Thermal Store Advice

[Taliz]

I am wanting some advice on Thermal stores.

Our old combi boiler has given up the ghost and I understand that this can be replaced with a system boiler in conjunction with a thermal store. My house has no header tank and no space for one so I believe I need an unvented cylinder.

I was looking at one of these,
http://www.advancedwater.co.uk/prod-480-088-2505.html
http://www.plumbnation.co.uk/site/g...vented-mains-pressure-thermal-store-cylinder/
my house has one bath and two showers. Does any one have any comments on these, or suggest an alternative (that’s no more money).

I do plan on getting solar panels in the future..
I am getting a wood burning stove with a back boiler, will this hook up to the thermal store ok? I was under the impression that wood burners can only work with open vented systems.

Any comments?

 

[flameport]

I was under the impression that wood burners can only work with open vented systems.

Correct, however a thermal store is NOT the same as an unvented cylinder.

Unvented cylinders connect to mains pressure cold water, the water in the cylinder is heated, and that heated water is what comes out of your taps.
These are unsuitable for solid fuel heating, as there is no way to reliably switch off the boiler when the temperature in the cylinder reaches it's maximum.

Thermal stores are vented, the water in the cylinder is heated but that water never moves. Hot water is provided by passing cold water through a coil inside the cylinder, where the stored heat is transferred to it. Some types have additional items such as an external heat exchanger and blending valve, but the principle is the same.

 

[Taliz]

I was under the impression that you can get open vented or unvented thermal stores, and that the water in the thermal store also rotates round the central heating loop.
Is this incorrect?

Because I am replacing a sealed combi boiler system, I assumed I had to get an unvented thermal store, hence my question about the wood burning stove.

Please clarify..

 

[gordonspants]

I've got an advance store, 2008 vintage, hence me typing this. Similar to the one you've linked to - and I'm very happy with it but haven't used it properly yet. Specced for a solar panel and a stove.
3 years on, no stove yet and my secondhand £70 solar flat panel was finally plumbed in on saturday and p ssed water out - it broken. Grr.

Stores can be vented with header tank - no good for you - or unvented ie a sealed system with a biggish expansion vessel.
There's also the terms direct and indirect - the rads, stove, boiler, solar and anything else can either be direct, using the same water as the store, or indirect, using a coil or plate heat exchanger to transfer the energy, separating the store water from the boiler/rads/whatever. Eg a solar coil.

Whether you can safely attach a stove to an unvented store depends on the stove and how you plumb it in.
You might have problems with a 'traditional' stove because that's also open vented and needs a header tank. You'd have to ask a hetas engineer what hetas recommend - I'm guessing open vented is all they're happy with. And possibly only on a vented store as well.

Some european stoves (eg greymetal) will work on pressurised systems and have quench coils within the stove water jacket - when the stove boils, a mechanical valve opens and cold mains water is flushed through the stove jacket and then to drain, cooling it down. They can run pumped-only because of this - no gravity feed to the store, and no header tank.
If the pump sending heat to the store fails - eg power cut - the quench coil will stop the stove boiling.

Linking a stove to a store needs a similar solution - if the stove overheats the store, there must be a way to dump the excess heat before it goes pop - so a heat dump radiator, quench coil within the store, or similar is needed.

The key with stoves is safety - they are uncontrollable - and unfortunately the UK is (generally) miles behind on stove technology, so you may struggle fitting a boiler stove without a header tank. Depending on the engineer.
The vast majority of plumbers will tell you to get a new system boiler, non-boiler stove and an unvented solar cylinder. That would be cheaper, and easier to get fitted, but if you want solar and more specifically a stove, want it all to integrate together and you're not planning on moving, go for it. You'll need to spend time finding a plumber who understands it all though. Navitron is a good start for research, erring towards mad scientist territory.
After three years of building, saving, underpinning, building, then saving some more, today I laid the hearth for my stove, on top of a new floor with some new underfloor heating pipes in it (but not under the hearth!). Plumber is here end of the week to start on the stove, so maybe I'll finally be able to use my store properly in the next few weeks.

 

[Taliz]

Thanks for the detailed reply. It has cleared up quite a few things..

I am building an extension at the mo and also considering linking up new underfloor heating in that part of the house. I shall speak to a few store manufacturers see if I can get it all worked out in my head.

Cheers