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  • Gazz
    replied
    I previously used a 35K btu propane heater but it takes awhile to warm the place up. Consider the iron ice cubes, the Index mill, SB 9" lathe, Atlas 6"shaper, several drill presses, anvils, 4x8'x 1/2' thick welding table, large war time Porter cable belt grinder, tool boxes, stock etc.. It's probably 30% iron / 70% air in there not to mention the frozen concrete floor. Those things sucked up most of the heat the 35k would make. It does give me plenty of time to procrastinate while things warm up though. I have used the forge to warm the place up in the past but have a tough time doing machine tool work or fabrication as when the forge runs, I should be forging and I have lathe work to do.

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  • Jerrythepilot
    replied
    85000 btu's is enough to heat a two story house. I would manifold your hundred pounders together and get home delivery. Your local propane dealer might hydro your tanks and manifold them together for you for a reasonable fee, and keep them filled through the winter.

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  • camdigger
    replied
    When our propane tanks stopped evaporating enough propane to run the 20 man camp, we put a couple 100 Watt halogen lamps aimed at the tank outlet regulators and tarped the tanks with plastic sheeting. Kept us from freezing to death in the -40 C weather.

    If you need a manifold to connect some small tanks together, look at the RV market. They almost all have a tank manifold for dual 20 & 30 lb tanks.

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  • Gazz
    replied
    Thanks for all the comments. As I stated in my original post, a two bottle manifold is not desirable. A 30 or 40 lb bottle might work but I would have to buy one and since I have three 100 pounders which are certainly past their certification, I think I will go with those after recertification. They could also be connected by a manifold and plumbed to run the forge as well and located outside the shop. I'm not to concerned with the weight as I have equipment to aid me in moving them into location. And yes, propane is more desirable for me since the kero heaters do stink.

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  • eKretz
    replied
    Originally posted by Ohio Mike View Post
    You need bigger bottles. But 100# cylinders are wicked heavy to move. I'd sell it and buy a kerosene heater, but that's me. I've used propane heaters indoors but I always feel sick later. Even for short runs. I don't have that issue with kerosene and its easier to get.
    Unless you're using a propane heater that is not running correctly that should not happen. Byproducts of propane combustion are water vapor and CO2. CO can be produced if air/fuel ratio is off.

    Kerosene on the other hand produces a handful of other nasties in addition to those that are the same as propane.

    Personally, I'll take the propane heater. Cheaper to run for the same BTU and no odor like the kero heaters.

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  • Ohio Mike
    replied
    You need bigger bottles. But 100# cylinders are wicked heavy to move. I'd sell it and buy a kerosene heater, but that's me. I've used propane heaters indoors but I always feel sick later. Even for short runs. I don't have that issue with kerosene and its easier to get.

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  • Bob Engelhardt
    replied
    It's an estate sale heater, maybe a $180 100lb tank (Lowes) is too much. Do they do home delivery for something as small as 100lb? Otherwise a full 100lb-er is 170lb and would be kinda awkward transporting.

    I would heat the 20lb-er with the heater. Find a sweet spot off to the side where the heating matches the cooling.
    Last edited by Bob Engelhardt; 12-23-2021, 08:30 AM.

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  • mikey553
    replied
    Originally posted by darryl View Post
    What is the temperature where the tank would be? A 100lb tank outside might be no better than a 20 lb tank inside- except for volume. Perhaps the best answer is to dedicate a hand cart to the larger tank so it's easy enough to move around. I wonder if there are any legal issues with having the larger tank inside- they don't even like you having a 20 lb tank inside.

    When it comes to heating the tank to ensure that gas will keep flowing, there's a parasitic drain right there. A tank that's cooling as it's being used is going to suck some of the heat that you're producing. I wonder what the numbers show- if you maintain the tank (and it's contents) at say room temperature, what percentage of the heat being produced by burning has to go into maintaining the tank temperature? Would it be 5%, less, or perhaps more?

    At any rate, 85000 btu seems like a lot for a 20 lb tank to handle. Assuming the tank didn't freeze, how much time would you get out of one fill?
    100 lb tank is much bigger than 20 lb tank and its surface area is bigger as well. When tank cools down during heater operation the surrounding air supplies the heat energy to the tank trying to equalize the air and tank temperatures. So the bigger the tank and the bigger the temperature differential, the faster would be a heat transfer. You may be surprised, but the cold air at -40F contains a fair amount of heat energy. If tank surface is colder than the ambient air, the heat transfer would take place. This is my explanation as to why bigger tank can produce more gas than a smaller one at equal conditions.

    As far as any legal issues with having the tank inside there may be some restrictions for that. I remember that many years ago in a city I used to live propane tanks were not allowed in the residential buildings. Separate machine shops may be another matter. You have to consult you local authorities if you want to be legal. Your insurance company may not like propane tanks inside the building either.

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  • darryl
    replied
    What is the temperature where the tank would be? A 100lb tank outside might be no better than a 20 lb tank inside- except for volume. Perhaps the best answer is to dedicate a hand cart to the larger tank so it's easy enough to move around. I wonder if there are any legal issues with having the larger tank inside- they don't even like you having a 20 lb tank inside.

    When it comes to heating the tank to ensure that gas will keep flowing, there's a parasitic drain right there. A tank that's cooling as it's being used is going to suck some of the heat that you're producing. I wonder what the numbers show- if you maintain the tank (and it's contents) at say room temperature, what percentage of the heat being produced by burning has to go into maintaining the tank temperature? Would it be 5%, less, or perhaps more?

    At any rate, 85000 btu seems like a lot for a 20 lb tank to handle. Assuming the tank didn't freeze, how much time would you get out of one fill?

    Leave a comment:


  • Dan Dubeau
    replied
    A 20lb bottle is too small for such a big heater IMO. I used to use 20lb cylinders for my turkey fryers to boil sap, but would run into the same issues of bottles freezing, and having to stick them in a barrel of water. I switched to 30lb bottles and the freezing problem is almost gone (will still freeze up when nearing empty). The fryers are only about 45000 btus. For your heater at around double the btu I would expect freezing problems no question. A 100lb cyl should be fine, but someone could do the math to be more accurate.
    Last edited by Dan Dubeau; 12-22-2021, 05:01 PM.

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  • eKretz
    replied
    Parallel the smaller tanks and you should be fine. That will reduce the flow from each and thus also the temperature drop. A dual manifold will probably do the trick depending on initial temperature.

    I have in the past (on work sites with no heat in winter) also occasionally placed a single tank in the peripheral output from the heater so it's warmed a little by the output, that does the trick in a pinch, just be careful not to get it too hot.

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  • Willy
    replied
    Here's link to a vaporization rate table for various size tanks at various temps and the amount in BTU that can be drawn at that temp.

    https://flameengineering.com/pages/propane-information

    I'm reminded of two incidents, one was when using two 100 lb tanks in 100° weather on an asphalt heater, even at that outside air temp both tanks would get about a half inch of frost at the liquid propane level in the tanks, felt good to rub up against them.
    The other extreme was driving into a truck stop way up north at -40 and saw that they had a pile of burning tires around one of their 1000 lb. propane tanks in order to draw enough vapor from them to keep the place warm. Look kind of sketchy but it worked.

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  • deltap
    replied
    A propane dealer can tell you what size tank you need for that input. Depending on lowest temp I will guess 200-500 gal tank. Large installations require a vaporizer to maintain pressure on a heavy draw.

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  • mikey553
    replied
    I don't have a propane heater, but can offer you some theoretical explanation. Propane is kept in the bottles in the liquid form under pressure. There is pressurized propane gas above the liquid level. This is known as a saturated condition. The pressure in the bottle depends on its temperature. At 70 F it is 110 psig, at 40 F - 64 psig, at 20 F - 41 psig, at 0 F - 24 psig. I gave you just a few points, but any temperature has its corresponding pressure.

    When the heater sucks propane gas from the bottle, the liquid propane boils trying to maintain pressure-temperature relationship. Boiling requires energy, so the bottle temperature drops and so does the pressure. At some point the pressure drops so much that the heater goes out. The only way for it to operate in winter temperatures is to get more heat energy to the liquid propane. This tlcan be accomplished by heating the bottle or by using a bigger bottle. Bigger bottle can get more heat from the surrounding air and will not freeze as quickly as a smaller bottle.

    So this is the theory behind your problem. I have not done this personally, but I have worked with pressurized gases for many years and learned a few things along the way.

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  • Noitoen
    replied
    Should check this table

    https://flameengineering.com/pages/propane-information

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