Generator conductors 115% rule

[Twoskinsoneman]

445.13 Ampacity of Conductors.
The ampacity of the conductors from the generator terminals to the first distribution device(s) containing overcurrent protection shall not be less than 115 percent of the nameplate current rating of the generator. It shall be permitted to size the neutral conductors in accordance with 220.61. Conductors that must carry ground-fault currents shall not be smaller than required by 250.30(A). Neutral conductors of dc generators that must carry ground-fault currents shall not be smaller than the minimum required size of the largest conductor.

If your generator has a built-in OCPD, do you not use the 115% rule? Or since the OCPD is mounted on the gen do you consider it the gen terminals and not a "distribution device"

 

[Buck Parrish]

IMOHP It's a generator.
But, I think since or if it is individual breakers on the generator then 115% would not be required.

 

[tom baker]

I posted the same question earlier. The answer is only from the generator to the first OCPD, if mounted on the generator thats the first OCPD.
I purchased the NECA NEIS Standard for Installing Generator Sets, and it has a good explanation of the code requirement for this, even a drawing!
But I agree its not clear.

 

[Twoskinsoneman]

I posted the same question earlier. The answer is only from the generator to the first OCPD, if mounted on the generator thats the first OCPD.
I purchased the NECA NEIS Standard for Installing Generator Sets, and it has a good explanation of the code requirement for this, even a drawing!
But I agree its not clear.

IF I may ask what is THEIR explanation?

 

[360Youth]

If your generator has a built-in OCPD, do you not use the 115% rule? Or since the OCPD is mounted on the gen do you consider it the gen terminals and not a "distribution device"

When you find out, let a few of us know. As Tom stated we had this discussion a few weeks back and the most that could be agreed upon was that the wording is not very clear. I have always read as, and continue to practice, that the conductors from genset to the ATS breaker or first field installed OCP should be sized at 115%, but I can more easily see the stance that the onboard OCP could be what NEC is refering to. It is probably an issue that needs updated wording because of the recent boom in generator design (ie, most every genset now comes with onboard OCP where years ago most did not.)

 

[Twoskinsoneman]

When you find out, let a few of us know. As Tom stated we had this discussion a few weeks back and the most that could be agreed upon was that the wording is not very clear. I have always read as, and continue to practice, that the conductors from genset to the ATS breaker or first field installed OCP should be sized at 115%, but I can more easily see the stance that the onboard OCP could be what NEC is refering to. It is probably an issue that needs updated wording because of the recent boom in generator design (ie, most every genset now comes with onboard OCP where years ago most did not.)

I have decided to purchase the NECA (National Electrical Contractors Associastion) document NECA 406-2003 Standard for Installing Residential Generator Sets. Since the NEC wording (IMO) is ambiguous I have decided to trust the opinion of the NECA on the matter. Their conclusion is that if the generator has an OCPD on it than the wires only have to be rated at or above the OCPD rating. I hesitate to reprint any of the document due to copywrite laws. If any one has any questions about the 1.6mb pdf document I downloaded from their website for $30 please PM me and I will be happy to share my answers with you.