Journeyman Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsHard
A commercial building utilizes a solar photovoltaic (PV) system with a maximum system voltage of 600V. The PV array is installed on the roof and the DC conductors run in metal conduit through an attic space to an inverter located on the ground floor. What is the minimum required temperature rating for these DC conductors, assuming they are within the scope of NEC Article 690?
- A105°C (221°F)
- B75°C (167°F)
- C60°C (140°F)
- D90°C (194°F)
Show answer & explanationAnswer & explanation
Correct answer: D. 90°C (194°F)
NEC Section 690.31(C) requires that PV source circuit and PV output circuit conductors shall be 90°C (194°F) wet-rated. This higher temperature rating accounts for potential high temperatures in attic spaces and exposure to elements.
Why the other options are wrong
- A. While acceptable, this is higher than the minimum 90°C required by the NEC.
- B. While common for general wiring, 75°C is not the minimum required for PV source and output circuits.
- C. This temperature rating is too low for PV conductors, especially when routed through attic spaces.
PV Conductor Temperature Rating
The minimum temperature rating required for DC PV source circuit and PV output circuit conductors, typically 90°C wet-rated, to withstand high temperatures and environmental conditions.
- Applies to PV source and output circuit conductors (NEC 690).
- Accounts for high ambient temperatures (e.g., attics, rooftops).
- Minimum 90°C wet-rated conductors are generally required.
Memory trick: Ninety degrees is the hot rule, for PV wires, don't be a fool.