I Have a worcester Bosch 28cdi. It's working in that we're getting hot water and heated radiators. However, the overflow pipe which exits the loft has just started to pour water onto our conservator roof. I have been up into the loft and track the this pipe from the just underneath the eaves of the roof back to the boiler where it seems to be the right most pipe entering the boiler.

Yesterday we day have an issue whereby we had no water. I checked the system and the pressure was low. I increased the pressure to about halfway (1-2) and everything was then okay. When I looked at the boiler again after this overflow issue the pressure was on 3 (three quarters of the way through). Could this have anything to do with it and can I also decrease the pressure as well?.

Regards

Gary King, January 2009

Its possible that the expansion vessel has lost its pressure, ill try and explain. The system is sealed (no water in , no water out, unless done so manually) When the heating system heats up hence the water expands thus increasing the pressure. To allow for this expansion we have the expansion vessel (metal cylinder with an innertube inside) The hot expanding water enters the cylinder and sits around the inner tube which has arround 1.2 bar of air inside. when the water cools the inner tube pushes the water back into the boilers water circuit. hence regulating the system pressure.

If the inner tube has no air or is burst, the system pressure increases with heat, has nowhere to go, so reliefs itself through the Pressure Relief Valve (PRV) When the system cools "We have lost pressure"

There is a screader valve on the vessel (like a car tyre valve) push this in, if Water comes out replace vessel, if nothing comes out inflate to 1.2 bar using a car foot pump.

Sorry about the story but hope this helps

Garry, January 2009