#2 copper main on 150amp breaker?

rwashington · July 31, 2012, 12:40am

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

jgromkoski · July 31, 2012, 1:10am

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

rmeier2 · July 31, 2012, 1:24am

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

jpope · July 31, 2012, 1:51am

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

jhagarty · July 31, 2012, 2:38am

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…

jjimenez · July 31, 2012, 2:46am

Is that an ungrounded conductor going into the ground bar?

rwashington · July 31, 2012, 2:49am

Here’s the rest of it.

jpope · July 31, 2012, 2:50am

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.

jpope · July 31, 2012, 2:52am

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…

jjimenez · July 31, 2012, 2:54am

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.

jpope · July 31, 2012, 3:00am

Why it was tripping, or why they were touching?

jjimenez · July 31, 2012, 3:03am

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

rmeier2 · July 31, 2012, 8:44am

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

jpope · July 31, 2012, 12:55pm

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.

jjimenez · July 31, 2012, 1:11pm

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

hcarvajal · July 31, 2012, 1:35pm

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:

Square D QO (recalled unit)

[LIST]
[LIST]
[LIST]
[LIST]

QO115AFI
QO115AFIC
QO120AFI
QOB115AFI,
QOB120AFI
QO115VHAFI
QO120VHAFI
QOB115VHAFI
QOB120VHAFI

[/LIST]
[/LIST]
[/LIST]
[/LIST]

Square D Homeline (recalled unit)

[LIST]
[LIST]
[LIST]
[LIST]

HOM115AFI
HOM115AFIC
HOM120AFI
HOM120AFIC

[/LIST]
[/LIST]
[/LIST]
[/LIST]

Bert

jpope · July 31, 2012, 1:47pm

Correct.

gwells · July 31, 2012, 6:33pm

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.

jjimenez · July 31, 2012, 6:43pm

You lost me at “and”

gwells · July 31, 2012, 8:04pm

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.