Leaking Pressure Release Value

[Poisonata]

I have a long standing issue with my combi boiler, a Ravenheat RSF 820/20 which I guess is 10 years old now. Over the years I have successfully replaced many parts HOWEVER one issue remains.

The 3 bar pressure release value leaks even at pressures below 1 bar. This I do not understand as the part is fairly new and is one of 3 I have fitted all of which seem to suffer the same fate.

For example, I decided that maybe the issue was with the water pressure gauge giving faulty readings. This I replaced having released the excess pressure from the system first using the pressure release valve. I then repressurised the system to 1 bar and the pressure release valve just slowly let the water trickle out of the overflow until the pressure dropped to nothing.

What I am missing here ? The valves are new and the issue persists with more than one of them. The pressure is correct, there isn't a faultly reading. Sometimes if left a while the pressure remains stable, then it drops right down. I repressurise the system only to find the next day the reading is now closer to 2 bar.

I might add that all adjustments are done when the system is cold and the heating has been off all day to avoid hot water influencing the readings.

Something is fundamentally wrong here and its driving me mad. Anyone any idea ?

 

[Rob]

Either filling loop is letting by, Guage is faulty or HE is passing.

 

[Poisonata]

Right thats interesting, the filling loop has never been removed so this is something I need to investigate. I know the gauge is correct as it's brand new.
Could you explain what you mean by HE is passing, I don't understand this.
Many thanks btw for replying.

 

[Rob]

You'll either have a plate HE or a four pipe. Its possible the plate HE is split inside and mains water is getting into the CH system. Its unlikely. Would check the filling loop first!

 

[Poisonata]

Guess what, the filling loop valves at both ends are leaking. The mains inlet valve even at the off position lets through a steady drip drip of water. The inlet valve at the central heating end (seems to be some sort of one way valve) is also leaking.

Thanks very much, I will see about getting these replaced.

Final question, I understand now that these leaky valves are causing the pressure to become unstable. However what bearing do these have on my pressure release valve still allowing water to be released even at pressures of less than 1 bar. Or does it need to 'bed in' and settle before it becomes stable.

Thanks alot rob884 really helped me out here.

 

[kevplumb]

For example, I decided that maybe the issue was with the water pressure gauge giving faulty readings. This I replaced having released the excess pressure from the system first using the pressure release valve.

don't use the prv you will get crud under the seat and cause the drips

 

[Poisonata]

Right now I understand. I will replace the PRV again and this time not use it to drain the system. There is an alternative way to drain the system via a tap, my own fault really. Thanks alot for pointing this out.

 

[Gasguru]

As said before the PRV is not a drain valve.

Disconnect the filling loop after use and cap off the fittings.

I can guarantee the boiler expansion vessel will be flat. Its quite possible the pressure rises to 3 Bar when the heating cuts in causing water loss from the PRV. Unless you are lucky (sufficient LHS clearance to re-inflate the vessel) you need to plumb in an additional expansion vessel.

And for reference its a bithermal heat exchanger.