Ferroli boiler dropping pressure

12 Oct 2014
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United Kingdom
Hi please can someone help
I have a Ferroli boiler which has been off all summer only supplying hot water, now that I have put the heating on it drops the central heating water pressure to 0 every day and won't fire up until I top it up and increase the pressure in the system, I have checked the whole house for leaks and can't find any, I have put Fernox leak sealer in the system and run it to see if this would help. But it hasn't. I have checked inside the boiler for leaks but there is no sign of any.
There is no water in the expansion vessel in the boiler. Although the pressure in the vessel was low. So I dropped the pressure in the system and recharged the expansion vessel to 1 bar this has slowed the drop in pressure in the system down slightly but still needs topping up daily.
I have now turned the C.H feed and return off at the boiler and the water pressure gauge on the boiler has maintained its pressure. No drop at all, but when I open the C.H feed and return at the boiler it still drops to 0 over a 24hr period. Anyone got any ideas ? i'm reaching the point of disspair
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There is a leak somewhere on radiators system, you just have to find it, check radiators valves, drain cock as well. Leave the heating off for 24 hrs and as the water is cold, easier to find it.

I have now noticed that when the central heating is on the water pressure is over 3 bar ? Any ideas ?
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Old thread but never got an answer so...

It sounds like the pressure vessel has failed and expanding hot water has nowhere to go until it rises above 3bar and discharges from the PRV

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