Using small propane tanks for storage

[churchillrow]

Nice forum.. so much good info.
I've been calling local propane companies and it seems that all the big used tanks around here (Nova Scotia) get refurbed so I can't find any for sale bigger than 120 US gallons. I'm wondering if because of the extra plumbing involved or for some other reason I shouldn't use these. I am planning in putting the boiler and the storage in my basement so one advantage of the small tanks would be ease of getting them down the basement stairs. Any input would be much appreciated.

Thanks

 

[Nofossil]

I think there are two disadvantages to smaller tanks:

1) More surface area per gallon, so more insulation will be needed

2) More complex plumbing - lots more fittings

As you say, they're easier to move around. Maybe it averages out. 500 US gallons is probably the smallest amount of storage that's needed to be useful, and 1000 gallons is a more common goal (though lots of folks can't easily manage to set up that much). You're looking at 4-8 tanks, so it should be manageable.

 

[churchillrow]

Both points taken NoFossil. Would any of the fittings be of the relatively expensive type or just t's and the like? In a multiple tank system what is required to to ensure all the tanks get heat evenly...or is it more desirable to have them heat in succesion to maximize the delta T available? If so does this require fancy control to achieve?

Thanks again...

 

[stee6043]

Fittings can add up fast. Especially if you're running large pipe like many of our boilers require. I'd guesstimate you're going to spend $20-50 per tank in fittings when you conisder the T's, nipples, elbows, etc. etc....

 

[churchillrow]

Fittings can add up fast. Especially if you're running large pipe like many of our boilers require. I'd guesstimate you're going to spend $20-50 per tank in fittings when you conisder the T's, nipples, elbows, etc. etc....

The guy who has a supply of these quoted me 150$ a piece...add 50 $ to be conservative and were looking at close to 2$ per gallon of storage plus insulation. Is this reasonable?

 

[Gooserider]

If you wanted to come to the US (not sure what's involved with border crossings and such) We did have a user a few days ago with some 500g tanks for sale in Maine... Check the For Sale section - not sure if he still has them or not.

Might also be worth looking to see if there are any other sorts of used tanks that might work - I've seen people mentioning Amonia nurse tanks (apparently from some sort of farm) and I'm sure there would be other options as well... Check w/ any salvage yards in your area - just say you want a pressure tank that can handle say 100psi or higher, 500-1,000 USG capacity, and see what they come up with....

Gooserider

 

[churchillrow]

Thanks Gooserider... I will look into that.

 

[potato]

Churchillrow,

If you are in Northern NS try this company near you in Moncton. I bought a tank there last year.

(broken link removed to http://www.triprovince.com/Resale-Yard.page)

 

[timberr]

Wouldn't stratification be difficult with a number of smaller tanks??

 

[churchillrow]

Churchillrow,

If you are in Northern NS try this company near you in Moncton. I bought a tank there last year.

(broken link removed to http://www.triprovince.com/Resale-Yard.page)

Thank you... This is awesome...... here is what is available

Propane Tanks 2500 Gallon
23ft length x 54" dia
$1,200.00
Propane Tanks 1800 Gallon
20ft length x 48" dia
$850.00
Propane Tanks 1000 Gallon
15ft length x 40" dia
$600.00
Propane Tanks 500 Gallon
9.5ft length x 36" dia
$450.00
Propane Tanks 334 Gallon
9ft length x 29" dia
$350.00

I'll have to see how I can fit these in the basement before I decide on what size to go with and how many. Is it possible to have too much storage? ;-)

 

[Gooserider]

(snip)
I'll have to see how I can fit these in the basement before I decide on what size to go with and how many. Is it possible to have too much storage? ;-)

Yes and no... In fact storage is slightly inefficient as it tends to lose heat over time (this is slightly less of a problem with an indoor install as the heat escapes into your house, but still) Also while you can run longer without a fire on a bigger storage tank, it also takes a lot longer to charge it back up again. You are better off from a practical standpoint to leave your fuel as fuel until you actually need the heat, we do storage not because it's a great thing, but because it is the best way to "buffer" the difference between the way a solid fuel boiler wants to run flat out for an entire load, and the more intermittent heat demands in our houses.

There are two main approaches to calculating your storage needs -

1. What is the minimum length of time you are going to be able to need to go without feeding the boiler at peak demand time - i.e. how long are you away from home on a workday... You need to be able to store enough BTU's to get you through that period of time, possibly assuming that you stuffed a full load of wood in the boiler just before walking out the door.

2. What volume of storage do you need to have in order to be able to soak up the entire output of the boiler going through a load of wood w/o having any other calls for heat - i.e. a shoulder season burn for DHW only.

For most of us, it seems the answer works out to between 500 and 1,000 gallons. Given that it is better to err slightly on the oversized side, and that our favorite LP tanks tend to come in 500 gallon unit sizes, I think the most popular size is probably 1,000 gallons, either as one big tank or two 500's. If you have the ceiling height for it in your basement, I think the slickest and most space efficient setup is two 500's stacked on industrial pallet racking, and plumbed in series. This minimizes the space the tanks take up, and gives very good stratification.

Gooserider

 

[churchillrow]

Storing the energy output of a full and hot burn of the boiler would be the criteria I care about as I work out of the house but I imagine it is the larger of the two anyway. Assuming that the 500 gallon tanks are stacked horizontally one above another I should have no trouble finding space for 1000 gallons in that configuration. I have questions about how hot water actually gets in and out of the tanks but maybe I'll leave that until they are actually here next to a boiler....

Thanks to everybody for all the good suggestions

 

[Gooserider]

Yes, I was talking in terms of stacking the tanks vertically - however the important thing to remember when doing this is that they are HEAVY and your racking needs to be extremely strong and rugged - you DON'T want to risk having that top tank start moving on you, and we are talking approximately 4,000 lbs of water plus the weight of the tank. That is why I was suggesting industrial warehouse pallet racking - which can probably be found used, especially in these financial times - it is strong and stable, designed for this kind of weight, and comes in sizes that are appropriate...

Getting the water in and out of the tanks depends somewhat on exactly what fittings come on the tanks - this varies a fair bit, but often there aren't enough fittings or ones in the appropriate size / place, and additional fittings will need to be added. Unless you are an experienced welder, this is generally a job for a pro, as the welds need to be strong and leakproof, but it isn't a terribly difficult / expensive task as such things go. It might make sense to plan for this in advance, as you might save money and headaches bringing the tanks home by way of the welding shop rather than having the welder do a house call...

In general, what you will want in the way of connections is to have the boiler sending in hot water at the top of the upper tank, and getting return water from the bottom of the lower tank. Ideally these inlets and outlets should be designed to minimize mixing action that would disrupt the stratification in the tank, but this can be a challenge depending on what you have to work with for fittings. The tanks should be tied together with a LARGE connection or two between the bottom of the upper tank and the top of the lower tank

The plumbing should be set up so that you won't have much need to get to the tanks once they are finished, as once all the plumbing is done, and verified to be leak free, then you will want to insulate the heck out of the setup. This is another advantage of the pallet racking, as it gives you the framing needed to build a big box around the tanks that can hold all the insulation and give a neat looking exterior.

Gooserider