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Author Topic: Home made Thermal store  (Read 16471 times)
Jonah
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« on: September 22, 2011, 11:52:38 AM »

Ok guys, I've got all my padding on ready to take a load of abuse but...

   Can I make my own thermal store from an Ibc tank and a load of 100mm celotex? We have a Rayburn in the kitchen which will burn most of the time through the winter and a combi that currently does the heating and hot water.  What I fancy doing is using the Ibc as a store with whatever amount of water works best for the Rayburn (250l or 750l or somewhere inbetween) just to heat the rads to wake up warm in the mornings without spending a fortune on gas (50 per week last winter) the water can still be done by combi, all rads are on a single level so presume I can just mount the Ibc above this level and pump around rads, Rayburn can the feed Ibc via gravity, timer on the pump...  Job done? No? As it's a 1000l Ibc with a max of 750l if I just vent from the top expansion shouldnt be an issue.

  What you all thing?
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Philip R
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« Reply #1 on: September 22, 2011, 12:04:17 PM »

Good idea, needs some more thought regarding seperation of the two systems.

Do not get the water hot or the HDPE will ooze through the steel cage and you will have a hot puddle outside you house with potential for damaging your brickwork. OK for low grade heat, but not higher temperatures.

The other problem is that the system will not be oxygen tight. Oxygen will permeate through the IBC wall and your radiators will rust away, then the water, hundreds of litres of the wretched rusty water will pour throgh your house if a radiator leaks.

Like the idea, need to get away from Mega priced thermal stores.

PhilipR

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2807
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« Reply #2 on: September 22, 2011, 01:33:19 PM »


   Can I make my own thermal store from an Ibc tank and a load of 100mm celotex?


Should be no problem at all, I have one of these under a lean-to outside the back of my house.

It is used as a thermal store in the true sense of the word, as I chucked 100M of 22mm plastic pipe in it to use as the heat exchanger.

The water in the 22mm pipe circulates through the manifolds of 96 58mm evac tubes and 180 47mm evac tubes and via a system of valves, the water can be used either to heat the thermal store for use after dark or the radiators directly when it is overcast.

I have had the water in the IBC upto 60 degrees with no problems.

2807
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longstroke
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« Reply #3 on: September 22, 2011, 06:56:23 PM »

Hi,
Just checking - Is your Rayburn a solid fuel type? And does it have the 'back boiler' built in?
If the Rayburn is solid fuel, it would be classed as an uncontrolled heat source which may not be the best thing to connect to a plastic IBC.

It may be worth checking the rayburns boiler is watertight before investing further.

IIRC a Combi boiler normally runs a pressurised radiator ciruit? This would make it difficult to connect the IBC heat store to the radiators without a heat exchanger, power operated valves and 2 (probably) pumps.


Thinking about the heat store which was your original question - 100mm of insulation is good for a start, ideally you then want to at least double that thickness and prevent any convection loss by ensuring no air flow through insulation is possible. (We have a thermal store outside with 100mm standard manufacturers insulation and the heat loss is huge)
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Jonah
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« Reply #4 on: September 22, 2011, 09:59:37 PM »

Thanks for that, the Rayburn is solid fuel and I have a new boiler to replace the Broken one in it.

I'm going to disconnect the combi from the radiators completely and was hoping to just use the Rayburn for heating but if needed I can keep one rad connected just to exercise the combi.

With the thermal store issues can anybody think of a vessel that could be used? 200mm isn't a problem really, would an air gap between both be better than 2x100mm together?

Phillip, is there a level that hdpe is safe to? How does a normal system deal with the oxygen thingy? I haven't come across this before. I have a 2300l diesel tank here but think it's too big for the Rayburn and losses and would really like something tall with small footprint rather than short with big footprint.

Thanks

Marc


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Jonah
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« Reply #5 on: September 22, 2011, 10:11:27 PM »

What about a 200 gallon aluminium lorry diesel tank? Not the ideal shape but waterproof?Huh
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longstroke
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« Reply #6 on: September 24, 2011, 03:38:48 PM »

An aluminium tank should work fine so long as there are no issues with having steel rads, copper piping and an ally tank. Whether for this it would be best to have everything bonded to the same earth value, or whether you would be better electrically isolating the ally tank I'm not sure.
Google on dissimilar metals electrolytic reactions or await someone more intelligent on that one!

If you used copper piping between the Rayburn and store it will take the temperature better than plastic. Then as you mentioned previously if you are disconnecting the rads from the combi boiler just connect them to the store with a pump inline, you could get into loading valves, and unloading valves but these (thermovar type valves) would cost around 70 a go and would overly complicate a potentially simple system.

If you are happy with your aim of providing some heating in the morning then allowing the rayburn to heat the store via a cold out the bottom (of the store) to the rayburn and a hot in connection near the top of the store would heat the tank from the top to the bottom, possibly with a division between hot water at the top and cold at the bottom unless the flow was high enough to destroy the stratification.
Whether it stratifies whilst standing over night is something of a mystery to me.
However, in the morning when your pump cuts in it will be pumping the hot from the top and returning to the bottom which would quickly destroy any stratification and mean you end up with a tank of warm water being circulated through the rads.
This is where a unloading valve would have the benefit on only taking the hotest water as needed to maintain the rads temperature, rather than a one shot system.

As you don't have a coil in the tank the heating circuit would need a gravity tank fitting and the thermal store being used as a totally sealed tank unless the thermal store was above the highest rad.

I hope this hasn't totally confused you?
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Philip R
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« Reply #7 on: September 25, 2011, 01:26:09 AM »

Aluminium is used in some condensing boiler heat exchangers, eg, Wrcester Bosch, some Glowworms.The use of an ally tank therfore should not be an issue. The use of a suitable aluminium inhibitor will help.

You could use some Hep20 or Speedfit to form a galvanic break between dissimilar metals. Just do not let the temperature get to high. Polyhene for cable insulation is rated to 90 degC conductor temperature, so will start to soften. Much warmer and it will boil, not good for a cubic plastic vessel.(IBC)
PhilipR
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Countrypaul
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« Reply #8 on: September 25, 2011, 08:52:50 AM »

I believe some copper hot water tanks ahve aluminium sacrificial anodes (cathodes?) in them. This suggest mixing copper and aluminium may not be straightforward. It may be that the boilers have a different aluminium alloy, and what alloy exactly a aluminium tank would be made of may be a challenge to find out.

Paul
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renewablejohn
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« Reply #9 on: September 25, 2011, 09:42:41 AM »

You can pick up 250L steel drums for under 10 each and have no worries of how high the temperature gets. Just put in a rust prohibitor or paint the inside with a waterproof system.
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knighty
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« Reply #10 on: September 25, 2011, 12:27:45 PM »

I pump hot lard into IBSs at work.... normally at 120'C+

we try to let them stand to cool before we move them, as the plastic is a bit soft so bumping them around with the forklift isn't a good idea....

but we've never had one leak on us,....
(apart from a few ibc's which have been delivered with holes in them, doh!)


if you put a coil of pipe inside it to transfer heat over to the radiators instead of using the heat directly, you can get past the problem of corrosion in the radiators etc... and you can also leave your combi boiler connected... that way you can always use it as a backup if needed :-)


and a good dose of antifreez in the ibc should stop any corrosion inside the ray burn and deal with the oxygen problem :-)
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Jonah
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« Reply #11 on: September 27, 2011, 03:00:34 PM »

I think renewable john and mr knightly win, I'm going for the all new TEXACO thermal store...   I'm going to try welding 2 together to raise the capacity a bit.

Do you think a coil made from 22mm copper will be ok for this? For the radiator coil...  Water in tank is heated directly from boiler and what length do you think will be best?

Should I disconnect from combi or leave connected?

Thanks all

Marc
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Jonah
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« Reply #12 on: September 27, 2011, 03:06:39 PM »

Im also thinking of trying not to use an f&e tank, do you think it's possible to just leave enough empty space in the tank with a safe 22mm vent pipe on the top and the coil sat down from the top of the water although it's a cold coil so could be placed slighty above water line when cold as the coil is pumped to.
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renewablejohn
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« Reply #13 on: September 27, 2011, 04:10:28 PM »

I'm going for the all new TEXACO thermal store...   I'm going to try welding 2 together to raise the capacity a bit.


Thanks all

Marc

If you are going to use a drum that has previously had oil or any sort of flammables in it make sure it is totally clean before you start welding because they do make very good bombs.
Why not just stack on top of each other and connect with large diameter pipe.
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wookey
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« Reply #14 on: September 27, 2011, 09:33:32 PM »

Jonah - yes you can simply have a space in the top of the tank instead of an F&E tank. DPS made a tank like that, that you simply filled with a hose.
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Wookey
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