Alpha CB28, pressure needs releasing every day

[markwm]

At least once a day we have to manually release the pressure on our CB28 in order to get hot water. The overflow is forever releasing water!

Any ideas what the problem might be? I have a plumber coming round to look at it but always worth getting a back of background beforehand.

 

[gas4you]

Have you checked the filling loop is not letting by?

Remove it from one end to confirm.

 

[Kingsway]

this depends on whether it is over pressurizing when hot or cold. If when cold, filling loop letting by or rarely heat exchanger faulty. if it is only when hot then either undersized expansion vessel for water volume or expansion vessel failed.

 

[Aquaheat]

If the pressure is constantly rising then it could be one of two things.

1. Firstly, as mentioned by gas4you, the filling loop may be passing or not turned off fully. Ensure that the valves are fully turned off to this loop and ensure that it is disconected from the pipework ( regulations state that it should be anyway!)

2. It may be the DHW heat exchanger passing. To test this isolate the mains cold water supply into the boiler and leave for a little while. If the pressure now remains stable it will require a new heat exchanger.

 

[markwm]

It seems my description of the problem wasn't entirely accurate.....(sorry, boilers aren't my thing)...

What's happening is the pressure is gradually failing and it needs topping up 3/4 times a day. So what I thought was releasing it, was actually topping it up.

First plumber we had says it needs a new 'pressure vessel'.....but he messed us around and never got the part. Second plumber we had says first plumber is talking *******s and seems to think there might be a leak someone on the central heating system. The only place this could be is under the living room floor and I'm very doubtful there is a leak on any joint as I check and double check especially when they're being enclosed underfloor boards. All the other visible joints, rads etc are fine.

When the pressure does go down (gauge into red) there's 3 joints on the boiler itself that 'weep' occasionally. Two on the 'heating flow' and one on the 'cold mains inlet'.

I'd rather not have to lift the floor and check all the joints to the central heating!