Combi Vibraiation

[Joe]

Dear all I have a Worcester 28Cdi Combi boiler fitted by British gas approx 2 years ago, and is still under a service contract.

In the last 3 months there has been a vibrating from with in the casing of the Combi. This usually occurs after any water in the house has been used (hot or cold). The vibrating is Intermittent. The vibrating will last 3-4 minutes and will then stop, but it can be stopped immediately by opening up any tap in the house (hot or cold)

British Gas have been in twice, but have been unable to fix the problem. Recently they adjusted the water pressure on the Combi from 1 to 1.5. The engineer then left as told me to log a new call if the problem re occurred.

I don?t want to fix the problem my self, just some ideas of what could be causing the problem so I can pass them on to British gas.

Just before the problems started the ball valve was changed in the main tank. Could this have anything to do with the vibrating, or it just a coincidence?

Joe

[Ed Sirett]

No this is probably not coincidence. Unless you need the stroage tank (in the loft?) to provide water for the WC(s) in the event of a mains water cut, then I would lose the tank.

[John Stumbles]

Sounds like a 'water hammer' problem: not necessarily a fault in the boiler but maybe an interaction between the new float valve, something in the boiler, and the configuration of the pipework in your house. You could try (a) tying up the float valve and/or (b) partly closing the incoming mains stopcock, and seeing if it affects the vibration: this would tend to confirm the water hammer theory.

If it is water hammer then you could alleviate or eliminate it by introducing a length of plastic pipework into the feed to the tank in the attic. (There are also custom surge arrestor devices you could plumb in, at a price, or another diy approach is to have a short stub of pipework continuing vertically from near the float valve, going nowhere but trapping a bit of air to reduce the hammer.)

-- John Stumbles

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