5.14.2 Brine Coil (PreHclBne21y)
The brine coil includes a pump and a brine flow temperature sensor. The control
depends on the brine flow temperature. A hysteresis of 1 °C (fix) and a minimum
run / pause time of 1 min (fix) for the pump prevent it from switching too frequently.
In case the temperature sensor is not configured, a configurable estimated brine
temperature for summer (cooling) and winter (heating) is used instead.
As the brine flow temperature is not measured correctly, when the pump has
stopped, the last value measured while the pump is running is taken instead.
The preheating coil can also be used for dehumidification, if dehumidification is
requested. Dehumidification is only possible, if the brine flow temperature is below
the dewpoint temperature of the room minus a configurable offset, depending on
the coil design.
Temperature conditions
Supply air conditions
Pump
command
TOa < TFlPreHcl
Heating requested
On
TOa > TFlPreHcl
Heating requested
Off
TOa < TFlPreHcl
Cooling requested
Off
TOa > TFlPreHcl
Cooling requested
On
TOa > TFlPreHcl and
Dewpoint - Offset > TFlPreHcl
Dehumidification requested. In case of conflicts,
dehumidification request overrules heating or cooling
On
No dehumidification requested and no heating or cooling
request
Off
Available parameters
Actual values
BACnet object
R/RW
Note
Brine pump command
PreHclPuCmd
BO,53 (Q1)
BO,68 (Q2)
BO,83 (Q3)
BVAL,244 (POS9)
RW
Flow temperature brine
TFlPreHcl
AI.57 (B3)
AI,63 (B4)
AI,79 (X8)
AVAL,316 (POS9)
AVAL,467 (AI1)
RW
Basic settings
BACnet object
R/RW
Note
Estimated brine temperature in winter
(TOa < 10°C)
TeaWinEst
AVAL,350
RW
Estimated brine temperature in summer
(TOa > 20°C)
TeaSumEst
AVAL,351
RW
Offset brine flow temperature to
dewpoint temperature
SpTBneDhu
AL,454
RW
Enable dehumidification via brine
preheater
EnPrhDhuCnf
BVAL,314
RW
0: No dehumidification
1: Dehumidification
released, if required
Testing and debugging
BACnet object
R/RW
Note
Preheater device mode
PreHclDevMod
MVAL,406
1: Off
2: Control mode
3: Fully open
Application functionalities
Preheating Functions
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