the pressure on the boiler when i set it at 0.9 bar rises to 3 bar yet the pressure on the washing machine says low pressure also the when i use the hot water the pressure drops to the point where there is a considerable noise in the boiler sounding like it is running dry it does not happen when the c/h is running on its own

paul h, December 2012

most likely the pressure vessel needs inflating for the pressure to rise from 0.9 to 3bar suddenly causing the prv to open cases a hammering noise. washing machine i cant help

kash, December 2012

Without model number. general. Might be a filter on HW inlet to boiler, could be scale build up in heat exchanger, I assume water is same with boiler off. SO a blockage in boiler somewhere. check for filter 1st, would be near to the cold inlet. otherwise blockage could be in heat Exch. could possibly be descalled, but might need replacing, especially as pressure goes up so much when going via exchanger. Without model No. Difficult

SD, December 2012