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Central Heating

Worcester r25 & 30 he combi boiler dropping to zero when heating turns off

The boiler pressure is dropping to zero when the heating turns off, this usually takes around 15-20 minutes.
When the heating is on the pressure is between 2-3 on the gauge.
The pressure does not move from zero when we run the hot water (when the heating is off).
There was a very small drop of water (one drop of water after 3 hours of the heating been on - had a green colour to it) leaking from the copper pipe that runs outside from the boiler.
There are no visible leaks around the boiler or radiators. We have not taken any floorboards up as yet.

1 Answer from a MyBuilder Heating Engineer

Best Answer

Your expansion vessel is faulty. It may have no air in it or the diaphragm has gone.You probably need to replace the blow off valve to now mind. Call a Gas Safe engineer to take the case off and check. It takes about 10 mins to test but can be a bit of a bugger replacing some of the vessels. An external one is often fitted as its cheaper, but only any good if the boiler is not on show.



Answered 21st Jan 2015

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