The primary purpose of this label is to alert individuals that a dangerous electrical shock hazard may exist even when a disconnecting means, like a switch or circuit breaker, is in the open position. Unlike traditional electrical systems where opening a disconnect typically de-energizes downstream components, solar PV systems can have energized terminals on both the line (utility) and load (inverter/PV array) sides due to the presence of a backfeed.
This warning is of paramount importance because it highlights a non-intuitive hazard. Someone working on a solar PV system might assume that opening the disconnect makes the system safe. However, backfeed from the PV array or other sources can still render terminals live, posing a severe risk of electrocution. This label serves as a critical reminder to treat all terminals as potentially energized and take appropriate safety precautions.
This specific label is necessary for all points of access to energized parts within PV systems, and where a disconnect might mislead individuals into believing the system is de-energized when it is not. If opening a disconnecting means does not de-energize all terminals downstream, this warning label is essential. The label is not required where all terminals are de-energized when the disconnecting means is in the open position. In those cases other labels will be needed.
The NEC mandates that this label be placed in a readily visible location, directly adjacent to the disconnecting means or any enclosure where live terminals may be present. This ensures that anyone approaching the equipment will immediately be aware of the potential hazard. The label should be permanent, resistant to the environment, and clearly legible, employing appropriate colors and symbols to convey the warning effectively.
