[RE-wrenches] Cable sizing for high current modules? NEC interpretation/guidance?

[Ray Walters]

12 Ga wire is not going to catch on fire, but the MC connectors might.  
I just went back on a 7 yr old Solarworld install, and had a bad series 
MC connector (module to module).  It got quite crispy, deforming and 
bubbling the plastic on both sides of the connection.  It was still 
passing current; I didn't get a chance to measure the volt drop.  It was 
completely plugged in, so not an installation issue.

This was not one of our connectors made up in the field, these were 
Solarworld factory connectors on both sides, same model modules.  That 
also means no mismatch of "MC4" connector type.

10+ amps continuous, moist environment, 30F+  hotter than ambient temp, 
all are tough on connectors.  I predict more connector failures as 
module current ratings increase.

Ray Walters
Remote Solar

On 11/9/2023 3:02 PM, Glenn Burt via RE-wrenches wrote:
>
> Good luck trying to convince your customer that their house caught on 
> fire because of a manufacturers flaw, and you have no responsibility 
> for it…
>
> It may be an out to shift the blame, but it only makes everybody get 
> some on them…
>
> *From:* RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> *On 
> Behalf Of *William Miller via RE-wrenches
> *Sent:* Wednesday, November 08, 2023 12:14 PM
> *To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
> *Cc:* William Miller <william at millersolar.com>
> *Subject:* Re: [RE-wrenches] Cable sizing for high current modules? 
> NEC interpretation/guidance?
>
> George:
>
> Appliance manufacturers have their own requirements that are not the 
> same as the NEC requirements.  As long as you are not modifying the 
> manufactured assembly you are not responsible for compliance of that 
> appliance.  By appliance, I mean the solar module, microinverter, etc.
>
> William Miller
>
> Miller Solar
>
> 17395 Oak Road, Atascadero, CA 93422
>
> 805-438-5600
>
> www.millersolar.com <http://www.millersolar.com/>
>
> CA Lic. 773985
>
> *From:*RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] 
> *On Behalf Of *George McClellan via RE-wrenches
> *Sent:* Wednesday, November 8, 2023 9:06 AM
> *To:* RE-wrenches
> *Cc:* George McClellan
> *Subject:* [RE-wrenches] Cable sizing for high current modules? NEC 
> interpretation/guidance?
>
> Team;
>
> With the move to larger cells, some modules have an Isc that is 
> pushing the limits of 12 AWG wire.  If I apply the rule of 156% (or 
> 125% solar derate*125% continuous load derate) to an 18 Amp Isc module 
> this will exceed the 25A that a 12 AWG wire can carry.  I understand 
> that the homeruns will need to be a larger AWG (10 ga), but do the 
> solar module cables (from junction box to MC4) also need to be 
> larger?  Any guidance or reference material would be greatly appreciated.
>
> Thx,
>
> George McClellan | Senior Technical Sales Manager | REC Americas LLC
>
> 330 James Way Ste 150| Pismo Beach, CA 93449| USA
>
> Cell phone +1 805 704 3226 | Fax +1 805 357 6104
>
> www.recgroup.com <http://www.recgroup.com/> | 
> george.mcclellan at recgroup.com <mailto:shannon.kent at recgroup.com>
>
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