Hi Chris,

Jumping in a little late here - I have been off for a bit but thought I would check the new Green Building Magazine website out (which is looking really good I thought), and ended up back here at this very nice forum.

180l is a DHW cylinder, not a thermal store. Its not even a large DHW cylinder at that really.

On the flip side it should not take ages, or loads of fuel, to heat that volume of water up from cold - not sure where the installers got that from - unless your boiler stove is tiny of course. What is the stove spec?

Alternatives:

If your immersion element is high in the tank raise the temp if you can. Use mixer on DHW if worried about scalding, etc. Is there a lower port you could use for immersion so you can heat a greater volume of water?

Using the 180l DHW cylinder for heating is a non starter I am afraid. If the stove is high enough capacity you could add in a second very simple store just for heating and keep the 180l for DHW?

I have what i consider a slightly undersized thermal store - 1000lt - around 400lt dedicated to DHW. But our heating demand is pretty low - we only ever really need to hit 1hr boost if it gets a little nippy.

Pellet boilers are automated, respond fast and dRHI is still pretty good?

Gas boiler as already suggested?

As Peter points out the stove should have been fitted with priority to DHW really - heating the cylinder first, then heating. Same goes for a gas or pellet boiler.
So your current setup would appear to be 'upside down', unless you prefer a hot house to being able to shower! :)

Hope something there might be helpful.

Cheers

Sune

Sounds like a good plan.

Posted By: JonGWe use a product that is essentially a blend of prop and ethylene glycol that is classed as being detoxified, not sure how true this is or whether I can name it on here, but in tests it fattened the lab rats but didnt kill them.

It retains many of the preferred quality of a pure ethylene glycol.

Please mention it

Several months later...

I have got a small thermal store and no back-up gas, and was not advised by my fitter what the ramifications would be. But...

The crucial thing with these systems is that you can run them from solar as well as wood. I know you opted to leave that until later (I did too), but once it is done the whole thing becomes much more worthwhile. I recommend you prioritise this. And solar thermal is great (I was told even by the PV company that solar thermal is more efficient) and I don't think getting PV would do what you want. Even if you live somewhere really sunny, or have an entire roof of modules, I still wouldn't think you'd want to run your heating from electric.

We now run up to six radiators from our wood-burner, as well as having free hot water (previously our wood-burner didn't have a back boiler). When it's cold. we want to light the fire anyway. When it's hot, hopefully it is sunny, and we heat the water with sun - and don't need heating. Yes we may have to light the fire when it's not sunny, but really it is so quick. The only thing is chilly mornings before the first person gets up - but we had that previously anyway.
We have more than halved our electricity bill. It helps to have a nice lot of firewood - I have done a chainsaw course and this year have set myself the goal of not buying in any wood.

Our other bonus was being able to fit a nice shower - because we now have mains pressure hot water. In winter we do try to time our showers for when the fire is alight. The store keeps it pretty warm, but without sun it makes its 'funny noise' until we light the fire again.