How long can you heat with a 9kg cylinder of LPG?
Question:I've just bought two gas cylinders for my gas heaters, which I intend to run for about 8 hours a day on the lowest setting, in coastal Otago.
How long is it going to be before I need to refill, what do you reckon?
Answers:
Tahini:
I assume it is CNG (i.e. compressed)?
(But see below for LPG numbers)
Then per the 1st below web-site:
BTU's per lb. of 20,161 or ~ 44,400 BTUs per kg.
Times 9kg = 400,000 BTUs in the 9kg cylinder.
I assume you have a 5000 BTU/ hour burner?
Prorating gives you: 80 hours per 9kg cylinder at full blast.
Assume lowest setting is 20% ==> 400 hours.
PS:
I have added a nice comparison of home heating fuel costs
PPS:
Since you explicitly said LPG --
I did find, finally, the "Liquified Propane Gas"
For LPG it is 9kg = 412,000 BTUs
For LNG it is 9kg = 414,500 BTUs
i.e. both numbers in line with my above 400,000BTU for the compressed gas. So the number of 80 hours burn time at full blast does not change much.
To say with difficulty. Depends on the possible minimum achievement of the heating emitters. Well, to think so energy-consciously.
Ask your supplier for (perhaps) empirical values.
The more important question to ask is,what is the vaporization rate of these tanks.As the heaters deplete the gas in the tanks they will not vaporize as much gas and at some point the tanks will frost over and the liquid will refrigerate.Full tanks at a higher temperature will vaporize a large quantity of gas, half empty tanks in a colder environment will have a much reduced rate.Tanks must be sized to accommodate the BTU's needs of the heaters when the tanks are close to empty at the lowest temperature they will be stored in.The tanks you have may have enough volume to run the heaters for many hours just by volume but when you put the vaporization calculations in they may only work for a couple of hours.The best place to get these calculations is from your LPG distributor.A quick calculation is length of tank x diameter x45[diameter and length are in inches and not centimeters,the multiplier will be different for metric],this will give a figure for the tank when it is 10% full. This will give you a rough idea of what the tank will do.You may have to manifold two or more of these tanks together to get the rate required.
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