What vessel type for indoor pressurized thermal storage?

[maplewood]

Hi Forum,

I am installing a new Econoburn 150, and am starting to think I should add thermal storage sooner than later.
We will be heating 3 floors, 3500 square feet, with infloor heating (one concrete floor, two wood floors).
What thermal storage vessel can I use? I've got to get it down a straight run of 16 stairs 3' wide, then install
it on a concrete floor next to my boiler.
I've heard some using old propane tanks, old oil tanks, plywood boxes with rubber liners, etc.
I can go fully pressurized, or non-pressurized and put in copper coils for heat transfer.
Of course, I want storage to gain efficiency, store excess heat, and I'll be heating my DHW from it, too.

Gladly take suggestions, experiences and horror stories!
Thanks!

Larry

 

[stee6043]

I believe my propane tanks were roughly 37 inches in diameter. You may potentially be able to find other tanks with a smaller diameter since I know they vary from manufacturer to manufacturer. But I'm not sure you'll find one small enough to squeeze down a 36" stair well with room to negotiate them?

If you do some reading here you will find that propane tanks are far and away the most simple, least expensive and safest way to run pressurized storage. With your square footage I'd say 1000 gallons should be your minimum size...

 

[DaveBP]

Larry,

If you're getting our leftover rain it might be perfect weather to curl up to your computer monitor and use the search function on the top of the pages here and look for terms like "storage", "tank", "propane", "pressurized", and so on. Probably give you a couple days worth of reading and education. There are hundreds of posts and discussions on this wide ranging topic.

While pressurized storage is arguably more efficient (but we NEVER argue on this forum. Right proper gentlemen and ladies, we are) it does come with its own set of complications and expenses that are not shared by non-pressurized storage tanks. Getting the bloody things down narrow stairs to the basement is one of the prime reasons people use non-pressurized systems. You can build your own tank and line it with an EPDM pond liner. You mustn't underestimate the hydraulic forces involved on the tank walls but think of it as a form for pouring concrete and you can do it safely. Or there are some excellent tanks on the market that can be brought downstairs in pieces and assembled in place.

Snoop around the various threads here and you'll learn a whole lot more than you might have imagined.

 

[Singed Eyebrows]

Hi Larry; You might look into used ASME air tanks. At about 200 gallons each you would need a bunch of them. They would be very safe pressure wise. Most are rated 200 psi & 450 degrees. These should go down the stairs just fine. Randy

 

[maplewood]

Thanks, Stee6043, Dave and Randy.
I'll source some air or propane tanks and link them together.
I like the idea of a pressurized system over non-pressurized, and I can use a side arm heater for my DHW.
Larry

 

[ManiacPD]

My 250 gallon propane tank is 30" OD by 93" long. It weighs 480 lbs empty. At this point I am only putting in one which, I know, I know, isn't a whole lot of storage. But for now it's what I've got and I can easily piggy back a second tank on top of it next year if I need more storage.

I'd hate to think I needed to put that tank in my basement if I didn't have a bulkhead door.

Also, if you use any propane tank, you will need to weld in some fittings for your piping, gauges, PR valve, expansion tank, etc. We did mine last night. The tank came with three 3/4" fittings and one 1-1/4" fitting. I left the gauge in it which is helpful to see how full it is. We added two 2" fittings for the return lines as I'm putting dip tubes in to ensure we are turning the water in the tank over top to bottom. And we put in two 1-1/2" fittings for the supply lines.

Also, if you do this, don't forget to roll the tank over and put a drain in the bottom in case you ever need to drain it!

Good luck!