LPG btu output in cold weather

ChrisJ · January 22

I'm guessing there's charts or something for this but how do you figure out how much LP you can evaporate at different tank fills vs outdoor temperature?

I'm looking at a 500 gallon tank that's down to 20%. Is there a way to know how much you can pull from it at say 0f? -10f?

pecmsg · January 22

at 0* no issue

At -20* the pressures going to drop so best to keep the level high.

Jamie Hall · January 22

The specific table is in here…

propane-tank-specifications-low-pressure-quality-steel-USA.pdf.pdf

BUT that table is set up for pure propane, a three carbon chain. LP may NOT be pure propane — in fact, usually isn't — but a mixture of propane and butane (four carbon), which has a lower vapour pressure and, therefore, does not evaporate as readily at various temperatures. So that chart will give you the maximum rate you can expect.

ChrisJ · January 22

https://forum.heatinghelp.com/discussion/comment/1883359#Comment_1883359

I'm looking at 400,000 btu/h worse case assuming full load on the generator etc.

Still no issues?

mattmia2 · January 22

you might rethink how you're looking at it. the draw is the average, it is dependent on the tank absorbing enough heat to replace the heat of vaporization of the propane. you're not going to be running a generator at full load for very long, you almost always are up against you are drawing the full 25 hp or whatever from the engine for a second or 2 while you start a big motor then you are drawing probably 1/4 of that once the motor is started.

ChrisJ · January 22

https://forum.heatinghelp.com/discussion/comment/1883365#Comment_1883365

That depends on an awful lot, but you are right.

But id rather know that it's far from being a concern at all.

hot_rod · January 22

vaporization charts here

http://www.gasequipment.com/content/38-TechnicalInforation.pdf

EBEBRATT-Ed · January 22

Kind of a scary thing I worked on once was a renovated State Police Barracks.

They had a big concrete pad with I think 3 2000-gallon tanks of propane manifolded together.

They also have a propane fired vaporizer which we replaced.

Having a flame burning appliance within feet of a propane tank didn't sit too well with me but especially being a State-owned building I looked it up and it was all code

mattmia2 · January 22

https://forum.heatinghelp.com/discussion/comment/1883378#Comment_1883378

like this?

https://www.michiganpublic.org/news/2019-01-30/fire-at-consumers-energy-facility-threatens-heat-for-1-8-million

Jamie Hall · January 22

I disagree with @pecmsg

A 500 gallon tank t 0 F, assuming that you have 100% propane, 20 full, will give you about 255,000 BTUh.

Nowhere near what you want. You need a 1,000 gallon tank.

hot_rod · January 22

https://forum.heatinghelp.com/discussion/comment/1883378#Comment_1883378

I worked at a ski resort that had the vaporizers in a concrete vault next to large tanks. You had to crawl down a ladder to service or relate the vaporizers!

Any small leaks and the lp settles to the bottom of the vault. Crazy design.

mattmia2 · January 22

https://forum.heatinghelp.com/discussion/comment/1883386#Comment_1883386

ChrisJ · January 22

This seems like it might be a ridiculous question but,

How well do propane tank heaters work? The kind that wrap around like a girdle. Would that be a wash because the generator running it is pulling propane to do so, or does it gain you a lot more output?

Jamie Hall · January 22

I would think they would work — but I'd sure want a rat of safety devices on them. The vapour pressure of LP is very temperature sensitive…. but they would be a net positive. The trick iis to get the stuff to vapourise, which does take some energy — but a whole lot more is released by burning the stuff, once you get it into vapour form!