Overwiring breakers

I have done only a few inspections but I have found two occasions where breakers had larger wires than what is acceptable. I have heard about this condition but I have not heard the risk or problems connected with overwiring - can someone explain??? The wires attatched to the 15 amp breakers are #10. Also these wires have no markings and I could not see the ends attatched to the breakers; how would I find out what type of wires these are? ( aluminum or copper)

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All 15A breakers I have seen will hold a #10 wire ok.
If no visible aluminum wiring is present then report that.
You might want to report that all branch wiring was not visible.

The issue with larger wires is that they are sometimes trimmed to fit the lugs and the remaining conductors might be scored which will cause them to break easy.

When conductors are installed in conduit they are required to be de rated depending on the number of current carrying conductors. When the number of CCCs exceeds 10, there is a 50% derating factor which results in the next size up being required. This requirement is for any raceway over 24" long and includes a conduit containing branch circuit conductors between the panel and the junction box where the Romex’s are spliced in, which is commonly done on service replacements.
Conductors are also upsized for voltage drop considerations and aluminum conductors.

If you don’t have any solid Aluminum neutrals or grounds, it’s a fairly safe assumption you don’t have any hots either. You are required (by most standards) to report the presence of solid Al. I wouldn’t bother reporting anything as absent, even if you were sure (unless, of course it a required component). Hell, you could write a very thick report on what’s **not **there.

By the looks of the equipment ground conductors, this is a copper wire installation. It also can be assumed from the bare equipment grounds that the wiring method is NM cable, that is why there are no markings on the individual conductors.

How did you know this is a 10 AWG conductor?
Some of the older cables had a different insulation on them which is heavier (thicker) than todays insulation.

Most circuit breakers that are 15 or 20 amperes can take up to 2 size larger AWG type conductors. It should be on one of the very small labels affixed to the circuit breaker.

I only know the size is comparable to a #10 wire, I don’t know if they are aluminum or copper since there are no markings on the wire. The incoming service lines are aluminum. This is a panel in a condo. Thanks for the replies.