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#78336 - 09/10/01 04:35 PM Temporary Generator  
Joe Tedesco  Offline
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
305-6(a), Exception No.1. What is the reasoning
for this exception? I know it's been in there for years. How can you tell if
you meet this exception? I know the obvious if its over 5 kw but say you got
a 4500 watt generator (which are common), how do you know if you meet this?
I was told one way if you have dual voltage 120/240 then you would not meet
that exception. Is that dual voltage reasoning (if true at all) because if
you had 240, you would have 2 hot wires and one neutral thus equal 3 wires?

[This message has been edited by Joe Tedesco (edited 09-10-2001).]

Joe Tedesco, NEC Consultant

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#78337 - 09/10/01 07:09 PM Re: Temporary Generator  
resqcapt19  Offline
Joined: Nov 2000
Posts: 2,148
Even if it is only a 2 wire generator, you can't use the exception. 250-20(b) requires the system to be a grounded system. There is nothing in 305 that says it doesn't have to be a grounded system and if it is grounded, then GFCI protection is required. If its not grounded, it is a violation of 250-20(b).


#78338 - 09/10/01 07:14 PM Re: Temporary Generator  
sparky  Offline
Joined: Oct 2000
Posts: 5,306
Joe, i think they mean the 120V receptacles on the 5kw and less units, regardless of other features.
I'll bet this exception was lobbied by the makers of generators.

#78339 - 09/11/01 11:49 AM Re: Temporary Generator  
Joe Tedesco  Offline
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Thanks for your replies. I expect that the person who asked this question will join in soon, I hope.


Joe Tedesco, NEC Consultant

#78340 - 09/11/01 10:11 PM Re: Temporary Generator  
buddy  Offline
Joined: Sep 2001
Posts: 8
I posted the question to the board and don't really agree with the responses and here's why. I don't think the generator has to be grounded and if it was, then what requires GFCI protection? That is what the exception is all about, not requiring GFCI's. What I basically want to figure out is how is an inspector supposed to know if a generator meets that exception? Thanks

#78341 - 09/12/01 09:03 AM Re: Temporary Generator  
resqcapt19  Offline
Joined: Nov 2000
Posts: 2,148
In my opinion, this exception could be used if you verify that there is not a bond between the frame of the generator and a circuit conductor. The exception also requires that it only be a 2 wire generator, which would preclude the use of a 120/240 volt generator. Are there any portable generators currently available that do not have a conductor bonded to the frame? I've never seen one without this bond.

Is a portable generator a separately derived system?



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