I SET THE PRESSURE GAUGE TO 1.5 BAR AND WHEN THE HOT WATER IS USED IT IS FINE, BUT AFTER THE CENTRAL HEATING SYSTEM IS USED THE PRESSURE GAUGE LOSES PRESSURE AND GOES DOWN TO NOTHING. I THEN HAVE TO REFILL THE PRESSURE TO 1.5 BAR BEFORE I CAN USE IT. WHAT CAUSES IT TO LOSE PRESSURE WHEN THE HEATING SYSTEM IS USED.
IDEAL BOILER 120

DARREN MCGORRIN, October 2007

did you ever get an answer to this problem as my Ideal 120 boiler is having same problem each day? cheers, carl.

carl, October 2010

Check to see if the safety valve is dripping outside, if so your expansion vessel is faulty or pipe to it choked. Professional required I'm afraid.

MCG HEATING, October 2007