[RE-wrenches] Does a Neutral Count as a CCC

[William Miller]

Peter:



I think it is a mistake to not locate a sub-panel in the house.  Running
branch circuits 45 feet to a separate building is not efficient or
practical.



Voltage drop:  1% VD is a choice, not a requirement.  Code requires 3% on
feeders and 5% cumulative on AC branch circuits.   I like to use 1% for
average voltage drop for PV because of the cost of wasted PV energy.  I am
more lax on AC circuits.  If I calculate a PV feeder for 1%, that drop will
occur only occasionally, when peak solar is achieved.  Analyze your load or
charging profiles and look for a calc that provides the chosen VD for
average use.  Analyzing PV energy curves over a given day, approximately
50% of the energy is under the bell curve.



Neutrals are current carrying.  Try powering a 120VAC load without one and
you will see what I mean.



William Miller





[image: Gradient Cap_mini]
Lic 773985
millersolar.com <http://www.millersolar.com/>
805-438-5600



*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On
Behalf Of *Peter Parrish
*Sent:* Thursday, April 21, 2016 8:57 AM
*To:* 'RE-wrenches'
*Subject:* [RE-wrenches] Does a Netral COunt as a CCC



I am working with a customer who is doing a complete remodel and addition
to his house: stripped to the open studs and floor joists, and rafters. Not
a wire in the house. We have designed a 14.4 kWp PV system with 16 kW of
storage for backup and load shifting. The main panel, inverters, critical
load subpanel and batteries are all going to be in the garage which is
about 45 feet from the house. The customer and I have identified the
critical loads.



The GC is running conduit from the main house to the garage. I have been
given seven (7) 1-1/2” PVC conduits, and I am currently doing conduit fill,
ampacity and voltage drop calculations for the branch circuits that
represent the critical loads.



So I have two questions:



(1)    Should I stick to a <1% voltage drop on all circuits?

(2)    Do 120 V neutrals count as current carrying conductors? I think they
do, but the electrician stated quite emphatically that  they didn’t. I
thought that the derating calcs for CCCs were based solely on ohmic losses
and phasing was not taken into account.



Does the NEC provide guidance on this latter situation?



-          Peter Parrish



Peter T. Parrish, Ph.D.

President, SolarGnosis

1107 Fair Oaks Ave.

Suite 351

South Pasadena, CA 91030

(323) 839-6108

petertor at pobox.com
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