My first stupid question: Propane

[dkoldman]

Originally Posted by twinboat

The correct info on what a 20 lb tank can hold is everywhere on the internet. 20 lbs.

It holds 4.7 gallons of propane which is 80% of the tanks capacity.

Take a look for yourself.

Propane tank refill vs exchange - eLivermore.com.

https://www.poynter.org/reporting-ed...nd-grill-tank/

The math checks out

[dkoldman]

My RV tank is rated to hold 18 gallons or 76 pounds. That is 4.22 pounds /gallon

If I had 4.7 gallons; that would be 19.84 pounds; which will fit perfectly in a 20 pound tank

What is missing by most?
These "20 lb" tanks are designed to take up to 20 pounds of propane. You may get a pound or 2 less, depending on the temperature of the tank and surrounding air when the tank was filled. Cooler = more propane in, hotter = less in. Tanks can actually fit another 20% in the tank, but that extra space is designed for expansion as the temperature rises.

But don't try to put more than 4.7 gallons or more than 20 pounds in a 20 pound propane tank

[KanzKran]

The only reliable way to know how much you can put in a DOT cylinder is to use the WC (water capacity) value on the ring. That's the weight of water it will hold filled to the top. Propane is about 51% as heavy, so multiply that figure by .51 for the weight of propane it will hold filled to the top. It will be somewhere around 25 lb for a "20 lb" cylinder.

80% of that is the legal capacity.

You can also just multiply WC by .41 (80% of .51) to get the 80% fill weight of propane. Every DOT cylinder has the WC value on the ring, as well as the tare (empty) weight (TW), so subtracting TW from actual weight tells you how much is in the cylinder.

Chassis mount ASME tanks, on the other hand, show total volume in gallons usually. You can fill to 80% of that, using the vent indicator to know when it's at the legal max. Multiply capacity in gallons by 3.4 lb/gal for the 80% fill weight of propane, if for no other reason than to compare to the common 20 lb cylinder.

My van holds 41 lb of propane. Small tank, but the Truma Combi is pretty efficient, and even though we travel mostly in cold weather and use the heat a lot, I've only filled it once. And it wasn't even close to empty.

[rkf]

Dish has add on dvr’s

[Isaac-1]

Google can also be your friend in looking for a places that fill propane, last October I was passing through Springerville, AZ in need of propane, the truck stop / gas station had a propane tank, but did not have the right fill adapter for my motorhome tank, google to the rescue, found a commercial / residential propane supplier 2-3 miles away along my route, called them they said come on by, filled up (32 gallon propane tank), and I was on my way.

[Ray,IN]

Originally Posted by Old-Biscuit

20# LP Cylinder ---- Milk Crate (Home Depot etc)
Great containment
Store in outside compartment etc
DO NOT Carry/Store INSIDE RV....should relief valve open vapor cloud under high pressure
DO NOT Carry/Store on it's side...should relief valve open LIQUID Propane spews out

Is your LP Tank service/vapor valve, fill valve, 'bleeder' valve etc right at side of RV?
OR
do you have a 'remote' panel and tank is mounted inboard between frame rails?
Stay awhile/extend a stay propane adapters can be installed between service/vapor valve and Main Regulator which allow connecting an external propane vessel
Ease of install depends on LP Tank location

The explosive force of propane is hundreds of times that of TNT. I would state specifics but I might arouse the interest of Homeland Security.

[aether_one]

Originally Posted by MotorPro

Tanks can only legally and safety be filled to 80%. So a 20 lb tank can only take 16 lbs.

Originally Posted by twinboat

The correct info on what a 20 lb tank can hold is everywhere on the internet. 20 lbs.

It holds 4.7 gallons of propane which is 80% of the tanks capacity.

Take a look for yourself.

Propane tank refill vs exchange - eLivermore.com.

https://www.poynter.org/reporting-ed...nd-grill-tank/

Don't confuse Internet propaganda with facts!

[jl.kauai]

Amazer, you have been given good advice. Stay away from some of the fill stations that require a 5 gal minimum as there are some in Ca. Most places will fill your tank for what it needs only. No minimum. Always ask. Do not hook up to your propane barbecue connection as it is a different pressure. Meant for a barbecue. An extend a stay is a good investment if you plan to be stationary. No question is stupid if you don’t know the answer. Take care, john

[twinboat]

Originally Posted by Ray,IN

[emoji144][emoji144][emoji144] The explosive force of propane is hundreds of times that of TNT. I would state specifics but I might arouse the interest of Homeland Security.

Propane is a flammable, not explosive gas.

It can BLEVE, but that takes prolonged flame inpingment on the tank.

[dkoldman]

Ok I got question for comments from the GPGs (Grand Propane Gods) :bow

So today, I decide to check on my propane, preparing for a trip in 3 weeks.
My tank specifications says 18 gallons and 76 lbs. 2019 Winnebago Sunstar 29VE.

The inside gauge LEDs read 1/3 of a tank remains.
The actual tank outside had indicator pointing straight up indicating half way full
I am in Dallas Texas ( can't see the sea; so I don't the know sea level; but it ain't too high in Dallas )
Outside Temperature 87 degrees

So I figure why not go fill it up. I drive to a local U-haul who charges $2.99 / gallon. If someone has a better price, I will listen?

THe U-haul Manager comes out and fills it up; but it is only 4.3 gallons!!!

I asked him was he sure and he was confident it was full. So I go inside and the LED gauge is now reading Full, I go to the tank outside and it too is reading Full all the way to the right.

I asked the Manager how could it be because I have 18 gallon tank and he says maybe I only have a 8 gallon tank?

The last time I purchased propane was 2/15/20. I bought 7 gallons then. I am pretty sure the LED gauge was reading Empty then; but I was NOT out of propane.

Any idea of what is going on?

RV USA confirms my specifications.
https://www.rvusa.com/rv-guide/2019-...n-29ve-tr41862

Picture of tank below, on bottom it has some specs stamped on tank case but I can't read it.

[twinboat]

I would find a way to read the tag on the tank. It will be the only way to know.

[KanzKran]

You can also measure diameter (or circumference and divide by pi - use a piece of string if that’s easier), square that, and divide by 4, then multiply by it’s out-to-out length. Multiply that by 0.91 to account for the not-really-hemispherical end caps, and divide by 231. That’s the approximate 100% fill amount in gallons. 80% of that is your legal fill level, also in gallons.

The end cap fudge factor gets you pretty close to actual, and it is certainly good enough to know if you have an 8 gallon vs 18 gallon tank.

Edit: You can also skim some light along that data plate and take a close-up photo. Skimming light along the surface highlights the stamped information. Usually. Unless the paint is just too thick.

[dkoldman]

Originally Posted by twinboat

I would find a way to read the tag on the tank. It will be the only way to know.

There is no sticker on the tank. The data we seek is stamped on tank; but so light you can't read it especially with the paint on the tank.

Why would Winnebago say it is 18 gal / 76 lb tank if it NOT?

I did get some crude measurements from the tank. It is about 28" long and about 14 wide in diameter. it round rectangular cylinder.

[dkoldman]

Originally Posted by KanzKran

You can also measure diameter (or circumference and divide by pi - use a piece of string if that’s easier), square that, and divide by 4, then multiply by it’s out-to-out length. Multiply that by 0.91 to account for the not-really-hemispherical end caps, and divide by 231. That’s the approximate 100% fill amount in gallons. 80% of that is your legal fill level, also in gallons.

The end cap fudge factor gets you pretty close to actual, and it is certainly good enough to know if you have an 8 gallon vs 18 gallon tank.

Edit: You can also skim some light along that data plate and take a close-up photo. Skimming light along the surface highlights the stamped information. Usually. Unless the paint is just too thick.

Using 14" dia and length of 28", I get 5.4 gallons when I factor 80% I get 4.3 gallons. That is only a 20 lb tank? I would think it is at least 40 lbs?

Edit: The math cannot be correct? I found receipt where I purchased 10.1 gallons last December. So 10.1 * 4.22 = 42 lbs.

So to have at least 42 lbs that means the tank would have to be rated for at least 53 lbs

But again, the Mystery is that Winnebago says it is rated for 76 lbs. So I sould be able to add 60 lbs (14.4 gal) when completely empty