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Old 08-22-2012, 08:04 PM   #1
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Here's the problem, what's the diagnosis: propane flow

Here's a tickler for you:

The water heater and the stove work fine during the later evenings, nights, and mornings, but during the hot afternoons the flow of propane is very anemic, practically impossible to use. (Yesterday afternoon, quite a hot one here in Santa Fe, I was completely unable to make my afternoon shot of espresso!)

I have my own hypothesis about what's happening, but I'd like to hear your opinions about it ...


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Old 08-22-2012, 08:22 PM   #2
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Have you drained the water out of your LP lines lately?
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Old 08-22-2012, 08:27 PM   #3
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Nope, haven't tried that yet, Terry, though I may try it when I get home. I kind of wonder if it's a major problem, though, because it stays relatively cool under the Airstream where the propane lines are. (This is Santa Fe heat, where the highs are in the 80s.)

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Old 08-22-2012, 08:33 PM   #4
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I mention the water because I had two Airstreams recently with intermittent function of the LP system. I undid a connection under each trailer, and got a bath of foul-smelling water, I assume from condensation.
Even if it doesn't work, it costs nothing to crack open a line underneath, and see if anything pours out.
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Old 08-22-2012, 08:44 PM   #5
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I am going to guess a bad regulator. Of course that is how I usually fix things. Start replacing parts until it works again!
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Old 08-22-2012, 08:49 PM   #6
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Isn't it funny how that replacing parts thing goes? It's always the last thing you change that was the problem.
Is it just my bad luck that this happens? LOL
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Old 08-22-2012, 08:52 PM   #7
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I am going to guess a bad regulator. Of course that is how I usually fix things. Start replacing parts until it works again!
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Isn't it funny how that replacing parts thing goes? It's always the last thing you change that was the problem.
Is it just my bad luck that this happens? LOL
I've found you can fix anything, if you throw enough parts and money at it.
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Old 08-22-2012, 09:00 PM   #8
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I mention the water because I had two Airstreams recently with intermittent function of the LP system. I undid a connection under each trailer, and got a bath of foul-smelling water, I assume from condensation.
Even if it doesn't work, it costs nothing to crack open a line underneath, and see if anything pours out.
I once helped a neighbor when I lived in the Texas Hill Country. She had a space heater connected to a propane tank in the yard. I got really cold, and nothing worked.

My hint was when she said, "I could hear it bubbling through the line before."

I took the line loose and we heated it with a hair drier. Sure enough, the ice melted and ran out. Heat worked again.

Although I'm not sure why water in the line would get worse in the heat. Like Terry said, it doesn't cost anything to try and if you do have condensation in the line, it needs to be removed.
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Old 08-22-2012, 09:15 PM   #9
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Ok, I'm going to throw out my hypothesis. It has to do with the vapor/air gaseous mixture at the top of the propane tank, above the liquid propane in the bottom.

Liquid propane turns to vapor at a certain temperature at sea level. Easy enough to look up. It's the sea level part that caught my eye: This involves air pressure. Obviously, if you dramatically lower air pressure, then vaporization occurs readily. If you dramatically raise the air pressure, then vaporization occurs far less readily.

Now consider that vapor/air mixture at the top of the tank, which is under pressure. In effect, what we have is an artificial environment of air pressure, pressing down on the liquid propane below it. If that artificial enviroment is heated, it expands, altering the pressure on the liquid propane below it.

I think you may get the picture here: Propane flow is reduced just in the afternoon heat because of the heat-enhanced pressure exerted on the liquid propane by the vapor/air mixture at the top of the tank.


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Old 08-22-2012, 09:25 PM   #10
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Isn't it funny how that replacing parts thing goes? It's always the last thing you change that was the problem.
Is it just my bad luck that this happens? LOL
Of coarse it's the last thing that you replace that fixes the problem. Only a moron would keep replacing more things after the problem was fixed!!
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Old 08-22-2012, 09:32 PM   #11
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Ok, I'm going to throw out my hypothesis. It has to do with the vapor/air gaseous mixture at the top of the propane tank, above the liquid propane in the bottom.

Two things:

First, your propane tank should have liquid propane below the liquid level and gaseous propane above the liquid level. There shouldn't be any air in the tank. If there is, at certain temperatures the propane/air mixture above the liquid would fall within the explosive limits, a most dangerous situation.

Second, the vapor pressure of a gas over a liquid in a closed container at equilibrium is independent of the partial pressure of any other gases in the closed container. (Dalton's Law)

I dunno what the problem is. The idea of draining the lines sounds to see if there's any liquid in them sounds worthwhile--and doesn't cost anything--and if that doesn't do it I think I'd replace the regulator on general principles. (otherwise known as eliminative analysis )
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Old 08-22-2012, 09:32 PM   #12
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It's related to cattle mutilations and those pesky chupacabras that frequent NM.
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Old 08-22-2012, 10:01 PM   #13
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I was told that problems can happen in old (or 'vintage', as we call them) trailers because the stinky stuff they include in the Liquid Propane (Ethyl mercaptan) pools in the supply pipes.

You can imagine the pooling that would be going on for 40 years or more in lots of trailers!

Apparently, the pooled Ethyl mercaptan can reach a point where certain fittings suffer reduced flow capacity, and potentially even blockage, so, all this to say, it is a Bad Thing to have this going on in your TT.

I was also told that the way to get rid of the problem is to renew the supply pipes to your furnace and heater.

Hearing Terry's tale of a few TTs with water in those pipes surprised me. Doesn't something have to be leaking, like say, the distribution valve, for that to be able to happen?
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Old 08-22-2012, 10:31 PM   #14
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Actually, what I've found when filling cylinders is that the pressure-sensitive pump I use will operate only very slowly for some cylinders, especially in the summertime. When I check those cylinders for pressure, I find that those that won't allow the pump to operate normally have tremendous pressure build-up inside.

In one fairly extreme instance, some folks staying over in Eagle Nest in July brought by their recently filled cylinders from their brand-new rig, saying that they couldn't get them to run the stovetop or anything else at all. I weighed the cylinders, determined that they were indeed fairly full, but then cracked one of the cylinders and found it to be VERY pressurized. No way would one have been able to pump any more propane into them. I simply released some of the pressure and sent them on their way. Happy campers.

It's now after 9:00 pm here and much cooler. The water heater didn't still want to work well at around 7:00 pm (though I did manage to get enough heat out of the weak flow at the stovetop to fix up a cup of espresso). The water heater started up like a champ just a few minutes ago.

Oh, one other thing. Since arrival here, I found that the fridge just won't cut the mustard on propane; does great on electricity. Odd because it seemed to work great on propane just before I left for Santa Fe from Angel Fire, where heat is rarely an issue. It's a fairly new fridge, a European Dometic, which was a better fit for the replacement of the old, dead one. Reading the documentation, I found that I probably need to do a clean-up of orfice area, etc. But now I'm wondering. Maybe I'll get to the bottom of the heat-related propane flow issue, then see if the fridge doesn't start acting right after all.

This still could be some kind of expanding non-propane liquid in the lines, and I plan to check it once I get the rig back home in early September. Wish I could check it all out here, though, because testing for heat-related flow decrease is kind of hard to do in Angel Fire. By early September, it's time to winterize up there.


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