Incorrect wire size for a 100 amp circuit breaker

Observed what appeared to be a #8 copper wire (red, black and white) installed on a 100 amp circuit breaker in the main Square D electric service panel and connected to a 100 amp circuit breaker in a General Electric sub panel. I think the wire should be at least 2-gauge. Trying to verify before I write it up. Any help is appreciated.05b905dd-bad1-4a79-a5b5-65f74dc16f8a-thumbnail-large d16fc6c1-459e-411e-8236-6828a9e1f34d electric pics

Am I seeing only 3 wires to the sub?
Is that a green bonding screw?

Are you sure it’s #8, it doesn’t look it from here.

Look like it could be #3 AWG which is good for 100 amps. They have removed the jumper between the two neutral bars and made the one on the left the EGC bar by installing the green screw. Only thing missing is the EGC with the feeder which could be the metal raceway if one was used for the feeder.

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Just a quick question…
What gauge wire should a 150 amp panel require. ??? SE conductors I mean. ???


Thanks Roy

that’s only if you are feeding the main panel -100% of the load.

Yes main panel. I am getting my conductors and breakers together in an effort to have all the components ready to upgrade my service panel. Also I like to question the experts at H Depot and cross reference this information. Thank all for the info.

Also copper SEC are always favored over aluminum correct???

Not necessarily. Correct size is.


Copper doesn’t ‘move’ as much alum. Expand and contract.

So 1 AWG copper SEC is required for a 150 panel. Correct ??? And that amperage would support a 1500 sf home with an electrical charging station in garage for an electric vehicle correct???

Is copper more expensive than aluminum.

The NEC no longer uses a table to determine the SEC size for a dwelling, now they specify that the SEC’s must have a minimum ampacity of 83% of the service OCPD size.

You would need a load calculation to accurately determine the service size. Car chargers come in various sizes. With a 100 amp charger in an all electric home 150 amps might not be large enough.

Copper is much more expensive.


I don’t want sub-standard wire in my new panel. I want the best preforming components in the panel. Also, when I leave this home, the next guy won’t have to worry about the power supply.

Wow, now I’m confused

It’s very simple… do load calculation and use copper if you’ve got $$$ don’t cheap out on service size. Upgrading 2s is more expensive.

This is an old example. Maybe some else has a newer one.

ResidentialLoadCalculations2.xls (1.2 MB)

What are you charging? a Tesla or something?
Jut go with/upgrade to 200 amp on 2/0 cu.