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Topic: Propane Tank - Vapor and Liquid valves (Read 4337 times) previous topic - next topic

Propane Tank - Vapor and Liquid valves

My propane tank has both vapor and liquid.  The liquid line goes off on its own behind the tank and the vapor goes into a manifold with 4 or 5 lines of it.  The generator appears to run with the liquid turned off, but maybe it was not off long enough.  Can anybody tell me what is with this set up? 
1994 U225
build #4514

Re: Propane Tank - Vapor and Liquid valves

Reply #1 –
Yes, your generator currently runs off the liquid propane line. 

And it will run for many minutes on the liquid stored in the line after you shut off the tank valve.

Many of us have converted our liquid propane generators to high pressure vapor to reduce the contamination of the on-generator regulator by the impurities in propane.

Brett Wolfe
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Propane Tank - Vapor and Liquid valves

Reply #2 –
Okay, then it is not converted.  Would a Propane distributor know how to do it?
1994 U225
build #4514

Re: Propane Tank - Vapor and Liquid valves

Reply #3 –
With this description, yes:


convert it to high pressure VAPOR. On your Foretravel, all that entails is shutting off the liquid gate valve at the propane tank and running the generator until out of gas. Then remove the hose to the tank and install a permenant cap on the tank valve.

Add a "T" between vapor port and house regulator. Also recommend installing a ball valve on the "T" so you could turn off propane to the generator while in storage. Connect the generator line to the "T" or ball valve.

Brett Wolfe
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Propane Tank - Vapor and Liquid valves

Reply #4 –
I may have a propane problem.  Everything is off the vapor side.  On this trip I noticed a variety in what the attendants are doing.  Some turn off the valve.  Some ask if everything is off.  One guy said it didn't matter when I told him everything was off.  Some turn the bleed valve open.  Some don't.  Even though it hisses, one guy told me mine must be broken as he seemed surprised that the tank had reached full as he was expecting the valve to start venting propane instead of air.  On our last night we stopped late at Cracker Barrel.  After an hour with the generator running for air conditioning and the water heater on the LP alarm went off.  I turned it off and back on but it kept doing the beeping it always does when you turn it on only it would't stop until I flipped the kill switch on both batteries.  Then it did its usual chirping and then went silent.  I didn't think much about it until tonight when I went to the rig which had been sitting at my house with everything off except the fridge (tank valve was obviously open).  When I went in, I noticed the smell of propane.  The LP alarm was flashing "on" but no alarm.  So I had an alarm with no smell and the next night a smell but no alarm sounded.  I guess I'm going to have to have it checked just to be on the safe side.
Dwayne Keith
1992 U240
3116/MD3060

Re: Propane Tank - Vapor and Liquid valves

Reply #5 –
Dwayne,

First, with the transverse mounted tank, to properly fill, the coach needs to be level side to side.  If it is leaning, it will be over or under filled.

And the proper way to fill is to turn off all appliances AND shut off the the tank valve.  Then crack open the vent.  Tank is full (80% of tank capacity= full) when liquid vs vapor starts coming out the vent.

And once a year, you (or someone else) needs to use a soap solution on all propane joints to prove they are leak free.  You can also do a leak down test if you have/make a manometer.

And propane detectors DO have a finite life.  If it gives too many false alarms, or particularly if it does not alarm and you smell propane, replace it.

Brett Wolfe
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Propane Tank - Vapor and Liquid valves

Reply #6 –
Brett,
I understand just switching the generator to high pressure vapor, but what if you wish to be able switch back and forth.  i.e.  Two winters ago when we left for the south it was -15 degrees at our house and it got down to lower than -25 while on the road the first morning.    I would think I would want liquid and not vapor under those conditions.  But when it is warmer, vapor would be nice!

Oh, thanks about the tank being level.  Never thought about that.

Pat
1994 U225
build #4514

Re: Propane Tank - Vapor and Liquid valves

Reply #7 –
Quote from: wolfe10 –

And propane detectors DO have a finite life.  If it gives too many false alarms, or particularly if it does not alarm and you smell propane, replace it.


If I'm remembering correctly, both propane and carbon monoxide detectors should be replaced after no more than 7 years (some models may be only 5) and smoke detectors after no more than 10.  The units should have the date of manufacture stamped on the back. 

Michelle
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Propane Tank - Vapor and Liquid valves

Reply #8 –
We have had similar problems, but do not have a propane generator.

This is what we found.
Propane detector needs a full 12 volt re-boot to clear, so I installed small switches next to all 12 volt wired detectors, to kill power for a moment. This has extended our detectors use for many more years.  Our original detectors are still in service.  When detector sounds off, we don't know if detector has problem or detector has found a small whiff of something or it is a full blown leak.  So we have redundancy with 2nd propane detector mounted near the floor across from the original detector.  If they both go off, I pay attention.

We also added 2 more CO2 detectors with digital readouts in the bedroom.  Don't want to not wake up because our CO2 detector failed or was too far away.

Sometimes when our propane hot water tank fires up we get an alarm, probably from some fumes finding their way inside.  We consider this normal and not a problem.  Filling propane tanks at other than a propane supplier's shop can be problematic as the service people at gas stations, etc are not well trained on propane and over time have learned incorrect habits.  Coach owners must be part of the fill and demand proper safety precautions, as it is our coach that could catch fire or blow up.  It is correct to turn off main valve AND turn off refrigerator, hot water tank and anything else that has automatic ignition.  We try to leave the bay door open for a while after filling and wait a bit to start up appliances.

As soon as the main valve is shut off, an appliance that was under flame will sense loss of gas and start to spark, which is not a good thing during a propane fill-up.  The 80% thumb-turn valve (also called a spit-valve) should be opened a few turns.  Behind this valve is a very small hole into the tank at the 80% liquid full level.  Valve can be replaced without any problem because of the small hole.

Older tanks did not have a float shut-off and during filling of liquid propane, vapor would be expelled when spit valve was open.  When liquid reached the 80% level, the liquid would start to 'spit' out, indicating it was time to turn off the propane pump.  Some untrained service people would continue to fill the tank as there was nothing preventing them from doing so.

Propane tanks need about 20% of tank space for vapor to accumulate.  Pressure regulator reduces the vapor pressure to what is needed by appliances.  All new tanks have by code a float shut-off which prevents overfilling.  Most tanks will shut off before 80% valve starts to spit.  So your guy who thought something was broken, was showing his ignorance.  Even removable tanks have floats these days.  Our valve never spits as our float cuts off liquid flow first.

Foretravel used to use a propane detector that had a gas solenoid at the tank that turned off propane flow when detector sensed something.  Since propane detectors false alarm so much and RV code does not require this solenoid, Foretravel stopped using the solenoid.  We removed our solenoid, as every false alarm had a long start-up delay after detector cleared and re-booted.

Appliances under flame will try to relight and if it can't get a flame going, will stay in a fault condition until reset.  This is a serious for refrigerator as food will quickly warm up if fault not detected.
 
I can't answer to your smelling of propane.  But electronic gas sniffers are available to help you determine that you do or do not have a leak.  We own one.

By the way we also have many smoke detectors for early detection.  We only use the combination type that has ionization & photo-electric sensor in one unit.  Ionization detects products of combustion and photo electric detect smoke.  We have 3 on the ceiling, several around electrical items behind TV and under couch.  And several in bays and behind refrigerator.

Re: Propane Tank - Vapor and Liquid valves

Reply #9 –
Thanks Barry.  Based on what you describe, I have figured out that what the service guy meant was that he was expecting liquid to spit out instead of just air hissing when some backup on either my end or his told him the tank was full (or as full as it should be) and he hurriedly shut down the pumping saying something about my spit valve being defective.  He knew it was full even though the spit valve never spit any liquid or at least something gave him that idea.  As for shutting things off and closing the valve...I do that based on what I'd previously learned from all of you.  I'm hoping that my propane alarm was a fluke.  I had it all closed up the next night with the valve open and the fridge on and didn't smell anything.  Unless I have something that leaks sometime and not others...I don't think I have a leak.  Nevertheless I plan to replace the detector as it appears OE.
Dwayne Keith
1992 U240
3116/MD3060

Re: Propane Tank - Vapor and Liquid valves

Reply #10 –
Why take out the original propane detector, when you could have two detectors if you leave it in?

Re: Propane Tank - Vapor and Liquid valves

Reply #11 –
Barry,

Because the detector also controls the propane valve.  If defective, propane flow is not guaranteed.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020