Frost protection thermostat
To protect the heating coil against freezing a frost alarm procedure starts as soon as the frost protection thermostat detects a frost alarm. If the frost alarm condition is returned to the normal position a frost recovery procedure starts.
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 and no discharge air temperature senors are 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 |