CH gurgling & bangs

[TBast]

Morning all.

Just spent the weekend draining my central heating and installing an extra radiator. Completely drained the system in my bungalow before fitting the extra pipework and connecting the new rad up.
Whilst the system was drained I took the opportunity to clean the PRV and pressure gauge (which were both full of gunk) Have suspected the expansion vessel to be knackered for some time (had to regularly top the system up) so while the system was empty checked it for pressure, a small amount of air came out. So following the instructions on here, used a bike pump to increase the pressure in it, then refilled the entire CH system. Bled the pump and all the rads. Everything appears to be working, rads are all good and hot, PRV doesn't drip and pressure doesn't shoot up between the system being cold and hot.

But as of this morning, noticed upon firing up the sound of rushing water and bangs from the boiler (Worscester 24i RSF combi) not everytime it fired, and would die down after 5 seconds. Suspect it's air in the system, but not sure where to go from here. Obvious ones to check are bleeding the rads and make sure the new pipework isn't leaking. If the expansion vessel is knackered, is it possible that any air I've pumped into it, could now be getting into the system, and if so, am I better off just letting the pressure out of the vessel and relying on topping the system up regularly (I'm planning on replacing the boiler in the next few months, so this would only be a temporary solution)

Any suggestions would be much appreciated

 

[ianmcd]

its just trapped air and nothing to do with the expansion vessel, it will work its self to the top of some rads and you can just bleed them nothing to worry about, check that the cap on the automatic air vent on your boiler is open , its just like a dust cap on a car tyre valve

 

[TBast]

Thanks for your reply Ian, after a quick look online, it appears the automatic air vent is within the boiler itself, so will have a look this afternoon.

 

[ianmcd]

yes it is within the boiler and they leak for fun so lots of them have the cap screwed down to stop them leaking with the intention of replacing the valve but just get left with the cap screwed down

 

[TBast]

So yeah the cap had been screwed down...and after loosening it and firing the system, I found out why...ha great.

So just to add to this, every time the boiler would fire, there would be the sound of rushing water, a few big bangs, the pressure would spike and the boiler would automatically cut off. Eventually got the system running, after releasing some of the pressure from the Expansion vessel (seemed to be the only thing to stop it from cutting out), then tonight, after running the shower for 10 minutes. The usual noise of running water and 5 big bangs a load of water dumped through the PRV and cut off again. Can't help but be a bit worried by this. :/

 

[terryplumb]

If you have used the exp vessel to reduce pressure in the system by letting air out of it ,you have now caused the prv to operate !!