High pressure problem in boiler

[vblackmore]

I have recently moved into a house with a Worcester 240 Combi gas boiler. The hot water is fine, but when the central heating comes on or is turned on, the pressure bar goes upto 3.5 within 20-30 mins. When the central heating is turned off it goes back to 1-1.5. I bled the radiators today which meant I had to repressurise the boiler but the central heating still increases the water pressure too much. The problem started about 2 days ago, but I am usually at work so it may have been happening before without me noticing! The Worcester services say that the water to water heat exchanger may need replacing. Any ideas or agreement?

 

[oilman]

You need to check the pressure in the expansion vessel. Release the water pressure first with the pressure relief valve. If it leaks after it's no good. If you don't open it you don't know if it's stuck. Take no notice of people telling you not to touch it in case it leaks after. Check water doesn't come out of the air valve by pressing the pin in, then check the air pressure. It well be zero. If water didn't come out, pump up the air to 1 bar.

This is a sign the boiler was never serviced properly.