Boiler loses pressure

[wenger]

I have an Isar HE30 - I know, never mind!!

Before Xmas, it sprung a leak inside and at the pipe outside when the pressure got high. Had an heating engineer in, who replaced 'bits/valves' in the boiler and now no more leaks. When he tested before he left, he noticed that the pressure crept up to almost 3 bar, so suggested changing the pressure release something or other. Left to get parts, but since then the pressure has behaved - well sort of.... I have a new problem which is even baffling the engineer (he now didn't feel the need to change the pressure release thingy):

The boiler loses pressure overnight and half way through the day. When I get up in the morning, although the central heating should have switched on, it hasn't because the pressure is zero. I have no leaks anywhere. To get my central heating on, I run the hot tap and then the central heating kicks in and the pressure climbs to about just under 2 bar. From then on it works perfectly until half way through the day, the pressure will fall again, so I turn on the hot tap and then the pressure builds again.

Most bizarre - anyone any ideas?

 

[Dan Robinson]

Engineer might be a bit of a dumbass, but we'll give him the benefit of the doubt and say he needs to check the expansion vessel and then change PRV.

 

[wenger]

He was going to change the vessel. Apparently with the HE30 model, the vessel is an absolute nightmare to get to - not much space, located at the top at the back, so he was going to put an external one and tap into the boiler - if that makes sense. But as the boiler pressure is not going high any more, he felt it wasn't necessary.

I described the problem I now have with the pressure going to zero and he was flummoxed. He's giving it some thought/asking around. This guy is a supervisor with a reputable well known Essex CH company, so I'm pretty surprised he don't know what's going on tbh.

Does the vessel need checking or replacing? I know that's a big ask without you looking at it!!

And as for changing the PRV (which I presume is the pressure release valve), is it an expensive fix?

I realise it's a crap boiler that I must replace, but it's not a good time right now. I have already spent £150 on the last visit, expect to spend the same again on the next, just sick of paying out when the problem isn't totally solved., which is why I want to pick your collective brains!!

Many thanks

 

[wenger]

Thought I'd bump this, any answer, as I'm stuck!?

Thanks