6.9 Frost protection
Boiler frost protection
Flow temperature < 8°C
▪
Burner is operated at minimum load.
▪
Outputs MFA and VA are active, if they have been parametered as heating circuit
pump or feeder pump.
Flow temperature > 20 °C:
▪
Burner switches off,
▪
Pump run-on is activated (parameter
41
).
System frost protection (with external sensor)
External temperature < system frost protection temperature (parameter
23
) minus
5 Kelvin:
▪
Outputs MFA and VA are active, if they have been parametered as heating circuit
pump or feeder pump,
▪
load pumps on eBus are active,
▪
thermal protection via boiler frost protection.
External temperature > system frost protection temperature (parameter
23
)
Pump continuous run is deactivated.
DHW frost protection (version W)
DHW temperature < 8°C
▪
Burner is operated at minimum load.
▪
Outputs MFA and VA are active, if they are parametered as feeder pump, DHW
load pump or circulation pump.
DHW temperature > 8 °C plus half the DHW switch differential (parameter
51
):
▪
Burner switches off,
▪
Pump run-on is activated (parameter
42
).
During DHW frost protection, the tap symbol flashes in the display.
Installation and operating instruction
Gas condensing boiler WTC-GB 90-A
6 Operation
83266502 • 1/2010-08 • La
47-95
