#2 copper main on 150amp breaker?

Am I missing something or is this as wrong as I think it is?

Sure sounds like the breaker is rated too high for the service conductor size.

According to NEC Table 310.15(B)(7) #1 AWG is the minimum size copper conductor permitted for a 150 amp OCPD.

Yep, it’s wrong. The breaker can be reduced to 125A or (as Robert posted) the SEC can be increased to #1AWG

Reduction of the Main Breaker may or not be acceptable…
(not sure of the total amperage draw from picture)
would need to see more of the Panel…

Is that an ungrounded conductor going into the ground bar?

Here’s the rest of it.

I would call it an improperly identified grounding or grounded conductor.

Attachment of an actual “ungrounded” (hot) conductor would trip the breaker or burn up the conductor in a hot-second - pun intended.

Without a load calculation, Joe may be correct, but it doesn’t appear there’s too much demand on that panel.

What year was that home built? Those AFCI breakers may be among those that have been recalled…

Duh I should have thought of that. I learned that a while back. A breaker kept tripping and I traced it back to a switch that had the ungrounded and grounding conductors touching. I don’t understand why though.

Why it was tripping, or why they were touching?

I didn’t at the time, nor do I now, understand the theory on why the breaker tripped when the grounding and ungrounded conductors were touching. I also don’t know why they were touching :stuck_out_tongue:

Since it terminates on the neutral bus that’s more than likely the GEC.

Contact between the ungrounded (hot) conductor and the grounding (egc) conductor creates a fault where there is no resistance in the “circuit.” Without the resistance of equipment, there is nothing to limit the current within the circuit other than (1) the size of the conductor or (2) the capacity of the breaker.

So since there is no resistance the current rises above the breaker rating?

Here is some information for those AFCI breakers that Jeff mentioned were recalled…

The recalled units were manufactured after March 1, 2004 and have a blue test button.

They have one of the following date codes: CN, DN, EN, FN, GN, HN or JN stamped in red on the breaker label located just above the wiring terminal (the breaker must be slightly or completely pulled to be able to see this code).

They have one of the following catalog numbers printed on a label on the front of the breaker:

  1. Square D QO (recalled unit)


  • QO115AFI
  • QO115AFIC
  • QO120AFI
  • QOB115AFI,
  • QOB120AFI
  • QO115VHAFI
  • QO120VHAFI


  1. Square D Homeline (recalled unit)


  • HOM115AFI
  • HOM115AFIC
  • HOM120AFI
  • HOM120AFIC




And (3), the transformer impedance. It is the transformer impedance that ultimately limits current and determines the class of equipment required. Residential systems are usually Class H. The fault current can be as high as 10,000 Amps. When you factor in line resistance and other variables, the actual amount of current that can flow is usually around 8,000 Amps.

You lost me at “and”

You asked “So since there is no resistance the current rises above the breaker rating?”

The current that can flow during fault can be 10,000 Amperes in a typical residential electrical system.