Going gravity to unvented, but also with Aga heat?

[locoloic]

Hi all,
Current water system is a borehole going to a gravity system. Cold water tank in the loft, a vented hot water cylinder on the first floor, and an Aga on the ground floor. The Aga has a water heat exchanger, and passively heats the hot water tank (i.e. no pumps - just by convection). In the summer when the Aga is off, we just rely on the electrical immersion heater for our hot water.

We've got the opportunity to go onto mains water, so I'm looking to move to an unvented system, and ideallly, I'd like to put the new hot water cylinder in the loft, freeing up a lot of room in the airing cupboard. However, I'd still like to have the Aga heat the hot water in winter, since it's on anyway.

So, my thoughts are to buy an indirect hot water tank which also has a couple of immersion heaters for the summer. There's room to get one in the loft, and weight will be similar to current water tank.

I'd like to extend the pipes to the Aga up to the loft, and maybe use a small open water tank to create a heating circuit for the Aga hot water system. I.e. currently the hot water going through the Aga is what comes out the tap, but I'm thinking of a closed system for heat transfer only, with some inhibitor in it, as you would have on a central heating system. I'd still have it passive, so no pump or anything.

Basic diagram of current and proposed system attached.

Any thoughts or recommendations very much appreciated!

 

[flameport]

What is the fuel source for the Aga?

 

[locoloic]

It’s oil fired.
Water jacket was leaking last year, so I ended up overhauling the whole aga. All the pipe work and internals are new or refreshed. I’m keen on keeping it going a few more years...

Separately, I also have oil fired central heating.

Cheers

 

[locoloic]

For future interested people, it seems you can't connect an Aga to an unvented tank:
http://www.tncook.co.uk/AGA_hot_water.html

So, I'm going to need to go fully electric water heating, and remove the water boiler from inside the Aga (frustratingly I only replaced it last year costing a couple hundred pounds).
On the plus side, the Aga should use 30-50% less fuel.

Cheers all.

 

[ianmcd]

Not true, an oil or gas AGA can be used in conjunction with an unvented cylinder, but has to be done by a professional , definitely not a DIY job

 

[dilalio]

For future interested people, it seems you can't connect an Aga to an unvented tank:
http://www.tncook.co.uk/AGA_hot_water.html

So, I'm going to need to go fully electric water heating, and remove the water boiler from inside the Aga (frustratingly I only replaced it last year costing a couple hundred pounds).
On the plus side, the Aga should use 30-50% less fuel.

Cheers all.

Erm... You might want to delete that attached file from your post!

 

[locoloic]

Thanks all. I think with the extra pipe work, general inefficiency of the aga and heat loss in pipes, etc it’s going to be best to go for a direct heat electric HW unit in the loft, and just cap off the pipe work for the aga, and remove the boiler. Less to service and go wrong, cheaper, and more efficient!

 

[dilalio]

Thanks all. I think with the extra pipe work, general inefficiency of the aga and heat loss in pipes, etc it’s going to be best to go for a direct heat electric HW unit in the loft, and just cap off the pipe work for the aga, and remove the boiler. Less to service and go wrong, cheaper, and more efficient!

Apart from the cost of leccie vs oil per kw/hr. Might want to do the maths on that first. Might be different in your neck of the woods.

 

[oilboffin]

You may be able to use a neutraliser in the system but they are very complicated things they are
made by dunsleys we use them quite a bit up here but you will need a diagram from them how
to plumb it.Bob