I have an ideal response 80 boiler. The pressure has been high on it (4bar) and last night I reduced this pressure by draining the system a bit. I now know this was caused by the filling loop being left attached and open.
The loop has been detached now.
System pressure was at 1.5 bar last night with the CH going. This morning it was at zero so boiler wouldn't fire.
I filled the system to 1.5bar and all appeared great.

After about 10 minutes of the CH running and using the hot tap for a wash the pressure was at 4 again.
Stopped using the hot tap, ten minutes later it's back to zero again.

Arghhhhhhhhh

Can anyone suggest a cause?
Many thanks

Graham, February 2010

I've not had a chance to inspect the expansion vessel yet.

But, I have recharged the system with water to 1 bar. When i operate the CH system the pressure rises to 4 bar after about 10 minutes operation. It reduces back to 1bar if I switch the heating off for about 20 minutes.

Could this be caused by a block of some description in the expansion vessel or pipework leading to it?

Graham White, February 2010

Thanks.

How do I get to the expansion vessel - I assume it will be inside the case of the boiler. Is it easy to locate one the cover is removed?

Graham, February 2010

1) with No water pressure on the boiler gauge.
check what air pressure you have in your EXPANSION VESSEL this may be EMPTY,(if water comes out the car valve the E V is SHOT replacement needed) Try re inflating up to 1 bar max pressure, using a car foot pump & tyre pressure gauge,
2) Now repressurise (fill up) on the water side via filler loop to 1.5 bar cold, disconnect the filler loop.

wirecutterman, February 2010