setpoint |
YH | Heating valve |
| YC | Cooling valve |
Q | Fan signal |
| Q1 | First fan stage |
Figure: 1-stage fan sequence
|
| |||
Y | Output signal |
| TR | Room temperature |
SpH | Effective heating setpoint |
| SpC | Effective cooling setpoint |
YH | Heating valve |
| YC | Cooling valve |
Q | Fan signal |
| Q1 | First fan stage |
Q2 | Second fan stage |
| Q3 | Third fan stage |
Figure: 3-stage fan sequence
Outputs
Staged fans are switched by triac or relays on the DXR2.
Minimum runtime
Each fan stage is always switched on for a specific minimum time before changing over to the next higher stage. So that the room automation stations control at this stage. The time is fixed at 15 seconds on all DXR2 applications.
Switch-off delay
The fan switch-off is delayed for a specific period on applications that have electric heating coils/reheaters. This cools down the electric heating coils/reheater with circulating air. The switch-on/switch-off time can be configured.
Description | Name | Default value |
|---|---|---|
Switch-off delay for hold signal for air volume flow heating | DlyOffAflHldH | 30 [s] |
Return air sensor
The fan must be switched on if room temperature measurement is made using a return air sensor in the fan coil system, to correctly acquire the actual room temperature. A minimum air volume is enabled in the dead zone by default for the operating mode Comfort on the DXR2. The parameter cannot be changed when using a return air sensor to measure room temperature.
In this case, note that a conventional room temperature sensor must be configured at the DXR2 input. The return air temperature sensor is then connected instead of the room temperature sensor. The room is now temperature controlled per the measured value from the return air sensor.
DXR2 does not support interval-type fan activities to periodically measure room temperature with the return air sensor.
Also note that DXR2 temperature control in the room can only have one measured return (temperature sensor) which is always configured and connected at the input of the room temperature sensor. The available configuration for a return air sensor is used for visualization on DXR2.
Locked by electric heating coils
Locking is a binary signal to protect fan coil equipment. The application locks electric heating coils even if no air flow is available through the fan. Or enabled if air flow is available through the fan.
Start of fan by heating demand
The fan is started for active heating or cooling demand in the room. The signal is sent to the fan from the heating or cooling register.
Description | Name |
|---|---|
Display of heat/cooling request in the room. It starts the fan to meet the heat request. | AirFlHReq/AirFlCReq |