Undersized breaker?

The wire looked like 1/0 or less. On a 30 Amp breaker. Only one wire seemed to be hot. Is this breaker undersized?

611 Maple Wellsville 056-400.jpg

Not if it represents 125% of the continuous load current/ampere capacity on that branch.

The wire is capable of safely carrying a much higher amperage, but the breaker will limit the load to 30 amps. There should be no danger, provided the breaker is not malfunctioning, sticking.
If only one leg is hot, there is a problem, and if the work appears to be unprofessional in nature, call for an electrician. Looks like a re-cycled wire feed out to the shop.

John Kogel

1/0 is rated for much more than 30 amps. 30 amps usually is supplied by #10 wire, many sizes smaller than 1/0.

What does this circuit feed? Without knowing what it feeds no one can tell if it is undersized.

Hard to tell from here but that sure looks like #2 or even #6 SEU. Maybe for a cooktop or wall oven, after a remodel did away with the freestanding range?

How did you determine only one leg appears hot? A non contact voltage tester is not adequate to give a conclusive test result.

The only question I would have is “what is the max wire size the breaker lug is rated for”? There is no problem using wire larger than the O/C device.
My guess is this wire had the virtue of incumbancy when they connected a 30a load (water heater, dryer?) and they used it instead of ripping it out and running a new wire.

It is generally very difficult to determine the maximum wire size for which the breaker is rated without removing the breaker or looking the information up in the manufacturer’s data. A tell-tale sign that the wire is too big would be if the inspector can see that some of the strands have been removed from the conductor to allow it to fit the lug. In that case I would call it out for further inspection by a qualified electrician; otherwise, I probably would not for wire size alone as the breaker gives it adequate protection. A hot lug on on or both of the lugs would be a definite call-out.

The lugs on that breaker will not accept 1/0 conductors, it looks like 6 AWG which would be at the upper end of the range of wire sizes a 30 A type CH circuit breaker of that era will acccept. The panel FYI is of a late 1950’s to early 1960’s vintage & the breaker is prob 1970’s …

(off topic):mrgreen: The 1 way screw on the bar in the center was a feature of the early vintage Cutler-Hammer loadcenters which could lock C/Bs into the panel, early Zinsco panels also had a means to lock the breakers into the interior.