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Author Topic: Air in the propane line  (Read 2492 times)

seilerbird

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Air in the propane line
« on: February 03, 2012, 10:39:22 PM »
I just bought a 1994 Damon Challenger class A motorhome and I am having some problems with the propane. When the prior owner gave me a walk through she told me the water heater would not light until I had lit one of the burners on the cooktop to get the air out of the line. Once she did that the water heater worked, the furnace worked and the cooktop worked. I tried it today and I could not get the cooktop to light so the furnace and the water heater would not turn on.

So if there is air in the line wouldn't I be smelling propane? I am not smelling propane either inside the RV or outside by the propane tank. There is about a 1/4 tank of propane. Does anyone have a clue as to what is going on?
« Last Edit: February 04, 2012, 11:29:31 AM by seilerbird »

RoyM

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Re: Air in the propane line
« Reply #1 on: February 03, 2012, 11:02:58 PM »
Start with a full bottle and check every fitting with a squirt bottle of soapy water before lighting anything. If everything checks out hold the primer button on each appliance for about a minute to bleed the air out. You should only need to bleed the system once after changing a bottle.
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captsteve

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Re: Air in the propane line
« Reply #2 on: February 04, 2012, 12:16:31 AM »
I have an issue like this. First make sure the soloniod is open, then light the stove. Once you get it to light, mine takes a minute or so, then all should be well.
If the solonoid is stuck, remove it. It is not required any longer. New gas detectors dont have them.
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scottydl

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Re: Air in the propane line
« Reply #3 on: February 04, 2012, 12:30:09 AM »
It's also possible that you're out of propane... those gauges are notoriously inaccurate, or so I was told by my local propane filling place.  It's more of a guideline as to what's left in the tank, rather than something to swear by.  If you're anywhere close to a filling station, have a few gallons put in and see what happens.
Scott, wife, 3 boys... and the dog
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seilerbird

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Re: Air in the propane line
« Reply #4 on: February 04, 2012, 12:36:17 AM »
Start with a full bottle and check every fitting with a squirt bottle of soapy water before lighting anything. If everything checks out hold the primer button on each appliance for about a minute to bleed the air out. You should only need to bleed the system once after changing a bottle.
This is not a bottle, it is a built in tank and I don't know of any primer buttons.

The lady told me I have to bleed the air out every time I want to light the water heater.

seilerbird

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Re: Air in the propane line
« Reply #5 on: February 04, 2012, 12:37:07 AM »
I have an issue like this. First make sure the soloniod is open, then light the stove. Once you get it to light, mine takes a minute or so, then all should be well.
If the solonoid is stuck, remove it. It is not required any longer. New gas detectors dont have them.
What solenoid?

seilerbird

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Re: Air in the propane line
« Reply #6 on: February 04, 2012, 12:38:41 AM »
It's also possible that you're out of propane... those gauges are notoriously inaccurate, or so I was told by my local propane filling place.  It's more of a guideline as to what's left in the tank, rather than something to swear by.  If you're anywhere close to a filling station, have a few gallons put in and see what happens.
The gauge on the tank and the gauge on the monitor both show 1/4 tank. There is propane sold here in the park so I will go add some tomorrow.

scottydl

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Re: Air in the propane line
« Reply #7 on: February 04, 2012, 12:57:38 AM »
The gauge on the tank and the gauge on the monitor both show 1/4 tank.

They likely are both using the same sending unit, which is just a magnetic float inside the tank.  That "signal" is picked up by the tank gauge, which probably has wiring connected that sends an electronic version of the signal to the interior monitor.  So those two will likely always show the same information.
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seilerbird

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Re: Air in the propane line
« Reply #8 on: February 04, 2012, 12:59:52 AM »
That's logical Scotty. I will report back tomorrow.

Lou Schneider

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Re: Air in the propane line
« Reply #9 on: February 04, 2012, 01:29:00 AM »
If she has been shutting off the propane between trips, I'd expect to find air in the lines due to temperature swings expanding and contracting the gas in the pipes.  Any pinhole leak around a threaded fitting, etc. would let air in when the piping cooled down at night and the gas inside contracted.

But it would be unusual to have that problem while the system is pressurized, i.e. if you don't turn off the tank.

The solenoid mentioned above is an electrically controlled valve in the propane line, probably at the tank, that's controlled by a propane leak detector and/or maybe a switch inside the rig.  If you have one, I'd also take it off as they're troublesome and no longer required.
« Last Edit: February 04, 2012, 01:31:31 AM by Lou Schneider »

kjansen

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Re: Air in the propane line
« Reply #10 on: February 04, 2012, 07:15:43 AM »
I bought my 5er used and it hadn't been used for several months.  When I turned on the gas-nothing.  I thought the tanks were empty but found this not true either.   What I found was a stuck regulator.  After leaving the gas turned on for a few days, presto I had gas.  The pressure form the tank must popped open the regulator .   After 2yrs of use I have not had a problem,  gas system works fine now.  Sielerbird, how long has your MH just sat?
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tvman44

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Re: Air in the propane line
« Reply #11 on: February 04, 2012, 07:37:10 AM »
Strange that you have to do that every time, never heard of that.  Will be curious to see what you find to correct the problem.

jje1960

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Re: Air in the propane line
« Reply #12 on: February 04, 2012, 07:49:34 AM »
I've usually had to purge after turning off the supply for extended periods of time, however only once until turning the supply off again.  However don't have built in propane system like the MH's have, do they have auto shut-off built in sensing idle flow or something?
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Gary RV Roamer

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Re: Air in the propane line
« Reply #13 on: February 04, 2012, 08:41:01 AM »
The major controls in an RV LP gas system are the main tank shut-off (may be multiple valves if more than one tank or bottle), the pressure regulator, and, in older systems, a remote control shut-off operated by the LP leak detector inside the RV. Your 1994 Damon has such a remote shut-off. If the LP detector is shut off, has detected a leak, or has lost 12v power, the remote control solenoid will be off and no gas can flow. Make sure your LP detector is turned on and working.

A clogged regulator can also prevent gas flow. Clogs are not terribly rare in old LP systems because oily residue in the LP and condensation moisture can form little blobs that can get sucked up into the regulator. The fix is to replace the regulator and that's not expensive. There is nothing unique about an RV LP regulator - it is a standard unit allowing 11 W.C. inches of pressure and available in most hardware stores, home centers, and gas service shops as well as RV dealers. If a new regulator also gets clogged, it may be necessary to have an LP gas service purge the tank to clean it out.  That is rarely required, though.

And of course the main tank valve must be turned on (but you knew that!).   ;)

Most modern RV LP appliances do not have primers. They are sometimes found on pilot ignition furnaces and water heaters, but rarely on DSI ignition units.
 
« Last Edit: February 04, 2012, 08:44:46 AM by Gary RV Roamer »
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Lou Schneider

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Re: Air in the propane line
« Reply #14 on: February 04, 2012, 09:39:19 AM »
Quote
There is nothing unique about an RV LP regulator - it is a standard unit allowing 11 W.C. inches of pressure and available in most hardware stores, home centers, and gas service shops as well as RV dealers.

If you replace the regulator, make sure you replace it with a two stage regulator like this one.

Single stage regulators are also available, but they're intended for propane grills and do not meet RV codes - their output pressure is not constant enough for RV use.

Water Dog

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Re: Air in the propane line
« Reply #15 on: February 04, 2012, 10:18:55 AM »
remote control shut-off operated by the LP leak detector inside the RV. Your 1994 Damon has such a remote shut-off. If the LP detector is shut off, has detected a leak, or has lost 12v power, the remote control solenoid will be off and no gas can flow. Make sure your LP detector is turned on and working.

This is a great point, and is what happened to us on our 1994 Flair. We had gotten to the camp ground and had no LP. After MUCH searching, we finally figured out that the dog had laid against the LP detector and bumped the switch off. If your stove would light initially, but there is no gas now, that is where I would start.
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seilerbird

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Re: Air in the propane line
« Reply #16 on: February 04, 2012, 11:28:58 AM »
I just went outside to check the propane tank for a shut off valve and there isn't one. The propane comes out of the tank, through the on/off valve and into the regulator. From there it goes off into never never land. But I did notice that I had shut off the valve for the trip from the Peoria to my park. I had not turned it back on. Does anyone think that might be the problem?

Don't bother me, I am busy right now. I have a lot of egg to wipe off my face.

Thanks for the help guys, the stove, hot water heater and furnace all work as they should now.

Tom

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Re: Air in the propane line
« Reply #17 on: February 04, 2012, 11:33:26 AM »
Quote from: Gary RV Roamer
And of course the main tank valve must be turned on (but you knew that!).

He did, but he forgot  ;D
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seilerbird

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Re: Air in the propane line
« Reply #18 on: February 04, 2012, 11:34:11 AM »
At my age I am lucky to remember my name...

John From Detroit

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Re: Air in the propane line
« Reply #19 on: February 04, 2012, 11:41:30 AM »
When the motor home is brand new and the propane tank never charged.. YES air can get in the lines.

Once you have gas in the tank and blead it I keep wondering how air can re-enter the lines.. (Well as it turns out it is possible)

Here is how.. If you turn off the valve on the tank so tank pressure is not present, then via expansion and contraction of the lines due to heat they can suck in a bit of air. IN THEORY, since the regulator will bleed excess pressure.

IN practice.. I've never see it happen.  But then I only close valve when re-filling.
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Re: Air in the propane line
« Reply #20 on: February 04, 2012, 12:04:19 PM »
When the motor home is brand new and the propane tank never charged.. YES air can get in the lines.

Once you have gas in the tank and blead it I keep wondering how air can re-enter the lines.. (Well as it turns out it is possible)

Here is how.. If you turn off the valve on the tank so tank pressure is not present, then via expansion and contraction of the lines due to heat they can suck in a bit of air. IN THEORY, since the regulator will bleed excess pressure.

IN practice.. I've never see it happen.  But then I only close valve when re-filling.

Yes John, when the line has been "charged" w/propane @ 11"w.c.  than the entry of any air is not possible..When tanks are exchanged and the "charge" is lost than there is the possibility f air incursion into the system. Also if there is a leak in the delivery system and the lines are allowed to DE-pressurize to atmospheric  conditions than propane being slightly heavier than air will leak out at which time your hypothesis   "Here is how.. If you turn off the valve on the tank so tank pressure is not present, then via expansion and contraction of the lines due to heat they can suck in a bit of air. IN THEORY, since the regulator will bleed excess pressure." can apply.
And again I agree w/you and applaud your post.
George


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