Overcurrent Protection & Conductor Sizing
Fuses, combiner boxes, OCPD sizing, PV Wire, conductor ampacity, DC disconnect, and inverter input limits.
- Explain PV source circuit fusing and OCPD sizing
- Describe combiner box function and parallel string protection
- Select appropriate PV Wire and conductor sizes
- Identify DC disconnect and inverter input limit requirements
- Explain NEC Article 706 for energy storage paired with PV
Leçon 1
PV Source Circuit Fusing & OCPD Sizing
Why Fuse PV Source Circuits?
Fuses are used on PV source circuits to protect conductors from overcurrent when multiple strings are connected in parallel. A fault on one string can draw reverse current from the other parallel strings, potentially exceeding the conductor ampacity and causing fire.
A combiner OCPD value is based on the PV module's maximum series fuse rating (listed on the module datasheet) and must be sized to protect the source circuit conductors.
Fuse Sizing
The minimum fuse size is 1.56 x ISC of the string. The fuse must also not exceed the module's maximum series fuse rating. The conductor ampacity must be equal to or greater than the fuse rating.
Fuses protect PV source circuits from reverse current when strings are paralleled. Size fuses at 1.56 x ISC minimum, not exceeding the module's maximum series fuse rating. Conductor ampacity must meet or exceed the fuse rating.