Assortment / System Description

Heat pump application
Control of staged fan
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20.3 Control of staged fan
Heat pump applications in the DXR2 include one to two-stage automatic fan
control. The fan stages are switched on or off with potential free relay contacts.
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 Q1 First fan stage
Figure: 1-stage fan sequence
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 Q1 First fan stage
Q2 Second fan stage
Figure: 2-stage fan sequence
Staged fans are switched by triac on the DXR2.
Each fan stage is always switched on for a specific minimum time before
changing over to the next higher stage. So that the room controller acquire
control at this stage. The time is fixed at 15 seconds on all DXR2 applications.
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]
Sequences
Outputs
Minimum runtime
Switch-off delay