Despite the use of the term national it is not a federal law.
National electrical code branch circuits.
According to nec article 100 a multiwire branch circuit consists of two or more ungrounded conductors that have a voltage between them and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is.
The national electrical code nec or nfpa 70 is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the united states it is part of the national fire code series published by the national fire protection association nfpa a private trade association.
Most local codes are based on the national electrical code nec a document that lays out required practices for all aspects of residential and commercial electrical.
These general guidelines will give you the basics of what electrical inspectors are looking for when they review both remodeling projects and new installations.
National electrical code introduction 5 electrical connections 110 14 d terminal connection torque 6 ground fault circuit interrupter protection for personnel 210 8 preface 7 210 8 for personnel 8 210 8 a dwelling units 9 11 210 8 b other than dwelling units 12 18 210 8 d specific appliances 19.