hello,the problem with my boiler is this,the hot water is not working,the dial is swiitched on to heating/hot water and in the summer to hot water only.what happens is when i turn on a hot water tap the burner fires up and within one minute theres a loud bang and the boiler releases the pressure through the pressure relief valve and water ends up pouring outside and the pressure gauge needle goes haywire and the system ends up in lockdown mode with the red light flashing. please please please can someone pin point this problem and give me the solution. many thanks jaymondo