Can you use flexible cables (flexible cords) to connect solar panels?

[alej27]

Hello everyone.

I'd like to know if it's allowed by the 2023 NEC to use flexible cables/cords to connect a solar array to a disconnecting means (switch/fused switch/circuit breaker). There are some considerations I have in mind:

• Since the cable will be used outdoors, I know it must be listed for wet locations in table 400.4, like SEW or SEOW or SEOOW (hard service cord), or SJEW or SJEOW or SJEOOW or SJOW or SJOOW or SJTW or SJTOW or SJTOOW (junior hard service cord), or SOW or SOOW (hard service cord), or STW or STOW or STOOW (hard service cord).
• Also, the application of the flexible cable must be listed in sec. 400.10(A) (uses permitted). In this case, I think the application falls under 400.10(A)(6): "Connection of utilization equipment to facilitate frequent interchange."

If flexible cable is not allowed by the NEC, or it is but shouldn't be used (not recommended):

• Is it okay to run simply wires for wet locations? Like THHW, THW, THW-2, THWN, THWN-2, etc.
• The wires should not only be approved for wet locations, but they should also by weather-resistant, like resistant against radiation (sun UV light), extreme temperatures (from ambient temperature and direct sunlight), rain, humidity, insect bites, etc.
• Sec. 310.10(D)(1) requires wires and cables installed outdoors exposed to sunlight to be listed as sunlight-resistant. How do I know which of the wet-approved wires (THHW, THW, THW-2, THWN, THWN-2, etc.) are resistant to sunlight? It's not specified in table 310.4(A) (for wires) nor 400.10(A) (for flexible cables).
• Also, must these outside wires be installed inside raceways? Like EMT, IMC or RMC. I haven't seen in section in article 300 that requires wires (indoors or outdoors) to be installed inside raceways. Perhaps sec. 300.4 applies since people can step on the wires or animals can bite the wires: "Where subject to physical damage, conductors, raceways, and cables shall be protected."

 

[don_resqcapt19]

My reading of 690.31(C)(4) is that flexible cables can only be used where connected to moving parts of tracking PV arrays.

 

[jaggedben]

For single conductors on arrays outside of raceways, the code only allows listed PV wire or USE-2. See 690.31(C)(1).

 

[Todd0x1]

Article 400 cords will experience insulation degradation over time. Even though marked sunlight resistant it doesn't last as long as the jacket on the proper solar wires and cables.

 

[Zee]

insulation on THHW, THW, THW-2, THWN, THWN-2, etc. will crack and disintegrate within years on a roof. I have seen it.