Amend NEC^® 2017, page 126:

250.140 Frames of Ranges and Clothes Dryers. Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be connected to the equipment grounding conductor in the manner specified by 250.134 or 250.138.

Exception No. 1: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor if all the following conditions are met.

(1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.

(2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.

(3) Any of the following:

1. The grounded conductor is insulated;
2. The grounded conductor is uninsulated and part or a Type SE service-entrance cable and the branch circuit originates at the service;
3. The grounded conductor is uninsulated and part of a cable assembly and all current-carrying conductors are protected by a ground-fault circuit interrupter at the origination of the branch circuit; or
4. A new 3-wire cable assembly not smaller than the existing conductors shall be permitted to be extended from the service to an enclosure where the existing conductors shall be spliced together and provisions are made so that the grounded conductors are insulated by tape, heat-shrink or other approved means inside the enclosure.

(4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.

Exception No. 2: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, an equipment grounding conductor sized in accordance with 250.122 shall be permitted to be run separately from the circuit conductors.

ELR commentary: The intent of the North Carolina amendment in this section is to make special provisions for an existing range or clothes dryer that is fed from an existing service panel that is being turned into a sub panel because of a service change or upgrade.

In this example, it is assumed that the existing range or clothes dryer was originally supplied directly from the service panel through a 3-wire branch circuit cable, having only two phase conductors and a grounded conductor. This example is code compliant with NEC^® 250.140 regardless of the NC amendment to this rule. However, if the existing meter box is changed to a new meter/main breaker combination type, the new meter/main breaker enclosure now becomes the service. In this case, if the existing 3-wire cable between the old meter box and the panel is allowed to remain then it would force the existing range or dryer circuit out of code compliance since the original text in NEC^® 250.140 requires  the existing range or dryer circuit to originate directly from the service which is now the new meter/main breaker enclosure.

Sometimes, an existing meter enclosure is replaced with a meter/main breaker combination, without replacing the existing 3-wire cable from the meter to the interior service panel, which in turn makes the main service panel a subpanel. In these cases, the North Carolina amendment would make specific allowances for the existing range or clothes dryer circuit. These provisions, along with the North Carolina amendments to NEC^® 250.142(B), and 300.3(B) could possibly allow the existing service panel to become a subpanel as long as the grounding requirements in article 250 are followed and the existing service panel was suitable for use as service equipment. If the service panel is “suitable only for use as service equipment” then it cannot be used as a subpanel without modification of the panel which would violate the product listing of the panelboard.