i have a problem with an icon 23t combi,pressure rising when in heatihg mode and lifting the prv.prv already changed last week by another engineer but didnt solve the problem! changed the expansion vessel for a larger one and fitted it in the return pipework (it was the only one i had to hand) but problem still there,anybody any ideas?
icon 23t rising pressure
- Thread starter jona
- Start date
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DHW heat ex 
assuming you have disscon the loop
assuming you have disscon the loop
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If the pressure rises from 1 Bar to 3 Bar only during the heating up period, you have a non-functioning expansion vessel (EV). Reasons for EV failure to operate include:-
Lack of air precharge in EV (including diaphragm failure), excessive air precharge (as mentioned by gasgeezer) and blocked connecting pipe from EV to system pipework.
Suggest you check precharge pressure. Do a search of the forum for description of how to do this. Precharge pressure should be about 1.0 Bar, or whatever the label on vessel says (often 0.8 Bar).
Lack of air precharge in EV (including diaphragm failure), excessive air precharge (as mentioned by gasgeezer) and blocked connecting pipe from EV to system pipework.
Suggest you check precharge pressure. Do a search of the forum for description of how to do this. Precharge pressure should be about 1.0 Bar, or whatever the label on vessel says (often 0.8 Bar).
ive fitted a new exp. vessel on the return pipework and charged it to one bar.ive been working as a plumbing and heating engineer for 17 years and ive not come across this before,i was wondering if anyone had encountered this on the same boiler because its got me beat!
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