Potterton Gold losing pressure

Daljit · 7 Dec 2014

Hi

I have a Potterton Gold 24he combi that keeps losing pressure, needing refilled every 24 hrs. Error code points to an issue with the fan, but i think there has to be another fault to account for the lost pressure?

When the flow and return pipes are switched off at the boiler, and left to stand for 5 hours, the pressure dropped from 2.0 to 1.8bar. However, when switched back on (to HW function only, with CH pipes still off) it dropped another 0.5bar immediately. Pretty sure there isn't a leak in the pipework as spoken to downstairs neighbours; rads also checked for leaks.

I've not been able to check the pressure relief pipe as it rises vertically for about 8ft and exits on to the roof of the building (a 4 storey block of flats). I'm aware this is against regs and looking to reroute the pipework.

CH engineer said i need to replace the fan (£150 + labour). However, before i go ahead with this, just want to check what others think might be causing the loss of pressure.

thanks

Daljit

St0rmer66 · 7 Dec 2014

How can a fan cause pressure loss?

. Sounds like you have more than one issue.

Daljit · 7 Dec 2014

Yip, I think the fan is a separate issue too. There was also an error code showing the was a fault "water pressure switch not operated" but this seems to have been overtaken now with the fan alert.

The loss of pressure: is that likely to be connected to a fault in the expansion vessel? Or could it just be a faulty switch?

Thanks

St0rmer66 · 7 Dec 2014

Much more likely to be a flat expansion vessel which just needs pumping up. The switches rarely fail, could get blocked but then it would be permanent, not just until you repressurise! Has the boiler been serviced recently? Usually it's checked on the service, it's not a hard job but requires access to the combustion chamber on this boiler so it's not something you can do yourself.

MeldrewsMate · 7 Dec 2014

Daljit said:
When the flow and return pipes are switched off at the boiler, and left to stand for 5 hours, the pressure dropped from 2.0 to 1.8bar. However, when switched back on (to HW function only, with CH pipes still off) it dropped another 0.5bar immediately.

Drop in pressure could be due to boiler cooling over that 5 hour period, the extra half a bar by differential pressure once the pump starts on DHW duty, so no real information there.

Safety relief leak (passing) or leaking expansion vessel....air side or perforated diaphragm.

Turn on the CH valves and read the pressure with the boiler off and cold. Start the heating and when hot turn it off and read the pressure again. If it's anywhere near 3 bar or above then suspect the expansion vessel.

Do not buy a fan until you've solved this fault.

Daljit · 9 Dec 2014

Hi

Thanks for advice above- much appreciated.

I disconnected PRV pipe and note that when CH switched on, pressure increases to 3.2 bar and then there's a steady discharge of mucky water. When the system cools down the pressure drops to below 0.5! I feel as if I'm making progress now.

Now, am I correct in thinking I have 2 options from here?
A) to recharge exp vessel to 1.0 and see if that corrects problem; if not then
B) buy and replace exp vessel.

Thanks

Daljit

St0rmer66 · 9 Dec 2014

3) unblock the pipe to the expansion vessel

.

You will almost certainly need to repressurise anyway so try that first.

Daljit · 9 Dec 2014

Hi

I removed expansion vessel, and drained it. Really dumb question, but is it possible to inflate a disconnected vessel? When I try air just escapes. Is this because it's disconnected, or should it still inflate to desired pressure.

I read elsewhere that when you have a problem with a exp vessel in the vast majority of cases you need to replace it - recharging is only a temporary fix. For this reason, I've ordered a new one which should arrive tmrw.

Anyway, should it inflate when disconnected?

Thanks

St0rmer66 · 9 Dec 2014

Well that's wrong info! The vast majority of cases it just needs pumping up, it should last the life of the boiler!

In your case though, it does seem like a failure; because you should be able to pump it up disconnected.

ALCPlumbing · 10 Dec 2014

Air will come out of the water connection to vessel as you pump initially. I remember thinking one had split due to this but eventually it held the pressure. Make sure before u throw away. Not sure with ur boiler but some are over £100.

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Potterton Gold losing pressure

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