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Author Topic: Store Volume v Insulation.  (Read 1956 times)
Stochengberge
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« on: June 11, 2012, 08:25:08 PM »

At last making proper headway and getting final quotes for the small thermal store / buffer vessel for my WBS project.

And then a supplier throws a spanner in the works... Undecided
The hole the cylinder has got to fit in is only so big. WBS with 8kW to water.
If I have what is the pretty well standard 50mm insulation, I get 145litres capacity, but if I drop this down to 25mm, I get 200litres - a 38% increase in volume!!!

The standard answer for a Thermal Store always seems to be "as big as possible" - but at what cost? The cylinder will be boxed in, in a cupboard, which would help negate the heat loss.

So, the question is in the title - do I go for volume or insulation?

Cheers,

SB.

More details at:- http://www.navitron.org.uk/forum/index.php/topic,17325.0.html
I've gone for the store option!!!!
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On the North Downs of Kent with 3.2kWp facing 12' west of south @ 33', 36 x 58mm Thermal tubes on an east / west split, 300ltr triple coil DHWC and an 8kW to water WBS.
Countrypaul
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« Reply #1 on: June 11, 2012, 11:16:56 PM »

The way you describe things suggest that the choice is for conventional round cylinders. Given that it will be boxed in, is there any scope for a square one which might make better use of the space and give you both the volume and the insulation?

Paul
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wookey
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« Reply #2 on: June 12, 2012, 01:42:40 AM »

Some stores have removable insulation so you get the tank in, then slide the insulation over the top. You can buy a bare store, box it in and fill in your own insulation, which can give very good levels, but is a faff for maintenance. 50mm is an absolute minimum for store insulation IMHO. I would never fit less than 80mm, and preferably a lot more. Stores lose a lot of heat because they are hot.
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Wookey
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« Reply #3 on: June 12, 2012, 02:25:26 PM »

Wookey,
I agree with that but add that a lot is lost through the pipes by conduction.  Insulation does not help very much with this as it just allows the heat to conduct further down the pipe.  Ideally one needs a thermal break but at least plastic pipe will help.

Ken
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sbchapman
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« Reply #4 on: June 12, 2012, 03:45:44 PM »

Dumb question ... but can you go for a taller (and possibly smaller diameter) store?
This would give you double win - more storage with better insulation and better thermal stratification meaning the store would be more effective at providing hot water (relative to the overall volume) and allow better efficiency should you choose to install solar thermal. Tall and thin is good, short and fat is bad - sure there's a metaphor there somewhere Smiley

It might have a negative effect on WBS temperature and thus cleanburn leading to sooting etc. though ..
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Boilermate Thermal Store
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Stochengberge
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« Reply #5 on: June 12, 2012, 11:38:19 PM »

Thanks for the responses so far.

To try and answer some of the questions raised:-
Quote
Given that it will be boxed in, is there any scope for a square one which might make better use of the space and give you both the volume and the insulation?
Only that it seems they are considerably more expensive, but I get your point. I will look into this further tho'.

Quote
You can buy a bare store, box it in and fill in your own insulation, which can give very good levels, but is a faff for maintenance.
Hmm, 3 sides of the box are existing and I haven't got a mass of room behind the cylinder, so could easily end up with air gaps if the insulation doesn't drop down properly.

Quote
It might have a negative effect on WBS temperature and thus cleanburn leading to sooting etc. though ..
Anyone got any thoughts on this? I suppose with lots of stratification it could take longer for the return temperature to come up.

The space it has got to go in is only 450mmx500mmx1.8m...

Cheers,

SB.
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On the North Downs of Kent with 3.2kWp facing 12' west of south @ 33', 36 x 58mm Thermal tubes on an east / west split, 300ltr triple coil DHWC and an 8kW to water WBS.
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