HELLO
i just had a similar problem my heating system was filling up through my hot water (heat exchanger damaged ) if pressure goes down when you open the hot tap it could be this.(blow off should kick in at 3 bar)
IM HAVING PROBLEMS WITH MY BOILER (SABRE 28)
THE LOCKOUT RED LIGHT IS ALLWAYS COMING ON I RESET THE LIGHT THEN IT LASTS ANYTHING FROM HALF AN HOUR TO A DAY BEFORE IT LOCKS OUT AGAIN
SITTING AT 1.5 BAR
BOILER 18 MONTHS OLD
WAS A BOILER CHANGE
COULD THE SYSTEM NEED FLUSHED ?