Overheating NextGen generator head

[redneckrob]

Thanks all. I changed my smaller fan from suck to blowing air in from the engine compartment, switched out the cb for a like cb from blue seas, and removed the cover over the belt where the cb is attached since it appears to impede airflow through the generator. I also adjusted the throttle, I was getting a drop to 100v under load so I bumped it up so it's at 110. The rub on that part is that the unit tends to "diesel" when you shut it down, so hopefully it won't do that when it get's hot. I was able to maintain 25 amps without the cb popping. It still got very hot in there, which doesn't make a lot of sense given that my 2 kW honda generator electrical head doesn't get hot at all, but hopefully it's not getting hot enough to damage anything. The duct vent wasn't collapsing, could be the forced air in is helping there as well, but the uber expensive airplane ducting is my backup there (and thanks for reminding me that as expensive as boat parts are, the pale in comparison to airplane parts, I'd forgotten in the 20 years since I owned one!).

[a64pilot]

How did you put a blower fan on the Stock Nexgen 3.5 enclosure?
Only way I can think of to do that is to blow the air backwards through the enclosure.

Speed wise you need to check hertz, your looking for ideally 60 Hz under load, don’t try to change voltage with the throttle, you change voltage by varying the capacitance of the capacitor.
A very effective, easy to use and accurate voltmeter/ Hz meter is a a kill-a -watt meter, also good for measuring exactly how much power something uses.

You want 120 or so volts ideally.
https://www.spgsamerica.com/informat...voltage-ranges

[Fast Tack]

Hi, Which March Air Conditioning pump do you use for your Nex Gen generator ? I have the 5.5 thanks

[redneckrob]

Originally Posted by a64pilot

How did you put a blower fan on the Stock Nexgen 3.5 enclosure?
Only way I can think of to do that is to blow the air backwards through the enclosure.

Speed wise you need to check hertz, your looking for ideally 60 Hz under load, don’t try to change voltage with the throttle, you change voltage by varying the capacitance of the capacitor.
A very effective, easy to use and accurate voltmeter/ Hz meter is a a kill-a -watt meter, also good for measuring exactly how much power something uses.

You want 120 or so volts ideally.
https://www.spgsamerica.com/informat...voltage-ranges

You're right, had to put an extra hole in the side of the enclosure to blow on the generator head, exhaust is out the installed hole in the top enlarged to 4" and vented outside.
You did get me thinking as I was looking at the capacitor regulator on the generator to figure out the hz vs volts issue (swear my frequency stayed the same and voltage went up when I adjusted the throttle) that what I probably really need to do is neutralize the power factor at each of my ac motors with capacitors and that may cut the load the generator is seeing by 20% or so. Will need to do a PF measurement this weekend to see the impact that's having.

[sailingchiro]

I was always under the impression that capacitance determines frequency by charge up and discharge speed. That is the way we created clock speed with op-amps in the 90's for our microprocessors. I could be wrong. Probably am. Anyway, I adjusted mine to 120 volts under load and the frequency stayed constant. The voltage dropped to about 105 with load. Adjusted the throttle back up to 120 under load and works great. Of course, I may be frying my components. I have a voltage and frequency meter permantly installed.

[Sailmonkey]

Originally Posted by sailingchiro

I was always under the impression that capacitance determines frequency by charge up and discharge speed. That is the way we created clock speed with op-amps in the 90's for our microprocessors. I could be wrong. Probably am. Anyway, I adjusted mine to 120 volts under load and the frequency stayed constant. The voltage dropped to about 105 with load. Adjusted the throttle back up to 120 under load and works great. Of course, I may be frying my components. I have a voltage and frequency meter permantly installed.

Rotor speed (# of poles dependent) determines frequency.

A 2-pole generator needs to spin @ 3600 rpm to produce 60hz. A 4 pole-1800, a 6-pole 1200, etc.

[a64pilot]

Originally Posted by Fast Tack

Hi, Which March Air Conditioning pump do you use for your Nex Gen generator ? I have the 5.5 thanks

I use the LC-3. 8 gpm pump, but feel certain that the 5 gpm LC-2 would be fine as well.
The -3 pump moves more water than the mechanical one did, but doesn’t cause any problems.
I picked the -3 pump because it’s the one my AC uses, and so that way one pump would be a spare for both systems, actually I intend it to be spare for my 6K AC too, it’s much larger a pump than necessary, but don’t think a little extra water flow would hurt.

[a64pilot]

Originally Posted by redneckrob

You're right, had to put an extra hole in the side of the enclosure to blow on the generator head, exhaust is out the installed hole in the top enlarged to 4" and vented outside.
You did get me thinking as I was looking at the capacitor regulator on the generator to figure out the hz vs volts issue (swear my frequency stayed the same and voltage went up when I adjusted the throttle) that what I probably really need to do is neutralize the power factor at each of my ac motors with capacitors and that may cut the load the generator is seeing by 20% or so. Will need to do a PF measurement this weekend to see the impact that's having.

You changed the airflow through the box then, as designed it of course flows air over the generator head first, the engine isn’t cooled much by air, it’s mostly water cooled.
The factory air flow looks to be pretty well designed, it looks to direct cooling air. Hopefully you didn’t change it too much.

I have always thought that sucking hot air through an electric blower to be a stupid design, I’d much rather they had designed it to blow air through the enclosure, that way the blower would be pulling cool air through it, not hot air.

Years ago my Father built a fire place insert, he had a huge 6’ wide fireplace, which is way too big, the insert was a metal box on each side with I believe 4” pipes interconnecting them, the logs were placed on these pipes like a fire grate.
He had a fan on one side to draw air though, the fans didn’t last, they kept burning out.
I put the fan on the other box and made it blow air through, then it lasted for years, the hot air was cooking the motors of course.

Speeding up or slowing down the motor will change both the Hz rate and the voltage, but it will certainly change the Hz rate, that is the only way to regulate frequency.
The Nexgen is sort of odd in that it’s geared to turn the generator head at 3600 RPM with an engine speed of 2850 I think.
Most designs have the engine direct driving the generator.

[Jeanneau 45.2]

I also have the NextGen 3.5 with 1100 hours. Had to replace "small stuff" like the Johnson raw water pump and the high temperature shut down switch. Most expensive repair as to purchase a replacement cog drive belt.

My question is about Power Factor (PF). After the genset has driven my 16K AC unit for 90 minutes or so, from a generator cold start, the PF drops from 1.00 to 0.56. I don't know what the PF measure means, don't know if this is an issue (but at PF = 0.56 my output is limited to about 15A before the Kubota genset engine bogs down), and what is the fix so I can get closer to the nameplate 3.5Kw rating (I note that a prior post mentions a capacitor on the "load" motor (in this case the AC compressor motor). Explanation and advice appreciated.

REPAIR TIP:
To install a replacement cog drive belt, the trick is to never take the TaperLocks (R) apart. Rather remove 2 of the three flywheel bolts, swing the flywheel towards the generator head to temporarily shorten the apparent belt length, slide on the belt, then gently lever the flywheel back into position aligning the bolt pattern, which tensions the drive belt, and reinstall the two bolts removed in step #1. This way the belt tracking (i.e. alignment of the sheaves) does not get screwed up, which is critical to belt life and preventing the belt from jumping a sheave.

[redneckrob]

Originally Posted by Jeanneau 45.2

I also have the NextGen 3.5 with 1100 hours. Had to replace "small stuff" like the Johnson raw water pump and the high temperature shut down switch. Most expensive repair as to purchase a replacement cog drive belt.

My question is about Power Factor (PF). After the genset has driven my 16K AC unit for 90 minutes or so, from a generator cold start, the PF drops from 1.00 to 0.56. I don't know what the PF measure means, don't know if this is an issue (but at PF = 0.56 my output is limited to about 15A before the Kubota genset engine bogs down), and what is the fix so I can get closer to the nameplate 3.5Kw rating (I note that a prior post mentions a capacitor on the "load" motor (in this case the AC compressor motor). Explanation and advice appreciated.

REPAIR TIP:
To install a replacement cog drive belt, the trick is to never take the TaperLocks (R) apart. Rather remove 2 of the three flywheel bolts, swing the flywheel towards the generator head to temporarily shorten the apparent belt length, slide on the belt, then gently lever the flywheel back into position aligning the bolt pattern, which tensions the drive belt, and reinstall the two bolts removed in step #1. This way the belt tracking (i.e. alignment of the sheaves) does not get screwed up, which is critical to belt life and preventing the belt from jumping a sheave.

How do you know what your PF is?

I could spend an hour trying to explain it but at the risk of oversimplification, basically think of it as increased capacity your generator needs to provide for certain type of loads like electric motors. A PF of .75 would require a 25% bigger generator, a Pf of .5 a generator twice as large. Interestingly the motor doesn't actually use 25% more power, but your generator effectively works as if it does. A capacitor bank matched to the PF at each motor is generally the solution. This is big boy electrical stuff though, so you'll either need an electrician who has worked in big plants with lots of big motors or an electrical engineer to do the math and get the right kind of capacitors. Very few typical electricians will have a clue what you're talking about, and in my experience (as an electrical engineer) they often start talking out of their behind when faced with something advanced they don't understand and it basically becomes "if I don't understand it then it doesn't exist. You need me to install you a bigger generator for you"

[deblen]

Originally Posted by redneckrob

I have a NextGen 3.5, new unit professionally installed last year. Runs great, but the thing will only do a little over 2kW (20 amps at 110V) continuously, anything more and after about 5 min the thermal circuit breaker mounted on the generator head trips and won't reset for about 10 min because it is overheated. It's in a sound box with the recommended exhaust fan. I figured that air flow might be the issue so hooked up an additional 4" duct with a fan of twice the recommended CFM in addition to the regular fan on a 3" duct, but it still tripped after a few minutes at around 24 amps. And this was with the engine off (it draws from the engine room) and 65 degree F outside air temp. The engine isn't overheating, it's got good water flow and coolant level is good. The fans are definitely working because they're exhausting very hot air.
Any ideas on why the generator electrical portion is getting so hot? I would expect a 3.5 kW system to at least be able to do 3kW continuously, and especially baffling is the fact that the NextGen uses the same electrical gen portion for both their 3.5 and 5.0 so it's actually a 5kW generator electrically. One wonders if you're also limited to just over 2kW continuously on their 5kW model since only the diesel engine is different? Any ideas?

Are you sure your Gen is rated 3-3.5KW from ONE 120vac outlet??
No N.American 120VAC appliance can draw more than 1350Watts on 120VAC. That is why standard 120vac outlets are breakered/fused at 15amps.If you have plugged several 120vac items into ONE 120vac outlet,you may have gone beyond the 1350w/15A max.

I suspect the 3-3.5kw rating is at 240vac, or both 120vac outlets putting out 1350-1500w Each.
If I'm correct and you try to draw more than 1350-1500watts from ONE 120vac outlet on your GenSet,it SHOULD kick the breaker for THAT outlet.


Len

[redneckrob]

Originally Posted by deblen

Are you sure your Gen is rated 3-3.5KW from ONE 120vac outlet??
No N.American 120VAC appliance can draw more than 1350Watts on 120VAC. That is why standard 120vac outlets are breakered/fused at 15amps.If you have plugged several 120vac items into ONE 120vac outlet,you may have gone beyond the 1350w/15A max.

I suspect the 3-3.5kw rating is at 240vac, or both 120vac outlets putting out 1350-1500w Each.
If I'm correct and you try to draw more than 1350-1500watts from ONE 120vac outlet on your GenSet,it SHOULD kick the breaker for THAT outlet.


Len

Just a gentle life tip for you, if you have an electrical engineer talking about power factors they maybe, just maybe, understand the capacity of a 115 outlet and breakers on circuits?

I am running 2 AC units and a charger. They total around 20 amps draw on the generator based on my amp meter measuring total draw on the gen. They are individually breakered but it isn't their breakers tripping, it's the 30 amp breaker on the generator. You don't need an electrical engineering degree to know that a 30 amp breaker doesn't trip at 20 amps because of the amperage draw on a 115 outlet! This is a thermal breaker and it's obviously tripping because the gen head itself is overheating, it's mounted on the head. There is absolutely no question that this is an issue of the generator head getting very hot, not of me being a moron who doesn't gasp electrical basics. But thanks for assuming!

[deblen]

Originally Posted by redneckrob

Just a gentle life tip for you, if you have an electrical engineer talking about power factors they maybe, just maybe, understand the capacity of a 115 outlet and breakers on circuits?

I am running 2 AC units and a charger. They total around 20 amps draw on the generator based on my amp meter measuring total draw on the gen. They are individually breakered but it isn't their breakers tripping, it's the 30 amp breaker on the generator. You don't need an electrical engineering degree to know that a 30 amp breaker doesn't trip at 20 amps because of the amperage draw on a 115 outlet! This is a thermal breaker and it's obviously tripping because the gen head itself is overheating, it's mounted on the head. There is absolutely no question that this is an issue of the generator head getting very hot, not of me being a moron who doesn't gasp electrical basics. But thanks for assuming!

Oh! You're an Iron Ring!

Then,why did you feel it necessary to ask for advice from the mere mortals on this forum?


Before I posted my first friendly suggestions:


I did read your first post .
I did note that you stated the thermal "breaker"(switch) mounted on the "head" was kicking off.
I did assume the "head" you spoke of was the generator & not the engine cyl. head.
I thought this info over & ta-da!-concluded the same as you. The generator (alternator) must be overheating,causing the heat sensing thermal safety switch to trip.
You had stated that the engine ran at normal revs & temp.


Now,what could cause just the alternator to overheat??


Len

[a64pilot]

Originally Posted by deblen

Oh! You're an Iron Ring!

Then,why did you feel it necessary to ask for advice from the mere mortals on this forum?


Before I posted my first friendly suggestions:


I did read your first post .
I did note that you stated the thermal "breaker"(switch) mounted on the "head" was kicking off.
I did assume the "head" you spoke of was the generator & not the engine cyl. head.
I thought this info over & ta-da!-concluded the same as you. The generator (alternator) must be overheating,causing the heat sensing thermal safety switch to trip.
You had stated that the engine ran at normal revs & temp.


Now,what could cause just the alternator to overheat??


Len

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.

[redneckrob]

Originally Posted by deblen

Oh! You're an Iron Ring!

Then,why did you feel it necessary to ask for advice from the mere mortals on this forum?


Before I posted my first friendly suggestions:


I did read your first post .
I did note that you stated the thermal "breaker"(switch) mounted on the "head" was kicking off.
I did assume the "head" you spoke of was the generator & not the engine cyl. head.
I thought this info over & ta-da!-concluded the same as you. The generator (alternator) must be overheating,causing the heat sensing thermal safety switch to trip.
You had stated that the engine ran at normal revs & temp.


Now,what could cause just the alternator to overheat??


Len

As they say in my neck of the woods, bless your heart.