Ravenheat Whitestar Combi

29 Dec 2008
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United Kingdom
Hi, I'm having trouble with my boiler, a Ravenheat Whitestar combi - non condensing. The boiler keeps losing pressure and needs topping up once a day now. When it's running the pressure increases to 3.5 bar and then I suspect the PRV opens and releases water - but I've never actually seen this. There was no air in the expansion vessel, so I topped it up. When doing this the gauge on the boiler went up as I pumped, should it do that? I also tried pressurising the boiler to 2.5 bar then closing off the supply and return valves when cold. 8 hours later the boiler side had dropped 0.5 bar and the pipework 0.25 bar. Any ideas as to what's going on please?

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read the FAQs and follow TO THE LETTER, post back when you have done this

Good call GG ;)


Turn the boiler off at the mains.

Find the PV valve which looks like a car tyre valve with just a threaded part sticking out and is often red. They can be accessed from the top of the boiler or behind the front drop-panel. Some boilers such as Ravenheat can be impossible to access!

If water comes out when you press the central pin, you need a new PV

Drain enough water from the system to drop pressure to Zero. Drain an extra 10 litres of water out, or leave the draincock open if none will come. This may draw air into the system.
Use any (car or bike)air pump to pump up the PV to eg 10 psi (0.7 bar).

Remove and refit pump to see how much pressure drops when you remove it and inevitably lose some air.
If the pump doesn't have a built in gauge, pump it up a bit high, then keep taking readings with a push-on gauge. Every time you do, the pressure will drop a bit.

During this phase it is IMPERATIVE that water or air is allowed to escape from the heating system as it is pumped out of the PV. Otherwise system pressure will resist your pumping and give a meaningless reading.
If you aren't sure, let some more water out when you have the air pressure at the right level. If that makes the air pressure drop, pump a bit more and release water and so on, until it doesn't.

The PV may be say 10 litres. If it was full of water you have to displace all of that water from the system side by your pumping up the air in the vessel. That's a whole bucket of water!

Top boiler pressure back up to 1 bar and switch boiler back on.

Some air may have got into the system so you should bleed rads too and then recheck the pressure.

DO NOT let water into a hot boiler. Let it cool first.

DO NOT let water in too quickly. 20 seconds for 0.5 to 1 bar should be OK.

DO NOT take the pressure above 1.5 bar- even if the system is warm as the switch may have stuck.

DO NOT allow the pressure to go too high when refilling Turn it off early to see if the gauge keeps rising a bit.

NEVER use the Pressure Relief Valve to let water out of a system – it will leak afterwards!
OK, thanks. I've got a better feel for what I need to do now. I'll try tomorrow and let you know how I get on.

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After pumping air into the expansion vessel - with the drain cock open, all is well. The boiler has run flawlessly for two weeks now.

Thanks for your help!

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