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Open Roads Forum  >  Tech Issues

 > LP GENERATORS

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rugersdad

colorado

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Posted: 02/08/12 10:02pm Link  |  Print  |  Notify Moderator

I have been having issues with my brand new Onan 5500 LP Genset that was installed in my 2011 Forest River Cardinal FW. It will not run on one full 30-lb bottle if you turn on the furnace. It will run the generator and the furnace at the same time if you have two 30 lb. bottles opened up at the same time. The dealer I purchased my camper from assured me that I would not have any problems with the LP Genset.... Here is my question, has anyone ever converted an LP generator to gas? There is alot of info on gas to LP conversions, but none on LP to gas.

Golden_HVAC

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Posted: 02/08/12 10:15pm Link  |  Print  |  Notify Moderator

Are you having a problem with the generator, or just not turning on both tanks at once gives you "Cause" for thinking the generator is somehow broken or using to much gas?

LP gas generators are not really highly recommended by those who own them. It does take a really large LP supply to run one for a few hours. Also LP gas only has 95,000 Btu's per gallon, while gasoline is 115,000 Btu's per gallon.

The one that I know about is on a diesel motorhome, with a large tank (I would guess 30 gallons) and it has two outputs, vapor for most of the appliances, and liquid LP fuel to the generator, where a carburetor heater warms the gas going into the generator.

So I guess the ultimate question is why are you not leaving both tanks open?

Yes you should be able to contact a Onan dealer, ask about the gas carburetor, and they should be able to install one. For a fuel tank, you might want to use a pickup truck fuel tank from a junkyard, with a fuel filler from a bus or truck at the junkyard, (I found one from a 18 passenger bus conversion for my friend's new auxiliary fuel tank in his RV at a junkyard).

Transferflow also sells a gasoline tank that is about the size of a propane tank, yet that option is close to $130. It is designed to be mounted on the hitch of a travel trailer, or you can mount it just about anyplace, including inside your storage space. It is also designed not to leak vapors as much as a normal tank.

Fred.

Ajones42

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Posted: 02/09/12 03:22am Link  |  Print  |  Notify Moderator

Golden_HVAC wrote:

Are you having a problem with the generator, or just not turning on both tanks at once gives you "Cause" for thinking the generator is somehow broken or using to much gas?

LP gas generators are not really highly recommended by those who own them. It does take a really large LP supply to run one for a few hours. Also LP gas only has 95,000 Btu's per gallon, while gasoline is 115,000 Btu's per gallon.



Let's clear some things up here. I have 3 generators that I run quite often. A 12.5kw Perkins diesel that runs 24/7 --running outside right now as we speak since we are working off grid completely. A 7kw Onan as a backup. The one on the RV is a 6.6kw Generac propane generator. It is 19 years old and has about 2k hours on it. Would I buy a propane generator again? Obviously not.

With that said, your problem is the surface area on the 30lb tanks is simply too small to feed the generator when you add the additional requirements of the furnace. If your problems have manifested themselves this winter during the cold weather they may go away when it gets warmer as the gas converts more easily to gaseous form when it is warm. Another thing to think about is when the weather does warm up, there will be no need for the furnace and your problem will go away.

Propane has multiple advantages over other fuels for an RV generator. Most RV generators are run only a few hours each year especially if it is on a trailer or fiver. Most folks with coaches accumulate the majority of their generator hours driving down the road with the roof AC on in the summer. Since most of us don't use the generator often, propane is a desirable fuel because it does not degrade over time. No gummed up carbs or fuel lines etc.

While propane does not produce the btus other fuels do, it is also cheaper. Last week, I purchased propane at $2.82 a gallon--which I thought was high. My generator uses .6 gal/hr at 70% load. A 40lb tank will run the generator approx 18 hrs straight.

Propane generators produce less deadly CO than a gasoline or diesel generator. Mostly, the byproduct of combustion is CO2 and H20. Some folks think the propane generators do not produce CO at all which is simply not true. A small amount of the deadly gas is produced during combustion.

Lastly, propane fuel is wonderful for the longevity of the equipment. It burns clean and produces less wear on internal components.

If you simply MUST find a solution to the problem ---other than simply running both tanks open at the same time, I would look at two things. Perhaps it would run better on a 40lb tank? while the surface area of all vertical tanks is identical, the larger tanks have higher pressure for a more sustained period of time. The only time I have had a problem with fuel supply on mine is when it was VERY cold outside, the tanks got low on fuel or I tried to use a 20lb bbq tank to feed it.

I would also look to see if a horizontal tank would work. They have more surface area because they are laying on their side.

A conversion to gasoline fuel would not even be on my radar.

Hope this helps....


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markandkim

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Posted: 02/09/12 03:41am Link  |  Print  |  Notify Moderator

Remember that LP gas will not flow when it is too cold. So the LP gas pressure will be to low to operate a generator. If you travel to cold regions, gas or diesel generators can not be beat.


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Mile High

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Posted: 02/08/12 11:39pm Link  |  Print  |  Notify Moderator

I would just fix the problem before I ran off and converted to gasoline. It is not normal to have that problem.

joe b.

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Posted: 02/09/12 03:51am Link  |  Print  |  Notify Moderator

Great explanation Ajones42. I have two standby generators at my house that I converted over to LPG from gasoline. The longevity of storing propane over gasoline, is what I like. However, all LPG generators started down the assembly line the same as gasoline ones, for the most part, till they got to the fuel delivery system. Gasoline engines get a carburetor and propane ones get a fuel delivery system, usually a venturi type with a fuel demand regulator. I just installed a venturi on my two so I can still run them on gasoline, if I want as the carburetors are still there.
Most LPG generators that came out of the factory are missing the carburetor and a fuel tank built in. Add both of those to a LPG generator and it should be workable on gasoline. However the gasoline fuel tank can be an issue finding a safe place to install it. Many/most LPG generators are derated from the gasoline version of the same engine. This is because of having a "fixed" fuel delivery system on LPG. On my converted generators, I have an adjustable fuel delivery system, so I can get the same power out of it as it has on gasoline. The generator will burn more gallons of propane than it would gasoline, to produce the same amount of work. (no free lunch on BTUs)
I just prefer LPG on generators that get limited use, such as the one I have in my truck camper. 30+ hours in 3 years, mainly maintenance running. I too have lived where I had to run my own generators full time and for that, nothing beats a diesel as mentioned.

The only way I would consider changing a propane generator over to gasoline in an RV, would be in a Class A or Class C that could run off the vehicle's fuel tank as I drove down the highway. One of our Class A units, we put over 200 hours, on the gasoline generator, during one month of touring the SW and mid west parts of the US. For trailer use or truck camper use, I would stay with LPG for the most part and go with a larger LPG tank.

* This post was edited 02/09/12 04:14am by joe b. *


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Posted: 02/09/12 05:28am Link  |  Print  |  Notify Moderator

We've had our Onan Marquis Gold 6500W propane generator for 8 years with no problems at all even operating in temps to zero degrees F. To date it has just over 400 hours on it. It's inefficient which was no surprise. I wish it were diesel powered but aside from that it's been a great generator. I alway's have both of our 30lb propane tank valves open so that when one tank runs dry the other tank will automatically continue the propane supply. I've never run our generator with one of our propane tank valves shut off so I don'tknow if that would be an issue. I'm not sure you really have a problem. Call Onan and see what they have to say. Good luck.

Happy camping!!! See y'all down the road!!!


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Posted: 02/09/12 10:46am Link  |  Print  |  Notify Moderator

Moved from 5th wheels to tech issues.
Frank


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Posted: 02/09/12 10:56am Link  |  Print  |  Notify Moderator

I own an 5500 watt Onan LP genny and I love it. Yes LP has less BTU than gasoline but its also cheaper and the idea that you burn alot of gas is misleading because your 30 pound bottle only has seven gallons of fuel in it so you would have to change that out more often than a guy with a twenty gallon gasoline tank but if you go to Onans website, they will list in detail the expected fuel consumption rates. Diesel is the best, followed by gasoline then propane but if your a bean counter, take into consideration the price of each fuel along with maintenance.

The only time I recall running my genny and furnace at the same time was when I was hooked up to a four hundred pound tank and I had no problems, not even in -20 degree temperatures. If I was going to run the genny on two bottles while camping, I would be more inclined to run an electric heater.

boondockdad

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Posted: 02/09/12 04:24am Link  |  Print  |  Notify Moderator

No problems with my tri-fuel Yamaha EF2400, runs only on LP. No reduced power issues, either.

Never had a problem with my Kohler 12kW NG backup house generator, but the pipe fitter I had do the gas line installation told me the regulator could be a bottle neck if I wanted to run gas dryer, furnace, and genny at the same time.

Maybe a larger regulator is all that's needed?


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