I have a Vokera pressurised central heating system, and gradually over last few days the pressure has been rising. It should run at 1-1.5 bar, but its up at 3.5 now !
How can i lower it,
I have treied switching off & lowering the heat settings for the rads, but as soon as i switch on again, it shoots back up.

Richard Cooper, April 2008

their will be a pressure relief valve on the boiler. to locate it follow the pipe that goes out through the wall to the outside of the building, now follow that up into the boiler and u will see a red knob push this in and turn it the pressure will drop. please note look at the pressure when the boiler is cold and use my instructions accordingly.

malcolm link, April 2008

To reduce pressure in your boiler, you actually have to remove some water from the system....do this by bleeding water off at the radiator bleed valves - it takes a while as you'll need to remove a few pints, but stick with it. If the pressure increases again, perhaps the filling loop valve is slightly open?

John, April 2008