Frost protection/ frost recovery after frost alarm

When the frost protection via the plant mode signal becomes active, the following action occurs:


Frost protection actions are normally performed in the respective output modules.


When the frost failure has been reset, there will be a start-up procedure at low outside air temperatures. To prevent frost alarm again, the supply air temperature setpoint will be temporarily raised immediately after the FanEnable input becomes true (=1) and afterwards slowly ramped down to its normal setpoint. The ramp-down time can be adjusted by parameter START-03.


Description

Default value

START-01: limit OAT/ frost  protection

6°C

START-02: supply air temperature setpoint raise

10 K

START-03: SAT control raised setpoint decrease time

600 sec