Re: [RE-wrenches] A related question - Individual AC conductors through separate conduits

Wed, 20 Nov 2013 11:12:36 -0800

Title: National Electrical Code 2008 Edition
Glenn,
Thank you for responding. Here's my exploration of 300.3(B):
(This is from a draft pdf version of the 2011 Code on my laptop.)

300.3(B) Conductors of the Same Circuit. All conductors of
the same circuit and, where used, the grounded conductor
and all equipment grounding conductors and bonding conductors
shall be contained within the same raceway, auxiliary
gutter, cable tray, cablebus assembly, trench, cable, or
cord, unless otherwise permitted in accordance with
300.3(B)(1) through (B)(4).

300.3(B)(1) refers to Paralleled Installations, so not relevant

300.3(B)(2) Grounding and Bonding Conductors. Equipment
grounding conductors shall be permitted to be installed outside
a raceway or cable assembly where in accordance with
the provisions of 250.130(C) for certain existing installations
or in accordance with 250.134(B), Exception No. 2,
for dc circuits. Equipment bonding conductors shall be permitted
to be installed on the outside of raceways in accordance
with 250.102(E).

250.130(C) refers to extending branch circuits, so not relevant.
250.134(B) refers to dc circuits, so not relevant.
250.102(E) refers to bonding jumpers, so not relevant.

So this section is not relevant.

300.3(B)(3) Nonferrous Wiring Methods. Conductors in wiring
methods with a nonmetallic or other nonmagnetic sheath,
where run in different raceways, auxiliary gutters, cable
trays, trenches, cables, or cords, shall comply with the provisions
of 300.20(B). Conductors in single-conductor Type
MI cable with a nonmagnetic sheath shall comply with the
provisions of 332.31. Conductors of single-conductor Type
MC cable with a nonmagnetic sheath shall comply with the
provisions of 330.31, 330.116, and 300.20(B).

300.20(B) Individual Conductors. Where a single conductor
carrying alternating current passes through metal with magnetic
properties, the inductive effect shall be minimized by
(1) cutting slots in the metal between the individual holes
through which the individual conductors pass or (2) passing
all the conductors in the circuit through an insulating wall
sufficiently large for all of the conductors of the circuit.

Cutting slots in the metal of a raintight enclosure for a single conductor? And there's only one "individual conductor". I don't think so.

It appears that technically, there's no way to do this - that adding the conductor in 2007 was erroneously passed, and it is certainly not a safety hazard. But as the original home was wired with buried Triplex from the meter to the home, the only way to meet the gnat's ass of Code compliance would have been to open up the trench and add a buried USE or UF cable.

I guess I could say that it's in the same trench, as it goes from the same point to the same point, via a parallel path.

Any other take on this issue? (Yeah, get an engineer's stamp, ignore it in hopes it will go away/be grandfathered in, bring extra doughnuts...)
Allan

Allan Sindelar
[email protected]
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, Positive Energy, Inc.

A Certified B CorporationTM
3209 Richards Lane
Santa Fe, New Mexico 87507
505 424-1112 office 780-2738 cell
www.positiveenergysolar.com

 

On 11/20/2013 11:31 AM, Glenn Burt wrote:

Allan,

You might also interpret 300.3(B) as requiring all conductors of the same circuit to be located in the same conduit.

 

(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).

 

-Glenn

 

From: [email protected] [mailto:[email protected]] On Behalf Of Allan Sindelar
Sent: Wednesday, November 20, 2013 1:05 PM
To: August Goers; RE-wrenches
Subject: Re: [RE-wrenches] A related question - Individual AC conductors through separate conduits

 

August,
Yes, that's relevant to my question. All metal boxes are grounded at both ends by existing EGCs. Only the PVC conduit is not. So when I read section 250.110 as you have cited, "all equipment fastened in place with exposed non-current carrying metal parts likely to become energized needs equipment grounding" is covered correctly.

This is not a huge deal - it's not difficult to pull the #4 out and add an EGC. I'm just trying to find the appropriate Code reference for an oddball situation. Thank you.
Allan

Allan Sindelar
[email protected]
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, Positive Energy, Inc.

A Certified B CorporationTM
3209 Richards Lane
Santa Fe, New Mexico 87507
505 424-1112 office 780-2738 cell
www.positiveenergysolar.com

On 11/20/2013 10:44 AM, August Goers wrote:

Hi Allan,

 

Per NEC 250.110 all equipment fastened in place with exposed non-current carrying metal parts likely to become energized needs equipment grounding. There are some conditions and exceptions listed in the code so you might want to check through that section and apply it to your situation. If you had used metallic conduit such as EMT then the raceway itself would count for equipment ground. However, since it sounds like you have non-metallic conduit you do indeed need a equipment ground wire sized per table 250.122. My general rule of thumb is that all metal boxes and raceways need equipment ground, period. We run equipment ground conductors even in EMT because there is a chance that fittings will loosen over time.

 

Anyway, that’s my take.

 

Best,

 

August

 

From: [email protected] [mailto:[email protected]] On Behalf Of Allan Sindelar
Sent: Tuesday, November 19, 2013 3:34 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] A related question - Individual AC conductors through separate conduits

 

Wrenches,
I need similar advice, please, especially a Code section citation.

In 2005 we installed an Outback system for a new home in town that was designed and installed to be a grid-backup solar home. It was, in essence, a stand-alone system to run most of the home with the utility serving the backup generator's role, both to provide backup charging when needed and to run a few specific loads. The home was built with two breaker panels side by side, with the PV system wired between them. The meter pedestal was 150' away at the edge of the street. The array was small at 1.32 kW.

Around 2007 the interconnection terms were quite good and we converted this system into a grid-intertied system. Doing this involved replacing the early Outback FX2024 with a GVFX3524. We also had to run an additional #4 conductor from the system (inverter AC interactive output) to the meter pedestal in order to carry interactive sell-back energy to a REC meter, which had to be located next to the revenue meter. We ran this single conductor in 1" PVC conduit with no other conductor. Given that all AC neutrals were properly bonded, that the conduit was non-conductive, and that all metal parts were properly bonded, we didn't run an EGC with this single THWN. We were permitted and and passed inspection.

Now we are adding an additional 1.3 kW of PV to the system, which requires full permit process, of course. And in the ensuing years the home has been annexed into the city, with its reputation for toughness in regards to Code compliance. Our design team tells me that we must pull that #4 out and repull it with an EGC, simply because every current-carrying conductor must have a grounding conductor as well.

My question: What Code section applies here? Is an EGC always required in conduit carrying a single current-carrying conductor?

We're trying to have our ducks in a row before contacting the inspector, and have never dealt with this particular situation before.
Thank you,
Allan

Allan Sindelar
[email protected]
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder, Positive Energy, Inc.

A Certified B CorporationTM
3209 Richards Lane
Santa Fe, New Mexico 87507
505 424-1112 office 780-2738 cell
www.positiveenergysolar.com

On 11/19/2013 11:22 AM, Dave Click wrote:

300.3(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4) [which don't help here].

On 2013/11/19, 12:38, August Goers wrote:

Hi All –

 

On a related note, I’ve become good friends with some of the inspectors in San Francisco and they called me yesterday with a question. Is it okay to run individual DC conductors through EMT for wire management purposes? We have always run paired positive and negative conductors in conduit so the question had never occurred to me. Obviously, you have to bond both ends of the conduit if it is over 250 v. I know that AC would have induction issues with running individual conductors but I’m not sure with DC.

 

Thanks,

 

August

 

 

August Goers

Principal

Luminalt Energy Corporation

o: 415.641.4000

m: 415.559.1525

www.luminalt.com

 

 

 

From: [email protected] [mailto:[email protected]] On Behalf Of William Miller
Sent: Monday, November 18, 2013 11:33 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] PV Wiring methods

 

Bill:

 

There is no need to stuff MC4 cables into standard conduit.  You can either slot the pipe using our easy method or install bulkhead type connectors.  The connectors are readily available.  I get them from PV Cables in Northern California..

 

Wire routing problems and some solutions can be found on our web-site:

 

http://millersolar.com/MillerSolar/practices/PV_wiring/_PV_Wiring2.html

 

Since the industry won’t provide wire management solutions, we are making our own.  Questions:  Just write or call.

 

William Miller

 

From: [email protected] [mailto:[email protected]] On Behalf Of frenergy
Sent: Thursday, November 14, 2013 7:46 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] PV Wiring methods

 

William, Bill....from another Bill,

 

        Two things:  For the rest of us (maybe it's just me?!) that's still trying to figure out how (or why) to stuff a MC4 connector into conduit and my hesitation in using SS wire ties for fear of the sharp edges cutting or chaffing into cables, I'm open for advice. Any wire I use on the roof is rated for that type of service and I have some off-grid systems that have been in the sun for some 25 years where the wire still looks nearly new even when flexing it to look for checking/cracks.  It seems the wire/insulation can take it, thus it seems like the key to "wire management is to keep the wire from moving and off the roof, secured to the racking, thus not compromising the insulation. 

 



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