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Old 02-03-2018, 05:06 AM   #1
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Northern Light genset tripping internal fuse

I have a NL M843 NW3 - it has shut down twice after being operated for some hours - all engine parameters are normal so it appears to be a hot generator head - although I can't find anything describing this in the generator head manual...

The symptons are: normal engine data, temperature is OK, water flow, oil pressure etc....then it suddenly looses RPM, then shuts down. The fuse on the generator head has popped out, and the way to get it started again is to reset the internal breakers and then reset the fuse....

So - I assume its the generator head that either overheats or overloads although there is no indication of either - except for the fact that it only happens after several hours of use at about 60-70% load.

Any idea?
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Old 02-03-2018, 05:35 AM   #2
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Why do you think its the genset and not whats running off it thats causing the problem ?
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Old 02-03-2018, 05:44 AM   #3
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That's another option, but it only happens when the genset has been running for some hours - not when its cold...
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Old 02-03-2018, 05:46 AM   #4
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Also, it requires some time to cool down after the fuse reset before being able to start again...
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Old 02-03-2018, 06:36 AM   #5
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Has this always happened with the same load, same time, same ambient conditions. If so then maybe your installation doesn't have enough air flow cooling, and the engine room gets too hot for it.

If it is in an enclosure, open it up, and point a small fan at the generator end and run and see what happens. If not in an enclosure do the same. If you can easily open up the engine room (not if access is from the cabin sole obviously) then do that as well.

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Old 02-03-2018, 07:53 AM   #6
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You state that both internal breakers trip, and an external fuse...both needing to be reset. Did you really mean external "fuse" that needs resetting? Or is it another breaker?

Can you post pics or describe where they are, what they look like, and their rstinhs?
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Old 02-03-2018, 01:09 PM   #7
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Could be a variety of breakers/fuses on this thing based on age and options:

DC control breaker
Exciter field breaker/fuse
Main output breaker
Maybe something else??

Figure out what is tripping/blowing.

There is no temperature sensor in gen end that causes a trip.

Note that DC control breaker has a thermal element in it, and if ambient temp gets real high (hot engine room), it can trip even if amps are lower than trip point.

Also, I have replaced several DC control breakers on NL units. Seems the vibes wear them out.

This does not really fit your scenario as a trip on the DC control breaker will cause an instant shutdown, not a loss of rpm THEN a trip.

And a loss of rpm due to fuel or overload will not cause DC control breaker amps to go high resulting in a trip.

An overload will cause rpms to drop, tripping either exciter field breaker or output breaker, but once that happens, engine will continue running. Unless they have changed the control logic since I last troubleshot one of these.
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Old 02-03-2018, 01:38 PM   #8
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I had a voltage regulator go out I put an blower to push more air into the gen to cool the regulator and the gen
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Old 02-03-2018, 05:51 PM   #9
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Quote:
Originally Posted by psneeld View Post
You state that both internal breakers trip, and an external fuse...both needing to be reset. Did you really mean external "fuse" that needs resetting? Or is it another breaker?

Can you post pics or describe where they are, what they look like, and their rstinhs?
The fuse blows, and can only be reset once I have turned the 2 breakers off then on again.

The fuse and the breakers are on the generator head control box inside the sound enclosure.

About the RPM drop....it happened really quickly so maybe theres just an instant shutdown.

The genset is 130 hours old...so age should't be the issue
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Old 02-03-2018, 05:53 PM   #10
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If it's a thermal trip of the generator head, will it then shut down the engine too?
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Old 02-03-2018, 06:56 PM   #11
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Quote:
Originally Posted by Searios View Post
The genset is 130 hours old...so age shouldn't be the issue
Is it still in warranty?
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Old 02-03-2018, 07:11 PM   #12
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As the end bearing old, the sealed in grease goes away. The bearing gets hot, transfers heat to the generator and would trip any thermal safety. End bearings in most generators I have used are supposed to be replaced about every 5 years regardless of hours.
ditto on high engine room temps.
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Old 02-03-2018, 07:56 PM   #13
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Quote:
Originally Posted by Searios View Post
The fuse blows, and can only be reset once I have turned the 2 breakers off then on again.

The fuse and the breakers are on the generator head control box inside the sound enclosure.

About the RPM drop....it happened really quickly so maybe theres just an instant shutdown.

The genset is 130 hours old...so age should't be the issue
never heard of a fuse being able to be reset, only breakers....

are the other w breakers A/C?
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