rooftop air

[boogiethecat]

Brian, I'm not too familiar with Proflex CSST.  My thoughts anyway:

Flexible stainless tubing can be made to be simply flexible- for easy installation but basically to be bent once or twice and that's it, and then it can be made to withstand constant vibration.  Two different things.  Unless Proflex is specifically rated for RV use, legally it shouldn't be used.   Ok, that said, if you were to use it anyway, and you did a clean job and tied it down every foot or two so that it couldn't vibrate, it would likely outlast you and your bus without problem.  Personally I would have little hesitation using it, but I'd make darned sure it's strapped down well everywhere and there were no hanging ends that could wiggle as you drive down the road.
But just remember that if it's not rated for non-stationary use, and if you use it, have a problem and get the clip-board holders in the equation, you may wish you didn't.  You know how that goes.   Check with the companies that make it... maybe there is some that is rated for RV. That would certainly be slick....

[jeepme]

Couple questions:
I would think running copper tubing for the rear vent would work? Kinda nervous about venting a propane tank that close to my diesel's air intake. Would it be better to vent it low so your first sign the propane tank is venting isn't that the engines running away and going boom? I'm thinking of it venting while running down the road...

Also, would a propane sensor by the tank be smart or are you just asking for alarms all the time?

Jason Whitaker
4104

[boogiethecat]

Copper tubing for the rear vent would be fine.  As long as it doesn't come apart, so solder the joints well and don't use compression fittings.   3/4" minimum is what I remember to be the spec.  If your bus isn't finished yet you may find iron pipe to be pretty easy to do.  And I use a short piece of propane rated hose or even RV rated stainless bellows hose to couple between the tanks' vent and the piping system, just to be sure movement of the tank doesn't break the pipes.
The best place to exit the pipe is as high as you can on the rear.  That way the stuff goes up and out.  I doubt it would get into your engine's intake... in fact it's likely it will never ever vent at all but if it does, you'll be glad its there...

Oh.. venting low... there's a very good reason not to do that.  I wish I had a copy... I actually saw a video of a guy who's truck tank vented, the vent valve got stuck in the "open" mode, and then the plume caught on fire.  He had a 100 gallon tank and the flame plume went up about 20 feet and back about 30 feet.  Fortunately for the guy, he was  on the freeway when it happened, and he simply drove until the tank refrigerated and the plume went out.  Had it been vented "low", it would have certainly toasted anyone behind him.  As it was, no-one was hurt and a spectacular video was created!! What a rooster tail!!!

Propane sensors near the tank are certainly a good idea if you expect leaks there.  During filling I'd guess they'd go off like crazy, because of the pee valve.
The biggest thing you DON"T want to happen is have propane puddle up somewhere (remember it's heavier than air and though invisible, it behaves a lot like water in it's puddling ability).  So mostly propane sensors are handy in places like inside your bus, in cubby holes where water heaters are installed, under the stove, under the fridge... any place a leak is likely to cause a puddle, you want to know about it.  Outside if the tank is hanging on the frame like mine, or in a religious bay ( has a very holy bottom) you'd probably be ok without a sensor although they can never hurt... if there's a problem they'll let you know and you can deal with it in ways much friendlier than "boom".

[Don/TX]

Unless 30 years old or older, small gensets are vapor units.  Don't work like fork lifts. 
My 1989 Executive diesel came with a liquid propane Onan, it is only half that old.  Not sure when they quit making them, but was more recent than 30 years!

[NJT5047]

Unless 30 years old or older, small gensets are vapor units.  Don't work like fork lifts. 
My 1989 Executive diesel came with a liquid propane Onan, it is only half that old. Not sure when they quit making them, but was more recent than 30 years!

Actually, I misspoke.  I was referring to the small RV and home gensets that are less than 7.5, or thereabouts.   Onan and several other manufacturers still offer liquid propane format...if specified, in smallish gensets.    Usually  the units are 10KW or larger, but Onan will set up a liquid 6.5 if one wants such.   They are generally, but as you state, not always,  used for stationary applications.   They are rare in MH applications.   Exectutive obviously did it that way. 
Lliquid propane avoids of  the supply tank freeze-up issues.   Liquid propane is likely an easier starting generator in cold weather also.  Vapor generators can be cantankerous in cold weather.   
Downside for all propane units in comparison to  gasoline or diesel is the reduced output for propane powered gensets.  They are rated down as much as 30%. 
Upside, LP unit don't require much maintenence.   They will sit for several years and fire right up.  So will a diesel...don't even think about doing that with a gasoline unit. 
Diesel is the safest fuel, gasoline is probably the next safest?   A liquid propane unit would seem to be by far the most complicated, and likely the most unsafe of all.   Liquid propane units have quite a few extra parts, and supply systems (one for all the RV systems and a dedicated liquid line)  that add complexity to the system.   Not something a backyard mechanic should be trying to repair.  IMHO. 
Why would anyone want an LP genset..why other than the lack of maintenence?   There cannot be any more expensive fuel for a generator?  I must be missing something!   Of course, if one is able to afford an Executive MH, the cost of genset fuel ain't an issue!

JR

[NJT5047]

I have a 4106 conversion with 2 coleman roof air units, also have a onan 25 kw propane powered gen. would like to

OOOOOOOOOOOOOOOHHH!    I really misread the original post....25KW Onan...that's a BIG generator!  May well be a liquid propane uint!   
How's the decision regarding operating the ACs while underway going?  Is there a resolution?
JR

[tucsontattoo]

I have a 4106 conversion with 2 coleman roof air units, also have a onan 25 kw propane powered gen. would like to

OOOOOOOOOOOOOOOHHH!    I really misread the original post....25KW Onan...that's a BIG generator!  May well be a liquid propane uint!   
How's the decision regarding operating the ACs while underway going?  Is there a resolution?
JR

    Thanks for asking, was begining to wonder if it had something to do with my copper tubing.
I think the original owner/builder must have installed some sort of motion switch as a safty device to stop the gen set from being used while driving. will tear into it next wednesday and see what I can find. has to be something simpel   Greg

[NJT5047]

    Thanks for asking, was begining to wonder if it had something to do with my copper tubing.
I think the original owner/builder must have installed some sort of motion switch as a safty device to stop the gen set from being used while driving. will tear into it next wednesday and see what I can find. has to be something simpel   Greg

I doubt it's a motion switch.  Does the generator not "start"...or not "run" when the offending interlock is activated?   Start the generator and see what happens when the bus engine is started.  What does the genset  do when you put it in gear?  Does it cut the ignition off, or turn the gas off and the generato dies slowly?  If the generator runs with the engine running but cuts off when placed in gear, there's a connection to the neutral switch on the shifter.  Or...if it won't run when the bus engine's running, there's an interlock on the bus ignition master.  An ignition interlock is the most likely.   May be more sopisticated and sense alt ouput or coach engine oil pressure.     
Look for an extra wire going to the generator or the remote control panel.    I don't know what model genset you have, but I'll bet finding the interlock won't be too difficult.     See what knocks off the genset and post the results...will make resolution easier. 
Don't forget the liability issue associated with defeating the genset interlock switch.   
May want to visualize all of your LP supply lines and system, especially flex lines (and if liquid system, all of the components related to that) in the generator compartment, for any possible problems that may cause leaks.    
\\An LP leak detector, attached to a cutoff solenoid and alarm,  in the genset box would be a good idea.
Best, JR

[tucsontattoo]

JR   
I;m currently going through the huge box of paperwork and receipts I was given when I bought the bus, hope to find some clues to what all I'm dealing with as far as components, I do have an alarm system, not sure it has propane sniffers or not yet, still reading. Have spoken with a local RV service shop, they were also puzzled  by the problem. One lead I,m following was the gen set may have too much oil in the crank case,, sounded totally unrelated but a quick read of the owners manual seems to reinforce this. go figure? They tell me ( they the RV repair shop) that older Onans are real touchy about this!!My only personal exp. with this problem is that it won't start while moving. A call to the fellow I bought it from confirmed this. He says if you start the gen. an then pull out the gen. will keep running for a while but eventually shut down.
   Thanks for the thoughts on starting the gen. and then starting the bus, and how exactly does it die. Should tell me allot. Will let you know Wednesday what more I,ve learned             

                                                          Thanks again for your input   Greg

[FloridaCliff]

Greg,

This may be a shot in the dark, but here goes.

We had a bunch of Onans on commercial bucket trucks and one thing we found was that the low oil warning sensor was very sensitive.

Even though they measured full we had to tilt them and over fill a little so that they would stay running when the vehicles were moving.

FWIW!

Cliff

[NJT5047]

Yep.  I agree with Cliff...seems like a little too much oil wouldn't shut it down...unless the oil is foaming up and getting sucked thru a crankcase breather.  Low oil sensor may cut it off if low...or sensor is bad.  Verify that the genset has proper oil level and disconnect (disable) the low oil sensor and see if it still dies when the bus engine is running or the bus is moving. 
Interesting problem.   You'll get it figured out.  How and when it shuts down will enable additional diagnostics! 
Best, JR

[NJT5047]

One other thing comes to mind...the propane alarm.    Propane sniffers are famous for false alarms and shutting off LP.   
You may have an auto LP shutdown with a sniffer in genset box or nearby...or even inside the bus.   
JR

[tucsontattoo]

 Well, home today and trying to figure whats shuting the gen down.. so far checked oil for over full.....not.  started gen then turned on main power ....... gen still running,  started engine...gen stillrunning..... brought rpm up to 1500.... gen still running,  back to idel placed transmission in reverse..... gen still running,  placed transmission in drive.... still running. Have not tried stoping and restarting gen with bus engine running or while driving, will try that next and see if I can get it to die.The fellow I bought the bus from says it die after you start driving,sometimes sooner sometimes later and won't restart without stoping. dosen't sound like an inter lock to me ,sounds more like a loose wire on an interlock. will let you know what I learn next later tonight. Thank Cliff and JR, this thing has me pulling my hair a little...        Greg

[DrivingMissLazy]

Well, home today and trying to figure whats shuting the gen down.. so far checked oil for over full.....not. started gen then turned on main power ....... gen still running, started engine...gen stillrunning..... brought rpm up to 1500.... gen still running, back to idel placed transmission in reverse..... gen still running, placed transmission in drive.... still running. Have not tried stoping and restarting gen with bus engine running or while driving, will try that next and see if I can get it to die.The fellow I bought the bus from says it die after you start driving,sometimes sooner sometimes later and won't restart without stoping. dosen't sound like an inter lock to me ,sounds more like a loose wire on an interlock. will let you know what I learn next later tonight. Thank Cliff and JR, this thing has me pulling my hair a little... Greg

I had a similar problem with my genset when I first got DML. The unit would just stop sometimes while driving.
I finally found an overtemp shutdown in the system. It was a Wrico Diesel 10 kw. The coolant in the genset was plumbed into the coach's coolant and if the coach got up to about 190-200 the genset would shut down. I think the O/T sensor on the genset was at 215 degrees, but due to lack of proper circulation, the genset was running hotter than the coach. Also, while sitting in the desert with the genset running it would sometimes quit after an hour or so.

I did two things to solve the problem. One, I installed a circulationg pump to assist the pump on the genset to get additional water flow to the radiator and back. Second, I installed two 16 inch electric fans on the coach radiator with a 190 degree thermostat to turn them on. Those two actions cured my genset problem.
Richard

[tucsontattoo]

   Now I've tried stopping and restarting under all the above conditions, still running fine. this problem only seems to be happening with the bus moving. I'm fresh outta ideas. will drive tonight first with the gen. running and see how long it lasts.If I don't get a stop I will shutdown and try to restart. Don't know how  much that will tell me but at this point I'm beginning to think there is nothing wrong, just want to see it do it again!!!