National Electrical Installation Standards

Standards as High as Your Own

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Wednesday, August 7, 2019

Question:

This question is about a single-family dwelling that has a 200-amp new panel with a 100 amp sub panel, the subpanel feeds all the branch circuits, and some of the branch circuits have an old two wire Romex 2 hots 1 bare ground for the oven and dryer and one hot one neutral for the other branch circuits, the city wants all the 220 volt Branch circuits to go all the way back to the main panel where it is bonded does this sound like a good correction?

Victor Gonzales
A

Answer:

Hey Victor thanks for your question. Maybe. The Word “Romex” is a registered trademark of Southwire Company. We have been asked to point that out, the correct term is Nonmetallic Sheathed Cable Type NM.

Using a grounded conductor for line to neutral loads while also using it as an effective ground fault current path is allowed for existing dryers and ranges as stated in 250.140 Exception. One of the exception conditions is that the conductor be insulated unless it is part of a Type SE cable and it terminates in service equipment.

The bare conductor in the NM cable is intended to be used as an equipment grounding conductor, not a grounded conductor. If that cable is replaced with a 3-wire cable (3 insulated conductors) plus a bare equipment grounding conductor, then it can be supplied from the 100 ampere panelboard or the 200 ampere service panelboard. The receptacles and appliance power supply cords will also need to be 4-wire and the bonding jumper between the grounded conductor (neutral) and equipment grounding conductors (frame) in the appliance needs to be removed.

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