? on LP heater

[Blu21]

I'm thinking of installing a ventless wall unit to use as part time heat and backup in my basement. The model is 30,000btu's. Is there a calculation or formula to give me a ballpark figure of propane usage? I want to know if the initial investment would be worth it in the long run. Thanks Tom

 

[cowboydoc]

I was wondering the same thing Tom. I wanted to put one in my barn. The only drawback I can see is that it is on all the time. You can only set from a low to a high setting. Supposedly you can run them on one gallon of lp per day.

 

[TWINKLE_TOES]

Propane is sold by the therm. one therm is equal to 100,000 BTU's.

Your furnace running for ~ 3 hours will delivery ~ 90,000 BTU's and burn ~ 1 therm of propane. Factor in the duty cycle the furnace runs, you know what you pay for a therm, you can figure out the cost per hour.

1 BTU will raise the temperature of 1 lb of water 1 deg F.

Al

 

[beenthere]

I had a ventless 30,000 BTu LP gas heater in my garage for three winters, and have taken it out. Going to go with a vented because there is so much moisture from the ventless system. The walls are wet, the floor is wet, and there is frost on everything when -20 outside.

 

[cowboydoc]

Twinkle Toes,
Here propane is sold by the gallon.

beenthere,
Thanks for the info. that effectively rules that out. What system are you going with now and what's the cost? Thanks for any info.

 

[beenthere]

I have a Dayton, 30,000 BTU in my shop (shed) and it hangs from the ceiling. I am planning to go the same route when my attached garage gets finished, but may boost it to 50,000. They are shown in the Grainger book, along with wall furnaces of about the same BTU. Prices are in the $700-$800 range.

 

[TWINKLE_TOES]

Cowboydoc,

Well not really, my bill say's gallons also but it's still therms. Propane is a liquified gas, propane volume (gallons) is a strong function of pressure and temperature. Heat energy (therms) is constant. A rough equivalency is 100,000 BTU's = 1 therm. 1 gallon = 91,600 BTU's.
Al

 

[cowboydoc]

beenthere,
Yep that's what I was told to go with as well.

Al,
Thanks for the info. I guess I never paid much attention to the bill. I just knew that when I called they told me how much per gallon or got my tank filled for the horse trailer or barbecue.

 

[heehaw]

i think a house could rot down from the inside out if a person used one of those ventless heaters as their sole heat!
i am installing one, with natural gas, as a back-up, in case the power fails, but sure wouldn't use or recommend they be used extensively.
heehaw

 

[PaulT]

Aren't liquids "generally" uncompressable. That is to say, once sufficient pressure has been applied to the propane to condense it into liquid, its volume won't change (for the sake of measuring 100's of gallons in a storage tank) appreciably? If that is the case, then gallons make sense as a unit of measure. I know here they sell propane in gallons. Since it is delivered in liquid form, using a standard measurement of liquid volume makes sense.

On the other hand, when I use it, it is a gas, and so measuring a LP burning device in therms or BTUs makes sense, especially because you can figure out how much heat it will produce that way. Even in this situation, a conversion factor to gallons would be useful for budgeting purposes. The conversion factor will have to take into account the temperature and altitude to be correct, since that is where the pressure and temperature sensitivities are relevant.

PaulT