my boiler water pressure keeps on goin up to nearly 3bar and expelling alot of water outside.CH works when i drop the pressure down to 1 using the pressure relief valve which leaks only while i drop the pressure.( joint leak) there is only about 10 seconds of hot water after this but the heating is fine till the pressure gets too high. i am regulating the pressure daily.there are no flashing lights on the panel. i have noticed that when the CH is on, the neon is lit normally but once i turn a tap on it goes out and the DHW light comes on instead (not both together) but no hot water. diverter problem perhaps?

james c, December 2016

From your description the system is getting repeatedly overpressurised. There are two ways that could happen: The filling loop and valve is allowing mains water into the system OR there is an intermnal leak between the mains side and the system.

My guess is a faulty DHW plate heat exchanger or a faulty diverter valve, for starters.

You could have also have faulty or non-pressurised expansion vessel.

You really need to think about getting a gas safe certfied engineer to look at it

XXX, December 2016