LP powered stanby generators

[NIXON]

I'm looking for an emergency generator in the 10-12 kva range . LP powered ,as that's what I have for heating etc ...
I'm sure Diesel or gas would be more economical . But I don't want the hassle of preserving fuel or having to go to the service station with fuel cans . Any experience with these ???
Good bad or otherwise ,inputs would be appreciated .
If this subject has been beaten to death..... Just point me to the corrct thread
All the best . John

 

[alco141]

northern tool has a couple of generators that are trifuel (lp/nat. gas/gasoline), and a few that are lp/ nat gas, most of the home automatic units are lp/nat gas or diesel. the only problem is that there is a decrease in the horsepower of the engine about 5-10% with the lp fuel instead of gasoline. and you need to hook them to a gas line permanently. other than that they are about the same.

alex

 

[Anonymous Poster]

The same generator that produces 1kva on gasoline will produce .8 to .85 kva on propane.
Once you get above 5hp of engine, you'either need to run liquid propane to the machine and have an evaporator at the machine to convert the liquid to gas, or have a HUGE propane tank to supply sifficient vapor.
LP tanks have a 10% annual storage loss that the suppliers don't want the customers to know about.
LP machines require rebuilding of evaporators and solonoids every few years, or you'll have problems when you need the machine most.
By the time you get done dealing with all that, you could have bought a brand new Kubota Diesel and set it up for the same money.

 

[NIXON]

Franz... Thanks for the input ! BUT ! where did you get this info ??? I'd like to make an informed decision . If you could supply me with a reference I'd really appreciate it .
All the best, John
I'm most curious about the 10% loss .

 

[alco141]

Re: LP powered standby generators

if you are using the lp gas to run your house why would you care that there is loss, as you use the gas on a regular basis. as far as a decrease in hp from the motor, just buy a big enough motor, and as far as evaporators, i have heard this arguement but have never seen it in writing. i would like to verify this . anyone have a reference. i have heard that you need a "wet " tank instead of a dry tank to give you enough vaporization at lower temeperatures, again this is not verified. i would hope that we could find out if these are urban legends or fact. i will tell you that we dont rebuild the evaporators on the liquid oxygen tank system every couple of years, could the lp gas evaporators be that much different?

still looking for a source.

alex

 

[Bird]

John, in 1988 when I was shopping for a new RV, I also read in some RV magazines that a car or truck or generator converted to LPG instead of gasoline lost about 10% in power or efficiency. So when I selected a 5th wheel trailer, I had the option of a 4kw Onan or a 4.5kw Kohler generator to run on LPG. I had owned Onan in the past and liked them, but that time, I went with the Kohler. I did have one very unusual problem while it was still in warranty, but not Kohler's fault. It would start, then almost immediately die, and after a considerable amount of checking we found that the automatic changeover regulator at the bottles was the problem. Of course, I only had that rig for 3 years, but never had a problem with the generator during that time, whether it was running for the air-conditioning in 100 degree Texas weather or for the furnace and electric heat in sub-zero Alaska weather.

 

[alco141]

try these folks they may have some answers about propane powered generators. they make propane conversion kits for generators.
http://www.propane-generators.com/

alex

 

[hayden]

If you look at the specs for gas/LP generators you will frequently see the difference in ratings from the two fuels, so I believe that one too.

The 10% LP dissapearance is news to me - can't confirm or deny. But if you are heating with LP, I think it doesn't matter.

I've got one of the RV Onan 4KW units running on LP just like Bird's old one. Mine happens to be built into a shed as aux power for an off-grid solar house, but it's the unit typically used in RVs. Onan offers two types of LP systems, one vapor and one liguid. It is true that you can't draw vaporized LP out of a tank faster than the LP actually vaporizes, and that vaporization rate is controlled by LP surface area and I think temp. A grill tank can only vaporize so fast 'cause the surface area of the liquid LP in the tank is limited compared to a larger tank. As a result, to "power" big devices like generators and furnaces, you need a bigger tank with a larger LP surface area to produce sufficient vapor at a steady rate. My Onan uses the Vapor system but I've got a 1000gal underground tank so vaporization rate is not a big deal.

If you want to pull LP out faster than the vaporization rate you need a more complicated system that draws off liquid LP, then does a forced vaporization prior to use. The Onan liquid vapor fuel system actually routes the liquid fuel line around the exhaust manifold to heat/vaporize it. I haven't seen one first hand, but my manuals spell it all out.

What can you power with what size tank? I have no idea, but I do know that I can run my generator, furnace, HW heater, stove, drier, etc, etc all at once using the 1000 gal tank. If you are heating with propane, I expect you can power a generator with no problem, but to confirm just ask your LP supplier. For reference, the Onan at full load (4KW) uses .8 gal/hr or 4lbs/hr of LP. That's about the same as a furnace.

The Onan I've got actually does not derate for LP, but I think that's because it's got a way-oversized engine for a 4KW generator (10-12HP I believe) so it can put out the full 4KW either way.

Personally I really like the LP approach. Endless supply of fuel, easy starting, especially in cold weather, and the fuel never gets stale because you are always using it for other things. The engine also runs cleaner and smells much less. I've got over 900 hours on mine and its been completely trouble free.

 

[BigDave]

Take a look at Amazon.com, they have a Gaudian 12K stand-by LP gas generator for about $3000. They also have larger & smaller.

You can find them under:
Home & Garden > Tools & Hardware > Categories > Job Site Equipment > Power Supplies > Generators

 

[chim]

I have an older Onan 5KW. Our house has LP for heat and hot water, so our tank is one of those long horizontal jobs. I used this generator for power when we built the house, and at first, tried to run it from BBQ grille tanks. Didn't work real well. Especially in colder weather, there wasn't enough surface area on the liquid in the little tanks to have it boil off into gas. I had a temporary 100 gallon tank brought out, and it worked like a champ.

Still need to complete some work to make it completely automatic. I have a transfer switch that will feed a small subpanel for the heat, water heater, freezer, fridge and the "candle circuit". The candle circuit powers outlets in most of the rooms for the window candles. The candles are only 5W each, but are plenty for navigation in the dark. The outlets make for easy connection to other loads with a short cord.

I played around during a power outage last year, and the generator ran all this stuff and more OK.................chim