(2) Flexible Wiring Methods. FMC smaller than trade size ¾ or Type MC cable smaller than 1 in. in diameter installed across ceilings or floor joists must be protected by substantial guard strips that are at least as high as the wiring method.

Where run exposed, other than within 6 ft of their connection to equipment, wiring methods must closely follow the building surface or be protected from physical damage by an approved means.

(3) Marking or Labeling Required. Wiring methods and enclosures containing PV source conductors must be marked with the wording “Photovoltaic Power Source” by labels or other approved permanent marking means suitable for the environment and placed with a maximum of 10 ft of spacing.

System grounding
To limit the voltage induced by lightning, one conductor of a 2-wire PV system operating at over 50V must be solidly grounded (connected to the earth) per 250.4(A)(1). [690.41]. The grounding connection can be at any single point on the grounded conductor of the PV direct-current output circuit [690.42].

PV systems with ground-fault protection that incorporates the system grounding connection must not have an additional grounding connection [690.42 Ex].

Equipment grounding (bonding)
Connect all exposed metal parts of PV module frames, electrical equipment, raceways, and enclosures to an equipment grounding conductor (EGC) of a type permitted in 250.118 [250.134 and 690.43(A)]. You must install an EGC between the PV array and associated equipment [690.43(B)].

Devices listed and identified for grounding the metallic frames of PV modules and associated equipment can be used to bond the exposed metal surfaces of modules and equipment to the metal racks [690.43(C)].

Metallic mounting racks used as an EGC must be identified as an EGC, or have identified bonding jumpers/devices connected between the separate metallic racks and be connected to an EGC as required by 690.43(A).

Devices and systems used for securing PV modules to metal mounting racks that serve as an EGC must be identified for such purposes [690.43(D)].

Devices identified and listed for bonding the metallic frames of PV modules can be used to bond the metallic frames of PV modules to the metallic frames of adjacent PV modules [690.43(E)].

All conductors of a circuit, including the EGC, must be installed in the same raceway or cable, or otherwise run with the PV array circuit conductors when they leave the vicinity of the PV array [690.43(F)].

For PV circuits having overcurrent protection, size the EGC to the rating of the PV circuit overcurrent device (OCPD) per Table 250.122 [690.45(A)].

Where no overcurrent protection is provided for the PV direct-current circuit, as permitted in 690.9 Ex, size the EGC to the PV circuit short-circuit current rating per Table 250.122 [690.45(A)].

Grounding electrode system
If installing a dc system, provide a grounding electrode system per 250.166 with a grounding electrode conductor per 250.64. A common dc grounding-electrode conductor can serve multiple inverters with the common grounding electrode and the tap conductors sized per 250.166. A splice or joint is not allowed in the common grounding electrode conductor [250.47(B)].

PV systems with direct-current modules having no direct connection between the direct-current grounded conductor and alternating-current grounded conductor must be bonded to the alternating-current grounding system by one of the methods listed in 690.47(C)(1), (2), or (3). This set of requirements is new, with the 2011 NEC:

(1) A separate direct-current grounding electrode bonded to the alternating-current grounding electrode system with a bonding jumper sized to the larger of the existing alternating-current grounding electrode conductor or direct-current grounding electrode conductor specified by 250.166.

 (2) A direct-current grounding electrode conductor sized to 250.166 run from the marked direct-current grounding electrode connection point to the alternating-current grounding electrode.
Where an alternating-current grounding electrode isn’t accessible, the direct-current grounding electrode conductor is permitted to terminate to the alternating-current grounding electrode conductor by irreversible compression-type connectors listed as grounding and bonding equipment or by the exothermic welding process [250.64(C)(1)].

 (3) An unspliced, or irreversibly spliced, combined equipment grounding/grounding electrode conductor run from the marked direct-current grounding electrode connection point along with the alternating-current circuit conductors to the grounding busbar in the associated alternating-current equipment.

Install bonding jumpers around equipment, so you maintain the bonding continuity if the equipment is removed [690.48 and 690.49]. This applies to exposed conducting surfaces of PV equipment and to the PV system grounded conductor.

Power source label
Apply a permanent label at the PV direct-current disconnect indicating [690.53]:

(1) Rated maximum power-point current (Imp)

(2) Rated maximum power-point voltage (Vmp)

(3) Maximum system voltage (Voc)

(4) Short-Circuit Current (Isc)

(5) Maximum rated output current of the charge controller (if installed)

For interactive systems, the point of interconnection of the PV system power source to other sources must be marked at an accessible location at the disconnect as a power source and with the rated alternating-current output current and nominal operating alternating-current voltage [690.54].

Any building or structure with a stand-alone PV system not connected to a utility service source must have a permanent plaque on the exterior of the building or structure, at a readily visible location. It must indicate the location of the stand-alone PV system disconnect and that the structure contains a stand-alone electrical power system [690.56(A)].

Any structure containing both utility service and a PV system must have a permanent plaque identifying the location of the service disconnect and PV system alternating-current disconnect (if they’re not at the same location) [690.56(B)].

Connection to other sources
For interactive systems, use only inverters and alternating-current PV modules listed as interactive [690.60].

An inverter or an alternating-current module in an interactive PV system must automatically de-energize its output to the electrical distribution system upon loss of voltage. It must remain de-energized until the electrical distribution system voltage has been restored [690.61].

Storage batteries
Install storage batteries per Article 480 [690.71(A)]. Additionally:

• For dwellings, the cells must be series connected (to operate at less than 50V, nominal) [690.71(B)].
• Live parts of storage battery systems for dwellings shall be guarded to prevent accidental contact by persons or objects regardless of voltage.
• Install listed current-limiting overcurrent devices where the available short-circuit current from the battery bank exceeds the interrupting or withstand ratings of equipment it supplies.
• Where used for battery interconnections, flexible cables identified for hard-service use and moisture resistant as identified in Article 400, must be a minimum size of 2/0 AWG. You can use flexible cables only between the battery terminals to a nearby junction box (where they must connect to an approved wiring method) or between batteries and cells within the battery enclosure [690.74].
• Where used for battery interconnections, flexible, fine-stranded cables must terminate in terminals, lugs, devices, or connectors that are identified and listed for fine-stranded conductors [110.14(A) and 690.74].

Article 705 of the NEC covers interconnected electric power production sources. There are requirements in Article 705 that apply to solar photovoltaic systems.

The production of power from solar resources is not a new concept, but it is an area of ever-changing technology and strong growth. The NEC requirements for this article have also changed and the solar installer must keep current with the Code requirements.