low pressure?

I'm not familiar with your particuler boiler but if you have three valves I would guess one is the flow pipe, one on the return pipe and the third will be to mains pressure cold water - probably by the gauge. If you have the boiler running then both flow and return pipes should be hot which will hopefully confirm the cold one as your water supply. Let the system cool down before you add pressure and then add it slowly probably to between 11/2 bar and 2 bar (see your instruction book if you have one). Good luck

Richard
December 2008