[RE-wrenches] 120% rule for hybrid inverters

[Mark Westbrock]

Hi Howie,

As usual, the code is not written as clearly as it could be, but
705.12(D)(2)(3)(b) starts out by stating "Where two sources, one a utility
and the other an inverter", so I think that the only logical interpretation
is that when it says "the sum of 125 percent of the inverter(s) output
circuit current and the rating of the overcurrent device protecting the
busbar", that the latter refers to the main breaker protecting the busbar
from the utility.

Cheers,

Mark

----
Mark Westbrock|  VP, Branch Manager |  Employee Owner
NABCEP™ Certified PV Installation Professional
NABCEP™ Certified
Technical Sales Professional
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On Fri, Aug 12, 2016 at 9:38 AM, Howie Michaelson <howie at suncatchervt.com>
wrote:

> Mark,  I read that section as stating that *both* must be true, which I
> would take to mean if one is using a 20 amp breaker to protect the output
> from a 3 kW inverter, you need to count it as 20 amps toward the 120% rule,
> not the 15.63 amps the 125% calculation would infer.  I know that 2014 was
> changed to allow for larger breakers to feed hybrid inverters, but I can't
> recite the code that allows that (unless I am misreading the intent of the
> section you quoted). Can you clarify this for me?
>
> Thanks,
> Howie
>
> *Howie Michaelson*
> *NABCEP Certified Solar PV Installer™*
> Sun Catcher, LLC
> Renewable Energy Systems Sales and Service
> VT Solar Electric Incentive Partner
> 802-272-0004
>
> On Fri, Aug 12, 2016 at 9:39 AM, Mark Westbrock <westbrock@
> positiveenergysolar.com> wrote:
>
>> Hi Mac,
>>
>> The wording changed because in the 2011 NEC 705.12(D) you had to use the
>> size of your backfeed breaker in calculating the busbar loading, but in
>> 2014, 705.12(D)(2)(3)(b) now says "125 percent of the inverter output
>> circuit current and the rating of the OCPD protecting the busbar shall not
>> exceed 120%".
>>
>> So, the 2014 wording basically allows all inverters to follow the
>> exception that used to be there for hybrid inverters.  I hope that helps.
>>
>> Cheers,
>>
>> Mark
>>
>> ----
>> Mark Westbrock|  VP, Branch Manager |  Employee Owner
>> NABCEP™ Certified PV Installation Professional
>> NABCEP™ Certified
>> Technical Sales Professional
>> NM EE98J Licensed Electrician
>> 510 S. Main St., Las Cruces, NM 88001
>> cell  575.640.2432 |  office  575.524.2030
>> mw at PositiveEnergySolar.com  <Your.Email at PositiveEnergySolar.com>
>> www.PositiveEnergySolar.com <http://www.positiveenergysolar.com/>
>>
>> <http://www.positiveenergysolar.com>
>>
>>
>> On Fri, Aug 12, 2016 at 7:26 AM, Mac Lewis <maclewis1 at gmail.com> wrote:
>>
>>> Hello wrenches,
>>>
>>> I am looking for the exception to the 120% rule in the 2014 code that
>>> allowed for compliance to the 120% rule to be based on the
>>> utility-interactive current as opposed to the backfeed breaker size for
>>> hybrid inverter.  I hope this still exists, but I'm having a hard time
>>> finding it in the 2014 code.  In 2011 it was 705.12(D)2 Exception.  That
>>> was nice clear language that all inspectors accepted, I'm hoping the same
>>> exists for the 2014 code.
>>>
>>> Thanks in advance code experts
>>>
>>>
>>>
>>> --
>>>
>>>
>>>
>>> Mac Lewis
>>>
>>> *"Yo solo sé que no sé nada." -Sócrates*
>>>
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