Multiable Propane Storage Tank Hook-Up

[sdrobertson]

I've lucked out and have located four 500 gallon propane tanks to use as pressurized storage with a EKO 60. My question is - is there any advantage to how I install the 4 tanks? Standing each tank on end or stacking two together? I only have one zone (forced air furnace with lines already installed from a OWB). This is new construction so I have the opportunity to set it up right the first time. With a pressurized system, is it possible to get much stratification and how do I take advantage of it? Also, I'm thinking about using two 80 gallon hot-water heaters for expansion tanks, so where is the proper place to locate them? Can't wait for spring so I can start building this project instead of thinking and figuring!!

 

[EForest]

propane tanks are the perfect solution for pressurized storage.
Try adding a DHW coil it could serve many functions if you added one to each tank.

 

[Nofossil]

If you have the room, I'd stack them in two rows, two high. That would give you the smallest volume to insulate. I'd plumb each vertical pair in series, and probably plumb the two pairs in parallel with each other. You'd like the charging flow to enter the top of the top tanks, exit the bottom of the top tanks, enter the top of the bottom tanks, and finally exit the bottom of the bottom tanks - top to bottom the whole way. Recovery flow would be the exact opposite. That should give you great stratification. You'd want to spend a little time thinking about how and where to weld in your pipe fittings to minimize turbulence and mixing.

 

[sdrobertson]

Is this what your suggesting? For the expansion tanks (two 80 gallon water heaters) should I place one in the boiler line and one in the zone line or can I place both in one line? Pressure is the same where ever I place them right?

 

[BrownianHeatingTech]

For the expansion tanks (two 80 gallon water heaters) should I place one in the boiler line and one in the zone line or can I place both in one line? Pressure is the same where ever I place them right?

Pressure will be "zero" (system static pressure - usually 12-15psi) wherever the expansion tank is located. You want to have your zones pump "away" from the tank, so that they are adding pressure instead of subtracting (that way, your zone pipes are always above atmospheric, which means air can't leak into the piping), and to prevent steam pocket formation on the pump impellers.

Figure out your water volume and operating temperatures, and I can post the calculations to see how many gallons of expansion you actually need.

Joe

 

[sdrobertson]

If I stand the tanks on end and still hook them up in pairs, then parallel, will I be able to run this setup like I have shown in the attachment? If I stand them on end, I'll use less floor space as I'm more concerned with space as to volume to insulate.

The water will be 2000 gallons (4-500 gallon tanks) plus lines and boiler. I'm figuring less than 2200 gallons.

 

[EForest]

Joe,
I was told to use 15% of total system volume to figure expansion required if only one pipe into exp tank.
Technically only cool water will enter exp tank in one pipe system?
30% if hot water will travel thru tank (two pipes). Any truth to this?

Ed

 

[Nofossil]

Your first diagram is exactly what I was thinking. Putting the tanks on end would also work, but I figure you get better guaranteed stratification with the first approach.

The circulator / zone valve approach is another whole issue. Some favor a multiple loop approach with circulators, while others favor a supply / return approach with zone valves. Each has benefits, but at some point it's a theological discussion.

There's a lot to be said for the idea of having a 'primary' loop that goes from the boiler through the tanks and back, with a secondary loop pulling off the top of the tanks and returning to the tank bottoms.

 

[wtom24]

I used 2 -1,000 gallon tanks. Stacked one on top of the other with pieces of 10" pipe welded to each tank. Stratification works well with this arrangement. I was also able to scrounge several shell and tube heat exchangers. I cut the shell off leaving about 6" of shell outboard of the parting flange and welded the assembly into the top tank for domestic hot water heat. My tanks are mounted at the end of the basement up against the rear wall and are insulated with a 4" layer of batt insulation with a layer of duct wrap on top of that. Good luck with your tanks...

 

[barnartist]

im watching this one a i too will have a similar setup. only 3 500 tanks.

 

[BrownianHeatingTech]

I was told to use 15% of total system volume to figure expansion required if only one pipe into exp tank.
Technically only cool water will enter exp tank in one pipe system?
30% if hot water will travel thru tank (two pipes). Any truth to this?

Expansion is based upon the temperature swing and the volume of the system. Expansion in the hot part of the system will push into the cold part of the system.

Now, if part of the system will never go above a certain temperature, you can calculate multiple expansion tank volumes (for each section's volume and the temperature swing of that section), and then add them together, which may give you a smaller expansion tank volume than if you assumed that all of the system goes through the full 60-200 swing.

Joe