Hi

Can anyone please advise me on why my Ariston Eurcombi A/27 MFFI pressure is rising from just over 1 Bar cold to nearly 4 Bar when the CH is running? I'm worried that this is dangerous as its running in the red. I had a local heating engineer around to look at it, he said that the main heat exchanger is blocked or scaled up and couldn't do anything with it other than fit me a new boiler for £2500. I was advised by another heating guy at work to put some Fernox F3 cleaner into the system via a radiator to see if it will clean the system, but am worried as to why the pressure is rising so high. I have been told to let the cleaner stay in the system for a week then drain and refill. Can anyone offer any advise.

Thanks
Neil

Neil, December 2013

If when you refire the boiler the pressure goes up dramatically the expansion vessel needs recharging,it is either a red cylinder located somewhere or it is built into the boiler,at the top is a shrader valve [like on a car tyre ]drop pressure in c/h system and check pressure of vessel if zero it will need to be pumped up using a foot pump etc, not forgetting that the vessel is probably full of water so will have to be displaced by opening the p/r valve while pumping exp vessel up,charge up to 1.5 bar then refill system and try again,if it works for several weeks then fails again the exp vessel is faulty

toptrish, December 2013

No nobody has mentioned the expansion vessel or the expansion relief valve? I opened the pressure release valve whilst the boiler was running at nearly 4 bar and the boiler discharged some water to the external overflow, and the pressure then slowly dropped and kept dropping to zero. I switched off the CH at that point and let the boiler cool before filling it back up to 1 bar, but have not let it run on the CH yet, as I wanted to make sure that the boiler stayed at 1 bar without dropping again, which it seems to have done. Any more suggestions as to what the problem is and why it was doing it?

Neil, December 2013

Did any of these so called experts mention the expansion vessel not having any pressure which is the first thing I would check,theoretically there should be an expansion relief valve in the boiler or by the expansion vessel which should discharge the excess pressure at 3 bar,in such circumstances the pressure would drop when cold over time to zero

toptrish, December 2013