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

Bill Battagin frenergy at psln.com
Thu Nov 9 22:24:01 PST 2023 

Ray,

             Exactly the same thing happened for me on a ground mount 
system, 3500 feet elevation the the Sierras so open cooler air, fully 
engaged MC4 factory connectors PV to PV connectors with SW285's, not 
passing current, melted.  No attempt to contact SW just made up new 
connectors.

             My calculation is with anything that is no doubt made up by 
the bazillion with a machine (connectors, light bulbs, pencils, chicken 
nuggets, etc) you're going to get some duds.  In 20+ years of installing 
PVs with factory made-up connectors, I've only seen this happen 2-3 
times.  Installing in the mountains we no doubt use ground mount much 
more often than most installs in urban areas which would make a hot, 
melted connector possibly more of an issue a couple inches above a comp 
or wood roof.  We've never seen any connectors fail beyond the 
melted/deformed but still "contained" stage .

             Back when SW was first transitioning from one connector to 
another, I remember them saying they (I think it was UTX and MC or was 
it UTX and Amphenol?) were compatible.  We NEVER mixed connectors 
despite their claim.

Bill

Feather River Solar Electric
4291 Nelson St. (Shipping)
5575 Genesee Rd. (USPS, UPS)
Taylorsville, CA  95983
530-284-7849, 258-1641(cell)
CA. C10 Lic # 874049
Solar Powered since 1982
Home of the Sunny Side Up

On 11/9/2023 4:31 PM, Ray Walters via RE-wrenches wrote:
>
> I'm trying to find a pic to post, but they were MC4 connectors, not 
> the UTX.
>
> Ray
>
> On 11/9/2023 4:57 PM, Brian Mehalic wrote:
>> Are they the Amohenol UTX connectors? SW had a recall on them, sounds 
>> like about the right timeframe.
>>
>> BREAKING: SolarWorld recalls PV modules with Amphenol connectors 
>> <https://pv-magazine-usa.com/2017/03/29/solarworld-recalls-amphenol-connectors-sold-with-pv-modules/>
>> pv-magazine-usa.com 
>> <https://pv-magazine-usa.com/2017/03/29/solarworld-recalls-amphenol-connectors-sold-with-pv-modules/>
>>
>> <https://pv-magazine-usa.com/2017/03/29/solarworld-recalls-amphenol-connectors-sold-with-pv-modules/>
>>
>>
>> Brian
>>
>>> On Nov 9, 2023, at 4:47 PM, Ray Walters via RE-wrenches 
>>> <re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>> 
>>>
>>> 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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