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Hot water cylinder with wood + sun

Posted: Wed Dec 05, 2007 1:33 pm
by Diana
We've got a low roof and our current hot water cyclinder is fitted on it's side.

We'd like to have a combination of solar and wood burning in a duel coil tank system. Does anyone know if these tanks can be fitted on their sides or if there's an alternative for height restricted places?


Posted: Wed Dec 05, 2007 6:21 pm
by snapdragon
these chaps might have an idea

Posted: Thu Dec 06, 2007 7:56 am
by Diana
Thank, I'll give them a shout.

Posted: Thu Dec 06, 2007 8:44 am
by Martin
yes it's eminently possible, you just order the appropriate thermal store - I really wouldn't bother with "neutralisers", they're a rather old-fashioned and expensive way of doing things - a properly designed tank has all the coils built-in. We use Newark, who produce some of the best :wink:

Posted: Thu Dec 06, 2007 9:26 am
by Diana
Sorry for the ignorance Martin, but thermal store?

Can the tanks with the twin cores (for both solar and other heat imput) be used on their sides?

Posted: Thu Dec 06, 2007 9:35 am
by Martin
you have to be careful because they use "stratification" (layers), so if you just turn an "upright" one on it's side, it won't work too well! :wink:
I'd suggest having a natter with Newark (they list horizontal units) :cooldude:

Posted: Fri Dec 07, 2007 3:56 pm
by Diana
Thanks Martin

Posted: Sat Dec 08, 2007 2:38 am
by Muddypause
As Martin says, with a conventional cylinder, stratification is the issue. You can put a conventional cylinder on it's side, but it's really not designed for it.

Most HW cylinders have the hot water draw-off at the top, because that's where the hottest water will be. You could fit a flange on the side of the tank so that it is at the top when the tank is on its side, but many modern tanks also have an internal diffuser on the cold inlet at the bottom of the tank to reduce turbulence and mixing of the stratified water. Putting the tank on its side will negate this. And I doubt that any coils in the tank will be able to work at their optimum because they will be at 90 degrees to the strata of the water.

Also, if you are using a wood burner as a heat source, you must have an open vented system, and this means having a header tank higher up than the cylinder. For this reason it is very unusual to have a hot water tank in the attic. The need for a header tank will be true for a thermal store, too (or at least the circuit from the wood burner), so you may need to do some careful planning over this.

Posted: Sun Dec 09, 2007 9:20 am
by Diana
Thanks for the info Stew.

I'm pretty sure our current cylinder is not designed to be horizontal (judging by the water temp :roll: ) and that it also has a header tank. So long as the header tank doesn't have to be a vast distance above the cylinder, then we should be OK. Absolutely no room to have the tanks anywhere in the house - they have to be in the loft (OH, for an airing cupboard...)

Posted: Sun Dec 09, 2007 11:23 am
by Stonehead
Diana wrote:Absolutely no room to have the tanks anywhere in the house - they have to be in the loft (OH, for an airing cupboard...)
Our house has the HW tank in what looks like a kitchen cupboard, but just around the corner into the dining room. It's not big enough to be an airing cupboard (sadly), but the HW tank just fits while the header tank is immediately above it in the loft.

When we bought the place, water pressure was almost non-existent but by lifting the header tank as high as it could go into the roof space (about 12 inches higher than before) we now have just enough pressure for a shower or to use the washing machine or to use the kitchen sink - but not two or three of those at the same time.

Another possibility is to put the HW tank in an insulated lean-to outside the house. I saw this done on two small croft houses that we considered buying before we bought our place. The header tank was in the loft against a gable wall with pipes passing down and then through the gable into the lean-to, then from the lean-to into the house.

The owner of one of the houses said thick insulation was critical in Scottish winters. He had a thermal store in the lean-to, with the store then covered with an insulating blanket. The lean-to had cavity walls with insulation in the cavity, plus another 100mm of insulation lining the inside of the lean-to.

The owner said that in winter, with the fire out, they were only suffering a three or four degree temperature drop overnight. (They had solid fuel, solar, and a dump from a wind turbine.)

Posted: Sun Dec 09, 2007 11:56 am
by Diana
Thanks Stoney. We are considering and outside boiler house so I guess if we went that route we could have a tank in there too. Hadn't realised the header tank was the key to pressure - had assumed it was the height of the cylinder.

Your house is somewhat larger than ours, so an additional interior cupboard isn't an option for us.

Posted: Mon Dec 10, 2007 9:54 pm
by Muddypause
One of the advantages of a thermal store is that the hot water which comes out of the tap is linked directly to the water mains, and is at mains water pressure. In this case, the small header tank is there just to keep the circuit that goes to the boiler/etc topped up and vented - like a central heating header tank. Sometimes this header tank is part of the thermal store, and sits right on top of the main tank. But there are variations on this theme.

With a conventional hot water tank, then Stoney's right, the higher the (larger) cold water tank the better. The location of the hot tank itself is less critical.