festerwl t1_j4lksnc wrote
The answer is maybe. Depending on how cold it gets where you are and how long of a run it is to the heater the small tank may not provide enough pressure. A 40lb tank might be a good compromise, still a larger size but small enough to be moderately easy to transport for filling.
KevinAnniPadda OP t1_j4lmh7y wrote
Ah, good thoughts! I'm in Coastal North Carolina. Rarely gets below freezing, but we've had a lot of nights in the 30s this winter. It's on the north side and will be regularly shaded.
The tank is just outside the fireplace. Maybe 4 feet of thin metal piping for it. Would insulating the pipe be worth it?
festerwl t1_j4lnly3 wrote
That close the 20lb tank should be fine. Depending on how large the heater is you may only run into problems when it's very cold and the tank is low.
dubforty2 t1_j4lprya wrote
Second this. I use a 100 lb tank for my entire off grid cabin in Alaska. It flows fine until about -30F or so.
LetsBeKindly t1_j4npxhs wrote
Unless you want to buy the tank, most places place a tank for free with the assumption you'll buy gas.
redarrow7216 t1_j4nch76 wrote
Wait what? The volume does not matter for pressure. For propane/butane tanks only the temperature is of importance as they liquefy on lower temperatures and the pressure decreases. Also pressure drop in tubing/piping is neglible in low flow short run conditions. Smaller tanks do run empty quicker though.
https://www.engineeringtoolbox.com/propane-butane-mix-d_1043.html
festerwl t1_j4neh8z wrote
The larger tanks have the ability to hold temperature better. If the heater is using a large amount of propane the smaller tanks can ice up quicker than the larger tanks.
And yes the pressure drop isn't noticeable in short runs but some use 1/2" black pipe like natural gas and a grill size tank will have a hard time if you're out like 20ft.
redarrow7216 t1_j4rgdzz wrote
An average 3-4kW chimney uses only about 500L of gas per hour. That are really low volumes, even for 1/2" pipe.
Joule Thompson effects are measurable over an orifice i.e. Regulator but not really in these cyllinders. Also with these low pressures 1-2bar JT effect would be +-1 degree Celsius for pressure drop to atmosphere entering the chimney. Yes, the tank can hold more heat as more fluid is present but will still quickly cool down/warm up with the ambient temperature.
I dont think OP has any benefit with a bigger tank looking at his consumption or other circumstances.
West-Advertising-545 t1_j4ne271 wrote
There’s a difference. It will be listed as a minimum tank size in the manual for proper performance.
thephantom1492 t1_j4oy89i wrote
A thing to note, propane have 91500 BTU per gallon. BBQ now are 40-60000btu.
How powerfull is that heater? If it is bellow the 40kbtu then it is not worse than a BBQ.
I do agree with the 40lbs tank.
Also, do not insulate the pipe or worse, the tank. They will get colder when you use propane, you want them to warm up. And yes, cold air is still warmer than the tank!
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