A genuine Propane Puzzler

[GrouchyOldMan]

In the spirit of giving something back, I offer the following story of a weird problem my wife and I experienced on our first cold weather trip. I now know the answer and I wonder if anyone here can nail it?

We recently purchased a 2016 Coachmen Freelander 21QB in Virgina and we've been packing in as many trips as possible before the really cold New England weather shuts us down. We were caught a little by surprise when that November Polar Vortex swept down on us while we were visiting Gettysburg, VA. The nights got down to 12 degrees and our Little House was damned uncomfortable when we woke up at 2:00 am to find that the furnace had stopped working. I started preparing to go outside and do battle, but the Saintly Spouse calmed me down. Instead we threw on an extra blanket and snuggled close to get through the night.

In the morning I tried the stove to perk a pot of java and it worked fine. When I turned on the furnace it also came back to life as if nothing was wrong. Perplexed and ever the optimists, we tried to believe it was just a quirk. That still seemed plausible the next evening when the furnace obliged and kept the place cozy all evening. Early the next morning however we woke to a cold house again.

I plowed through a few hundred forum posts and youtube vids and came to the conclusion that the regulator was probably bad. Annoying in an almost new RV, but it's pretty well known that Forest River doesn't always use the highest quality components. I think the term of art is "Value Engineered." In any event I was lucky to find a nearby RV shop that had the correct replacement regulator and was willing to install it while we waited. We tested the fix by lighting up every propane appliance we had: genset, furnace, hot water, refer, even the stove and oven. Couldn't make it fail, must be all fixt. Cool beans.

No deal. Next night, on the road back to Cape Cod it got *really* cold and the furnace wouldn't even light up in the evening. Stranger yet, the stove worked fine, even the oven. The water heater lit up normally and I could hear the furnace trying to light, even getting flame but then going out. Then things got worse as even the stove top burners got really low. Finally, there was only enough gas to keep one burner barely burning.

Sheesh! New regulator, full propane tank, what the hell? I had read that propane could freeze up if there was a large volume running through the pigtail behind the regulator, so I pulled out the little electric space heater and when I held it up to the propane pigtail hose my wife reported that the stove flame immediately leapt back to normal size. We tried the furnace and voila! Too strange.

Our trip ended and I took the RV to our friendly dealer, Majors RV up in Bourne. Their "propane guy" David was out at the time but he called me back later that day and after patiently listening to the details, he nailed it in one shot.

I realize that this is a long winded story, but there are probably some expert propane folks on this forum and I thought I'd challenge you to diagnose this problem. I'm not going to provide any hints beyond the details above, but I'll check back here in a few days and see if anyone can solve this puzzler.

Cheers,

-Grouchy

[Dutch_12078]

The previous owner must have knowingly bought butane. The HD5 "consumer" grade LPG sold in the US is required to be no less than 90% propane, and no more than 5% propylene, with the remaining 5% other gases, including butane, iso-butane, methane, etc.

[ktmrfs]

MEXICOWANDERER wrote:
with regard to reading vapor pressures = temperatures, the amount of boil off must be taken into consideration. A pot, cylinder or tank with low amount boil off surface area will become COLDER than the liquid was when starting off. Expansion. When the expansion rate is very low the tank temp will remain near ambient temp, when the expansion rate is very high (high amount of boil off) the temperature can *easily* sag -20F.

In extreme areas, 97% propane and 3% methane is the mix to achieve proper vapor pressure. The Soviets transported LNG into the remoter regions of Siberia where -80F was not unheard of.

In the winter in the mountains I always had pots of butane to start charcoal with. Some liquid was allowed to soak into the carbon then when set alight it burned furiously for a few minutes. And not a hint of taste contamination.

I reality, a 7.5 gallon propane tank, filled with propane, not propane butane mix, is marginal for a 30Kish furnace or HWH anyway. It will usually do fine when full, but as it gets depleted the mass of the remaining liquid is low enough to really drop the temp as you mentioned, which reduces vapor pressure and how much you can draw. On my tanks, if the furnace is the main draw in the morning even at 45F or so and is near the bottom, after the furnace runs for 30 minutes or so tanks will switch. But if I switch them back the "empty" tank still has 10-20 percent capacity and will do fine for the fridge or stove till evening.

One chart I saw says that 10lbs of propane in a cylinder will support about a 30KBTU draw at 0F PROPANE temperature. but that 1/3 tank of a 7.5 gallon tank, or 1/2 a 5 gallon tank.

[RJsfishin]

For a spare because apparently it wasn't bad,....?? Maybe I missed it, duh ?

[Farmboy666]

Curious as to why you kept a regulator that you thought was bad?

[MEXICOWANDERER]

with regard to reading vapor pressures = temperatures, the amount of boil off must be taken into consideration. A pot, cylinder or tank with low amount boil off surface area will become COLDER than the liquid was when starting off. Expansion. When the expansion rate is very low the tank temp will remain near ambient temp, when the expansion rate is very high (high amount of boil off) the temperature can *easily* sag -20F.

In extreme areas, 97% propane and 3% methane is the mix to achieve proper vapor pressure. The Soviets transported LNG into the remoter regions of Siberia where -80F was not unheard of.

In the winter in the mountains I always had pots of butane to start charcoal with. Some liquid was allowed to soak into the carbon then when set alight it burned furiously for a few minutes. And not a hint of taste contamination.

[SidecarFlip]

So, what is the 5 dollar answer to the 64 dollar question? I'm sticking with frozen water in the supply line.

[YC_1]

Wow, I haven't heard that one in over 50 years. I can remember that as a kid. Why, where, and how I became aware of it is a mystery except we lived in a mining camp in the mountains. We had many large tanks of "butane".

[SaltiDawg]

Back in my Submarine Sea Going days, I think I navigated past Gettysburg while at Periscope Depth.

[wa8yxm]

I would ask how warm it was when it worked.
Propane does not freeze or to be more precise does not refuse to boil (Turn to vapor) in the temps you cited, it is good down to about -40 give or take a couple degrees.

BUTANE however, remains a liquid at around the freezing point of water.

Second. Moisture in the pigtails CAN freeze, and clog them (or anywhere in the lines or regulator

On removable tanks not having the ACME connector properly tightened can cause the safety valve to close.

And last but not least, IF you have a propane detector which controls a cut off valve.. Yup, forget to turn it ON perhaps? Or low batteries.

[gbopp]

SaltiDawg wrote:

GrouchyOldMan wrote:
... We were caught a little by surprise when that November Polar Vortex swept down on us while we were visiting Gettysburg, VA. ...

It's a trick question? No Gettysburg in VA. :B

But, there is a Virginia Monument in Gettysburg. Does that count? 🙂

[GrouchyOldMan]

WE HAVE A WINNER!

Actually, two winners, The observant SaltiDawg shames me into acknowledging that this WAS actually a trick question; Gettysburg is in PA not VA (where we purchased our RV)!

The grand prize however goes to our LPG guru ktmrfs who, in an admirable stepwise diagnosis, fingers Butane as the culprit.

As it turned out, the original owner had taken his one and only vacation in the RV down to Florida and while there he filled my gas tank with Butane. Apparently this is a frequent practice down South where it doesn't freeze in winter. Butane is significantly cheaper than Propane, and even though it doesn't have the equivalent BTU output as Propane, it's "Good enuf" for most folks.

When we bought the Freelander, it had almost a full tank so when we topped it off it only took a couple of pounds of Propane. If you think about it, the mix of Propane and Butane was the key to the puzzle because it created an intermittent failure that only showed up when it got below freezing and also after all the propane already "gasified" had been consumed by the appliances. The regulator of course had nothing to do with anything so now I have a spare reggy.

The solution in the end raised another interesting topic, purging the tank of butane. There's a Big Red thingy on the bottom of my (built-in) propane tank labelled "Purge," but I have been cautioned never to touch it.

I was advised to just turn on the furnace and let it run until the tank was empty.... it took three and a half days! When it was completely empty I put a couple of pounds of nice fresh Propane in the tank and all is well. The last time it froze here I sat out in the RV with the furnace blazing and watched the NE Patriots dominate the field in total comfort.

So, thanks for playing everyone! All hail ktmrfs as the golden gawd of LPG wisdom.

Cheers,

-Grouchy

[ktmrfs]

since the tanks were full, low temp shouldn't affect the draw and boiling issue. However, two things could be an issue, one is ice in the line. The other is that what you got was LPG liquified petroleum gas. Now LPG is not necessarily all propane. In some areas, especially in the summer it can have a fair amount of isobutane or butane in it to help keep the pressure down when the tanks are hot. Now drop the temp and you have a real problem. butane boils at somewhere just below freezing, not -40C, and the vapor pressure is also lower. so..... when it gets cold you can't draw much or for very long.

So..... did you have a tank that was propane/butane mix? Or was it ice in the line.

[SaltiDawg]

GrouchyOldMan wrote:
... We were caught a little by surprise when that November Polar Vortex swept down on us while we were visiting Gettysburg, VA. ...

It's a trick question? No Gettysburg in VA. :B

[sch911]

Sail switch?