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Supported on Messenger vs Free Air
- Thread starter Zyb
- Start date
Deltaforce
Senior Member
- Location
- India
- Occupation
- Electrical Engineer
Free air table not good choice if pv wires bundled not spaced, confinement and high temperatures
solarken
NABCEP PVIP
- Location
- Hudson, OH, USA
- Occupation
- Solar Design and Installation Professional
I would not use either. Is this rooftop or ground mount? Are there places where the PV wire is bundled together under the array? In general, I use 10AWG PV wire for all jumpers within the array and for string home runs. Usually the ampacity is way higher than the max string current, but if I had to I would consult 310.16. And it works well when transitioning to THHN in EMT where you may need to derate for more than 3 CCC's. If you are talking about a large commercial or utility ground mount system with combined strings, that's a different story and I think the tables you mentioned would be appropriate depending on the details of how the cables are supported and routed in the home runs.Which is appropriate table to use for PV Wire under the module, 2017 Table 310.15(B)(20) Supported on a Messenger OR 2017 Table 310.15(B)(17) Free Air?
Under module wiring that is bundled and attached to the racking or module frame should be sized the same as conductor in conduit. It's not in messenger (wire) supported hangers. Even if it's a single conductor, being strapped to something like a rack and close to a heat source like a module would negate the open air requirements to use the free air table.
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