I'm trying to replace a regular 20A circuit breaker with an AFCI circuit breaker. I understand an AFCI circuit breaker requires both hot and neutral wires. I assume I need to connect the hot and neutral wires from the same single Romex cable, correct? (i.e., I can't just pick any random neutral that's in the panel).

The problem is, my panel is really filled up and I cannot visually trace the hot wire to identify its corresponding neutral wire. I see like ten neutral wires. Is there an easy way to find which one of those coresponds to the hot wire that I want to put on AFCI? Thank you.

  • 4
    You may have to cut the main breaker and push wires around a bit to follow it. But yes, you will need that neutral. It's very important hot and neutral wires be matched and not crossed . Commented Feb 6, 2022 at 4:24
  • 1
    If you have Romex it should be a cakewalk. If you've got conduit it's a different trick altogether but with cable they're together right in the box. Wear gloves, but don't be shy about moving conductors around with one hand to follow where they go.
    – J...
    Commented Feb 6, 2022 at 13:23

1 Answer 1


the same single Romex cable

That is the key. If you were in conduit, this would actually be more complicated. But with Romex (or any NM cable):

  • Trace the hot wire from the existing breaker to where it enters the panel.
  • At that point, you should find a small bit of the cable sheath surrounding hot (black), neutral (white) and ground.
  • Trace that neutral wire to the neutral bar and remove it for attachment to the new breaker.

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