7.5JB restrap, make it double delta?

[Mikey4026]

I sold my 4.0CCK and bought this 7.5JB for $500. It was already natural gas\propane so it saved me some work and $$$. I don't currently have the plumbing for natural gas, so since it has a dual fuel carb, I was able to run it on gasoline until I can get it all sorted out. I nearly blew the windows out of the house with it backfiring all over the place until I found the bad condenser. I am sure my wife thinks I am an idiot for buying and packing all this stuff home!
I don't normally deal with this small of unit and don't have any manuals for the generator end, so I thought maybe I would pose the questions.
This unit is a 7.5JB18R which appears to be a 12 lead reconnectable unit.
It is 120\208 volt currently used as single phase, but maybe just using just two legs of the 120 and may have a third leg in the connection box that I have not located yet.
The high side was cranked up to 240 volts without restraping so the low side was like 140 volts.
Reducing the voltage regulator setting made the numbers make more sense (now 120\208 volt).
I am guessing it is currently wye connected. The connection box cover is the only part missing from this generator so I can't look there, and the lead numbers are missing or unreadable. So no matter how I connect it I have to identify leads.
I would like to have 120\240 volt single phase, so should I double delta or zigzag connect it? Which is the most efficent?
I read somewhere that there is a harmonic problem with double delta? Much more so that the self canceling effects of wye connected units, or is it just a minor issue?
I am going to put it into service here at home. I need something my wife can just push the button and flip the switch. I am never home when there is an outage within 200 miles, so it has to manage itself.
I have been here lurking on the site for some time and have seen some really good and thoughtful questions and answers, lot's of thought and knowledge is apparent in both!
Thanks for any input.
Mikey

[Jack Hottel]

Mikey,
My manual on the YD Genend (900-0184) and my JC operators manual (967-0120) both show identical connection diagrams, none of which is Zigzag. Double delta is what I use on the JC. I'm sure that some of the experts will know why Onan does not recommend Zigzag and also a procedure to identify the leads. The JB operators manual (967-0123) should be readily available.
Good luck,
Jack Hottel
15.0JC

[flynfol]

Is that a continental 220? Never saw one with that huge flywheel........tank version? I think you are in good company with what the wives think.................until the power goes out

[Mikey4026]

Flynfol:
No, it's a 250, tank engine. Last ran in 1953.
Just for making noise in the backyard.
My brother in-law and I resurected it. He did most of the work, he is retired, I still get to work!
We made the flywheel because the prop that was on it was delaminating (someone made a prop adapter for the tank spline). I am looking for a test club? Got any laying arround?

[Jim Rankin]

Mikey,
Since you know what connection you have now, (I agree, you have 2 parallel wye connection for 120/208) you have a leg up on what the leads are numbered. It is also possible the numbers are covered by the insulating tape on the splices.

Anyway, as you disconnect the splices, you should have T1,T7 on a line, T2,T8 on a line, T3,T9 on a line and T4,T5,T6,T10,T11,T12 in a single connection to N.

T4 is the end of T1, T5 is the end of T2, T6 is the end of T3, T7-T10, T8-T11, T9-T12 etc. So with an ohmeter you can find the opposite ends of any known leads.

I can look up the procedure of deriving the zigzag connection when no leads are known if you find you need it.

[Mikey4026]

Thanks Jim
I removed the control and splice box and was able to read some of the numbers down close to the opening in the stator housing. I was able to go end for end with an ohmeter on the wires to number the ends I could not ID. I used my marathon generator strapping book to identify all six coils. I numbered them well for the next time!
I wired it up double delta and connected it up to the loadbank, It will pull 40.1 amps at 59.5 cycles, at 240 volts, I think that is about 9.5 kilowatts, not bad for a 7.5 KW set. It seems to performing quite well on gasoline, anxious to see how it does on natural gas. I still have to pour a slab and get that plumbed up. That is something that will just have to wait until spring!
Thanks for all the help guys!
Mikey