Chris --- Good question! As our inspector explained, there are two reasons for the second pipe. One is immediate safety --- too many big wires together in the same pipe may overheat. The other is long-term safety --- with input and output wires coming out of same pipe, you can't tell if the box is properly wired. If improperly wired, turning off the main shutoff switch would still leave juice flowing throughout the box --- bad news!
As an Amazon Associate, I earn a few pennies every time you buy
something using one of my affiliate links. Don't worry, though --- I
only recommend products I thoroughly stand behind!
Also, this site has Google ads on it. Third party vendors, including
Google, use cookies to serve ads based on a user's prior visits to a
website. Google's use of advertising cookies enables it and its
partners to serve ads to users based on their visit to various sites.
You can opt out of personalized advertising by visiting this site.