Six reasons not to install a thermal store...

tom.harrigan · 2008-12-02T15:35:58+00:00

I was going to buy a thermal store and heat it with a woodburner. Iplanned for it to deliver hot water and perhaps pump the centralheating from it - though this could be pumped directly from the stoveif it had enough connections. I don't have oil or gas and would preferto keep it that way, but decided to plan for an oil boiler in thefuture if necessary.The bad news is:1. Thermal stores need to be maintained at a high temperature (70 -90degrees) according to manufacturers. This is bad news for heat loss,and makes the utilisation of a future condensing boiler problematic.2. The operating range of temperatures for hot water is quite small(~20 degrees) which means they can't produce as much hot water as youmight hope without frequent input from a boiler.3. Your typical (say 250l) thermal store will not stratify - thewater inside will mix through conduction and convection, particularlyif the heat exchanger is internal. This is in contrast to an unventedtank, with fresh cold water comming in from the bottom.4. Although they don't require an annual inspection, neither dounvented cylinders, so this isn't a benefit.5. You can incorporate multiple heat sources with a thermal store, butyou can do that with a sealed system as well - again no benefit.6. You can't put radiators and store anywhere - you can with a sealedsystem.The good news:1. You don't have to involve building control with a thermal store.So, I've decided on a sealed system and unvented tank powered by amultifuel stove, to which I can add an oil boiler (which willcondense) when I get too old to carry logs.T

Dec 02, 2008 24 Replies

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Doctor Drivel 17 years ago

Because the installer self certifies the installation

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tom.harrigan 17 years ago

I agree. I said there was involvement, but didn't claim it to be onerous!

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Andy Dingley 17 years ago

Apart from that whole "pressure" thing.

And the "few bits" being quite a few, and quite complicated.

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Doctor Drivel 17 years ago

A basic thermal store is not complicated at all.

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Doctor Drivel 17 years ago

To those who think condesning boilers can't be used because the stores always 80C and all of it top to bottom, look hard.

On-line temps, in real time, of a heat bank system:

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