
Ryan, Bill, Wrenches,

Every couple of code cycles I spring for the hardbound code handbook. It's two
inches thick, costs $115, and has....PICTURES :-)  .....and lots of additional
text in an all too often vain attempt to try to explain the actual, official
text. You know you're in trouble when you need a book to explain a book about
electrical safety. It is not user friendly. Its dry as dirt. The index sucks.
Ask ten electricians or PV techs how they'll interpret the code, particularly as
regards grounding, and you're lucky to reach a concensus. Most of you who post
on this list have much more PV experience than I do. I have mostly lurked here,
for years. I try to read it twice a day. You're my most valuable resource. Thank
you all!

Article 100 defines Service, Service Cable, Service Drop, Service Entrance
Conductors, Service Equipment, Service Lateral and Service Point. 

The basic idea is, in general, a structure should be connected to the serving
utility at only one location, using one set of conductors, using a maximum of
six switches. The code is all about safety. In case of an emergency situation
you want to be able to disconnect the entire structure from the serving utility
as quickly and efficiently as possible. There needs to be a pretty good reason
for the utility to provide another, entirely separate SERVICE DROP to the
building, usually in a different location on the building, to provide for an
additional, separate SERVICE.

Ryan Wrote:
I'm not sure I see the reason a UI inverter can't be viewed as a parallel power
production system and be eligible for the allowance under 230.2(A)(6). The
definition of a utility 
interactive inverter is "an inverter intended for use in parallel with an
electric utility to supply common loads that may deliver power to the utility."
This is the exact reference I have 
used to connect a PV system on the supply side of a MDP that had 6 service
disconnects in it already.

Reply:
If you've connected the PV system to the supply side of the MDP, you're still
connected to the same utility SERVICE DROP the MDP is connected to. It's not a
separate SERVICE unless its supplied by an entirely different set of conductors
from the utility's system. Picture, for instance, two separate overhead cables
from the utility's pole mounted transformer connected to two distinct sets of
SERVICE EQUIPMENT (each with its own meter) on the building. 

It appears you've added a seventh switch to the building's single SERVICE. I
think most inspectors would consider this a violation. However, it would most
likely have been quite costly to reconfigure the existing SERVICE EQUIPMENT to
have six or less switches including the one for the PV. Six, seven, what's one
more? An inspector might let it fly. It's their call, but six has been in the
code a long time.

Ryan wrote:
705.12 actually uses the language "interconnected electric power source" not
"parallel power production system" (this is probably splitting hairs though). I
don't see how 705.12(B) and (C) preclude a PV system to be included in the
230.2(A)(6) allowance. Am I understanding you correctly?

Reply:
Busted! I agree about the hair splitting though, because I can't find "Parallel
power production system" anywhere in the code, other than 203.2(A)(5).

The six Special Conditions of 230.2(A) which do permit a separate SERVICE, seem
to address the issues of safety, law, and power reliability / redundancy. As
much as we all like PV, it's hard to see non-battery backed up PV included in
this list. It still gets cloudy. It still gets dark every night. If the grid
goes down, so does the PV. Article705.12(C) does allow a separate SERVICE for
PV,  ......as long as it's over 100kW or 1000 volts.

Ryan wrote:  
I am also confused by "The much more common situation permitted by 705.12(A) is
ONE service." Wouldn't the new PV connection constitute a new service
disconnect?

Reply:
The new PV connection definitely constitutes a new, additional switch
(disconnect) (#7) in the existing, single SERVICE. It, in no way, can be
considered a separate SERVICE, because it shares the existing utility SERVICE
DROP with the MDP, rather than being SERVED with it's own, separate utility
SERVICE DROP.

Hope this helps,
Dick


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