Combi Boiler Problem

[rwalters]

Hi guys,

A quick bit of advice or your thoughts if I may. We have a 15 year old Vaillant combi boiler which is working pretty much ok, has a few minor glitches every so often, but in the whole it is ok.

Over the last fortnight I have noticed something strange happening. When we turn on a cold tap anywhere in the house, and then turn the tap off again, as soon as the tap is closed the boiler fires up. No flames, just the pumps start whirring.

It only happens if you have a good fast flow of cold water coming from the cold taps and then close them. If you only allow a trickle of cold water out of the cold tap and then close them, the boiler doesn't fire, only when there is a significant flow old cold water.

From what I can see, inside the front of the boiler there is a black lever which a spring attached to it, connected to some form of diaphram in a unit. The lever presses again a small micro swtich. As the cold tap is closed, this black lever moves as if the hot water was flowing. It only moves for a split second, then it goes back to it's resting position, but the movement is enough to fire the boilers pumps up.

Any ideas, baffles me.

Many thanks for your thoughts.

Richard W

 

[Agile]

Its normally caused by some air in part of the hot water pipework. A part called a deadleg. Usually a bit of HW pipe going into the loft and capped off there.

The standard solution is to add a non return valve on the DHW outlet of the boiler.

A better solution is to find the deadleg and remove it.

Tony Glazier

 

[rwalters]

Tony,

Thanks for that bit of information and you could probably be right. We have our en-suite gutted at the moment as I am in the process of replacing it all and the hot and cold feeds to the WC, sink and shower are capped off. So that could be where the air pocket is.

I presume then that if the air pocket is there, when we refit the wc, sink etc the problem should resolve itself.

Richard