Assortment / System Description

Heat pump application
Control of modulating fan
20
A6V10866237_en--_b_08 169 | 275
The fan must be switched on if room temperature measurement is made using
a return air sensor in the heat pump 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 heat pump 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.
The fan is started for active heat or refrigeration demand in the room. The
signal is sent to the fan from the heat or refrigeration register.
Description Name
Display of heat/cooling request in the room. It
starts the fan to meet the heat request.
AirFlHReq/AirFlCReq
20.4 Control of modulating fan
The DXR2 heat pump 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 heat pump TR Room temperature
SpH Effective heating setpoint SpC Effective cooling setpoint
YH Heat pump heating YC Heat pump cooling
Q Fan signal
Figure: Modulating fan sequence
Analog outputs on the DXR2 control modulating fans.
Return air sensor
Locked by electric
heating coils
Start of fan by heating
demand
Sequences
Outputs