Labeling Requirements: Page 2 of 4

Intermediate
Labeled Combiner Box
In addition to the Code-required warning labels at this SMA combiner box, engraved black placards identify these system components.

GFDI Labeling

Most grid-connected PV systems are required to have ground-fault protection per Section 690.5. One of the section’s requirements is to install, in a visible location near the ground-fault indicator, a label stating:

WARNING:
ELECTRIC SHOCK HAZARD.
IF A GROUND FAULT IS INDICATED,
NORMALLY GROUNDED CONDUCTORS
MAY BE UNGROUNDED AND ENERGIZED.

If a battery bank is part of the system, this label must be installed in a visible location at the battery bank. This label indicates to service personnel that voltage potential between conductors and grounded surfaces may differ from normal conditions after a ground fault has occurred.

Single 120 VAC Supply

In stand-alone systems, a 120 VAC inverter commonly provides power to service equipment that is designed for connection to 120/240 VAC, split-phase utility power. Section 690.10(C) allows this, which is accomplished by using a suitable jumper to connect both bus bars in the service equipment to the same single 120 VAC phase from the inverter. To reduce wire expense, multiwire branch circuits—where a single neutral conductor is used with two “hot” conductors on separate phases—are commonly installed in new construction. The neutral conductor never carries the sum of the current from the two circuits since they are out of phase with each other. However, if the two hot conductors are on the same phase—for example, being supplied by a 120 VAC inverter—then the currents will be additive on the neutral conductor, possibly overloading it. Because of this, the following label must be applied to the AC service equipment:

WARNING:
SINGLE 120-VOLT SUPPLY. DO NOT CONNECT
MULTIWIRE BRANCH CIRCUITS.

Disconnecting Means

Section 690.14 contains two provisions for marking disconnecting means. Section 690.14(C)(2) states that PV system disconnecting means must be permanently marked as such. Section 690.14(D), which allows utility-interactive inverters in locations that are not readily accessible, refers again to 705.10, and requires directories at the locations of all service disconnecting means, interconnected power production sources, and accompanying AC and DC disconnects. Similar requirements are found in IFC 605.11.1.1 and 605.11.1.4.

New to the 2011 NEC is the requirement that disconnecting means be within sight (visible at 50 feet or less) of all fuses that cannot be isolated from energized circuits. This applies to source-circuit fuses in combiner boxes as well as fusing in larger inverters with re- or subcombiners. When the disconnecting means are more than six feet from the associated fuses (even if they are still visible), a directory indicating the location of the disconnecting means must be installed at the fuse location.

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