using horizontal 250-300 gallon propane tank for expansion

[rkusek]

Anybody see a problem with using this?

After realizing that a $500 86gal bladder tank is probably just a little too small for 1100gal system based on EW Dudley's formulas, I've been wanting to go the cheaper route. Found 2 500 gal tanks from big propane dealer in town for $100 apiece. One had been sandblasted and repainted before they realized it didn't have the tag. The other one looks good too and still had about 10% of propane in it. He had a 120 gal upright tank but it was still usuable for propane and not big enough. None of the 250-350? sizes I see have ports on the ends which makes it difficult to use it upright without welding. Not to mention I would need some kind of stand welded for it even in a corner. Can I get away with using a 250 gallon tank setting horizontal using the dip tube for air pressure connection. Not sure but I thought the dip tubes go almost to the bottom since they pull out the liquid by design. The gauge would provide for an easy method to keep track of water level too but would be useless if I mounted it vertical. I had to waste the space for 3 tanks setting horizontal but I think if I boxed the 2 500's in someday it would make a nice shelf along the wall. Any thoughts?

 

[leaddog]

You can use the tanks vertical. Just tap a 3/8 pipe in the bottem for the 3/8 to 1/2pex adapter to connect to the line and tap an 1/8 or 1/4 pipe thread for a sharder air fill valve. The metal is thick enough to hold up to 3/8 npt. The gage can be made to work by removing and turning 90*. You need to shorten the arm and then you can calibrate it by lifting it up and down and noting where the gage reads.
A vertical tank is better as you will have less surface area to water.
Weld a tire rim on the bottem for a stand.
been there done that
leaddog

 

[goosegunner]

Anybody see a problem with using this?

After realizing that a $500 86gal bladder tank is probably just a little too small for 1100gal system based on EW Dudley's formulas, I've been wanting to go the cheaper route. Found 2 500 gal tanks from big propane dealer in town for $100 apiece. One had been sandblasted and repainted before they realized it didn't have the tag. The other one looks good too and still had about 10% of propane in it. He had a 120 gal upright tank but it was still usuable for propane and not big enough. None of the 250-350? sizes I see have ports on the ends which makes it difficult to use it upright without welding. Not to mention I would need some kind of stand welded for it even in a corner. Can I get away with using a 250 gallon tank setting horizontal using the dip tube for air pressure connection. Not sure but I thought the dip tubes go almost to the bottom since they pull out the liquid by design. The gauge would provide for an easy method to keep track of water level too but would be useless if I mounted it vertical. I had to waste the space for 3 tanks setting horizontal but I think if I boxed the 2 500's in someday it would make a nice shelf along the wall. Any thoughts?

Why would the 120 gallon tank be too small?

gg

 

[Singed Eyebrows]

What Leaddog said! If it was me I'd put in 2 250's for about 250 gallons acceptance with the 1100 gallon storage(I'm not suggesting you do this). Atmos specs very large acceptance for "power balancing" whatever that means. I just don't like to see pressures rise much, Randy

 

[woodsmaster]

Hope I didn't figure wrong. I plan on using a 124 propane tank for expanshion on my systym of aprox. 1100 gal.

 

[Singed Eyebrows]

Hope I didn't figure wrong. I plan on using a 124 propane tank for expanshion on my systym of aprox. 1100 gal.

If you did miscalculate it's not a big deal to add another tank. Because of my location I can't have high pressures, Randy

 

[rkusek]

You can use the tanks vertical. Just tap a 3/8 pipe in the bottem for the 3/8 to 1/2pex adapter to connect to the line and tap an 1/8 or 1/4 pipe thread for a sharder air fill valve. The metal is thick enough to hold up to 3/8 npt. The gage can be made to work by removing and turning 90*. You need to shorten the arm and then you can calibrate it by lifting it up and down and noting where the gage reads.
A vertical tank is better as you will have less surface area to water.
Weld a tire rim on the bottem for a stand.
been there done that
leaddog

Thanks Leaddog,

Tire rim, perfect. Will fit much nicer in the corner vertical too. I think I will still keep the 2 500 gal storage tanks horizontal though. Not sure the 4" concrete floor would handle 4000 lbs over such a small area. Had I been thinking a couple of years ago, I would have poured footings and anchor bolts and could have had excellent stratification and more floor space. Oh well, others seem to do fine this way too. As far as the acceptance volume requirements, I think since the floor of the pole barn is about 15 feet lower than my basement floor elevation wise making my acceptance requirements were more like ~10% which would be around 115 gals. The 120 gal propane tank would only give about 60 gal acceptance I believe. Check the thread discussion from earlier this summer that went into great detail. If you can get by with 5% for your situation then it might work. The biggest bladder tanks are 86 gal which shows to be 46 gal max acceptance. Too small even if you just figure 5% volume. I was wondering if anyone has tried putting a layer of motor oil on top of the water or tried using nitrogen for the air bubble. Probably overkill since none of the guys using propane tanks have seemed to have any problems maintaining the air bubble.

 

[DaveBP]

The difference between the elevation at your basement floor and your pole barn will effect the range of pressure the expansion tank will operate through, but I don't know why it would effect how much the same volume of water will expand and contract with the same temperature change. From coldest to warmest the water will expand about 4%, maximum. The pressure (within real world limits) won't effect that.

Like Randy said, the larger the expansion tank for a given system volume, the less the pressure will build as the system heats up.

 

[ewdudley]

Not sure the 4" concrete floor would handle 4000 lbs over such a small area.

Spread out by a tire rim it doesn't sound so bad at all if the grade is firm enough. If you parked a dump truck inside over the winter would you expect the concrete to crack and settle [much]?

[T]he floor of the pole barn is about 15 feet lower than my basement floor elevation wise making my acceptance requirements were more like ~10% which would be around 115 gals.

How about putting the expansion tank up in the rafters of the pole barn in an insulated chamber with a little bit of heat ducted up there. Elevation can really slash the tank size requirements. You would need to go up past the bottom of the tank to an air-vent high point and then back down if it was a bladder tank.

Also although 30 psi is the normal boiler blow-off pressure, it is possible to use a higher maximum system pressure.

I was wondering if anyone has tried putting a layer of motor oil on top of the water or tried using nitrogen for the air bubble. Probably overkill since none of the guys using propane tanks have seemed to have any problems maintaining the air bubble.

Nitrogen might make sense, but I would speculate that oxygen would pass through an oil membrane over the life of the system, which is probably no better than getting it over with earlier. They use mineral oil in expansion cisterns that are vented to the atmosphere, in which case it makes sense to try to slow down the rate of oxygen absorption since there's an unlimited supply of oxygen above the oil layer, unlike a system that is sealed 'forever'.

--ewd

 

[DaveBP]

The difference between the elevation at your basement floor and your pole barn will effect the range of pressure the expansion tank will operate through, but I don’t know why it would effect how much the same volume of water will expand and contract with the same temperature change. From coldest to warmest the water will expand about 4%, maximum. The pressure (within real world limits) won’t effect that.

Huskers, my confusion was based on the assumption that your boiler was in the basement near the top of the system, not down in your pole barn. Don't know why I thought you described it that way. When I re-read your original post I realized you never said that. You know what they say about ASSumptions and those that make them.

Larger expansion tanks are available but they are crazy expensive. I'd try the propane tank route, too. I found a new stainless tank rated for 80PSI on Ebay that for some reason went for about the price of the metal in it but I'm not going to use it pressurized. They usually are a whole lot more than propane tanks.