Per Section 690.16(B), disconnecting means that are not load-break-rated, such as module quick connects (leads) and touch-safe fuse holders in combiner boxes, must be marked “Do not open under load.” Typically, these components will already be marked by the manufacturer. However, this label warning is a reminder to those working on the system that the absence of current must be verified, to avoid a potentially dangerous arc.
Section 690.17 requires the following label be applied to any disconnecting means where both the line and load side terminals may be energized when the switch is off.
ELECTRIC SHOCK HAZARD.
DO NOT TOUCH TERMINALS.
TERMINALS ON BOTH THE LINE
AND LOAD SIDES MAY BE ENERGIZED
IN THE OPEN POSITION.
In particular, this applies to the DC side of PV systems. When the DC disconnect is off, the line-side terminals can still be energized by the PV array, and the load-side terminals can still be energized by the inverter’s capacitors. (This is also the reason why manufacturers typically require a five-minute waiting period after all power sources have been shut off before removing the inverter cover.) For the majority of disconnect switches, which are similar to the disconnect on the AC side of a grid-connected system, this is not a normal condition. Rather, when the AC disconnect is off, it is still energized on the line side via the utility, but the load side of the switch is not energized since the inverter is required to shut down after a loss of grid power.
New to the 2011 NEC are marking/labeling requirements in 690.31(E) for any exposed raceways or cable trays, pull box covers and junction boxes, and conduit bodies (with unused openings) inside a building that contain “Photovoltaic Power Source” conductors. They must be labeled as such, using a “permanently affixed label or other approved permanent marking.” This Section further states that the labels must be visible after installation; spaced not more than every 10 feet; suitable for the environment; and, when there is a separation, such as a conduit running through a wall, must appear on both sides of the wall. The 2012 IFC Sections 605.11.1.1, .2, and .4 extend these requirements, with similar language and intentions, to the outside of the building. They add the requirement that the labels be reflective, with a white-on-red background; the letters be all capitals, with a minimum height of 3/8 inch; and that the labels be placed within 1 foot of all turns or bends.
Ungrounded PV arrays are becoming more common for a variety of reasons, including their enhanced ground-fault protection. Because neither the positive or negative conductors are connected to ground, the only potential should be between positive and negative, not between either current-carrying conductor and ground. The following label is required at “each junction box, combiner box, disconnect, and device where energized, ungrounded conductors may be exposed during service.”
ELECTRIC SHOCK HAZARD.
THE DC CONDUCTORS OF THIS
PHOTOVOLTAIC SYSTEM ARE UNGROUNDED
AND MAY BE ENERGIZED.