Ravenheat rsf 820/20 possible prv problem

Hi all,

I've signed up as i think i have a problem with the prv on the above boiler. Basically last night my pilot light went out, had a look and the pressure was 0, so i fired up pilot light and topped the water up, albeit to pretty much nearly 3 bar by accident. didn't think anymore of it until this morning when the heating came on and it wasn't very hot, and saw the pressure was just over 1 bar with it on.

I switched it off and got my fiancee to check it when it was cold and the pressure was 0 again. She topped it back up at lunch, popped the heating on for lunch, then switched it off and when we came home after work it was 0 again.

Topped up to 1.5 bar and after 10 minutes it showed 3 bar so i emptied some water from one of the radiators until it was back down to around 1.5 bar but again after 10-20 mins it was back up, albeit not as much. being a tad frustrated i flicked through the installation manual in front of the boiler and after 5 mins or so the pressure had dropped nearly half a bar.

Checking the pipe which goes outside from the prv it is dripping constantly, not every now and then but constant, which would explain why i'm losing water very quickly.

So the question is, is this the sign of a knackered prv or something more? would the boiler going out cause the pressure to drop to 0, or should i have waited longer after firing it back up to see if the pressure would rise before topping up and inadvertantly adding a lot more water than was needed causing the prv to open and said problem occuring?

Sorry for the long post but want to make sure.

i don't know if this is of any relevance but the pipe that comes out of the prv is quite hot when the boiler is heating water, would this indicate that the pvr hasn't closed properly? could it also be the expansion vessel, or would there be different symptons, as the hot water and heating works fine, just keep losing water/pressure.

Hi the 820/20 boiler pilot will go out as it is coupled to the overheat stat
so as the water has drained from the boiler it will produce steam in the heat exchanger then it will go into over heat mode
it sounds like you could have a problem with the expansion vessel
in the rear of the boiler if there is when the boiler is working there is nowhere for the water to expand so it goes over 3 bar and discharges out the p r v, and as its an old boiler and an old system debris will settle on the rubber washer in the valve, so firsty just replace the valve and the refill
to do this you will need to turn off the iso valves but beware they always leak and sometimes cure themselves once turned back on and heated up
if i was you as it is drained down check out the pressure in the expansion vessel it should be about 0,7 bar

best of luck mick

gasmick2 said:

Hi the 820/20 boiler pilot will go out as it is coupled to the overheat stat
so as the water has drained from the boiler it will produce steam in the heat exchanger then it will go into over heat mode
it sounds like you could have a problem with the expansion vessel
in the rear of the boiler if there is when the boiler is working there is nowhere for the water to expand so it goes over 3 bar and discharges out the p r v, and as its an old boiler and an old system debris will settle on the rubber washer in the valve, so firsty just replace the valve and the refill
to do this you will need to turn off the iso valves but beware they always leak and sometimes cure themselves once turned back on and heated up
if i was you as it is drained down check out the pressure in the expansion vessel it should be about 0,7 bar

best of luck mick

Click to expand...

cheers mick.

i have also noticed that overnight the pressure goes up, yesterday for example i manually opened the prv and emptied it. i filled it up to 1.3 bar and it rose a little then dropped to just under 1. put the heating on and switched it off overnight and this morning the pressure was up to over 2 bar. signs of a knackered expansion vessel?

Hi if the pressure rises then the fill up loop must be passing through meaning the tap is not turning off fully
By the way the fill up loop should not be left connected owing to cross contamination could happen as it is connected to the heating pipe and could get the heating water back into the drinking water try removing it after you have set it to 1 bar then leave it overnight
If it stll rises then its a heat exchanger fault
If you have been opening the prv then it will need replacing as i have said before dirt gets on the seating they can be taken to bits and cleaned if you are carefull but its easier to replace
mick