10 NEC Codes Every Installer Should Know

As a solar installer, you should have a working knowledge of NEC 690. Here is a rundown of 10 NEC codes every installer should know (based on 2017 code edition).

WIRING

1. ‘Photovoltaic System Direct Current Circuits on or in a Building. Where PV system dc circuits run inside a building, they shall be contained in metal raceways, Type MC metal-clad cable that complies with 250.118(10), or metal enclosures from the point of penetration of the surface of the building to the first readily accessible disconnecting means.’
   – NEC 690.31(G)

Interpretation: Usually the first accessible disconnecting means for the DC conductors is at the inverter, therefore, on the DC side of the inverter only metal conduit can be used inside a building.

2. ‘Conductors in raceways shall be continuous between outlets, boxes, devices, and so fourth. There shall be no splice or tap within a raceway unless permitted by…’
   – NEC 300.13(A)

Interpretation: Spliced conductors shall not be contained within raceways. Splices should only occur at junction boxes.

EQUIPMENT

3. ‘If the PV system is connected to the supply side of the service disconnecting means as permitted in 230.82(6), the PV system disconnecting means shall be listed as suitable for use as service equipment.’
   – NEC 690.13(C)

Interpretation: The disconnect used for a line tap must be listed as service equipment. A breaker in an enphase combiner cannot be used as the disconnect because the combiner is not listed for use as service equipment.

4. ‘Supply Side Equipment. A grounded circuit conductor shall be permitted to ground non-current-carrying metal parts of equipment, raceways, and other enclosures at any of the following locations: (1) On the supply side or within the enclosure of the ac-service disconnecting means.’
   – NEC 250.142(A)

Interpretation: As required by most jurisdictions, neutral to ground bond is permitted to occur at the AC disconnect. No ground wire should be run from the disconnect to the interconnection point since the neutral is acting as the ground.

5. ‘Load-Side Equipment. Except as permitted in 230(A)(1) and 250.32(B) Exception, a grounded circuit conductor shall not be used for grounding non-current carrying metal parts of equipment on the load side of the service disconnecting means…’
   – NEC 250.142(B)

Interpretation: Any load side connection, including load side taps, the neutral and ground shall NOT be bonded at any point.

6. ‘Fastening. Listed plug-in-type circuit breakers backfed from electric power sources that are listed and identified as interactive shall be permitted to omit the additional fastener normal required by 408.36(D) for such applications.’
   – NEC 705.12(B)(5)

Interpretation: Systems without backup (non-standalone systems) do not need to have fastening clips installed at the breaker connection. “Interactive” means the inverter shuts off upon loss of grid.

GROUNDING

7. ‘For dc circuits, the equipment grounding conductor shall be permitted to be ran separately from the circuit conductors.’
   – NEC 230.134(B) Ex. 2

Interpretation: Only on the DC side is the ground permitted to be run separately from the conductors.

8. ‘Equipment Grounding Conductors Smaller Than 6 AWG. Where not routed with circuit conductors as permitted in 250.130(C) & 250.134(B) Exception No. 2, equipment grounding conductors smaller than 6 AWG shall be protected from physical damage by an identified raceway or cable armor unless installed within hollow spaces of framing members of buildings or structures and where not subject to physical damage.’
   – NEC 250.120(C)

Interpretation: When the ground is run separate it must be protected by an enclosure unless it is 6 AWG or larger.

9. ‘Size of Equipment Grounding Conductors. Equipment grounding conductors for PV source and PV output circuits shall be sized in accordance with 250.122. Where no overcurrent protective device is used in the circuit, an assumed overcurrent device rated in accordance with 690.9(B) shall be used when applying Table 250.122. Increases in equipment grounding conductor size to address voltage drop considerations shall not be required. An equipment grounding conductor shall not be smaller than 14 AWG.’
   – NEC 690.45

Interpretation: Ground wires are sized based on overcurrent protection such as a breaker. Since there is no overcurrent protection at certain points in a PV system the ground will be sized based on the current.

Typically when conductors are upsized, the ground must be upsized accordingly as well. This is not the case when the conductors are being upsized to limit voltage drop in PV systems.

10. ‘Buildings or Structures Supporting a PV Array. A building or structure supporting a PV array shall have a grounding electrode system installed in accordance with Part III of Article 250. PV array equipment grounding conductors shall be connected to the grounding electrode system of the building or structure supporting the PV array in accordance with Part VII of Article 250… For PV systems that are not solidly grounded, the equipment grounding conductor for the output of the PV system, connected to associated distribution equipment, shall be permitted to be the connection to ground for ground-fault protection and equipment grounding of the PV array’
    – NEC 690.47(A)

Interpretation: Any building or structure such as a carport or detached garage must have a grounding electrode system installed to which the PV ground is connected to.

Today’s PV systems are not solidly grounded therefore NO ADDITIONAL GROUND IS REQUIRED in addition the inverter output ground wire. That is to say, no additional ground from the array or DC side is required. Neither is an additional array electrode required.

LABELING

Bonus : ‘A permanent plaque or directory denoting the location of all electric power source disconnecting means on or in the premises shall be installed at each service equipment location and at the location(s) of the system disconnect(s) for all electric power production sources capable of being interconnected. The marking shall comply with 110.21(B).’
– NEC 690.56(B), NEC 705.10

Interpretation: In previous versions of code no directory was required when the PV disconnect was grouped with the utility disconnect. However, in the 2017 a directory is required no matter where the disconnect. See our labeling post for exact requirements.

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