Boiler operating pressure

rich tee

Is it normal for a boilers pressure to rise when it's being used and then go down when it's Idle.
My boiler goes up from 1.2bar idle to 1.7bar.

Thanks

steve iow

That's perfectly normal, the internal pressure vessel takes care of any rise in pressure just check every now and again that the operating pressure at idle is the same if this drops due to expansion just top it back up,if it goes to the RED area then you have a problem, call your heating engineer.

Trollslayer

My combi has a set pressure of 1.5 bar and when operating it can fluctuate between 1.0 and 2.0 (this is the green area).

rich tee

Basically what happened was, the pressure was low I thought so I topped it up.
I put too much water in but the gauge was in the top half of the green area.
When I checked it again about a week later it was in the red.

Heating engineer drained the boiler and it went to 1.1 bar.
Every day though it's risen by .1 bar up to idle pressure of 1.5 some 4 days later. Then an operating pressure of 1.8.
I bleed a radiator yesterday and it dropped to 1.2 idle, 1.5 operating.
Tonight I ran the central heating for about an hour it went to 1.8 operating and now the rads are cool it is reading 1.3 idle.

steve iow

Hi Rich. When was the boiler  last serviced and was the pressure vessel checked, if the needle keeps going in the red area the pressure vessel will probably need recharging,your heating engineer should have checked this with the  problem you are experiencing get him back if he hasn't all the best Steve.

rich tee

Hi Steve

The boiler was new in 2009, Vaillant Ecoplus 831, it had 2 free services, the last service took about 10 mins, the guy just checked it worked.

I missed last years service as I was due to move house.
I've been reading the service manual and I think the internal pressure vessel needs repressurising like you said.

Yesterday the boiler was idle and read 1.3bar today it's 1.4bar tomorrow I reckon it will be 1.5bar

steve iow

Hi Rich is the pressure increasing when the boiler is idle if is the case , is the filling loop still connected, this really must be disconnected after refilling,as the valves might not be shutting off probably and letting water bye into the system, which will increase the pressure up slowly. Hope I have been some help, Steve
PS .would still  get pressure vessel checked out as I don't suppose it was on any of the services you have had

rich tee

Hi Steve

I wondered about that, the boiler is a Vaillant ecoplus 831, and filling the boiler is done by 2 grey taps under the boiler.
I opened them today and put a tiny bit of water into the boiler, the pressure stayed the same at first then it went up by .1 bar.

Yesterday after using it to run a bath it went up by .1bar again

I bled a rad on Friday and it went to 1.2 idle, it's now 1.6 idle.

It was drained to 1.1 bar last Tuesday and by Friday it went to 1.6 idle.

I'm trying to get a friends friend to look at it, he's a gas safe engineer.

steve iow

Hi Rich glad to see you have everything in hand, I personally would get a Valiant eng to check it out,how long is the guarantee , i thought they came with 7 year  anyway best of luck steve

rich tee

Hi Steve

I just spoke to a decent gas engineer, he's told me to disconnect the filing loop to see if the pressure maintains, he said if it doesn't then it's likely to be the heat exchanger being cracked.
He recommended getting a vaillant engineer in, or opting for the £99 british gas deal and then joining their warranty.