"dpb" wrote in message ...
Ken wrote:
...

... Apparently there is some rule about replacing
main breakers in industrial and/or commercial buildings at 5 year
intervals.

I'd guess it's something different than just a 5-yr interval...


I have worked at a large industrial plant for 20 years and the plant was
built in 1965. As far as I know the original breakers are still in use
except for a few that have failed.
There are breakers from 120 volts at 15 amps to the very large 13.200 volt
main breakers. Nothing gets changed unless it fails or an inferred scan
indicates it may fail.