A client is installing a new solar photovoltaic (PV) system with a maximum system voltage of 600V. The PV output circuit conductors are rated for 75°C. What is the minimum temperature rating required for the terminals of the overcurrent protective devices (OCPDs) and disconnects used in this PV system, according to NEC?
- A90°C
- B60°C
- C105°C
- D75°C
Show answer & explanationAnswer & explanation
Correct answer: A. 90°C
NEC 690.43 (PV Disconnecting Means) and 690.9 (Overcurrent Protection) refer to the general rules in 110.14(C)(1) and 110.14(C)(2) for conductor termination temperature limitations. Specifically for PV, NEC 690.31(C) states that PV source and output circuits shall be considered outside of the scope of 110.14(C)(1) and (C)(2) and shall be permitted to use the 90°C conductor ampacity, but the terminations must be rated for at least 75°C, or 90°C if the equipment is specifically listed for it. However, the question asks for the *minimum* temperature rating of the terminals themselves. NEC 690.31(C) specifically states that conductors shall be sized using the 90°C column, and then implies that the terminations need to handle that, which typically means 90°C rated terminals for PV circuits unless otherwise specified. A more direct answer comes from the understanding that PV system conductors are often sized using the 90°C column, which implies that the associated equipment terminals should be rated for 90°C, especially with the high temperatures experienced in PV installations. While 75°C terminals are common, PV specific rules often push for 90°C where possible due to operating conditions. The most conservative and often required rating for PV terminals is 90°C to match the conductor's effective temperature rating.
Why the other options are wrong
- B. 60°C terminals are generally not acceptable for PV circuits due to higher operating temperatures.
- C. 105°C is higher than typically required and would be for very specific applications.
- D. While 75°C is a common terminal rating, PV specific requirements often mandate or imply 90°C for robust operation, especially when conductors are sized from the 90°C column.
PV Terminal Temperature Rating
Terminals for overcurrent protective devices and disconnects in PV systems often require a minimum temperature rating of 90°C to accommodate conductor ampacities derived from the 90°C column and withstand typical PV operating temperatures.
- Applies to PV source and output circuits.
- Related to conductor ampacity calculations (90°C column).
- Addresses elevated temperatures in PV installations.
Memory trick: PV terminals: 'Ninety' degrees, for the sun's hot embrace.