secondary expansion vessel

[traumapat]

hi all.
had a corgi guy out to our sime super 90 plus combi boiler.

problem was/is that system holds 1 bar fine until running where it climbs to 3 bar and once cooled shows .25 of a bar.

the engineer recharged the expansion vessel and didnt find water. system ran fine whilst he was here.. maxing to 1.5bar.
after he had gone i noticed the pressure was just under 1 bar. got it up to 1bar exactly and ran it an hour ago. just noticed its hit 3 bar again!
water is coming out the overflow? -pipe through wall.

he suggested if this failed fitting an adjacent expansion vessel under the boiler would be cheaper as boiler would have to come off the wall.

considering no water came out the vessel which must mean the diaphram is sound.. could it be the pressure release valve?
im happy to fit another vessel but worried it wont fix it.

any ideas or any way to test the valve?

many thanks
pat

 

[sbgasman]

if no water coming out of schrieder valve it is likely to be leeking air replace valve all covered in FAQ i think

 

[agbagb]

As an easy test and to keep you warm before the plumber can get to fit the exteral vessel. Half drain one of your rads. This will give some air space to take up water expansion so the pressure shouldn't get to blowing the relief valve.

 

[traumapat]

i will check out the FAQ . wasn't aware you could just replace the valve

half emptying a rad sounds like a great idea... and i imagine also it would confirm an expansion vessel issue. nice one!

 

[WDIK]

several points.

so your corgi registered operative repressurised your expansion vessel?

did he open the system and allow 7-9lts of water to discharge as the vessel filled?

if not he didnt charge your vessel.

fact.

you cant charge against a dead head.

many times the vessel due to sludge in the hydro bloc the vessel isnt even actually connected to the system.
the bag in the vessel may be stuck to the sides of the vessel.

get an engineer who actually understands pressurisation not some corgi muppet with an acs ticket

 

[pipeslice]

As an easy test and to keep you warm before the plumber can get to fit the exteral vessel. Half drain one of your rads. This will give some air space to take up water expansion so the pressure shouldn't get to blowing the relief valve.

Bravo spot on.

Had this happen on one of my systems before. Fit a extra vessel to allow for more expansion

 

[ChrisR]

Could be the exp vessel connection pipe is blocked solid. It's common.

 

[traumapat]

several points.

so your corgi registered operative repressurised your expansion vessel?

did he open the system and allow 7-9lts of water to discharge as the vessel filled?

if not he didnt charge your vessel.

fact.

you cant charge against a dead head.

many times the vessel due to sludge in the hydro bloc the vessel isnt even actually connected to the system.
the bag in the vessel may be stuck to the sides of the vessel.

get an engineer who actually understands pressurisation not some corgi muppet with an acs ticket

so there should have been plenty of water sitting outside the discharge pipe? it didnt look like 7-9 ltrs!

im going to do the job myself today... drain all pressure via prv and then repressurise the vessel, close prv and refill.
its a 3 bed house so vessel should be at 1bar? cant see anything on boiler itself that tells you.

if it turns out to be blockage from sludge can this be cleared/flushed?

thanks
feel much more able to have a go today.