Frost protection function
while unit is in operation
The application uses a two-stage antifreeze with 2 special setpoints, which is
intended to prevent freezing while the ventilation is still normally active, and to
protect the device when prevention has not been sufficient. The temperature
sensor TFrPrtHcl is required for this function and must be located at the coldest
point of the water heating coil.
Stage 1 - Frost risk:
If the temperature of TFrPrtHcl falls below the set frost risk setpoint (e.g. 10°C), the
pump is switched on (if not already switched on) and the valve is controlled
according to the temperature of TFrPrtHcl at risk of frost. When the temperature of
TFrPrtHcl reaches the frost hazard set point, the frost protection function is
automatically terminated.
Stage 2 – Frost protection:
If the temperature at TFrPrtHcl falls below the set frost protection setpoint (e.g.
4°C), the pump is switched on (if not already switched on), the valve is opened
100%, the ventilation is switched off, any fresh air dampers are closed and the A
alarm is activated.
A restart can only take place, after the alarm is acknowledged, the temperature is
higher than SpFrPltOnHcl and the plant is reset.
Frost protection while the
unit is not in operation
During the times when the ventilation unit is switched off for any reason (must still
be connected to power supply), the temperature of TFrPrtHcl has an additional
setpoint (e.g. +25°C) to secure the start-up situation. If the heating coil is constantly
kept warm, it will not drop to the frost protection limit during start-up, even in cold
outdoor conditions.
The pump runs constantly during the non-productive times of the ventilation unit. If
the temperature of TFrPrtHcl falls below the set temperature limit during the device
failure times, the valve is PI-controlled to reach the idle setpoint. The alarm is not
activated until the temperature at the TFrPrtHcl drops below the frost protection set
point.
If one of the frost protection parts is active, the standard temperature control has
no priority (constant or cascaded).
The function is activated automatically when HclHw11y is commissioned.
Available parameters
Current value
BACnet object
R/RW
Note
Return temperature setpoint for frost
SpFrPrt
AVAL,216
R
°C
Return temperature value
TFrPrtHcl
AI,58 (B3)
AI,64 (B4)
AI,80 (X8)
AVAL,317 (POS9)
AVAL,468 (QBM)
R
°C
Basic settings:
BACnet object
R/RW
Note
Frost protection limit
FrPrtLm
AVAL,217
RW
°C, plant shutdown,
valve open, pump on
Setp.frost prot.if plant on, heat.coil
SpFrPltOnHcl
AVAL,218
RW
°C
Setp.frost prot.if plant off, heat.coil
SpFrPltOffHcl
AVAL,219
RW
°C
Max.delay frost protection for startup
When passed, startup is stopped and frost
alarm is raised
DlyMaxFrpSttUp
PINTVAL,109
RW
sec.
Application functionalities
Heating
5
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A6V10733786_en_c
