darkstar Posted January 4, 2012 Report Share Posted January 4, 2012 Apologies in advance if this isn't a good place to ask a question like after browsing threads here for a few minutes this but this forum seemed to have quite a few people knowledgeable in the HVAC field so I figured I'd give it a try: Ok, here's the deal. I have a gas furnace (installed last year) that is converted to run on LP gas (because natural gas is not available in my area). Anyhow, my tank is almost empty and my LP provider won't be bringing me a delivery until next week. Is it possible for me to run it temporarily off of a 20lb. propane tank? If not, is there a way to easily "fill" my larger (100 gallon) tank by transferring from the 20lb. tank a couple of times? I know none of this is ideal, just looking for a solution to keep me running for a few days until I get refilled. Link to comment Share on other sites More sharing options...
Marc Posted January 4, 2012 Report Share Posted January 4, 2012 I don't see how the furnace could tell whether it's a 100 gal or a 20 gal tank feeding it. Just make sure the gas pressures at the furnace remain the same. Marc Link to comment Share on other sites More sharing options...
Bain Posted January 4, 2012 Report Share Posted January 4, 2012 Be aware that you're going to have to disconnect the line from the larger tank and reconnect it to the smaller tank. I'm guessing you'll have to change couplings, as well. If this isn't something you have expertise in, you could blow your head clean off. Furthermore, a 20 lb. propane tank holds something under five gallons. It isn't going to last long depending upon the size of the furnace and how much it's running. Link to comment Share on other sites More sharing options...
Jim Katen Posted January 5, 2012 Report Share Posted January 5, 2012 . . . Is it possible for me to run it temporarily off of a 20lb. propane tank? Sure it works fine. You just need get the right fittings to make the handshake between the 20# bottle and your regulator. It can be tricky. I once rigged up a connection that included a section of shrink tubing. Worked great for almost a month. If not, is there a way to easily "fill" my larger (100 gallon) tank by transferring from the 20lb. tank a couple of times? I'm not sure how the propane would know that it was supposed to go from the little tank to the big one. If you invert it to "pour" the propane it, I believe the little one's safety cutoff will engage. I'd stay away from this idea. Link to comment Share on other sites More sharing options...
John Kogel Posted January 5, 2012 Report Share Posted January 5, 2012 Don't do it. Call the gas supplier and tell them it's an emergency, and the baby's gonna die if they don't fill the tank. The big tank will quite often have a big pressure regulator and a high pressure line to the house. Then there may be another regulator at the appliance to drop the pressure to the proper level. You could end up doing damage or causing a leak, and still no heat. I recall pumping propane from a large tank to a small one with a hand pump, but that is a specialized item you don't have. When I had a camper trailer, I sometimes filled my spare tank half full with another full tank. These were the days before easy 20 lb tank exchanges. With the two tanks on a T, tilting the full tank upside down and opening both valves allows the LP to flow into the empty until the pressures equalized. This bad practice destroyed the seals on my good tank, because slag from welding rolled out and got lodged in the valve. Also, as Jim rightfully points out, the new tanks have a safety valve that won't allow you to pour the propane. Link to comment Share on other sites More sharing options...
Les Posted January 5, 2012 Report Share Posted January 5, 2012 Here in wonderful Michigan, we always have a regulator at the house. As long as the tank has enough pressure to operate the regulator, it will work. We operate furnaces and water heaters using small tanks couple dozen times per year. Our common tanks are 20. 30, 40 and 100 lb. Link to comment Share on other sites More sharing options...
darkstar Posted January 5, 2012 Author Report Share Posted January 5, 2012 Thanks for the replies. I looked at it last night, the connector going into the tank will thread right into the 20lb tank, they're identical. However because it is a "hard" plumbed line there's not a safe way for me to get the line to the 20lb. tank so I'm going to hold off (I'd have to prop the little tank up on something to get it to that height and I don't feel safe doing that). I have a pellet stove and a heat pump that will keep my house in the mid to high 60's until next week. Link to comment Share on other sites More sharing options...
Tom Raymond Posted January 5, 2012 Report Share Posted January 5, 2012 My cousin in Smithfield, NC runs his range, DWH, and furnace off of 100 pound bottles. It's far less expensive, and he can shop around for the best price. Tthe local gas station fills propane tanks, so he can get fuel even if he runs out on a Holiday. There's also the bonus of no big tanks in his yard. If there's a down side, it's that the colder it is the more frequent the tank changes are. Link to comment Share on other sites More sharing options...
darkstar Posted January 5, 2012 Author Report Share Posted January 5, 2012 Here in wonderful Michigan, we always have a regulator at the house. As long as the tank has enough pressure to operate the regulator, it will work. We operate furnaces and water heaters using small tanks couple dozen times per year. Our common tanks are 20. 30, 40 and 100 lb. I was looking at Lowe's last night hoping to find an "extension" to get the line down to the ground to operate the 20lb. tank with no luck but I did fine 100lb. tanks for $129 that I may grab at some point to have as a spare since they are the same height as my 100 gallon tank. Link to comment Share on other sites More sharing options...
Chad Fabry Posted January 5, 2012 Report Share Posted January 5, 2012 A 20lb tank probably won't work if it is placed safely outside the building. With low exterior ambient temps there is not enough surface area for the propane to boil at a sufficient rate to supply a furnace that requires 60K to 100K btu's of input. When it's 20 outside, you're hard pressed to barbeque at 20k btus. A photo of our Y2K new year's eve party would show a group of men standing in the snow, smoking cigars, drinking Maker's Mark, cooking a tenderloin on a gas grill. Had we not pointed a salamander heater at the propane tank, we'd still be waiting for dinner. Link to comment Share on other sites More sharing options...
Jim Katen Posted January 5, 2012 Report Share Posted January 5, 2012 A 20lb tank probably won't work if it is placed safely outside the building. With low exterior ambient temps there is not enough surface area for the propane to boil at a sufficient rate to supply a furnace that requires 60K to 100K btu's of input. When it's 20 outside, you're hard pressed to barbeque at 20k btus. A photo of our Y2K new year's eve party would show a group of men standing in the snow, smoking cigars, drinking Maker's Mark, cooking a tenderloin on a gas grill. Had we not pointed a salamander heater at the propane tank, we'd still be waiting for dinner. If you point a propane torch at the 20# tank, you can get the propane inside vigorous enough to boil quite nicely. Link to comment Share on other sites More sharing options...
John Kogel Posted January 5, 2012 Report Share Posted January 5, 2012 Here in wonderful Michigan, we always have a regulator at the house. As long as the tank has enough pressure to operate the regulator, it will work. We operate furnaces and water heaters using small tanks couple dozen times per year. Our common tanks are 20. 30, 40 and 100 lb. I was looking at Lowe's last night hoping to find an "extension" to get the line down to the ground to operate the 20lb. tank with no luck but I did fine 100lb. tanks for $129 that I may grab at some point to have as a spare since they are the same height as my 100 gallon tank. 100 Lb is a good size for what you need. But you should know that to transport the full tank, it needs to be strapped upright such as in the back of an open truck. I bought a 60 lb tank for cheap when they appeared at the local box store. But the kid at the propane depot can't fill it. It is not on his weight chart, so he can't fill it by weight. Link to comment Share on other sites More sharing options...
Marc Posted January 5, 2012 Report Share Posted January 5, 2012 FYI: 42 degrees below zero is when liquid propane boils at atmospheric pressure. Marc Link to comment Share on other sites More sharing options...
Chad Fabry Posted January 5, 2012 Report Share Posted January 5, 2012 FYI: 42 degrees below zero is when liquid propane boils at atmospheric pressure. Marc True, (-42 Celsius, -44 Fahrenheit) but if you're suggesting that low temps wouldn't have an effect on volume, let me assure you they do. Most tanks serving furnaces in my area are horizontal to increase surface area and most distributors won't fill the tanks above 75% to ensure that there is adequate surface area to boil. Boiling is one thing, boiling at a rate sufficient to deliver 100K Btu through a 1/2 copper tube when it's ten or twenty degrees is another thing. Boiling water in a ten inch pan produces steam at a certain rate, pouring the same volume of water on a red hot plate that's four feet across, produces steam at a different rate. The rates do not change the fact that all the water boiled at 212. If that's not what you're suggesting and you were offering up a fact for consideration, then never mind. Link to comment Share on other sites More sharing options...
Marc Posted January 5, 2012 Report Share Posted January 5, 2012 Low temps has an effect on the pressure of the propane in the tank. Also, the evaporating propane cools the tank just as evaporating refrigerant cools the cooling coil on an AC. Same mechanism. This 'surface area' angle, I feel you, but I don't agree it's a significant factor in this scenario. Maybe bury the tank. Keeps it a little warmer. Marc Link to comment Share on other sites More sharing options...
Chad Fabry Posted January 5, 2012 Report Share Posted January 5, 2012 pdf explaining relationship between surface area and output capacity The link doesn't work. Email me if you want a copy of the document. Link to comment Share on other sites More sharing options...
Marc Posted January 5, 2012 Report Share Posted January 5, 2012 There must be a page sequence needed because the link doesn't bring anything up. Marc Link to comment Share on other sites More sharing options...
John Kogel Posted January 5, 2012 Report Share Posted January 5, 2012 A 20lb tank probably won't work if it is placed safely outside the building. With low exterior ambient temps there is not enough surface area for the propane to boil at a sufficient rate to supply a furnace that requires 60K to 100K btu's of input. When it's 20 outside, you're hard pressed to barbeque at 20k btus. A photo of our Y2K new year's eve party would show a group of men standing in the snow, smoking cigars, drinking Maker's Mark, cooking a tenderloin on a gas grill. Had we not pointed a salamander heater at the propane tank, we'd still be waiting for dinner. If you point a propane torch at the 20# tank, you can get the propane inside vigorous enough to boil quite nicely. Why mess with a wimpy BBQ at 20 below? Doesn't anyone have a recipe for tiger-torch turkey? [] Link to comment Share on other sites More sharing options...
Chad Fabry Posted January 5, 2012 Report Share Posted January 5, 2012 There must be a page sequence needed because the link doesn't bring anything up. Marc I emailed it. Link to comment Share on other sites More sharing options...
Marc Posted January 5, 2012 Report Share Posted January 5, 2012 Got it. Thanks. Marc Link to comment Share on other sites More sharing options...
Denray Posted January 26, 2012 Report Share Posted January 26, 2012 I bucked up and got my son and I a place to stay right in the middle of Kirkwood Ski area once. It was pretty cold that night. Perhaps 15F or so. In the morning my son's stove, with the screw on bottles, wouldn't even light. Dad's stupid white gas stove worked very well.[:-party] Click to Enlarge 49.69 KB Link to comment Share on other sites More sharing options...
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