Losing pressure when heating flow & return valves closed

[Sponge]

I've been having problems with my boiler - randomly losing pressure. Ultimately, the boiler stopped working. I have a service contract with NPower, so finally called them out.

NPower came and got it working again, but said the issue with losing pressure needed further investigation. He suggested turning off the flow and return to isolate the heating. If the pressure still went down, then it's a problem with the boiler and not a radiator leak.

(He checked the EV and it was fully charged. He checked the PRV and there was no sign of water.)

I did as he suggested and the pressure did drop to zero and eventually the boiler stopped working. So I called them back again. They came this morning.

Unfortunately, it wasn't the same guy again. He came at the problem without experience of what's already been done. He's convinced it's the PRV and has ordered the part for next week. In the meantime we're left with a system that will probably stop working again, leaving us with no hot water or heating for the umpteenth time.

He said we should just keep topping up the boiler to 1bar every time it drops. If the boiler stops working. Refill and reset. Rinse and repeat.

I got home from work at 1900 and the boiler was at 0. I topped it up to 1 bar and placed a bag over the PRV pipe outside.

An hour and a half later, the pressure has dropped to 0.5 bar and there is no water in the bag. Well, there is, but it looks more like very mild condensation; not what I'd expect from a dripping PRV. Unless that's what it would look like?

I'm just curious as what else it could be, if not the PRV?

 

[Gas2Air]

What boiler is it????????

 

[Sponge]

What boiler is it????????

Sorry, I've been writing so much about it in other threads, I forgot to mention it in this one. I assumed everybody already knew.

Vokera Compact 25

 

[TCCHeating]

If the prv is not leaking, and you are still losing pressure after isolating the boiler flow and return, then possibly the isolation valves are not completely shutting off, so could still be a leak in the system.

 

[picasso]

If you can check the condensate pipe (I am assuming its a condensing boiler) when the boiler is cold and switched off, and see if you have water coming from the condensate pipe.

 

[gigz]

Most isolation valves i've come across don't close completely, so you can never really tell unless you actually blank them off. Have you looked under floorboards/boxings etc ?

 

[ianmcd]

do as picasso says it is likeley your recuperator heat exchanger has pin holed hope it is covered as they are expensive

 

[dcawkwell]

Not a problem. You have a npower maintenance contract
so keep calling them out until they fix it.

 

[Sponge]

Agreed. And believe me, I will. They're booked in for Wednesday morning. It's just annoying they have to go through all these little steps before I get a working boiler, each taking days at a time. Meanwhile, I'm without a reliable source of hot water or heating. I've got three kids, 7, 5 & 2.

I know there's nothing I can really do myself, but I am a practical chap and like to know what's going on. It helps to be a little informed so as not to have the wool pulled over your eyes, if you know what I mean.

There're no signs of any leaks from upstairs. That is, the rad valves are dry and there are no ceiling stains, etc.

I have access to the floor space at ground level and again, can see no leaks. I've looked where I can, but that's not to say there is a leak somewhere unseen.

As far as the condensate pipe - I will check.

On that subject, the NPower guy said the way the condensate exits is not good. He's the first of 4 different engineers to mention it and they have all seen it.

The boiler is mounted on an external wall and the condensate pipe goes out of this wall and into external pipework that accepts the waste from a cloakroom basin and understairs toilet. (I'll try to post a picture.)

He says it needs an air break.

I've been doing some reading and I am correct to say the boiler will have a condensate trap, but I need something like this to prevent dirty water coming back into the boiler in the event of a blockage?

 

[Sponge]

NPower came out this morning and this engineer agreed it wasn't an issue with the PRV. (I'd placed a bag over the pipe and it was empty.)

He's concluded it's the heat exchanger and it's being replaced tomorrow. It finally looks like it's going to be fixed.

 

[J_N30]

I'd have also suspected the hx passing down the condensate. Glad it's getting sorted.