Article 710 Stand-Alone Systems.

Stand-alone systems are electric power production sources operating in stand-alone mode.
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Stand-alone systems are electric power production sources operating in stand-alone mode.

Code Change Summary: A new article was added to address Stand Alone Systems.

Stand Alone Systems are electric power production sources operating in stand-alone mode. Examples include some generators and PV systems. A Stand Alone system has no interconnection to the electric utility.

In the 2014 NEC®, Stand Alone Systems were covered in Articles 690, 692 and 694 which address PV, fuel and wind systems. In the 2017 NEC®, all of the requirements were removed and relocated into one new article to address all Stand Alone Systems.

The new article includes provisions for the following:

710.6 Equipment Approval.

710.15 General.

(A) Supply Output.

(B) Sizing and Protection.

(C) Single 120-Volt Supply.

(D) Energy Storage or Backup Power System Requirements.

(E) Back-Fed Circuit Breakers.

(F) Voltage and Frequency Control.

Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC® edition of NFPA 70.

2017 Code Language:

710.1 Scope. This article covers electric power production sources operating in stand-alone mode.

710.6 Equipment Approval. All equipment shall be listed or field labeled for the intended use.

710.15(B) Sizing and Protection. The circuit conductors between a stand-alone source and a building or structure disconnecting means shall be sized based on the sum of the output ratings of the stand-alone sources.

710.15(C) Single 120-Volt Supply. Stand-alone systems shall be permitted to supply 120 volts to single-phase, 3-wire, 120/240-volt service equipment or distribution panels where there are no 240-volt outlets and where there are no multiwire branch circuits. In all installations, the sum of the ratings of the power sources shall be less than the rating of the neutral bus in the service equipment. This equipment shall be marked with the following words or equivalent:

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

The warning sign(s) or label(s) shall comply with 110.21(B).

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Article 710 Stand-Alone Systems.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is required for a single, 120-volt supply in a Stand Alone System?

A: The sum of the ratings of the power sources shall be equal to the rating of the neutral bus in the service equipment.
B: Stand-alone systems shall be permitted to supply 240-volt single-phase service equipment.
C: Multiwire branch circuits are NOT permitted.
D: Multiwire branch circuits are permitted.
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