5.14 Preheating Functions
Optional preheating functions optimize operation of the HRV especially in winter
conditions. An earth to air heat exchanger or a brine coil allow the use of
environmental energy from the ground, warming up or cooling down the outside air
before reaching the heat exchanger. Alternatively, an electric heating coil can be
used as additional heat source. All preheating functions reduce the danger of icing
on the heat exchanger by increasing the incoming air temperature in winter times.
This is especially recommended, when using a heat exchanger without humidity
transfer (plate heat exchanger).
5.14.1 Earth to Air Heat Exchanger (EaHExg21y)
Earth to air heat exchanger include a damper to force or to bypass the air flow
through the earth duct. The control depends on an estimated earth temperature
which can be configured for winter (heating) and summer (cooling) conditions. A
hysteresis of 1 °C (fix) and a minimum time of 1 min (fix) for damper open / bypass
prevent the damper from moving too frequently.
If there is no demand for heating or cooling, the bypass damper remains in its last
state in order to use free energy as much as possible.
Temperature conditions
Supply air conditions
Damper position
TOa < TEarth Winter
Heating requested
closed
TOa > TEarth Winter
Heating requested
bypass
TOa < TEarth Summer
Cooling requested
bypass
TOa > TEarth Summer
Cooling requested
closed
Available parameters
Actual values
BACnet object
R/RW
Note
Bypass damper position
EaHxDmpbCmd
BO,54 (Q1)
BO,69 (Q2)
BO,84 (Q3)
BVAL,245 (POS9)
RW
Basic settings
BACnet object
R/RW
Note
Estimated earth temperature in winter
(TOa < 10°C)
TEaWinEst
AVAL,353
RW
°C
Estimated earth temperature in
summer (TOa > 20°C)
TEaSumEst
AVAL,354
RW
°C
Testing and debugging
BACnet object
R/RW
Note
Preheater device mode
PreHclDevMod
MVAL,407
1: Off
2: Control mode
3: Fully open
Application functionalities
Preheating Functions
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