Any propane gurus out there?

[Carol]

Propane questions!

Can I estimate how much propane is in my 20# cylinder by tank weight? If my cylinder has a 16.5 pound tare weight and it weighs 26.5 pounds, that means I have used half of my tank, correct?

Since temperature and pressure are proportional, what impact would the ambient temperature around a cylinder have on the performance of a heater? Will I get the same performance at 15F that I will at 40F?

 

[jks9199]

I think the weight is going to be constant, whatever the temperature. Weight is a guide, in fact there are mounts for grills and campers and such that do just that. One catch, though, is whether you actually started at a "full" tank... For a while, the tank exchange programs were keeping their cost constant by putting less gas in the tanks.

As to performance and temp -- I suspect, as it seems you do, that it'll decline somewhat at lower temps. However -- doing some research, it looks like the boiling point is somewhere around -44 F for propane, so I kind of guess it won't be a huge effect. Maybe Elder can give a more accurate answer. I know that, when camping in cold weather, we'd often keep a propane tank (and a water bottle) in the tent, sometimes in the sleeping bag. Made cooking breakfast a lot easier that way...

 

[Takai]

Propane is about 4.11 lbs per gallon at 77F. It expands at a rate of about 1.5% per 10 degrees of change.

The BTU's in propane will not change with temperature. The performance will be roughly the same. Though at 15F you will probably be huddling closer to the heater because it will take longer to raise the ambient temperature.

 

[Carol]

Thanks all, that helps a lot. I've been trying to get some feel for how I can best predict how often I'll need to refill my tank, since it seems that winter is not in any hurry to go away.

I'm a little surprised/annoyed at the difference in quality between the cheap 1# bottles from Wal-Mart and the not as cheap brands I've found at smaller retailers.