Combi Boiler loosing pressure. PRV?

[Sam]

Got an C&M Britony boiler that has been loosing pressure for a while.

It appears that the pressure release valve drips to the overflow releasing the pressure over time, or suddently gives way (say at 2 bar) and drops the pressure. So far I have lived with this, and just topped up as required.

However! yesterday a leak started within the boiler, after examination the leak has been progressive (i.e substantial limescale etc) and therefore been leaking over time from the "air seperator". The leak is to the extent that any water in the system is lost.

Obviously the air seperator needs replacing (cost about £25.00), would it it wise to replace the pressure release valve at the same time?

[andrewpreece]

I've had two boilers, and the pressure release valve was set to 2.4bar on one, and 3bar on the other. It might actually say on the valve if you have a look.

2 bar seems a little low to me for an overpressure valve, on the other hand 2 bar seems a slightly high pressure to run a CH system at. Can you test the overpressure valve by filling the CH loop until the overpressure valve blows off: I presume you have a pressure guage on your combi. Also, what is the pressure of your boiler when cold, and what does it climb to when it fires up the CH? There are other faults that could cause your overpressure release valve to appear to be acting up. It should not drip water out of the overflow if the pressure is below its calibrated operating point though.

Andy.

[Ed Sirett]

The SealedCH Faq may help you.

[Sam]

Can you test the overpressure valve by filling the CH loop until the overpressure valve blows off: I

Operates at about 3bar, but "drips" virtually continously till pressure get down to 0.

When refilled, usually take it to 1 bar, when operating (hot) may reach

1.5-2bar.

[Christian McArdle]

If it is reaching 2 bar when operating, I'd consider adding an additional expansion vessel.

Christian.

[<me9]

Alternatively, has it lost precharge from the pressure vessel? that would also give excessive hot pressure.