Assortment / System Description

Fan coil application
Control of modulating fan
17
A6V10866237_en--_b_08 97 | 275
17.4 Control of modulating fan
The DXR2 fan coil applications can automatically control modulating fans (DC
0…10 V). In addition, the fan can be enabled or locked with a potential free
relay contact.
Y Output signal TR Room temperature
SpH Effective heating setpoint SpC Effective cooling setpoint
YH Heating valve YC Cooling valve
Q Fan signal
Figure: Modulating fan sequence
Analog outputs on the DXR2 control modulating fans.
The switch off of a fan 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 holding signal for air volume flow
heating
DlyOffAflHldH 30 [s]
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 are 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.
Locking is a binary signal to protect fan coil equipment. The application locks
the electric heating coils if no air flow is available or enables if available.
Sequences
Outputs
Switch-off delay
Return air sensor
Locking