I have had a new Worcester Bosch Oil Condensing Combi fitted (Aug 07). The installer set the red gauge at 1.5 bar, the pressure reading (black gauge)seems to fluctuate from around 1 bar when the system is cold , up to 3 bar when hot water and/or heating is on. My old oil combi (not condensing) always stayed at 1.5 bar even when cold, is this normal? or do l need to re-pressurize the system when it falls below 1.5 bar.
I have checked the sytem and radiators and there are no leaks

Alan, March 2008

Hi
It could be the expansion vessel is too small for the amount of radiators in the system. You can reduce the pressure to .8bar, then at normal working temp the pressure should never go above 2bar. How many rads have u got
hope this helps

Warwick, March 2008

hi if it is the new worcester condenser with the expansion vessel on top of the boiler to the left it could be a twisted hose connected from boiler to expansion vessel. i had this a couple of months ago on a boiler and the hose had been twisted on istallation so there was no expansion thus pushing up system pressure. hope this helps. martin

martin, March 2008

You can expect a small rise in pressure when the boiler is actually heating - in your case I suspect that the expansion vessel (usually red, inside the boiler casing) has lost some air pressure. There is a tyre valve connection usually near the top and it should be pressurised with air to about 10 psi, or whatever the manufacturer states.

John, March 2008