Gas pressure...

[mrcaptainbob]

What's the pressure in a propane tank? Like one of those 300 gallon ones by the house?

[paul52446m]

What's the pressure in a propane tank? Like one of those 300 gallon ones by the house?

Temperature and pressure are related, The higher the outdoor temp the more pressure you will have. Most LP gases boil off at about 45 degrees below O.
So at less than 45 degrees below, no pressure, as the temp goes up so does the pressure. all gases are that way. Later paul

[HayZee518]

propane has a boiling point of minus 41 degrees fahrenheit. I have a 200# tank at my house. a full tank has 47.5 gallons of propane. it is normally filled to 80% to allow for expansion.

[mrcaptainbob]

Tank pressure.

Yes. I am familiar with P1/V1=P2/V2. But there's a pressure regulator in line before the entry point to the house. I was wondering what the nominal pressure would be in a propane tank to drive it to and through that regulator to the furnace. I know the furnace is measured in inches of water, but was wondering about the outside propane tank itself. There must be some kind of psi to drive that gas through the system. For kicks and giggles, suppose it's a 500G tank, 50% full at 50*.

[paul52446m]

Yes. I am familiar with P1/V1=P2/V2. But there's a pressure regulator in line before the entry point to the house. I was wondering what the nominal pressure would be in a propane tank to drive it to and through that regulator to the furnace. I know the furnace is measured in inches of water, but was wondering about the outside propane tank itself. There must be some kind of psi to drive that gas through the system. For kicks and giggles, suppose it's a 500G tank, 50% full at 50*.

It does not make any difference how much is in the tank,100 or 50 gal., pressure will be the same depending on temp. There are two system used on tanks.
two regulator system, reg. on tank goes down to 10 lbs., reg. on house goes from 10 lbs. to about 13 in. of water column, which is less than 1/2 lb.
There is 29 in. of water column to one lb.
The other system has just one reg on the tank that goes from tank pressure to 13 in. of water column. Later Paul

[HayZee518]

check out this site - will explain the whole process. and I stand corrected BP is minus 44 degrees.
Propane Facts & Comparison Charts

[pushkins]

So does pressure relative to air temp. explain why in winter my BBQ doesn't have as big a flame (bottle stored in the BBQ) ? Currently 36 F too damn cold for NC...lol

[paul52446m]

So does pressure relative to air temp. explain why in winter my BBQ doesn't have as big a flame (bottle stored in the BBQ) ? Currently 36 F too damn cold for NC...lol

Very well could be true. In your small tank you might not be boiling off fast
enough to fire the btu that you are trying to burn. That happens a lot in the winter. I have a salamander 150,000 Btu. I put it on a 100 lb tank. I have to aim
the salamander so it warms up the tank in a cold unfinished house or after a short time the flame will start going down.
another factor we have is, your gov. said we need to make these LP tanks
safer for you, so they came up with these new valves that you had to put in you small tanks. Well guess what, this new valve won't pass as much gas as the old valve so in some cases, less Btu on you equipment. put it safer.
Paul

[paul52446m]

check out this site - will explain the whole process. and I stand corrected BP is minus 44 degrees.
Propane Facts & Comparison Charts

The things they don't tell you about LP gas. Lp gas is a manufactured gas
So you have different co. making it. Some Lp gas may be worth 98,000 btu per.
gal, and others might be worth 96,000 btu per gal. Because of factors like this,
and how hi you are above sea level varies the boiling off temp. Paul