Code Corner: Labeling Requirements: Page 4 of 4

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

Chapter VI. Marking

NEC Sections 690.51 and 52 apply to the rated and operating characteristics of PV modules and AC modules, and should be marked on the products by the manufacturer as part of the NRTL testing and listing requirements. Section 690.53 requires the DC PV power source disconnecting means be marked by the system installer with:

  1. The rated maximum power point current (module Imp × number of PV source circuits in parallel).
  2. The rated maximum power-point voltage (module Vmp × number of PV modules in a source circuit).
  3. The maximum system voltage, calculated per Section 690.7.
  4. The short-circuit current, with an informational note referring to Section 690.8(A) for calculating maximum circuit current (module Isc × 1.25 × number of PV source circuits in parallel). Note that this terminology is slightly confusing, but calculating the value as Isc × 1.25 ensures that, even during high irradiance, current will not exceed the value on this label.
  5. The maximum rated output current of the charge controller (if installed) per its specifications.

This label will be specific to the installation, as the values will vary based on the array configuration and size, the modules used, and the location (and corresponding low temperature value). Note that the Section 690.17 label is also required on this disconnect.

Section 690.54 requires that all points of interconnection between grid-connected systems and the utility be marked at the disconnecting means with:

  1. The rated AC output current (per the inverter specifications).
  2. The nominal AC operating voltage.

When energy storage is part of the PV system, Section 690.55 requires that the maximum voltage, the equalization voltage, and the polarity of the DC system grounded conductor (positive grounded, negative grounded, or ungrounded) be labeled, though the location of this label is not specified. Additionally, if it is a stand-alone system, then Section 690.56(A) requires a plaque or directory that states that the building has a stand-alone power system, and notes the location of its disconnecting means. This must be located on the building’s exterior, in a readily visible location that is acceptable to the AHJ and, possibly, to the fire marshal or fire chief.

Article 705

Dealing with all types of power production systems interconnected to the grid, Article 705 has additional labeling requirements, as well as restating some of the PV system-specific requirements of Article 690. As mentioned, Section 705.10 requires directories at each service equipment location, as well as at the locations of all interconnected power production sources.

For load-side interconnections as permitted in Section 705.12(D), the location of all breakers supplying power to a load center or panel board must be marked—this applies to the main service disconnecting means as well as all back-fed PV system (inverter output circuit) breakers. Additionally, when the 120% allowance—permitted in Section 705.12(D)(2)—is being utilized and the sum of the breakers supplying power to the bus bar exceed the bus bar rating, the back-fed PV breakers must be located opposite of the main service breaker, and be marked:



Brian Mehalic is a NABCEP-certified PV installer and ISPQ-certified PV instructor. He has experience designing, installing, servicing, and inspecting both PV and solar thermal systems. He is a curriculum developer and instructor for Solar Energy International and a project engineer with O2 Energies.

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