Mains pressure rising when boiler is on .

homewardbound11

Can anyone shed some light .
We have a pressurised system and oil boiler . When the boiler is off we have in and around 2.5 bar . This is the reading on the up gauge from the mains . When
The oil Boiler is turned on (water and heating) the gauge pressure from the mains rises to 5 bar .
What could be causing this .

The water tank pump is bypassed. Sotheby's gauge should be reading mains pressure.

Kealyboy

homewardbound11 wrote: »

Can anyone shed some light .
We have a pressurised system and oil boiler . When the boiler is off we have in and around 2.5 bar . This is the reading on the up gauge from the mains . When
The oil Boiler is turned on (water and heating) the gauge pressure from the mains rises to 5 bar .
What could be causing this .

The water tank pump is bypassed. Sotheby's gauge should be reading mains pressure.

I presume you mean boiler/system pressure. For starters the system pressure should be 1 bar when boiler is off (system cold). If the pressure rises when heating is on this indicates that the mostly likely cause is your pressure vessel is shot.

Filling loop should be disconnected when system is topped up to required pressure also

Wearb

Why the hell is it rising to 5 bar. You have a very dangerous setup. The system should be protected by a 3 bar pressure relief valve. I would not use it until sorted.

homewardbound11

Thanks for the help.

Better get the plumber in so .
The gauge I see is the one at the mains after the water pump ( in the garage)

So in the garage it is mains to 500l tank with pump to gauge .
There are other things in the loop but I just wouldn't know . Think they are bypass option and auto fill. Also some connections on the oil boiler there too.

The only reason I got alerted was the outside tap was leaking . It was connected to the mains just before the gauge .

As soon as I get the plumber in ill post back .

Wearb

Good. Make sure to ask your plumber (1)why your heating boiler is driving that gauge up. (2) why your boiler pressure relief valve isn't letting water by at above 3 bar.