Reliance inlet control valve 3/4.5 is overflowing

[benawhile]

My unvented domestic heating and hot water system incorporates a RWC CWIC 2000 3/4.5 bar pressure control which recently has begun to overflow periodically outside the house.

The system is only 3 years old.

I am not fully sure of the 5 RWC connections but the two regulated outlets feed the central heat system via a “Zilio” white expansion tank and then the balance pipe, and the direct feed to the Gledhill mains pressure hot water cylinder.

I have needed to top up the pressurized heat system about 2-3 times a year via the balance pipe. I never top up above 1.4 bar.

The unreg output is easy to identify but which of the two regulated outputs is 3 bar and which is 4.5 bar?

I have needed to top up the pressurized heat system about 2-3 times a year via the balance pipe. I never top up above 1.4 bar.

Is the overflow caused just by the mains supply variation, or could the safety valve be too weak, or some other problem?

 

[ShaunCorbs]

When was your unvented cylinder last serviced should be yearly

 

[benawhile]

When was your unvented cylinder last serviced should be yearly

I didn't know that, it's never been serviced in 3 years. FWIW it has always banged when water is first run, I was going to ask this next, but the installer said it was nothing to worry about. He restricted the supply but it made no difference.

 

[benawhile]

I will arrange a service tomorrow

 

[ShaunCorbs]

I will arrange a service tomorrow

They need to hold there g3 certificate eg unvented certified etc