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 |