potterton powermax he?

Then you get a qualified gas engineer in to repair and check boiler at the end

B Penny
February 2009

Have just realised you may be talking about the other pressure release, the one from the hot water cylinder. This is a common problem with mains pressure hotwater systems. which are not maintained regularly. Turn off the cold water mains supply to boiler - open the nearest hot tap and just let it run until it stops (leave it turned on). On the side of your cylinder is a brass hook looking thing, this is a pressure release valve which should drain into a black plastic funnel. Hinge the hook outward and hot water will gurgle down the funnel keep holding the hook out until gurgling stops and then let go (this may take several minutes. What's happening is that you are replenishing the air gap inside the cylinder which allows stored hot water to expand into - similar to the 4% expansion of water in the radiator system, only this time it's 4% of 185 litres (nearly 8 litres!) Now turn off the hot tap you opened earlier and then turn on the cold mains supply and your back in business. You may still need to replace the red 3bar pressure release valve to stop any drips, but I doubt it.

robbie repairs
December 2008

Sounds like pressure vessel has no air in it. As heated water expands by four percent, and on a 100 litre system this amounts to four litres, you need four litres of air inside the expansion tank. (An empty radiator with one end turned off will do.) You'll need a car footpump and connect it onto what appears to be a car tyre valve connections on a metal container inside the boiler casin (the pressure vessel). Somehwere inside same casing is a red pressure release valve, open this and allow pressure to reduce to zero - leave it in the open position and pump the pressure vessel up until dial on pump indicates about one bar while the boiler pressure dial indicates zero. Disconnect pump and close release valve. Re-pressurise boiler to just over one bar. Now either press the reset button or turn boiler power off for ten seconds and then turn it on again (makeshift reset) Job done! This should work on most pressurised combi boilers.

robbie repairs
December 2008

renew valve, may require full pressure valve removing or just possible the 8 bar pressure valve removing, try smallest valve first

Powermaxing you into the future
September 2008