Frost protection

To protect the heating coil against freezing a frost alarm procedure starts as soon as a frost alarm occurs. If the frost alarm condition is returned to the normal position a frost recovery procedure starts.

A frost alarm will be generated at the output "FrostAlarm" in three different conditions:


In any of these conditions the following frost alarm and recovery procedures will occur.


To assure a correct frost procedure (setting the plant mode to frost protection) , connect the output "FrostAlarm" of this macro to the "FrostThermostat" of the plant strategy macro.

The reset of the frost alarm (plant mode = 20) is managed by the plant strategy macro.


Description

Default value

RWT-06: frost protection limit return water sensor

6 °C

SAT-01: supply air frost protection limit

10 °C

SAT-02: supply air frost protection limit delay

600 sec


Frost alarm procedure:
If a frost alarm occurs, the heating coil will:


Frost recovery procedure:
When the frost alarm condition returns to normal, the following happens:


See the ramp function to normal control in the next figure.


 

If no return water senor is connected, the valve position, defined by parameter FEZ-03, returns to its normal control position via a ramp-down function defined by parameter FEZ-04 whenever the:

The heating coil starts whenever the PlantMode changes from any un-occupied mode to any occupied mode.

Description

Default value

FEZ-01: frost protection RWT/ DAT setpoint raise

15 K

FEZ-02: raised setpoint decrease during frost recovery

1 K/min

FEZ-03: valve position during frost protection

100 %

FEZ-04: valve raised position decrease during frost recovery

10 %/min