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Old 04-17-2011, 08:38 PM   #1
Mini-Skoolie
 
Join Date: Dec 2010
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Year: 1997
Coachwork: Blue Bird
Chassis: Bookmobile
Engine: Cummins/Allison
Need help with 21kw genset

Still working on the GameRV (GameRV.com) and having an issue with generator. This is an Isuzu / Norpro diesel genset (model 4LE1) with analog controller. Problem began with PMA alternator not putting out 14 volts so we decided to replace the 20 amp pma (replacement quoted at least $500) with a standard / traditional automotive alternator rated at 60 amps for $125. When I fire up one system and ac's on low cool, system is stable. Fire up all 16 tv's and xbox 360's along with max cool on all 4 ac's, after a while (30 minutes or so) generator dies. It is acting like it can't handle the load, but at 21kw there should be plenty of power available for the tv and xbox's (2amps draw each for a max total of 32 amps) and 4 ac's. Tomorrow I will test with fluke multimeter to determine if battery draining faster than can be replenished by alternator. Did I mess up by replacing PMA with regular alternator? What am I doing wrong so generator won't stay on?

Thanks as always in advance for any and all help,
Mike
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Old 04-25-2011, 11:26 PM   #2
Bus Crazy
 
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Re: Need help with 21kw genset

Quote:
Originally Posted by GameRV
. . . after a while (30 minutes or so) generator dies. It is acting like it can't handle the load, but at 21kw there should be plenty of power available for the tv and xbox's (2amps draw each for a max total of 32 amps) and 4 ac's. . . . .
Look at the other post. It is sounding more and more like a vacuum in the fuel tank. If you take the cover off of the fuel tank filler, does the cap hiss, and the genny start running smoothly with the cover off? Just a thought, YMMV.
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Old 06-11-2011, 03:18 PM   #3
Mini-Skoolie
 
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Location: Willard, OH & Charlotte, NC www.jamboreeinthehills.com
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Year: 1996
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Re: Need help with 21kw genset

How long are your extension cords? What gauge are they? How many amps are you drawing per outlet? (I tried using a small window air conditioner in a school bus window one time with a 100 foot 16 gauge extension cord and the extension cord got really hot and the ac eventually turned itself off)

Those AC's are probably drawing close to 15 amps each, so that means 60 amps right there.

60 amps * 110 volts = 6,600 watts (air conditioners)

32 amps * 110 volts = 3,250 watts (tv's and Xbox's)

This is a total of 10,850 watts and 92 amps which means your generator is strong enough (167 amps continuous and 183 amps max), but there is a voltage drop or battery issue somewhwere else. I would use some bigger batteries and more batteries and change your power cables to 4 gauge or 2 gauge. 60 amps for the alternator does not sound big enough. Ebay has some 150 amp alternators for cheap. I would use heavier extension cords too and make sure you aren't overloading one outlet. Spread out the current draw more evenly. Also check your coolant. You should have 6.8 quarts so you don't overheat. Make sure your fuel pump is operating correctly and getting 12 volts.
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Old 06-12-2011, 02:40 PM   #4
Mini-Skoolie
 
Join Date: Jan 2011
Location: Willard, OH & Charlotte, NC www.jamboreeinthehills.com
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Year: 1996
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Chassis: TC2000 - Flat nose
Engine: 5.9 Cummins Turbo Diesel
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Re: Need help with 21kw genset

AC watts / 12.1 * 1.1 = DC watts

Let us know how your results once you put in a 150 amp alternator.
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Old 07-25-2011, 03:15 AM   #5
Skoolie
 
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Re: Need help with 21kw genset

From what yo are indicating and not much information at that is the generator shuts down when everything is running?
Have you tried starting the equipment in stages and watch what happens until you start something and generator shuts down?
As one poster mentioned check the fuel and see if you are getting a vapor lock; but from what you mention the generator runs fine until you turn on everything? All AC's running at high is fine until you turn on the xboxes and TV's?
You also did not include a diagram in your power hookup?
This model genset output through four power legs indicating three phase into 220v or split into two 120v?
L1/L2/L3/neutral
You may be overloading one side of the genset fields with an unbalanced load and causing a field to overheat and shut the genset down.
If you have your AC's on one leg split you are over loading it if you have the xboxes and TV's on the other leg..
Also the guage of the output legs are 4/0. Depending on how long your cable run is? The longer the larger gauge you will have to use..
I think your unbalanced from what you say genset runs fine with the AC's all on low?
This genset was made for marine applications and a majority run on three phase.
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Old 10-31-2013, 03:10 PM   #6
Skoolie
 
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Re: Need help with 21kw genset

I guess Im a little late but here goes. The PMG would put out over 60 volts for use by the AVR so a 12 volt altenator will not work. Next you can not use two legs of a three phase gen to power 220 or 240 loads. check your line to line voltage you will find its lower then 240 closser to 208. Plus the phases are only 120 dgrees apart instead of 180 so you lose power when you try to do this even if the l-l volts is 220 you only have a power factor of .8 on a 3 ph gen set will not run a 1ph 220/240 motor correctly. What seems to be happening is shut down due to low excitation voltage. JMHO

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