Combi Boiler pressure range

fatnbald

Hello DIY heads

I have a disturbing happening with my combi boiler, it is a Wrocester Bosch 28si model with varying pressures on the pressure gauge.

If I set up the pressure to 1 psi cold and then run the heating the pressure rises up to over 2 bar and stays there or thereabouts, this reading does seem to increase the more rads that are tuned on.
Once the heating is switched off and the system cools the pressure is invariably down well below 1 bar and requires a top up. The heat exchanger was replaced 18 months ago with a new one and it has worked fine since then, thia is the first time we have used it since last winter. The hot water side works perfectly OK.

The system was inherited when we bought the house and there is a known piping problem where some of the rads that the previous owner added have been plumbed in series not in parallel so to have one on you need both on, having this bizarre loop on or off makes no difference.

What is the normal pressure range most people see with their combi's between hot and cold and what are the possible reasons for a higher range of the pressure?

fatnbald

The problem has been sorted, the expansion vessel, which is very well hidded on this boiler, had lost its pressure and needed pumping back up again to the required amount, pain of a problem, simple solution.

Just though I would post the solution as no one seems to know the cause of the issues we were experiencing.