Generator puzzle - ground wire

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  #1  
Old 12-03-13, 07:00 AM
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Generator puzzle - ground wire

I've just set up a Honda 6500 generator for emergency power... put in a four connector male plug on a transfer box on the house, utilizing the 240 volt output on the generator. (The transfer box was professionally installed). That's a black and red for the two hot wires, green to ground and white to neutral. Even with the transfer switch off, the generator circuit breaker trips immediately. Since the black and red are going nowhere (the switch is off), the only real connections are the white neutral and green ground, and the breaker trips. If I disconnect the green ground wire, it works normally... no circuit breaker trip, and voltages read as they should.

What's going on?? And is there a problem running it like this, with no connected ground to the generator?
 
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Old 12-03-13, 07:12 AM
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Does it have GFCI protection and is it the GFCI tripping? Are the ground and neutral bonded to each other?
 
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Old 12-03-13, 09:12 AM
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The generator has a note which says all outlets are GFCI protected. In the transfer switch box, the neutral is not directly connected to ground, but of course would be at some point up the line, I'm sure.

I see that there's a lug on the generator with a "ground" symbol... should that actually be connected to a ground or ground rod?
 
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Old 12-03-13, 09:35 AM
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Sounds like the problem is both the genset and the house have the neutrals bonded to ground.
 
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Old 12-03-13, 09:48 AM
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This is a problem often encountered on these forums. Here are three of dozens of previous posts on the issue. Bottom line though it may be a violation for a portable generator is to unbond the ground and neutral at the generator. Also you should use a three pole transfer switch that interrupts the neutral. It sounds like your transfer switch only interups the hots.

http://www.doityourself.com/forum/el...-ground.html#b
http://www.doityourself.com/forum/el...nd-bond.html#b
http://www.doityourself.com/forum/el...nerator.html#b
 

Last edited by ray2047; 12-03-13 at 12:35 PM.
  #6  
Old 12-03-13, 11:31 AM
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With the Honda generators, you have to disconnect the ground wire from the inlet in the inlet box. Otherwise the gfci will trip out.
 
  #7  
Old 12-04-13, 05:35 AM
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Solving the puzzle:

You have three choices sorta'.

1. Unbond ground and neutral in the generator.
2. Unbond ground and neutral in the panel.
3. Unbond ground and ground somewhere in between (see previous reply; also you tried something similar that is topologically the same and works just as well).

I personally rule out #1 if that can't be done easily or according to the generator instructions.
I personally rule out #2. if that is very complicated such as re-arranging the entire panel innards.
That leaves #3.

For those eavesdropping and who haven't installed anything yet, there are some advantages to moving the circuits eligible for generator power to a subpanel:
* You don't have to call the power company to coordinate installing a transfer switch upstream of your main breaker,
* With a correctly installed subpanel, #2 above is already done.
 
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