The primary distribution box has no ground wire
The most common and simplest solution for an ungrounded circuit is to install a Ground-Fault Circuit Interrupter (GFCI) device. Depending upon the tool cable length and the number of spindles and how they are connected, there are two different alternatives how to meet this requirement. A simple three-light receptacle tester is the quickest way to check a three-prong outlet, using a pattern of lights to indicate common wiring issues, including an open ground. If you've ever found yourself scratching your head over whether that metal door on your distribution cabinet really needs a grounding wire, you're not alone.
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