Onan Generator

[TomT13]

I removed my 8kw Onan generator from the boat to do some preventative maintenance through the winter. I also wanted to soda blast and paint the unit. I fabricated a stainless steel drip pan and new motor mounts since the old one was so rusted. After removing the stator, rotor and exciter I noticed a great deal of the varnish is peeling off. Does anyone know of a shop in the NJ area that cleans and dips or refurbishes the varnish coating? The unit generates electricity fine and a new stator is about $1,500.

 

[TedZ]

Any shop that rewinds electric motors will check it out and dip it. There are a lot of them. Switchboard comes to mind as a way to find them. Ill do it for you if you tell me what city.

Ted

 

[TomT13]

I am near Somerville, NJ. I heard of a place called Bishop Electric Motor and I found them on Swithcboard.com. After 4 attempts to call them yesterday, no answer, I decided to place a post here. Thank you in advance for your assistance.

Tom

 

[REBrueckner]

Tom, it's not likely, in my opinion, that recoating the windings with varnish will accomplish much. New varnish will potentially coat areas you can see, but those are not the portions subject to shorts. The varnish insulation is applied BEFORE assembly. It's the tightly packed wire to wire contact areas that need the insulation and where it's least likely that new varnish would penetrate.
I would suggest you discuss the winding condition with a reputable shop and ask appropriate questions. On the other hand, if recoating is, say, a hundred dollars, I guess there is not much to lose.

You mentioned rusted engine mounts: if the windings also appear to be subject to corrosion, perhaps from errant water spray, perhaps rewinding with new wire is appropriate.

Also: when replacing engine mounts, be sure to use ones appropriately sized to your 8 KW ONAN weight. Oversize mounts will simply transmit vibration to your hull...they must flex to block vibrations.

 

[TedZ]

New Jersey Electric Motor is right in Somerville...try them. Bunch in Green Brook - whereever that is - also.

I seem to be on the wrong side of every issue lately but we rebuild a lot of motors and always have them dipped and baked. It is true the copper wire is coated with varnish ahead of time but it gets scuffed also when being wound. The shops we use dip also as an added protection, real or imagined. Rewinding stators is a bad idea. Don't believe me, try it and get a guarantee.

Ted

 

[yachtsmanbill]

Yer right! Dipping is merely an ounce of prevention. It will do nothing for the internal winding. If there is a short or a ground in there you need to rewind or replace. Our stuff that got wet was baked and dipped and meggared. Once its dis-assembled ALL the components-collector rings, iron bars, wedges and insulators need to be gone over with a fine tooth comb, and then you better hope that some DILLIGENT winder is putting it back together. ws

 

[TomT13]

Rob,

I fabricated a new drip pan and brackets the motor mounts bolt up to. I purchased the exact replacement parts from Cummins MetroPower for the actual motor mounts. I do not believe I will have a problem with vibrations.

Tom

 

[TomT13]

Rob,

I didn't perform a thorough inspection of the windings themselves but from a cursory review it looked as though the varnish was intact. The areas where the varnish seems to be peeling are from the flat surfaces of the exciter ring and the interior of the stator housing itself. I appreciate the offer to take a look at them and offer your opinion. Like I said in the original post the unit operated fine. The generator has never had any faults in the three years I have owned the boat.

Tom

 

[TomT13]

After a detailed look at the windings it seems that the varnish on them is fine. However, I did drop the generator components off at a place called Bishops Electric Motor Exchange in New Brunswick, NJ. They are going to megger test and scope the components and let me know the status. The owner said worst case they can rewind them they have been doing that for 68 years. They will then clean all the surfaces and re-varnish and paint. Bad news about the whole thing is the city is taking his property over through emanate domain to build houses. He has to be out by March 2008 and the owner is not reopening.

 

[TomT13]

Update for anyone who wants to read about it. The genny parts checked out within tolerances and were re-varnished and painted. It seems there is a better product than varnish used in the motor world today. It almost looks like a red plastic paint. Regardless, $500 later all parts are back together. After completing all the other maintenance on the engine the unit was run. Everything works great. The cost quoted to me for a new stator from Cummins Metro Power was $1900. I am very happy to have saved $1400.

 

[yachtsmanbill]

Was that paint General Electric "GLYPTAL" enamel? I painted an old beater T bird with it using a 3/4 nap roller. BLACK. Looked good and kept people from rubbing against it... ouch! ws

 

[REBrueckner]

Althought not up to date by any means on electrical winding technology, the rubber like/perhaps plastic black coating has been used for many years. I believe the "varnish" (in appearance) wire coating is still in use and is applied to wire as insulation before winding. It sure isn't varnish because when winding wire is wrapped/curved the coating does not crack as hard varnish would.

The black finish discussed here seems to be almost a surface sealer to coat the outer windings and help prevent intrusion of dirt and moisture rather than as an insulating product. It could also serve to "glue" wire windings togther dampening/preventing vibration of wires that would rub the varnish at contact points and lead to shorts.

 

[Trojan]

They still use varnish on the wire itself. But the exteriors of the windings are painted with the new coating to keep dirt and moisture out. Glad you made out so well and saved that chunk of change. You'll feel a lot better now every time you crank it up.


BILL