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Anti-freezing Auto drain valve


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There's a valve on the Truma Combi Boiler which opens at low temperature to empty the boiler to prevent frost damage. The info doesn't say what cold thing is being monitored - is it the water in the

boiler or the air temperature. If the system is kept running and warm, does this stop it draining?

I have no experience in operating this boiler in cold weather and would appreciate some advice.


Neil B

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thebishbus - 2015-09-29 8:12 AM


The dump valve will only open automatically if the temperature round it drops to 2 degrees . If the system is on, it will not get that low. and not dump water .

Brian B.


ps If it has opened because of low temperature ,it will not re-set below about 8 degrees.

But you can then run the heater in heating only mode (i.e. without water heating), even with no water in the jacket, which will soon boost the temperature in the enclosure high enough to re-set the valve and re-fill with water.

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