Propane Amount Question

[BFL13]

I still don't understand my propane situation. Any help appreciated.

I have a "76 lb tank" which I take to be "full" at 80% or 61 lbs. I am used to having two "30 lb" bottles, but when they get filled I am charged for typically 30 lbs, and they are only filled to 80% as well?

So it seems my "76 lb tank" is about the same as two 30s in real life?

As an example my first time to refill the tank it was showing about half full, and they put in 26 litres to fill it. I got charged by the litre for the tank instead of by the pound as with cylinders.

My Manchester hand- out says 4.24 lbs/gal (US gal no doubt) and that would be about 3.8 litres/gallon? so a 30 lb cylinder would be about 27 litres which is about what they put in my "76 lb" tank at about half full, so I am thinking all I have here is a sideways two 30 lbers same as I had in the 5er.

Is that about right? Or how do you figure propane amounts?

I also don't understand the "liquid propane" deal, where I had to go to a sort of gas pump that did propane to fill the tank instead of to the usual cylinder fill place. Don't cylinders get "liquid propane" too? But they charge by the pound to fill a cylinder, but by the litre to fill the tank.

[BFL13]

It starts with the 80% rule, where you must know "80% of what?"

So your tank size is one thing and your full amount of LP is another thing. Then some people call the tank size by the full amount "size"

I will think of mine as a "70 litre" tank if that is what it holds when "full" and they charge by the litre.

I got into this mess by trying to relate what my tank holds to what my 30lb bottles held. How naive! 😞

[time2roll]

BFL13 wrote:
I agree it is all too silly. Another case where the people who invent these things have never gone RVing.

Or maybe they have customers that would otherwise run out and find it is better to have a reserve.

Same with the fuel gauge. Vehicle does not stop at E but actually continues 10 to 40 more miles.

When the tank is on E by all means fill it up. If you have a long distance and feel more comfortable filling at half that is fine too.

[MrWizard]

Full is full, and the volume posted on the tank, is the correct volume
Mechanical gauges on tanks do sometimes get out of calibration

Run until you run out, get it filled, make a note of the amount

Use it until the guage reads empty
Refill and make a note, that difference is your reserve
What you still have when the guage reads empty
A few fill ups, and a few trips, and you will know your use pattern

"Trends and tendencies"

[BFL13]

I tend to think now that 1/2 on the tank gauge is more like 2/3 of what LP the tank holds when "full" At that time, the range hood monitor was showing three lights out of four. (Shows four lights indicating full when the tank is full showing 3/4)

Somebody mentioned the confusion of "thirds" vs "quarters" between these two gauges in another thread. Anyway, it seems that the range hood monitor is a little "over" what is really there, while the tank gauge indicates less than what is there, so somewhere between should be close.

I agree it is all too silly. Another case where the people who invent these things have never gone RVing.

[Jayco-noslide]

I think when the gauge says its half full, then its half full. But when you have it "filled" the gauge will only say around 80% full because that's all they are allowed to put in. So full isn't really "full" 100% but the gauge is accurate and says 80%. Could that be any more confusing.

[MEXICOWANDERER]

https://www.youtube.com/watch?v=Sj4hqYFNRqY

[BFL13]

MrWizard wrote:
1995 34ft Safari 26 gal

1997 36ft Bounder 24 gal, 24*4.24=101.76, aka round off 100#

Yes, but "full" is 80 lbs. I have also seen 4.14 as the conversion factor. Marshall hand-out says 4.24. Apparently nobody is in charge! 🙂

[ktmrfs]

Dutch_12078 wrote:

ktmrfs wrote:
BFL

if your talking about a MH mounted tank, what happens if you fill it when you are slightly off level? I don't know how these tanks are constructed with the spit valve etc. but if how do they accomidate (or lack theroff) if your filled off level? that might account for the difference.

The dip tube for the fixed liquid level gauge "spit" valve is located at the center of the tank. Being off level has virtually no effect on the amount it takes to fill the tank.

that makes sense. seems like it would be designed from a safety standpoint to not rely on it being level when filling.

[MrWizard]

1995 34ft Safari 26 gal

1997 36ft Bounder 24 gal, 24*4.24=101.76, aka round off 100#

[BFL13]

Gas station lots are fairly level, as where this one was. Another factor is at colder temps the tank holds more LP. It was around 40F at the time.

Have to get used to this way of doing propane. I liked the two bottles, where you knew when the first one went empty, about how long you had before the last one went. (Not quite as long as the first one of course)

I will have to learn when I should get a fill so I don't run out at an awkward time. That's why I have been trying to figure out how all this works. They don't make it easy---1/2 does not mean half etc? Who needs that? I think I have it sort of figured out now thanks to the help here.

[Dutch_12078]

ktmrfs wrote:
BFL

if your talking about a MH mounted tank, what happens if you fill it when you are slightly off level? I don't know how these tanks are constructed with the spit valve etc. but if how do they accomidate (or lack theroff) if your filled off level? that might account for the difference.

The dip tube for the fixed liquid level gauge "spit" valve is located at the center of the tank. Being off level has virtually no effect on the amount it takes to fill the tank.

[time2roll]

Keep a chart of the tank level and how much you put in.
Try to fill at 3/4, 1/2, 1/4, 1/8 and see what goes in.
You really want to know capacity run it until the furnace quits.
It is what it is.

[BFL13]

red31 wrote:

BFL13 wrote:
It doesn't come out right that 26 litres is half a tank, so I will have to get more info next time it is "filled" and confirm the tank's gauge too.

The existing 1/2 or 50% plus an addition 30% = 80%, ie 26 litres represents ~1/3 of a tank or 30%.

Now I have had several coffees, this almost makes sense!

So the tank gauge reads about 3/4 when the tank is "full" which is the 80%, and it sends to the range hood monitor which then shows four lights as "full" (from a previous thread on here when I was asking about that)

So I went in with the tank gauge down from 3/4 to showing 1/2 (range hood was at three lights) and they put in (I think it was) 26 litres and the tank was full again.

So "1/2" isn't half either! 🙂 Full would be about 3 x 26 = 78 litres or about 20.5 gallons , which is off because my reading of "1/2" was very approximate so it is all in the ball park for around 19 gallons, so now I think I get it! 🙂 Oops, that is just when you get in trouble---.

[BFL13]

DrewE wrote:
23.2 gallons would be the water capacity. LPG capacity is about 80% of that, allowing for headspace. Thus, when properly filled, it would hold just about exactly 70 liters of LPG, or around 75 pounds, or the equivalent of two and a half 30 lb bottles.

Good--that's what I was guessing after all this.

My 1991 MH brochure says the 28 footer has a 76 lb tank. ( Their 24 and 26 footers had 45 lb tanks it seems)

Mr Wiz says he has a 24 gal tank "or 100#" Not clear on that. I saw some articles where they talked about "100 lb tanks" Perhaps that is more of a nick-name than an actual size?

EDIT- I see the 20ft Born Free MH specs show:
PROPANE CAPACITY
19.5 gallons (80 percent filled)

So I suspect that is the same tank at around 19 US gallons, not sure. That is a big tank for a 20 ft MH, but could be.

Maybe we all have exactly the same size tank and have different ideas of its size? 🙂