Onan genset

Propane, Butane, LPG, GPL, C3H8, C4H10
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darren
Posts: 37
Joined: Mon Jan 06, 2014 11:19 am

Onan genset

Post by darren »

Any body have any experience on
Converting a onan 30k ek genset from
Ng to propane it's got a Ford 300
My first question is can it run on vapor and if
That is possible what is necessary for tanks
Temperature etc
Thx

C3H8
Posts: 1046
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Onan genset

Post by C3H8 »

Sure it can run on vapour. You don't say where you live and that is important to provide an accurate answer. The fuel use has to be calculated for the 300 first. A 300 CI engine uses about 126 CFM of air at 1800 RPM. If my calculations are correct that should be about 36L/hr or 880,000 BTU's.

The minimum tank size to produce 800,000 BTU's at 40 F (4C) is 1000 gallon horizontal. It would be reasonable to consider a larger tank if you live in a location where the temperature gets colder.

Considering that you will likely have to change the regulator anyways to accommodate propane you would be better to consider a liquid regulator which would allow you to use a liquid withdrawal tank. This would allow operation at the coldest temperatures you are likely to see. I am assuming this being a Ford 300 that it has an IMPCO mixer. If so removing the NG regulator and replacing it with an IMPCO model E and electric lockoff/filter would make an easy cost effective conversion. If I have guessed wrong bring us up to date on the existing equipment.

Once you change you will also have to recalibrate the timing curve for LPG.

darren
Posts: 37
Joined: Mon Jan 06, 2014 11:19 am

Re: Onan genset

Post by darren »

Thx c3h8
Is there a chart or calculator to calculate
What a 20lb , 100lb cyl etc gives in vapor
At a given temperature?

C3H8
Posts: 1046
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Onan genset

Post by C3H8 »

Handy book called "The Propane Technical Pocket Guide.

http://www.buildwithpropane.com/uploade ... -guide.pdf

Try this link or just type the name into your search engine.

darren
Posts: 37
Joined: Mon Jan 06, 2014 11:19 am

Re: Onan genset

Post by darren »

Excellent resource
Thank you c3h8
This particular genset is 15kw and air cooled
So a water heated vaporizer is out
Do you have any recommendations for
Air heated vaporizer that works good
Thx

C3H8
Posts: 1046
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Onan genset

Post by C3H8 »

I do but I'm confused a little. In your first post you said it has a Ford 300 CI engine? These are all water cooled.
Please clear that up. Also tell us what equipment they are using for the NG system. Example, do you know if it is using an IMPCO mixer or some other brand which uses a venturri styled mixer? What year is the generator? If it is an air cooled engine what size is it? HP?
For an air cooled engines there are options. Your current and best option is to draw vapour off a correctly sized tank so that you don't need to convert the liquid to gas with a heated regulator. You will have to change the NG reg for an LPG reg but I can't suggest a model until I know what LPG mixer or carburetor you have. IMPCO LPG systems run at a negative pressure. Other manufacturers run at negative or positive pressures.

One option is the install all IMPCO components but that increases the price.

Bottom line, need more info?

darren
Posts: 37
Joined: Mon Jan 06, 2014 11:19 am

Re: Onan genset

Post by darren »

Sorry about the confusion
I have two gensets one is the 30 k with
The Ford 300 which yes is water cooled
Which I agree the impco type e would
Work
But the other is a15k with an Onan 4cyl
Air cooled engine . Right now it is set with
a"KN" reg and gaseous fuel carburetor that
Was running on ng
I'm wanting to use liquid just because it
Is impractical for a big storage tank
Are those finned air heated vaporizer s
any good if placed in the air stream coming
Off the cylinders
Thx Darren

C3H8
Posts: 1046
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Onan genset

Post by C3H8 »

Thanks for clearing thatup.
The air heated regs are actually quite good with the correct placement. They need to be mounted quite close to the cylinder head of the engine and shielded from any cold air blast.

IMPCO manufactures the AHR-50-D capable of handling 21 HP. Century used to make a similar reg. but I can't remember the part number. Also keep in mind that the Onan engines are normally low HP. The largest KN reg is rated at 25 HP on NG and 40 HP on propane. Part # T52B. The T52N is rated at 12 HP NG and 15 HP LPG. Your Onan must be less than 40 HP. Based on this the storage tank would not have to be very large for the Onan. Since it is already set up for NG this means its max HP with the T52B KN would be 25HP or less. BTU's per HP?hr is 2550 or 63,750/hr. Depending on the length of time you want to operate this genset it would not take a very large tank to operate it. Motor homes with Onan generators were known to operate using vapour on tanks that were in the 14 inch diameter range and 30 to 40 inches long. If you plan on running this as a stationary unit for hours on end a larger tank would be required but an example of a tank that could easily do the job would be an 80 gallon stationary tank or called by it's pet name in the industry, a Pig. These are sold or rented out by local propane companies. The companies fill these on site. Another option depending on your local regulations is to use multiple cylinders attached together to provide adequate surface area. This would allow you to transport the cylinders to refill them yourself.

Retaining the KN reg would only require a primary reg to reduce the pressure coming out of the tank. The T52B has a maximum inlet pressure of 5 PSI. The T52N has a max inlet pressure of 8 Ounces. Both primary regs are inexpensive and easily accessed from local propane suppliers.

If you are running both gen sets off the same tank you could use liquid for the Ford and vapour for the Onan.

C3H8
Posts: 1046
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Onan genset

Post by C3H8 »

Darn. After writing all that I realized I referenced the wrong model of reg for the HP requirements. The KN reg is rated at two different HP. The standard KN is used in applications up to 30 HP on NG (40HP on LPG). A high flow model will do 40HP on NG (50HP on LPG). The rest of the post remains the same. KN regs in either model are limited to 8 oz inlet pressure.

darren
Posts: 37
Joined: Mon Jan 06, 2014 11:19 am

Re: Onan genset

Post by darren »

Thx for that
My 4cyl Onan is a " jc" model engine
42.5 hp at 2700rpm
So does that change things

C3H8
Posts: 1046
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Onan genset

Post by C3H8 »

No, not really. I'm going to go out on a limb and presume that rating is for operating on gasoline. The minor increase will be immaterial in the picture. If it has been operating on CNG satisfactorily it will operate on propane just as well.

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