Venting a non vented tank

[smellmyhamster]

Hello all
Is there any reason why I couldn't convert a non vented thermal store to a vented version by removing the AAV on top of the tank and replacing it with a header tank?

 

[SimonG]

Got a picture of the tank?
What's feeding the tank? Heat wise.

 

[smellmyhamster]

To be heated by a back boiler of a log burner, I don't fancy a pressurised system

 

[SimonG]

You cant have an unvented anything off of an uncontrolled heat source.

 

[Ric2013]

Nah, I the OP's thinking alternative technology. Can he convert the unvented cylinder into an unvented cylinder by plumbing it in as if it were a vented cylinder? I.e. taking the pressure out of the equation entirely.

But, looking at the link and the OP's actual wording, what he's linked us to is not an unvented cylinder at all... it's a thermal store, so the PRIMARY would have to be vented rather than the secondary. It's not a G3 item and the 28mm tappings mean it should gravity feed perfectly well. So my feeling is provided he fits his backboiler with the correct vent and feed arrangements, it might not be a problem. What I would suggest though is he contact the manufacturer and see if the insulation etc. will cope with potentially boiling or near-boiling water which is always possibile with a woodburning stove (though risk is mitigated with a heat-leak radiator correctly sized).

My concern is, though, the OP doesn't really understand what he's doing. Why would he remove the AAV? Please talk - a little knowledge can be dangerous...

 

[siricosm]

Why would he remove the AAV?

I think he wants to put the header tank there. I wonder how big the connection is on the top, I suppose if it is too small, the vent could be piped in from the boiler loop. I would just call them and ask, maybe they sell a similar version with a built in header tank.

May I ask what that tank costs? I like that the plate exchanger sits inside, that has to reduce heat loss, but can it be replaced it if it goes wrong?

 

[Ric2013]

I think he wants to put the header tank there. I wonder how big the connection is on the top, I suppose if it is too small, the vent could be piped in from the boiler loop.

I agree that's probably his thinking, but it makes me think he's looking at it as if it were a vented cylinder which needs the vent on the top. This being a thermal store, I would certainly be using the boiler loop for the vent and I can't really see why this would be a problem. Hence my concern he may not quite know what he's doing which is a concern if the plan is to install a woodburning stove without notifying to Building Control. If he knows what he's doing and does it right, I don't really care if he notifies or not!