Heat storage tank outdoors?

sandiapaul said:

Anyone? I know some here, notably nofossils, have done it.
I talked to Tarm the other day and mentioned it and was told "no way", I asked, surely one of their customers has done this, and was told not one that they knew of. They told me also they have a pressurized system in the works, for maybe Sept.

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My tank is inside the boiler room but is in a shed that isn't insulated. It is made out of walkin freezer panels. 4in foam. You can put the tank any place that will work for you but it will take insulation. How much? Mine has 4in foam and another 4in of fiberglass and I'm sure more would be better. I'm planning on changing my system to 4-500gal propane tanks and putting them against my house wall and will use the foam panels plus atleast 12in of fiberglass.
leaddog

So you are saying that 2000 gallons is an ideal amount of storage for you? Yeah, I am finaly a burning chunk.

Dunebilly said:

So you are saying that 2000 gallons is an ideal amount of storage for you? Yeah, I am finaly a burning chunk.

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That is what will work best for me for where I want to put them and my situation. I have a 16ft space between windows on my outside wall back side of my house that I can fit the tanks into. Any heat loss will go to that wall which isn't insulated the best anyway so I kill two birds with one stone. Plus I want my storage as close to my house as posible. That way I will only be pushing Hot water from my boiler underground when the boiler is running. 2000gal might be overkill for most people but that will also give me alittle more time if I'm gone that someone will have to feed the boiler.
leaddog

Hey leaddog, thanks for the info, roughly how big is your house? Are you using radiant floor heat?

I've been away - sorry not to reply sooner. I have an 880 gallon tank outside. I'd suggest 12" minimum on the sides and bottom, and 18" or more on the top. Keep in mind that the temperature difference is MUCH greater than between your living space and the outdoors.

I calculated that if I let my solar panels heat the storage tank in August, I could go away for the entire fall and winter, and the tank wouldn't freeze.

It sounds like your storage tank is above ground. I'm in the process of building a garage and space is a premium. I was wondering if it is possible to bury a propane tank underground and insulate it?

quinn0507 said:

It sounds like your storage tank is above ground. I'm in the process of building a garage and space is a premium. I was wondering if it is possible to bury a propane tank underground and insulate it?

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Yes, although it would be better to have a "basement" for the tank, so the insulation does not get wet, and the tank is accessible in case it eventually needs to be replaced.

sawdustburners said:

underground tank & EPA =sounds tricky.

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Propane tanks are no problem to bury. Oil tanks are the issue.

Joe

Thanks for responding.


Some of the other discussions recommended using 4 inches of corebond spray insulation, attaching a couple of annodes, putting down a layer of sand, providing adequete drainage and insuring that the tank was painted according to code. Do you have other suggestions or comments?

quinn0507 said:

Some of the other discussions recommended using 4 inches of corebond spray insulation, attaching a couple of annodes, putting down a layer of sand, providing adequete drainage and insuring that the tank was painted according to code. Do you have other suggestions or comments?

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My suggestion: there's no such thing as too much insulation. Personally, unless I could put 12" or so on it, I wouldn't bother burying it. Putting it in an attached shed and using more insulation would be better, since it avoids the trouble of burying and would give you better thermal performance.

Joe

sawdustburners said:

unless antifreeze is involved?

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Unless you're made of money, you don't antifreeze a thermal storage tank. You'd spend more than the cost of the tank, and antifreeze only lasts a couple years, typically.

In any case, heating system antifreeze (propylene glycol) is non-toxic, and does not pose any hazard. You can literally drink the stuff, in small quantities (it's in Dunkin' Donuts flavor syrups, among other food products).

Joe

Any thoughts on what it would cost to insulate the tank with 12" of foam?

Would I be better off to try and locate a 500 gallon tank that would fit inside?

Any thoughts on what it would cost to insulate the tank with 12” of foam?

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Spray foamers generally charge by the board foot. Times that by 12 for the thickness. Kaching
Will

You could always tell them you want 8 or 10 inches and ask them not to cut off the excess. When they sprayed the inside of my roof the foam expansion was difficult to control so they went beyond the amount I paid for then cut off the excess.

Not sure if this has been mentioned, but one advantage of having the storage outside is that if you use your wood boiler to heat your DHW in the summer, any heat lost from the tank won't be heating your house. Of course the same heat is lost in the winter, but at least there is a small advantage in the summer if you heat your DHW.

When they sprayed the inside of my roof the foam expansion was difficult to control so they went beyond the amount I paid for then cut off the excess.

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Was your foam open or closed cell. generally speaking open cell does the huge expansion thing that needs to be trimmed. Closed cell can usually be controlled for approximate thickness. Mostly more bang for the buck with closed cell.

Will

I might suggest considering 4" foam board without ribs instead? (eliminates thermal bridging, ~R25) - that should lose less than 0.3 degrees overnight, even at 180 degrees inside. Here is a link to a homemade, outdoor storage tank with some good design discussion, especially at the end of the document:
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Construction.htm
and also updates to the design at:
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Changes2007.htm