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Onan 20 ES - Switch from Natural Gas to Propane


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  #1  
Old 04-18-2017, 05:49:26 AM
tek42879 tek42879 is offline
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Default Onan 20 ES - Switch from Natural Gas to Propane

Hi guys,

I'm new here and new to generators in general. Over the weekend I acquired an Onan generator. I got it home and got it unloaded so I would be able to tinker with it in my spare time. I put it battery in it and it started cranking.

Unfortunately for me, this generator was hooked up to Natural Gas and that utility isn't available in my area. I would like to be able to convert it to propane, but I have no idea how to do this. I'm a CNC machinery guy so this thing is way outta my league.

The good news (I think) is that it only has 200 hours on it and the oil is clean.

I have attached some photos of the generator - serial and model # included. I have located the user manual with the help of the sticky posts on here, but I don't see anything in it in regards to switching from natural to propane.

Also, would it be safe to use a pressure washer on the engine and the generator? It has a layer of wood dust stuck to it everywhere.
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Old 04-18-2017, 05:53:00 AM
tek42879 tek42879 is offline
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

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Old 04-18-2017, 07:03:40 AM
GMGuy GMGuy is offline
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

Just my 2 cents, and I am sure the experts will chime in, but I would stay away from a pressure washer (electricity and water are not a good mix), and perhaps use compressed air to blow it off and clean it out.
It looks like a great set.
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Old 04-18-2017, 07:11:43 AM
Max Thompson Max Thompson is offline
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

Within reason, yes you can pressure wash the engine end. I would keep the water away from the gen-end and control box. Lots of air will likely disperse he dust from the electrical areas.

Nat gas to propane; remove the primary regulator (the aluminum one, not painted green). Remove the spring and turn the next one 180 so it is pointing down. I will attach a document provided us by Billy that explains this process. Beyond that a little tweaking of the mixer adjustments should be all you need.

Download a copy of the T-015 gaseous fuels manual from the twainslan site http://www.twinslan.net/~n0nas/manuals/onan/ you will also find the generator service manual at this site.

I wonder why the 20 ES single phase set is only rated at 18 KW????
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Old 04-18-2017, 07:15:51 AM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

The smart guys will be along any minute to help you. But #1 is to replace the timing belt that is who knows how old. The good part it's cheap as it's a Ford engine such as used in a lot of cars in the 70's to early 90's. An auto parts store should have the belt and idler for you.
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Old 04-18-2017, 08:16:03 AM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

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Originally Posted by Max Thompson View Post
...
I wonder why the 20 ES single phase set is only rated at 18 KW????
Derated for natural gas ?
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Old 04-18-2017, 09:03:02 AM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

I agree I would change the built now. You can wash the engine but stay away from the control box. Use air to blow out the control box. I would use a water hose to rinse off the engine. Not a pressure washer unless it is a low pressure one.
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Old 04-18-2017, 09:23:51 AM
grif grif is offline
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

Billy,,, does this have the mechanical governor that to tight belt will damage?

Lots of threads on the Ford 6's, lots of docs floating around. I chased this info looking at a 30EK

http://www.pittauto.com/default.aspx...es/pl_ford.htm
http://engineguy.com/ford-lincoln-me...300-cui-1.html

I think all of the ford engine stuff has ended up on Twinlan, if you can't find the manual you need, but know the onan part number of that manual, there are several of us that can get it to you.

Did you post the whole model/serial number yet?
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Old 04-18-2017, 09:31:51 AM
tek42879 tek42879 is offline
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

Quote:
Originally Posted by grif View Post
Billy,,, does this have the mechanical governor that to tight belt will damage?

Lots of threads on the Ford 6's, lots of docs floating around. I chased this info looking at a 30EK

http://www.pittauto.com/default.aspx...es/pl_ford.htm
http://engineguy.com/ford-lincoln-me...300-cui-1.html

I think all of the ford engine stuff has ended up on Twinlan, if you can't find the manual you need, but know the onan part number of that manual, there are several of us that can get it to you.

Did you post the whole model/serial number yet?
Model and serial are in the photo, but here they are for copying and pasting if needed.

Model No. 20.0ES-3R/9132B
Serial No. G860829753

Quote:
Originally Posted by Max Thompson View Post
Nat gas to propane; remove the primary regulator (the aluminum one, not painted green). Remove the spring and turn the next one 180 so it is pointing down. I will attach a document provided us by Billy that explains this process. Beyond that a little tweaking of the mixer adjustments should be all you need.
Thanks Max, I will do this one day this week.

Once this is done, how to I hook the propane up to it? I assume there is a special fitting that I will need? The natural gas line looks to be much larger than propane lines that I am used to seeing.
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Old 04-18-2017, 10:08:41 AM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

Quote:
Originally Posted by grif View Post
Billy,,, does this have the mechanical governor that to tight belt will damage?

Lots of threads on the Ford 6's, lots of docs floating around. I chased this info looking at a 30EK

http://www.pittauto.com/default.aspx...es/pl_ford.htm
http://engineguy.com/ford-lincoln-me...300-cui-1.html

I think all of the ford engine stuff has ended up on Twinlan, if you can't find the manual you need, but know the onan part number of that manual, there are several of us that can get it to you.

Did you post the whole model/serial number yet?
Look at the first picture in post 2. The round item just in front of the carb. Two wires going to it. Is the electronic gov. Controller for it is in the main control box. Don't recall the ES coming with a mechanical gov.
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Old 04-18-2017, 11:02:46 AM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

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Originally Posted by Max Thompson View Post
Nat gas to propane; remove the primary regulator (the aluminum one, not painted green). Remove the spring and turn the next one 180 so it is pointing down.?
What do you mean by "turn the next one 180"? Are you meaning that I need to rotate the same regulator that I am removing the spring from so that it is "upside down" from its current position?
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Old 04-18-2017, 11:28:35 AM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

The one marked Maxitrol is the one you remove the spring from and flip it over. The one not painted is a shut off valve.
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Old 04-18-2017, 12:52:32 PM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

The document that Max posted says the instructions are for Impco carbs. My carb says Zenith on the side....same thing?
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Old 04-18-2017, 04:00:50 PM
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

Yes the same thing. The instruction sheet is from 1968. Onan just changed suppliers over the years. You will not be using the carb section. Just the mixer section on top.
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Old 04-18-2017, 10:12:57 PM
Dennis19508 Dennis19508 is offline
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Default Re: Onan 20 ES - Switch from Natural Gas to Propane

Quote:
Originally Posted by tek42879 View Post
Once this is done, how to I hook the propane up to it? I assume there is a special fitting that I will need? The natural gas line looks to be much larger than propane lines that I am used to seeing.
You need a large propane regulator. Should be rated at 300,000 BTU per hour or larger and it will reduce tank pressure down to 11" water column pressure. It will have a 3/4" pipe thread outlet. If the pipe on the generator is larger just use regular pipe fittings to adapt. Regulator from a BBQ will not cut it.

Also regulator will need to be within 10 feet of generator to meet the flow requirements using 3/4" pipe. If you need a longer distance between tank and generator you can either use larger pipe, or two regulators. 10 psi at tank, and then the final stage to drop to 11" at the generator.

Also you will need a large tank to run under load continuously, gaseous fuel manual will tell you what you will need. Can use a 20 lb tank for testing but might not be able to run at full power without the flow limiting valve closing. For permanent installation you will want a 100 gallon or larger tank.
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