Amend NEC^® 2017, page 126:

(B) Load-Side Equipment. Except as permitted in 250.30(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 or on the load side of a separately derived system disconnecting means or the overcurrent devices for a separately derived system not having a main disconnecting means.

Exception No. 1: The frames of ranges, wall-mounted ovens, counter-mounted cooking units, and clothes dryers under the conditions permitted for existing installations by 250.140 shall be permitted to be connected to the grounded circuit conductor.

Exception No. 2: It shall be permissible to ground meter enclosures by connection to the grounded circuit conductor on the load side of the service disconnect where all of the following conditions apply:

(1) No service ground-fault protection is installed.

(2) All meter enclosures are located immediately adjacent to the service disconnecting means.

(3) The size of the grounded circuit conductor is not smaller than the size specified in Table 250.122 for equipment grounding conductors.

Exception No. 3: Direct-current systems shall be permitted to be grounded on the load side of the disconnecting means or overcurrent device in accordance with 250.164.

Exception No. 4: Electrode-type boilers operating at over 1000 volts shall be grounded as required in 490.72(E)(1) and 490.74.

Exception No. 5: It shall be permissible to ground an existing panelboard enclosure by connection to the grounded circuit conductor for a one- and two-family dwelling where all the following conditions apply:

(1) When relocating or installing an additional main disconnecting means;

(2) Enacting 250.142(B) Exception No. 5: (1) redefines the existing service entrance conductors as a feeder as set forth in Article 100;

(3) An equipment grounding conductor in the existing panelboard is not present;

(4) Replacement of the existing service entrance conductors either requires the removal of the building finish or is deemed impractical by the authority having jurisdiction.

(5) All grounding electrode conductors are removed completely from the existing panelboard; and

(6) The grounded conductors are insulated by tape, heat-shrink, or other approved means except where covered by the sheathing of a cable assembly or as needed for joints, splices, and termination purposes.

ELR commentary: In North Carolina, a new exception 5 was added. The intent of the North Carolina amendment in this section is to make special provisions for an existing service panel that is being turned into a sub panel because of a service change or upgrade to replace the electric meter with a meter/main breaker type.

Sometimes, a permit is issued to replace an existing meter enclosure with a new meter/main breaker combination type. There can be a conflict when requiring the walls and ceiling to be torn up to replace the existing 3-wire cable from the meter to the existing interior panel with a 4-wire cable containing an equipment grounding conductor to comply with NEC^® 250.142(B).

In these cases, the North Carolina amendment would make specific allowances to use the existing grounded circuit conductor in the existing 3-wire cable to ground the non–current-carrying metal parts of the existing panelboard on the load side of the new service disconnecting means which is now located at the new meter enclosure.

This amendment, along with the North Carolina amendments to NEC^® 250.140, 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.