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Fusing & Wire Sizing guidelines for solar panels

Fusing & Wire Sizing guidelines for solar panels 2022-04-10

This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what size the OCPDs need to be.

There is also guidelines for wire sizing for the solar array but the paper does not cover temperature adjustments for the wire size.

Click on the orange
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button at the top of the screen to get the paper.

As with all of the resources I develop, comments, corrections and reviews are welcome.

Note, this resource is a duplicate of the resource with the same name found in the Beginners' Resources section. The download is the same.

Updates:
10/13/21: Added page discussing using a circuit breaker as a PV Array Output Circuit Disconnect.
10/22/21: Fixed reference to Appendix B.
01/22/22: Added calculations for voltage drop on home run.
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FilterGuy
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Great info, diagrams and explanation.

However, even though a PV array of 2 strings doesn’t require OCPD per physics, per NEC it does. Refer to sec. 690.9(A)(1) item (2) of the 2020 NEC, and also https://explorist.life/how-to-fuse-a-solar-panel-array-and-why-you-may-not-need-to/.

Basically, if the sum of the short-circuit currents of each PV string in a PV array isn’t greater than the max OCPD rating of the panel (along with another condition), then no OCPD is required. Or equivalently, if the sum of the short-circuit currents of each PV string in a PV array is greater than the max OCPD rating of the panel, then an OCPD is required
Explanation of DC circuit breaker polarity and its proper use in 3 (or more) parallel strings of solar panel wiring found on page 12, Fuses vs. Breakers Directional or Polarized DC Breakers, is very precise. It was not immediately recognizable by me without the explanation.
High level data with code references.
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