[RE-wrenches] NM Cable temp rating, ampacity, application

[August Goers]

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-bounces at lists.re-wrenches.org] *On
Behalf Of *eric at harvesthesun.com
*Sent:* Tuesday, April 04, 2017 2:50 PM
*To:* RE-wrenches <re-wrenches at 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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