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

[Ray]

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