Potterton system boiler PRV & EV failure

[thedigger]

Hi all, I have a Potterton Gold system boiler & unvented cylinder.

The pressure has been dropping regularly over the last few months and I've been topping it up weekly via the loop, but today the PRV gave up completely and will not hold any pressure at all and water flows through the tundish as soon as I allow it into the system.

I suspect the external pressure vessel has gone (I get zero bar on a pressure gauge, and no "hiss" when I press the schraeder valve), and this has caused the PRV to fail.

Can I (legally) change these parts myself - I'm not gas safe registered etc, but this isn't a gas fault.

Also, while my boiler is out of operation, will the immersion heater in my unvented cylinder work, or do these generally rely the system being pressurised?

 

[muggles]

No, you need to be G3-registered to work on unvented cylinders I'm afraid. Time to call a G3-regd man in

 

[thedigger]

Argh, there's always a reg to adhere to. Cheers, I'll make some calls in the morning - does it sound like an hour's labour + parts? (assuming my diagnosis is correct, of course)

 

[mfarrow]

This doesn't sound like an unvented cylinder? Just a closed central heating system.

 

[copea]

Also, while my boiler is out of operation, will the immersion heater in my unvented cylinder work, or do these generally rely the system being pressurised?

It sounds as if you're talking about the PRV in your boiler, which is nothing to do with the cylinder (save for the fact the water heated by the boiler indirectly heats the water in the cylinder).
The cylinder will still be pressurised by the incoming water main.
The heating coil is separate and the fluids don't mix.
The immersion should still work.

 

[slippyr4]

If it's not the unvented cylinder's PRV and EV, and they are not integral to the boiler, then they aren't part of the boiler.

A photo might help.

 

[thedigger]

I'll take a photo tonight if it helps. Just to be clear, I don't think there's a problem with the hot water cylinder (the megaflo clone)... the EV has no pressure (and won't take any air if I pump it up), and the PRV on the boiler is constantly releasing (even if the pressure is <1 bar).

I suspect the EV failed, system heated, water expanded, pressure exceeded 3bar and the boiler PRV opened and has failed to close.

Good to know the immersion can be used as an emergency water heater in this scenario though

(I've edited the title as it made it sound like the unvented cylinder had failed before)

 

[Agile]

"I suspect the EV failed, system heated, water expanded, pressure exceeded 3bar and the boiler PRV opened and has failed to close."


I think that you are trying to think too much.

All I can say is that I don't expect what you think is necessarily related to your problems.

It seems you did not read the lovely FAQ on how to repressurise an EXV ?

But you should only try to repressurise orange EXVs and NOT white ones!

Tony

 

[thedigger]

Thanks Tony. I have an engineer coming tomorrow morning to look at it. Out of interest, what is the difference between orange and white EXVs? Mine is white, but has a schraeder valve

 

[thedigger]

Googled it, mine is potable. I can't see any reason to not repressurise white ones though?

 

[Agile]

Orange ones are used on heating systems and you can repressurise them.

White ones are used on unvented cylinders and only a G3 qualified person should work on them!

Tony

 

[DP]

Orange ones are used on heating systems and you can repressurise them.

To be precise and exact, red also. Use to be orange, silver too

White AS WELL AS blue for unvented. Have seen silver too