Hi folks, further to my recent post (suspected faulty gas valve and scaled/sludged heat exchangers) I've run a sludge remover thru the system but noticed the pressure does not return back to the previous pressure at cold. I've reset it twice now to 1 bar (filling loop is off!) but when the heating is on it rises up to 3+bar even at low. I'm replacing the secondary HE tomorrow and will look at the primary HE and check the pressure vessel . I can understand why the pressure might rise while heating but can't understand why it doesn't return when cold...any thoughts?
Combi pressure not dropping back down when cold
- Thread starter Dirntknow
- Start date
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the plate heat ex might be holed passing mains water into the system. if you pressure boiler to 1 bar, does pressure rise on its own if you don`t use the heating for a few hours? ( disconnect filling loop)
I've not noticed it rise when cold but tbh the heatings been on most of the time! I know what you mean about the plate exchanger, the mains pressure is higher than the system pressure . Perhaps the hole/crack is small enough that at cold it's sealed and only opens when heated?
I'm changing it later today (hopefully!) so will post later if there's any results...
I'm changing it later today (hopefully!) so will post later if there's any results...
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sadly water flowing through schraeder valve means the diaphragm inside exp. vessel is perforated, time for a new one sadly 
New plate heat exchanger and expansion vessel fitted and under test as I type. A few strange noises and a couple of leaks at first but all now stopped. It seems to be working better already but i'll need to address them leaks!
Edit: There's a rushing water sound, not too dissimilar to when a toilet is refilling after flushing every couple of minutes. Does this sound like 'kettling' from the primary heat exchanger?
Edit: There's a rushing water sound, not too dissimilar to when a toilet is refilling after flushing every couple of minutes. Does this sound like 'kettling' from the primary heat exchanger?
Could just be air that hasn't vented from the system yet. Give it day to settle down, bleed your radiators, and report back if the problem persists.
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