ECN Forum Forums Code Related Discussion NEC & other Code issues Temporary Generator

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,
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).
Don(resqcapt19)

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.

Thanks for your replies. I expect that the person who asked this question will join in soon, I hope.

Joe

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

Buddy,
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?

Don(rsqcapt19)