worcester 240 BF problems

[stevenflight]

Hi, Having problems with pressure in my boiler, overnight the pressure will build up to 3 bar or just below, had a new expansion vessel fitted but still just the same, any ideas ?.

[John Rumm]

Does the pressure build even if the boiler is off?

[stevenflight]

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Hi John, yes the pressure builds up if the boiler is on or off, overnight the pressure builds up to nearly 3 bar

[ARWadsworth]

Hi John, yes the pressure builds up if the boiler is on or off, overnight the pressure builds up to nearly 3 bar

It there any chance that the filler loop is open?

Adam

[stevenflight]

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Hi, no the filling loop is disconected.

[Ron Lowe]

Hmm, then you need to start thinking logically where the pressure is coming from.

If it's not thermal expansion ( boiler off ), and it's not from the fill loop, then where else is it coming from?

The only other possibility that comes to mind is:

Do you have an unvented HW cylinder? ( eg magaflow etc )

A leak in the indirect coil would push mains pressure water ( typically 3 bar or more ) into the primary loop and cause this. I've never seen this in a real installation, however.

You need to start shutting stuff off to eliminate things.

[Ed Sirett]

It's worse than I thought - you must have a hole in the 2ndry heat exchanger letting mains water into the primary all the while.