Stator failure- Northern Lights 6kw

[David Hughes]

Had guests on my boat last week, and while at anchor in Pelican Bay, Cayo Costa, FL ( hot as blazes), after about 10 hours of running the Air Con units, smoke began pouring out of the engine room- more specifically the generator sound containment box, and even more specifically the windings end of the generator. It was a LOT of smoke. They shut down the gen, donned life jackets are were nearly ready to jump. The smoke soon abated after shutdown and they spent the remaining couple of days at South Seas and Tween Waters so they could run shore power. All that is preamble to my question: Has this happened to anyone else and did you have to spend the $4000 for the new stator/windings unit, or did you have it simply rewound by someone. If rewound, about what should that cost? Tomorrow, Gulf Coast Marine Electric ( who I like and trust) is coming over to look, but it would nice to not be a complete ignoramus about it. Thanks!


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[boatbod]

Had a stator failure on a customer's Westerbeke. We ended up swapping in a complete new generator head onto the existing engine.

[David Hughes]

Thanks. That's what I'm thinking will happen, for $4000


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[boatbod]

Sounds like about the right price.

[crabcake]

Originally Posted by David Hughes

Thanks. That's what I'm thinking will happen, for $4000


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Question please: About how old and about how many hours on the NL before failure?

[David Hughes]

It's a 2008 build, in a 2009 commissioned boat, and has about 4600 hours on it.


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[Dockhead]

Sorry this question may not be immediately helpful to the OP, but why would this happen? A defect? Or overloading the genset?

I would certainly not like this to happen to mine. I limit the output to about 85% of the rated power by using the current limiting function of my Victron Multiplus.

[crabcake]

Originally Posted by David Hughes

It's a 2008 build, in a 2009 commissioned boat, and has about 4600 hours on it.


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THANKS!

[techmans]

Originally Posted by Dockhead

Sorry this question may not be immediately helpful to the OP, but why would this happen? A defect? Or overloading the genset?

I would certainly not like this to happen to mine. I limit the output to about 85% of the rated power by using the current limiting function of my Victron Multiplus.

I would think that running a high load for an extended period of time in hot weather with the unit well insulated in a box could easily drive the stator temp up to dangerous levels.The diesel engine is nicely cooled but the generator part of the unit relies on air cooling which has to be weighed against livable noise levels.
If you weigh that wrong the windings start smoking.

What surprises me is that there seems to be no functioning thermal protection on this unit to prevent this from happening.Is even more of a safety issue than with your home appliances which all have fused thermal protection.

[Dockhead]

Originally Posted by techmans

I would think that running a high load for an extended period of time in hot weather with the unit well insulated in a box could easily drive the stator temp up to dangerous levels.The diesel engine is nicely cooled but the generator part of the unit relies on air cooling which has to be weighed against livable noise levels.
If you weigh that wrong the windings start smoking.

What surprises me is that there seems to be no functioning thermal protection on this unit to prevent this from happening.Is even more of a safety issue than with your home appliances which all have fused thermal protection.

Wow. This is a real eye-opener. That would be absolutely ghastly, to have a $4000 failure, just like that. Surely there should be some thermal protection.

I will start checking the temperature of mine. I never thought about the generator section; thought it was bulletproof.

I think I will derate mine even a little more. I always thought I have a big margin of error -- my generator is a 6.5EFOZ which makes 6.5kW at 220v, but the whole unit is designed to produce 8kW at 110v. So I thought that was already some headroom even at max output. I further limit the power drawn from the generator with the current limiter on my Victron Multiplus. Max output is 29.5 amps at 220v; I have always been setting the Victron on 24 amps, which is about 5.3kW. Maybe I'll lower it a little more.

I'll also watch engine room temperature. I have manually switched blowers and have forgotten once or twice to put them on. Normally in summer engine room doesn't get over about 35C, but if I forget to turn on the blower then it can go up to nearly 50.

My generator is one of those things I really rely on, and has always been one of those few things on board which just always works, and I sure want to keep it that way.

Apologies to the OP for the thread drift, but your experience is valuable to many of the rest of us.

[Pelagic]

This is my biggest beef with sound shields....you never know what is going on underneath when running.

Inspection hatches do not allow you to see everything.

Something as simple as a pin hole leak at the wet exhaust manifold, feeding a thin salt water spray into the Gen side could have cause the massive short.

[David Hughes]

Originally Posted by Dockhead

Wow. This is a real eye-opener. That would be absolutely ghastly, to have a $4000 failure, just like that. Surely there should be some thermal protection.



I will start checking the temperature of mine. I never thought about the generator section; thought it was bulletproof.



I think I will derate mine even a little more. I always thought I have a big margin of error -- my generator is a 6.5EFOZ which makes 6.5kW at 220v, but the whole unit is designed to produce 8kW at 110v. So I thought that was already some headroom even at max output. I further limit the power drawn from the generator with the current limiter on my Victron Multiplus. Max output is 29.5 amps at 220v; I have always been setting the Victron on 24 amps, which is about 5.3kW. Maybe I'll lower it a little more.



I'll also watch engine room temperature. I have manually switched blowers and have forgotten once or twice to put them on. Normally in summer engine room doesn't get over about 35C, but if I forget to turn on the blower then it can go up to nearly 50.



My generator is one of those things I really rely on, and has always been one of those few things on board which just always works, and I sure want to keep it that way.



Apologies to the OP for the thread drift, but your experience is valuable to many of the rest of us.

I don't find this to be thread drift at all. I really appreciate all this great information. Ironically, one of the reasons I thought the sound box was a good thing was exactly to protect the generator from salt spray. My motor had sprayed the engine room once with salt water and I was glad for the box. In net, I still think the box is better than no box...


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[boatbod]

Stators burn up when the lacquer insulation on the wire fails. Can be overheating due to excessive current, lack of airflow or simply old age.

[Pelagic]

David, I hear you about the water protection from an outside leak (main engine or fresh water pump), but you can protect just the gen vents from that and leave the engine side open for full inspection.

Of course the Sound Issue is a lot worse unless you redo the whole engine room to a much higher Standard, so the box is probably the best solution for your installation.

It will be interesting to know what failed, (probably some cracked and degenerated insulation at the main connection), but take a look at the condition of the whole package when all the shields are off and ask yourself if you were surprised by what you discovered?

If yes, then schedule complete removal of box on a regular basis for preventative maintenance.

Good luck with the repairs.

[DotDun]

FWIW, this issue is what drove my decision to look at Mase. Mase has a line of generators (IS - "intercooler") that has a water/air heat exchanger on the raw water line between the inlet and raw water pump. The alternator cooling fan circulates air through the heat exchanger keeping the air in the case vs. a NL design where it dumps the hot air into the engine room. Even with 90°F raw water temp, the temperature inside the case never goes above 105°F (Mase's claim, I've never measured it).

Yes, the additional heat exchanger is yet another failure point, and yes, I've replaced one due to my own stupidity ($250), but I think it's worth it to keep the unit a lot cooler. With the heat exchanger ahead of the raw water pump, if it does develop a leak, the raw water pump sucks air and the unit shuts down. Which is better than on the other side of the pump where it would spray water all over the inside of the case.

Clever design, IMO!