Kubota Generator on Propane

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Old 07-24-16, 10:55 AM
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Kubota Generator on Propane

I have a Kubota ARX 6500 as a standby generator for our house. It has been here since before we moved in, and it works OK. It has a provision to run off gasoline or off propane and I switched it to propane some time ago when Hurricane Ivan came through. Ran flawlessly for several days until power was restored without having to fill it up every two hours with gasoline.

To the point. Does anyone know if the generator can run directly off tank pressure or if it needs a regulator? It has two regulators on the side of it, and I can post pictures if needed. It has become sluggish lately and I have pulled it from its house and taken it to the shop for an overhaul. While I am down there I would like to run it off a 20# tank if possible, but I don't want to mess it up or become a danger. Running it without a regulator (if it is proper) will help with my connection at the tanks at the house, too. I have two 100# tanks, and I can dedicate one to the generator while the other one can be regulated to my emergency stove and gas logs. We are total electric otherwise.
 
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Old 07-24-16, 11:45 AM
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The specs on that genny don't mention operation on propane so that means your generator has an aftermarket propane kit on it and those definitely use at least one regulator.

Did they leave you any information on the type of kit used ?
 
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Old 07-24-16, 11:54 AM
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The first regulator is no more than 4 psi. Most likely 10 to 14 oz. Straight pressure from a tank will be near 200psi. Not a safe scenario.

Motor regulators are 'demand' regulators as they only allow gas to pass when the outlet sees vacuum. Otherwise the gas would flow continuously and cause flooding of engine.
I am currently running a 8 hp Briggs with a 4# primary regulator and a demand valve just before carb. This setup is working great.

Buy another regulator if you must test the engine from the 20 # tank. It could save your life.

RR
 
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Old 07-24-16, 12:01 PM
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Good information, thanks. I'll pick up a 4# regulator just to be on the safe side, then install it on the main tank when I connect it back up. I have already talked wifey into a 22,000 Generac, so that won't be too far behind, and I'll sell the Kubota. I have my 5k jobsite generator connected up to the system now, just in case.

We were without power from 0730 until 1600 due to a mid-yard break at the bottom of the valley....all underground. I finally got tired of waiting, so I connected the jobsite unit and as I flipped the last switch on my switch gear, the air conditioner came on, indicating power was back on, since it isn't on the gear. Never fails.
 
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Old 07-24-16, 12:54 PM
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Pete, Kubota does offer aftermarket kits, but not sure which one this is. There was little paperwork left and the people from whom we bought the house have passed on, so it's like a new search for me. Thanks.
 
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Old 07-24-16, 12:58 PM
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The kits come with different jets and regulators. You're going to have to do some experimenting.
 
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Old 07-24-16, 04:46 PM
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I actually found the folder with the generator book, the Gentran transfer switch book, sales receipt for the generator and LP conversion kit together, but absolutely no information as to how the LP stuff works. As you say, Pete, I'll have a bit of experimenting to do.
 
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Old 07-24-16, 05:39 PM
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I have already talked wifey into a 22,000 Generac,
I install 2 of these a week.. They are 281K btu units you know right?

Yes they need 11" WC so will need a regulator... All units need a regulator running off propane
 
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Old 07-24-16, 05:46 PM
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There are high pressure carb kits... dont know if you have that as not common around here, But with those you would never be able to go back to gasoline without a new carb
 
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Old 07-24-16, 05:47 PM
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How do your customers like the Generac's? Looks to be the better deal here, locally, they run about $4600 including the transfer switch gear. In terms of the BTU you mention, is that a gas guzzler or fairly economical? Not that it would get much use. Probably the weekly testing and a one day run occasionally when the power company is playing around. Would a 100# tank handle that type load?
 
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Old 07-24-16, 05:50 PM
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It has two regulators on the side of it,

I would like to run it off a 20# tank if possible, but I don't want to mess it up or become a danger. Running it without a regulator
Why would you remove regulators... Run any propane source through them...
 
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Old 07-24-16, 06:02 PM
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How do your customers like the Generac's? Looks to be the better deal here, locally, they run about $4600 including the transfer switch gear. In terms of the BTU you mention, is that a gas guzzler or fairly economical? Not that it would get much use. Probably the weekly testing and a one day run occasionally when the power company is playing around. Would a 100# tank handle that type load?
Generacs are good as you run one conduit for both electric and communications... Kohlers suck in this regard... The load shed modules are also great as they get mounted at the source...

BTU is @ 100% 281K btu... I never seen these things run at or near 50%.. And when they excercise weekly they run in an 1800 rpm mode I belive... Id have to look more into the specs but do know how we install them...
 
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Old 07-24-16, 06:11 PM
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Did 2 - 22K's this week... Its the go too when you need power... People are happy and when all or most electric this is what we install..


[IMG][/IMG]

[IMG][/IMG]
 
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Old 07-24-16, 07:42 PM
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I'm not removing the regulators, just mentioned that they have two on the unit. I also have a red regulator on the 100# tank. Glad to hear the information on the Generac's.
 
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Old 07-24-16, 08:33 PM
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You may or may not have that cause they ran a smaller line... it all depends on what you got...

Propane High Pressure Regulators

There are many stages you can have..

Its all about the WC to the unit,

http://www.propane101.com/highpressureregulators.htm
 
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Old 07-24-16, 08:40 PM
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Larry, can you post a few pictures of your set-up? The red regulator at the tank(s) is a primary to drop the tank pressure to about 10 psi and then you probably have a secondary regulator dropping the pressure to 11 inches of water column. The third regulator is most likely a zero pressure governor that is actuated by the manifold vacuum and controls the amount of fuel actually fed to the engine.
 
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Old 07-24-16, 08:47 PM
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Yep. It's at the shop, but will get pictures and post them tomorrow. Thanks.
 
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Old 07-25-16, 03:47 PM
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Here's a picture showing the propane regulators.

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Old 07-25-16, 03:59 PM
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Post any information that is on the regulators such as manufacturer name (IMPCO, Century, REGO, etc) model and serial numbers. This will help those with propane experience figure what you have and how to advise you further.

Guessing from your picture you may have step down regulator connected to a demand valve. Possibly you might not need additional regulators.

Good luck!

RR
 
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Old 07-25-16, 04:04 PM
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Is this a two cylinder engine? Both of those are zero governors and the only reason for two is if the engine has two cylinders without an intake manifold.

Okay, one other possibility is that one has been optimized for propane and the other for natural gas although that would be quite unusual. Do they have the same intake piping, i.e. a single hose to the propane tank serves both governors?
 
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Old 07-25-16, 04:39 PM
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They look to be in series and look to be electrically controlled. Maybe power needed to open.

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Old 07-25-16, 04:48 PM
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They have solenoids that, when energized, press in the diaphragm to open the fuel valve manually. These are only used to "prime" the gas flow. They DO look to be piped in series and that makes no sense whatsoever.

Although difficult, a few more pictures may be helpful.

Maybe, just maybe, the first one is not a zero governor but a "fuel lock-off" but I have never seen one that also had a primer solenoid.
 
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Old 07-25-16, 04:49 PM
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RR, I'll get the information and post it. Pete, as your enhanced photo shows they are in series, as the one on the right takes the fuel directly from the tank set up with a short hose between the one on the right to the one on the left. Yes, they are electrically connected. I am not sure if the motor is augmented by the impulse of the wiring, or if something on the other end of the wiring is changed by the RPM or something.

I've really got to clean it up and check all the wiring for mouse chews as well as the spark plug and its gap.
 
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Old 07-25-16, 04:52 PM
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Furd, you bring up a good point about them being in series. I'll get better pictures from different angles and verify the piping connection. So the diaphragm doesn't move except at start up? I note they do not move when running, but are "depressable" manually.
 
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Old 07-25-16, 06:01 PM
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Yes, the diaphragms move. During normal operation the manifold vacuum of the engine causes the diaphragm to flex "inward" and since the diaphragm is mechanically linked to the fuel valve it also causes the fuel valve to open. This incoming fuel then has a tendency to raise the pressure in the chamber behind the diaphragm which in turn closes the fuel valve slightly, the result being that for any particular engine vacuum there is a corresponding diaphragm position and consequently specific fuel flow.

The solenoid (or finger pressure on the exposed button) flexes the diaphragm inward to manually open the fuel valve. The solenoid is usually energized by the electric starter relay (solenoid) so it is only causing the fuel valve to open independent of the engine vacuum during starting. It is really a simple, yet at the same time complex, action that changes the fuel flow rate to correspond with the power output of the engine.

The more I think about it the more I am convinced that the unit connected to the propane tank hose is what is called a "vacuum fuel lock-off device" and its purpose is to prevent fuel flow when the engine is not running. The NFPA (National Fire Prevention Agency) requires fuel lock-offs on generators when the engine exceeds a specific size, which off hand I do not remember. Fuel lock-offs are made both in vacuum and in electric models and I am more familiar with the electric models which are just solenoid valves built for propane.
 
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Old 07-25-16, 06:09 PM
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You might find this link to be of help in understanding the operation.

https://www.propanecarbs.com/princip...nversions.html
 
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