[RE-wrenches] multiple points of grid connection and the opposite end of the bus rule

[Isaac Opalinsky]

Al,

Will you be relying on the 120% rule for your interconnection (i.e., do you anticipate exceeding the ampacity of the conductors you’re connecting to?)?  If not, you don’t have to worry about going to the opposite end of the busbar.

If you’re on the 2014 NEC, the feeder taps rules for inverters are clarified a bit at 705.12(D)(2).  The way I read it, you can either make sure the feeder is sized for both the primary OCP and the inverter -OR- you can verify that the OCP on the load side of the tap doesn’t exceed the feeder ampacity.  This would mean that the interconnection can basically be sized to the feeder ampacity.

Other than that, I don’t see any other issues other than making sure you treat each interconnection as a separate “system”, which would include disconnect, labeling and directory requirements.

Isaac Opalinsky | Technical Trainer | SunPower Corporation
Desk 443-569-3476 | Cell 443-277-6286

On Wed, Oct 22, 2014 at 9:15 AM, Allen Frishman <amfrish at aeonsolar.com<mailto:amfrish at aeonsolar.com>> wrote:
Wrenchers,
I am working on a multi building complex that is part of a isolated grid (multiple buildings are fed from one central building).    All of the power from the utility enters one central building via a 4000AS/4000AF Service Switch.   The 4000A Service switch feeds a 3 section cabinet with (5) fused switches per section.    The fused switches in each of these sections then feed a different building in the complex.    My plan is to install a solar array with inverters on each of these buildings and grid connect to the conductors at the individual building entrances.   The majority if not all of the solar power will feed directly into the building that the array is located on however since the point of solar grid connection is to the conductors feeding the building that originate in the central buildings switch gear I am trying to get my head around the need to comply with the opposite side of the bus rule in the 3 sections located in the central building.

I am hoping I am missing a rule in the NEC that will allow the multiple grid connections described to connect to all of the fused switch positions in the central buildings switch gear.

All feedback is appreciated.

Al Frishman
AeonSolar
(917) 699-6641<tel:%28917%29%20699-6641> - cell
(888) 460-2867<tel:%28888%29%20460-2867>
www.aeonsolar.com<http://www.aeonsolar.com/>



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