AAV On Grant Combi 90 MK2

[jimjones235]

The AAV on my Grant Combi is blocked - so I keep getting air in the system, then it over heats.

I've got a replacement AAV, presumably the old one just unscrews and new one screws in (once the system is drained obviously)?

Does it need any kind of seal on the thread, or are the washers on the new part sufficient?

 

[simond]

I would PTFE or similar as it takes ages to drain it all down again/fill up.

NB: You shouldn't be getting lots of air, so that is where you should be concentrating your efforts.

 

[jimjones235]

Thanks - I realise that about the air in the system.... but we're undergoing a house renovation so have had to drain the system down a few times, and everytime we refill we get an airlock in the boiler itself as the AAV has seized - the last time we had to crack the existing AAV which thankfully resealed, but I wouldn't want to keep repeating that....

 

[leakydave]

They can be a total pain to actually get at. I once broke the soldered joint on the pipework changing an AAV on a Grant Combi. Luckily I was able to solder it up. I know use a spanner on the brass bush that the AAV screws into and one of these:-

http://www.reginproducts.co.uk/specialist+tools/REGT30

 

[Boilerman2]

You DO NOT NEED to drain the boiler down, simply discharge the system pressure to Zero by operating the pressure relief valve once the system is at zero you can simply whip out the old AAV in wind in a new one it'll take 5mins maximum!

 

[slapper]

Tis fatal to drain thru PRV, especially if theres carp in the system. Valve probably wont reseat itself on fill up.

 

[simond]

Yep, better order a PRV along with the AAV if you are going to do that.

 

[Boilerman2]

I seldom have problems with Grant PRV's not seating it is a bigger problem with boilers with the valve at the bottom such as the Wallstar combi, or most gas versions!