onan commercial 6500 generator

rampeyboy · August 18, 2010, 03:20:47 PM

Guys I have run across one for $100, but something is locked up. I'm not too afraid of gambling a $100 on it, but my concern is this...the dataplate says 120/240 3 phase. Reading online, it looks like it can be used as single phase or 3 phase. I'm no electrician, and wonder if someone here can shed some light on this for me? Should I walk or run! haha

desi arnaz · August 18, 2010, 04:04:26 PM

if you need to shed light on it,go buy a flashlight......

steve wardwell · August 18, 2010, 04:08:54 PM

I bought a German schooner with a 6kw onan in it. 50 hertz, 220 volts. One line out some 45 ish amps if I can remember

when I rewired the boat to 50/ 240 I had to open it up at the brain box and separate (I think) one wire from another which then became the two separate leads for 50 amp 120 volt 7.5 kw onan then I had to speed up the engine to get to 60 hertz ( i think it was at like 1500 rpm and went to 1800 rpm) found it in the manual .. I know that onan was pricey to maintain .hope this helps P.S. It's coming back now we over the years had 3 different 7.5 onans. 2 cyls the one thing other than the $ to keep em up was that they were always unscrewing them selves and sorta falling apart and really LOUD....mind you these were all marine with keel cooling

steve wardwell · August 18, 2010, 04:23:30 PM

The $ right if it will run....... but please park wayyyyy over there...........really really L O U D.....(We often found the TV volume maxed out)

rampeyboy · August 18, 2010, 06:07:38 PM

Steve, I don't think it will be too loud, as it is one of the 1800rpm units, and has a really nice looking muffler(big as some on import cars!) made to the unit. It is however, air cooled, and not necessarily an RV unit. Somewhere I read they are made for "service vehicles" that have a need for electrical power. I believe the engine to be a 14 or 15hp Kohler. It has a screw on oil filter, is gasoline, and has a side draft looking carb..
It will not run as is. I am told something is locked and it won't spin over when you hit the start button. I think if the gen head is good, it might be worth $100 to take a chance on.
I haven't taken one of these apart, but I am thinking the gen head is a direct drive off the crankshaft. So, it could be the gen head locked up or the gas engine....
I am less worried about it being locked up, than I am about the 3 phase thing!
Maybe I'll let it sit a few weeks, and make a offer...

steve wardwell · August 18, 2010, 06:13:44 PM

gotcha, this is nothing like the diesel we had... oops !

gus · August 18, 2010, 06:43:00 PM

Yeah, I had one of those quiet 1800 rpm Onans a few years ago. It shook the whole bus in spite of 3" thick cushion mounts and could be heard three blocks away.

I gave that 500lb monster away and never looked back.

The myth of gensets being quiet just because they're 1800rpm goes on and on.

My little gas, 3600rpm, Honda 6KW liquid cooled, 250lb genset is very quiet and can't be felt anywhere in the bus. Life is good!

rampeyboy · August 19, 2010, 02:24:14 AM

Now Gus you just had to muddy the water didn't you? I thought that 1800 rpm thing was the one thing I could count on! Now I'm back to square one! lol

Busted Knuckle · August 19, 2010, 06:18:59 AM

also be careful of why it's locked up! I was talking to a friend not long ago that had just taken delivery of 22 "great buys" from an insurance sale of items still left over from Katrina! (he buys and rebuilds/resales sticks and staples)

BK

Sean · August 19, 2010, 09:48:06 AM

Most three-phase gensets can be rewired to single phase and some can be wired to split phase.

However:

You will not get the full rated power, which it only delivers at three-phase. Three-phase stators rewired to single-phase will only deliver 2/3 the nameplate power. Your 6500-watt generator will thus deliver only 4,330 watts. To put that in perspective, it's just a tad larger than a 30-amp shore service. You might be able to run two air conditioners on it.

Also, it is not as simple as moving one or two wires. Three-phase generators that can be rewired to single phase have 12-wire heads, and you'll need to fiddle with all 12. Not complicated, but not for the faint of heart: it requires precision, as a wiring mistake can blow up the head.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

artvonne · August 19, 2010, 09:14:41 PM

If I could ask a quick gen question here..... I have a 6.5KW diesel generator. Its an Onan DKD, but as far as I can determine its really all Kubota, probably the gen head too. Its currently wired for 120 volt, single phase. I am not up on generators to well, but is split phase where you have two 120 volt legs for 240 volt? What would something like this put out if it was wired for 240? I have assumed about 8K with a 10K plus surge??

Sean · August 20, 2010, 12:39:19 AM

Quote from: artvonne on August 19, 2010, 09:14:41 PM
... I have a 6.5KW diesel generator. ... Its currently wired for 120 volt, single phase. ... is split phase where you have two 120 volt legs for 240 volt? What would something like this put out if it was wired for 240? I have assumed about 8K with a 10K plus surge??

You don't get more power out of a generator by strapping it for a different voltage. If you have a 6.5 kW set and it's wired for straight 120, it will supply about 55 amps. If you rewire it for 120/240 split phase (if that is even possible with your model), it will supply about 27 amps. Either way it's 6,500 watts.

Three-phase generators with the proper wiring can be re-strapped to produce single or split phase power at a penalty of 33% of the nameplate rating. So if you had a generator that was producing 6,500 watts single-phase, but it had been converted from three-phase to begin with, you could change it back to three-phase and get 9,750 watts out of it, but only if you use three phases. Also, the nameplate rating will always be the higher, three-phase rating, so if the unit says 6.5kW on it, that's the most it will produce.

-Sean
http://OurOdyssey.BlogSpot.com

gus · August 20, 2010, 02:41:54 PM

Boyce,

It sounds just like the one I had. Sorry to disillusion you but this is my actual experience with this monster.

Also, changing from three to single phase will make it 5500 Watts instead of 6500. Mine had been converted when I got the bus.

It also had an oddball set of ignition points that I never could find.

It was stout and way overbuilt and would probably be a great stationary standby power plant, which is what it was made for, but it is no good for a bus.

From what I've read in the past year on this forum about Cummins support of Onan gensets I would never buy any Onan, new or used.

On the other hand, if you can get it for $100 and not spend a lot to get it operating you may be able to live with it. You may have a greater tolerance for noise and vibration than I have.

It easily ran my two 13.5 ACs and the frige underway but would overheat when parked.

Sean · August 20, 2010, 03:49:38 PM

Quote from: gus on August 20, 2010, 02:41:54 PM
... Also, changing from three to single phase will make it 5500 Watts instead of 6500. ...

I'm not sure where that number is coming from.

Most three-phase generators will be reconfigured to split phase using the "low zig-zag" pattern. If you really know what you are doing and have good schematics, you might be able to do "double delta".

In either case, the output will drop to about 2/3 of original rating. That's just 4,330 watts for a 6.5k unit.

I don't know how to get 5.5 k single-phase out of a 6.5 k 3-phase generator.

To understand how generators work and are wired (and can be re-wired), I recommend this link:
http://www.anoldman.com/modules.php?name=Articles&page=generator.html

From that same site, he shows how he re-strapped his own 3-phase unit to split phase. Towards the bottom of the page is the discussion on de-rating the power output:
http://www.anoldman.com/modules.php?name=News&file=article&sid=21&mode=&order=0&thold=0

-Sean
http://OurOdyssey.BlogSpot.com