August;
Thanks for pointing out some of those code references, I'm always
learning new things. In case Eric's situation is not subject to
physical damage (as covered in 230.50) I found that 230.43 lists many
more allowable options for service entrance wiring, but NM still is not
on the list. I think the confusion may be with the definition of
"Feeder". Eric wrote that they tapped into the "feeder" between the
Meter and the Main disconnect. I may be mistaken, but technically that
is not a feeder; it would be considered a service conductor. Service
conductors are from the utility to the main disconnect (service
equipment), while feeders are all the conductors after the Service
equipment. I think the Old school guy might have won that one.
R. Ray Walters
Chief Technical Officer, RemoteSolar.com
BS Mech Engineering, 1988
Former NABCEP Certified, 2004-2016
Licensed Master Electrician, Colorado
303 505-8760
On 4/4/17 5:17 PM, August Goers wrote:
Hi Eric,
Regarding the supply side connection, check out this article:
http://iaeimagazine.org/magazine/2013/11/16/supply-side-pv-connections-a-closer-look/
Check out 2014 NEC 230.50 – I don’t think NM is allowed. In our neck
of the woods we need to use RMC or IMC.
Secondly, I’d recommend referring to the NM cable’s spec sheet to
determine ampacity. Also see NEC 334.80 which limits the ampacity to
60 deg C.
50 A x 1.25 = 62.5, so your NM has to be rated at this or higher.
http://www.southwire.com/products/RomexSIMpullTypeNMBOEM.htm - regular
NM 60 deg rated #6 55 A
I’m not familiar with 90 degree NM.
August
Luminalt
*From:*RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>] *On Behalf Of
*e...@harvesthesun.com <mailto:e...@harvesthesun.com>
*Sent:* Tuesday, April 04, 2017 2:50 PM
*To:* RE-wrenches <re-wrenches@lists.re-wrenches.org
<mailto:re-wrenches@lists.re-wrenches.org>>
*Subject:* [RE-wrenches] NM Cable temp rating, ampacity, application
Hi Wrenchers,
I recently butted heads with an old school electrician who has been
scrutinizing a recent install (fully permitted & PTO'd last year) and
I wonder how applicable and valid his concerns are. I'm not interested
in an ego war with this guy; I just want to be code-compliant and
safe. This sparky (let's call him Karl) has questioned my
electrician's (let's call him Dave) use of NM cable on the AC side of
the solar install.
The first issue that Karl raised was that Dave installed Romex for our
supply-side connection, i.e., from our fused disconnect to the Polaris
vampire clamps on the feeder conductors between the meter and the main
disco. Karl contends that the Romex, by extension off of the utility
feeders, is now a service entrance conductor and that NEC Article
334.12 dictates that Romex cannot be used as service entrance
conductors. Wondering how you all might interpret this scenario.
(note: We have the opportunity to pull new conductors, should the
consensus be that we violated the NEC)
The second issue is that Dave ran 6AWG Romex from the fused disconnect
to the main breaker in the combining subpanel and landed the circuit
on a 70A breaker. The inverter circuit is rated at max current of 50A
continuous. Karl is telling us that the #6 Romex is rated at 60
degrees and 55 amps. It is my understanding that all NM cable is now
rated at 90 degrees. However, I also understand that there may be some
merit to Karl's assessment regarding limited ampacity of the 6AWG
Romex. Can someone illuminate this issue for me as to whether or not
NM cable is rated at 90 degrees AND therefore a 6AWG conductor in NM
cable would have a 75A rating?
Cheers,
Eric
SunHarvest
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