Worcester Gas condensing boiler R25 HE (4 Years old)

3 Jun 2009
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United Kingdom
Worcester Gas condensing boiler R25 HE (4 Years old)

Just recently i am experiencing increased pressure shown on pressure gauge up until the relief valve operates and reduces pressure. I depressurised the system using the relief valve down to 1 bar and disconnected the filling loop and the pressure still increases even with the boiler not operating ( about 1 bar rise in approx 2 hrs ).When the boiler is operating for domestic hot water the pressure increases more rapidly up untill the relief valve operates , i have been advised it is either the expansion vessel needs repressurising or that the heat exchanger is faulty. Could anybody assist with a cause of the problem. Many Thanks
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What is a R25, a system boiler or a combi? :confused:

I don't know the WB range too well.

If a combi then the plate HE, if a system boiler, then if you also have an unvented cyinder, I would suspect a hole in your cylinder coil.
Almost certainly a perforated DHW heat exchanger. Good idea to change the PRV and check the EV air pressure also.

Oh, first of all, disconnect the filling loop to check it's not letting by.
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Thanks am almost convinced its heat exchanger as pressure has now risen to 3 bar without operating the boiler.
Many Thanks.
Ps Is replacement of Heat Exchanger simple enough for layman ? ( as far as i can see only invoves water side of combi boiler)
to check drop the pressure again and turn of cold main supply to boiler
if it doesnt rise your 100%

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