Valliant 637 system pressure fluctuation

[Vhans]

Hi,

I had a Valliant 637 with an indirect megaflo installed. All was working fine then the pressure dropped to 0.4bar. Someone suggested this meant there was a leak somewhere, however, I checked very carefully and found none. I filled the system again and it sank once more. The only thing im noticing is that the consensate is discharging a lot of water (approx a cup full every few minutes). It is not dripping, rather "coughing" it out. I checked the PRV outside and no leaks.

Today I filled it again to 1.5bar, bled the radiators, and cranked up the heat. For most of the day the pressure remained at 1.9, then tonight it has shot up to 3.9. I have now turned the boiler off.

I can't call the installing engineer as he's no longer around. Just hoping someone has an idea of what the problem can be please. I don't think it is a leak, thankfully, but am concerned a brand new boiler could be at fault. I'm hoping it won't be too expensive to fix.

 

[twgas]

Most likely, the expansion vessel needs re-pressurising.

 

[Dan Robinson]

If you genuinely need a 37kw boiler then the internal expansion vessel will not be adequate.

You will need an extra one.

Filling loop could be passing.

Also unless you have inspected every joint don't rule out a leak.

Top Up pressure. Turn system off and isolate the boiler service valves. And monitor for 12 hours. If pressure drops then you need a new heat exchanger.

If pressure rises you need to look at the filling loop.