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Old 13-05-2019, 05:17   #31
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Re: Overheating NextGen generator head

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Originally Posted by a64pilot View Post
Easy now, people are just trying to help.

I agree your breaker is tripping from an high ambient temp.
I think it’s from either inadequate or now that you have modified the enclosure, from incorrect air flow over the gen head.
As you know the gen head is air cooled.

After installing a smooth bore hose that won’t collapse, I can now run my generator at 27 amps continuously, which is about the point that the engine begins to sag in RPM. That is about 3.25KW.
I can pull 30 amps from it, but at that amp draw the RPM of the engine drops to a point to where the voltage also drops, so that I’m actually pulling no more power, but at no time does the breaker trip, not since going to a better hose.
That's good to hear from someone with the unit re airflow, I think I'll suck it up and pay for the aircraft tubing regardless. It's just a matter of turning off the "push" air blower to test if that's the issue since the "suck" blower is in the factory location. Correcting the PF on the inductive loads can only help so I'll update the thread when I get around to that with results. It occurs to me that there might be a little side business fixing that for anyone with a generator and AC units, it seems like it should be stock on marine units but doesn't appear to even be recognized as an issue by any of the manufacturers.

As an aside, there's trying to help and then there's the 2LT who walks by when you're into day 2 of troubleshooting an engine problem and asks your mechanics if they checked the oil level, "....cause if you run with no oil it SHOULD cause problems for THAT engine."
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Old 17-05-2019, 16:26   #32
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Re: Overheating NextGen generator head

You would be surprised at how many "highly educated" people neglect to check the oil,----even engineers.
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Old 17-05-2019, 18:21   #33
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Overheating NextGen generator head

Try as best as you can to return the intake ducting to original, as itís designed to direct airflow to where itís needed.

Not sure if this came out in the thread, but I believe the generator is a 6KW generator, so it should be able to make 6000W without overheating, just the little one cylinder Kubota is what limits power output, if the motor was stronger it would make more power.
So our generators are only making about half of what the generator is capable of.
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Old 18-05-2019, 05:32   #34
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Re: Overheating NextGen generator head

REDNECKROB: Thank you for your explanation. I measured the line frequency, voltage and power factor using a KILL-A-WATT (R) device.

Kill A Watt Meter - Electricity Usage Monitor | P3

I get the proper line readings for the three items with both shore power and NexGen generator both at idle and with resistive loads such as my water heater and battery charger. My PF problem appears to occur solely when I apply loads from my AC units or my 120V water maker on both generator and shore power. Interestingly, the low PF is the approximately the same 0.56 value with each of the three devices, which I find odd since the motor horsepower is different for each of the motors.

The generator has a 400V 40UF capacitor. Not sure of its function, but given the commonality of the problem among three different AC motor loads, could this capacitor be the problem? Doesn't seem likely since the problem occurs on both generator and shore power.

Thanks - Alan
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Old 19-05-2019, 03:20   #35
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Re: Overheating NextGen generator head

Someone up-thread mentioned contacting NexGen for support. I would second the suggestion. They have been very helpful. I was having a problem similar to OP when our 3.5 was new. They shared that they had discovered that a slightly larger thermal breaker was needed when using the unit inside the sound enclosure - sent one to me & I haven’t had a problem since. I don’t remember the capacity of the replacement breaker & just left the boat for the he summer (heading back north) so can’t check. Worth a call to Ken or Jonas. We also had a problem with the collapsing vent hose but was able to fix by supporting externally with a zip tye from above. Finally, important to change the water pump impeller at least annually. Ironically, it is not mentioned that in their otherwise thorough preventive maintenance instructions.
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Old 19-05-2019, 08:44   #36
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Re: Overheating NextGen generator head

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Originally Posted by Jeanneau 45.2 View Post
REDNECKROB: Thank you for your explanation. I measured the line frequency, voltage and power factor using a KILL-A-WATT (R) device.

Kill A Watt Meter - Electricity Usage Monitor | P3

I get the proper line readings for the three items with both shore power and NexGen generator both at idle and with resistive loads such as my water heater and battery charger. My PF problem appears to occur solely when I apply loads from my AC units or my 120V water maker on both generator and shore power. Interestingly, the low PF is the approximately the same 0.56 value with each of the three devices, which I find odd since the motor horsepower is different for each of the motors.

The generator has a 400V 40UF capacitor. Not sure of its function, but given the commonality of the problem among three different AC motor loads, could this capacitor be the problem? Doesn't seem likely since the problem occurs on both generator and shore power.

Thanks - Alan


The cap is what regulates output voltage.
Decrease the value to lower voltage, increase to increase if Iím remembering correctly.
Apparently the generator manufacturer will vary the cap to adjust voltage within spec, mine came with a 37.5 and I had low voltage output, changing to a 40 brought it back up to the 120ís which is what I wanted.
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Old 20-05-2019, 18:42   #37
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Re: Overheating NextGen generator head

Update to everyone, first off thanks for the helpful suggestions. In the end I think it was a combination of two things, airflow and the generator 30 amp breaker. It was not the power factor, I measured that and everything was at .95 or better except my 8 amp small AC which was .9 so not really worth correcting. I did notice that the fixed vent louvers at the generator exit were facing back toward the engine instead of to the right where they would roughly direct the hot air into the installed exhaust vent port, so I swapped sides on that and it made an appreciable difference in the temperature in the sound enclosure. I also replaced the installed Sensata 30 amp thermal breaker with a nearly identical Blue Seas 30 amp breaker. Finally, I removed the rear cover that covers the belt on the generator because it seems to impede airflow through the core of the generator, but may put that back on since it is a guard for the belt. Was able to run more or less indefinitely at 25 amps, so fixed as much as I need it fixed for now.
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Old 20-05-2019, 18:49   #38
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Re: Overheating NextGen generator head

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Originally Posted by Jeanneau 45.2 View Post
REDNECKROB: Thank you for your explanation. I measured the line frequency, voltage and power factor using a KILL-A-WATT (R) device.

Kill A Watt Meter - Electricity Usage Monitor | P3

I get the proper line readings for the three items with both shore power and NexGen generator both at idle and with resistive loads such as my water heater and battery charger. My PF problem appears to occur solely when I apply loads from my AC units or my 120V water maker on both generator and shore power. Interestingly, the low PF is the approximately the same 0.56 value with each of the three devices, which I find odd since the motor horsepower is different for each of the motors.

The generator has a 400V 40UF capacitor. Not sure of its function, but given the commonality of the problem among three different AC motor loads, could this capacitor be the problem? Doesn't seem likely since the problem occurs on both generator and shore power.

Thanks - Alan
As already mentioned the capacitor on the generator is for regulation, nothing to do with PF. What you're observing is generally what you would expect, resistive loads have a PF of 1 and inductive loads have a lower PF. PF is based on the load, not the source of your electricity, so it should be expected to be the same on shore power or the gen. The only weird part is the drop from 1 to .56. First off it's almost impossible to get 1, you may see .95 at best, from a motor. So the original reading is odd. The drop itself is also odd, I'd suspect your meter except you say it luggs down the gen which it should do, it's effectively nearly doubling the load on it. My one suggestion now would be to look at how the motor is loaded. PF goes up dramatically when a motor is unloaded, so is your AC somehow unloading the motor after an hour, while still running it? Is it some kind of variable speed setup?
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Old 21-05-2019, 05:45   #39
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Re: Overheating NextGen generator head

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As already mentioned the capacitor on the generator is for regulation, nothing to do with PF. What you're observing is generally what you would expect, resistive loads have a PF of 1 and inductive loads have a lower PF. PF is based on the load, not the source of your electricity, so it should be expected to be the same on shore power or the gen. The only weird part is the drop from 1 to .56. First off it's almost impossible to get 1, you may see .95 at best, from a motor. So the original reading is odd. The drop itself is also odd, I'd suspect your meter except you say it luggs down the gen which it should do, it's effectively nearly doubling the load on it. My one suggestion now would be to look at how the motor is loaded. PF goes up dramatically when a motor is unloaded, so is your AC somehow unloading the motor after an hour, while still running it? Is it some kind of variable speed setup?
Sorry, realize I meant to say PF goes DOWN dramatically when a motor is unloaded, i.e. you may see that .56 reading due to an unloaded motor.
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Old 22-05-2019, 09:07   #40
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Re: Overheating NextGen generator head

RNR: I'll take this additional data you've provided and check out the situation from this perspective. Also, I think I'll call NextGen and ask for their thoughts. Forum, stand by for my update. Alan

A64: Glad to hear the capacitor change to 40 resolved your issue. Wonder why they installed a 37.5 when my manual specifies 40. Parts availability or just their error?
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Old 22-05-2019, 12:14   #41
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Overheating NextGen generator head

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Originally Posted by Jeanneau 45.2 View Post



A64: Glad to hear the capacitor change to 40 resolved your issue. Wonder why they installed a 37.5 when my manual specifies 40. Parts availability or just their error?


I assume the generator manufacturer bench tests them and ships them with whatever cap puts the generator closest to spec, not Nexgen.
I assume Nexgen takes it out of the box puts a pulley or whatever they need to do and bolt it together with the engine.
Average cap value is most likely 40 so that went into the manual, maybe one with a 37.5 is rare?

Lots of assumptions here so I may be wrong.

Thing to remember though is that voltage can be adjusted by varying the uf value, slightly.
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Old 22-05-2019, 20:02   #42
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Re: Overheating NextGen generator head

The only thing in my manual that is the same as what was delivered is the Kubota engine. I'm not the least bit surprised that the cap is different than what's stated in the manual.
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Old 16-08-2019, 14:30   #43
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Re: Overheating NextGen generator head

I wanted to post an postscript to this thread in case anyone refers to it in the future. I ended up replacing the factory supplied 30 amp push button circuit breaker made by Sensata which was what kept popping, leading me to believe it was overheating. I replaced it with a 30 amp Blue Seas pushbutton circuit beaker of the same type, close to a drop-in replacement although it's not threaded so you need to buy nuts to mount it (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 it's Blue Seas model number 2140) My problems went away, although I had done several other things at the same time so I couldn't be sure it was the cb.
Now many months later I installed an isolation transformer on my shore power input that need a 30 amp breaker. I decided I'd recycle the Sensata breaker I had, after all the isolation transformer didn't really get hot and is mounted inside an air conditioned space instead of the hot generator enclosure like it was before. And what do you know, but the thing pops 15 minutes after I start both AC units, at about the same amperage as it was when it was mounted in the generator. So I can pretty definitely say that in my situation the circuit breaker supplied by the OEM was faulty and was the problem all along. So if you've got a problem with the generator 30 amp breaker popping I'd highly recommend you replace that first in your troubleshooting steps!
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Old 17-08-2019, 19:28   #44
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Re: Overheating NextGen generator head

Thank you very much. I think you found the problem and I will take under advisement if I have trouble with the breaker. This is a great forum for specific problems just like this. Thanks again.
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