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

[James Rudolph]

Straight from Mike Holt:

*Neutral Conductor*

The neutral conductor of a 3-wire single-phase 120/240V system, or 4-wire
3-phase 120/208V or 277/408V wye-connected system isn’t considered a
current-carrying conductor.

The neutral conductor of a 3-wire circuit from a 4-wire 3-phase 120/208V or
277V/480V wye-connected system is considered a current-carrying conductor.

When a 3-wire circuit is supplied from a 4-wire 3-[phase wye-connected
system, the neutral conductor carries approximately the same current as the
ungrounded conductors.

The neutral conductor of a 4-wire 3-phase circuit is considered a
current-carrying conductor where the major portion of the neutral load
consists of nonlinear loads. This is because harmonic currents will be
present in the neutral conductor, even if the loads on each of the 3 phases
are balanced.

Nonlinear loads supplied by 4-wire 3-phase 120/208V or 277/480V
wye-connected systems can produce unwanted and potentially hazardous
triplen harmonic currents (3rd, 9th, 15th, etc.) that can add on the
neutral conductor. To prevent fire or equipment damage from excessive
harmonic neutral current, the designer should consider increasing the size
of the neutral conductor or installing a separate neutral for each phase.
 see 210.4(A) FPN, 220.61 FPN 2, and 450.3 FPN 2.

Grounding (earthing) and bonding conductors aren’t considered current
carrying.

For individual dwelling units or one-family, two-family, and multifamily
dwellings, Table 310.15(B)(6) can be used to size 3-wire single-phase
120/240V service or feeder conductors (including neutral conductors) that
serve as the main power feeder. Feeder conductors are not required to have
an ampacity rating greater than the service conductors [215.2(A)(3)].

Warning: Table 310.15(B)(6) doesn’t apply to 3-wire single-phase 120/208V
systems, because the grounded neutral conductor in these systems carries
neutral current even when the load on the phases is balanced
[310.15(B)(4)(6)]. For more information on this topic, see 220.61(C)(1).

*Grounded Neutral Conductor Sizing.* Table 310.15(B)(6) can be used to size
the grounded neutral conductor of a 3-wire single-phase 120/240V service or
feeder that serves as the main power feeder, based on the feeder calculated
load in accordance with 220.61.

Because the grounded neutral service conductor is required to serve as the
effective ground-fault current path, it must be sized so that it can safely
carry the maximum fault current likely to be imposed on it [110.10 and
250.4(A)(5)]. This is accomplished by sizing the grounded neutral conductor
in accordance with Table 250.66, based on the total area of the largest
ungrounded conductor [250.24(C)(1)].

aloha and happy trails...

On Thu, Apr 21, 2016 at 10:28 AM, Peter Parrish <
peter.parr...@calsolareng.com> wrote:

> 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
>
> peter...@pobox.com
>
>
>
> *From:* RE-wrenches [mailto:re-wrenches-boun...@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
>
>
>
>
>
> [image: Gradient Cap_mini]
> Lic 773985
> millersolar.com 
> 805-438-5600
>
>
>
> *From:* RE-wrenches [mailto:re-wrenches-boun...@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

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

[Ray Walters]

However, in this case, Peter's installing lots of 120 vac branch 
circuits, so all of those neutrals will be carrying full current (unless 
they are shared neutral circuits).  Mike Holt's exception would apply to 
240vac circuits if they had a neutral.  Further, Holt's exception would 
not be applicable on any off grid system that was 120 vac only.


R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 4/24/2016 12:58 AM, James Rudolph wrote:

Straight from Mike Holt:

*Neutral Conductor*

The neutral conductor of a 3-wire single-phase 120/240V system, or 
4-wire 3-phase 120/208V or 277/408V wye-connected system isn’t 
considered a current-carrying conductor.


The neutral conductor of a 3-wire circuit from a 4-wire 3-phase 
120/208V or 277V/480V wye-connected system is considered a 
current-carrying conductor.


When a 3-wire circuit is supplied from a 4-wire 3-[phase wye-connected 
system, the neutral conductor carries approximately the same current 
as the ungrounded conductors.


The neutral conductor of a 4-wire 3-phase circuit is considered a 
current-carrying conductor where the major portion of the neutral load 
consists of nonlinear loads. This is because harmonic currents will be 
present in the neutral conductor, even if the loads on each of the 3 
phases are balanced.


Nonlinear loads supplied by 4-wire 3-phase 120/208V or 277/480V 
wye-connected systems can produce unwanted and potentially hazardous 
triplen harmonic currents (3rd, 9th, 15th, etc.) that can add on the 
neutral conductor. To prevent fire or equipment damage from excessive 
harmonic neutral current, the designer should consider increasing the 
size of the neutral conductor or installing a separate neutral for 
each phase.  see 210.4(A) FPN, 220.61 FPN 2, and 450.3 FPN 2.


Grounding (earthing) and bonding conductors aren’t considered current 
carrying.


For individual dwelling units or one-family, two-family, and 
multifamily dwellings, Table 310.15(B)(6) can be used to size 3-wire 
single-phase 120/240V service or feeder conductors (including neutral 
conductors) that serve as the main power feeder. Feeder conductors are 
not required to have an ampacity rating greater than the service 
conductors [215.2(A)(3)].


Warning: Table 310.15(B)(6) doesn’t apply to 3-wire single-phase 
120/208V systems, because the grounded neutral conductor in these 
systems carries neutral current even when the load on the phases is 
balanced [310.15(B)(4)(6)]. For more information on this topic, see 
220.61(C)(1).


/Grounded Neutral Conductor Sizing./ Table 310.15(B)(6) can be used to 
size the grounded neutral conductor of a 3-wire single-phase 120/240V 
service or feeder that serves as the main power feeder, based on the 
feeder calculated load in accordance with 220.61.


Because the grounded neutral service conductor is required to serve as 
the effective ground-fault current path, it must be sized so that it 
can safely carry the maximum fault current likely to be imposed on it 
[110.10 and 250.4(A)(5)]. This is accomplished by sizing the grounded 
neutral conductor in accordance with Table 250.66, based on the total 
area of the largest ungrounded conductor [250.24(C)(1)].


aloha and happy trails...


On Thu, Apr 21, 2016 at 10:28 AM, Peter Parrish 
mailto:peter.parr...@calsolareng.com>> 
wrote:


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 

peter...@pobox.com 

*From:*RE-wrenches
[mailto:re-wrenches-boun...@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%