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Old 09-30-2011, 12:52 AM
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175lt2 175lt2 is offline
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Default Onan propane generator

I recently acquired 2 Onan 7.5kw 3 phase natural gas generators, these were backup power in a couple of buildings at a private school that I do a lot of work for, they got new ones and were going to scrap these so I agreed to give them a good home. I cleaned up one of them and built a cart for it to make it portable (if you can call this 500lb beast portable), it runs great on propane and makes good power but only one of the three phases are 120 volt the other two are 208v. I cant find much info about these generators but I've heard they can be wired in different configurations, I would like at least 2 of the phases in 120v all three would be even better. If anyone can help me out it would be greatly appreciated

the model number is Onan 705cckb-4r31/1b
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Old 09-30-2011, 10:22 AM
Axehandle Axehandle is offline
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Are you sure you read the tag correctly ? You may have transposed it wrong .
Check this list I found:
http://www.stationary-engine.co.uk/Onan/OnanSpec3.htm

This link is for the CW series generator manual (5MB)
http://www.estephan.net/eds/images/O...log_051027.pdf

Copy and paste this in google and it nets ten results, maybe norrow it down for you:
Onan 705cw-4r wiring

Last edited by Axehandle; 09-30-2011 at 10:32 AM.
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Old 10-01-2011, 03:20 PM
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175lt2 175lt2 is offline
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Quote:
Originally Posted by Axehandle View Post
Are you sure you read the tag correctly ? You may have transposed it wrong .
Check this list I found:
http://www.stationary-engine.co.uk/Onan/OnanSpec3.htm

This link is for the CW series generator manual (5MB)
http://www.estephan.net/eds/images/O...log_051027.pdf

Copy and paste this in google and it nets ten results, maybe norrow it down for you:
Onan 705cw-4r wiring

Thanks for the links they were somewhat helpful. I read the tag right , apparently this combination of generator and engine were not common maybe a special order. what I really need to find is a wiring diagram for a 7.5kw 4 wire three phase never mind the engine model, guess i'll keep looking, at least I can narrow down my search.
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Old 10-01-2011, 04:59 PM
J R Adams J R Adams is offline
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Quote:
Originally Posted by 175lt2 View Post
Thanks for the links they were somewhat helpful. I read the tag right , apparently this combination of generator and engine were not common maybe a special order. what I really need to find is a wiring diagram for a 7.5kw 4 wire three phase never mind the engine model, guess i'll keep looking, at least I can narrow down my search.
Google Delta and Wye transformers. Wye 208 /110 volt systems pretty well went out of favor in the 40's /50's. You may be able to internally rewire the generator to get a 220/110 system. Ran into this in the 60's when a WWII ammunition factory was converted to manufracturing but can remember the details. An old electrician might be able to help you.
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Old 10-02-2011, 11:40 PM
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Quote:
Originally Posted by J R Adams View Post
Google Delta and Wye transformers. Wye 208 /110 volt systems pretty well went out of favor in the 40's /50's. You may be able to internally rewire the generator to get a 220/110 system. Ran into this in the 60's when a WWII ammunition factory was converted to manufracturing but can remember the details. An old electrician might be able to help you.

I really didn't want to get into rewiring the generator internally, I found some refurbished 208 to 120 transformers on ebay for a couple hundred bucks I think that might be an option. It's still cheap electricity when you consider I got two of these gennys for free, I think if the transformer works I'll clean up the second generator and sell it to cover some of my costs.
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Old 10-03-2011, 12:53 PM
J R Adams J R Adams is offline
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Originally Posted by 175lt2 View Post
I really didn't want to get into rewiring the generator internally, I found some refurbished 208 to 120 transformers on ebay for a couple hundred bucks I think that might be an option. It's still cheap electricity when you consider I got two of these gennys for free, I think if the transformer works I'll clean up the second generator and sell it to cover some of my costs.
Check this thread, you should be able to get additional single phase 120v without a trandformer.

www.electrical-design-tutor.com/threephasetransformers.html

Hope I got the link in so it will work.
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Old 10-04-2011, 07:08 PM
kamont kamont is offline
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Manuals are available according to ONAN -- service $26.00 operators $15.00 or parts $18.00 they can be reached (skype) 1-800-888-6626 http://www.cumminsonanstore.com/howto/ (or the service department may be able to answer questions for you. Hope this helps

Last edited by kamont; 10-04-2011 at 07:14 PM.
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