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

[Peter Parrish]

William,

 

I agree about the subpanel in the house situation. The customer is a bit eccentric, and I have tried to bring him around. And I have explained to him that his approach will be more expensive. He doesn’t care. In the end, there is no safety risk. So I’ll plan for 4 branch circuits per conduit and take the 0.70 derating.

 

- Peter  

 

Peter T. Parrish, Ph.D.

President, SolarGnosis

1107 Fair Oaks Ave.

Suite 351

South Pasadena, CA 91030

(323) 839-6108

petertor at pobox.com

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of William Miller
Sent: Thursday, April 21, 2016 10:25 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Does a Neutral Count as a CCC

 

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

 

 

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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