This is one of the FAQs from our Electrical Safety Panel Discussion with John Kolak MS CSP, Charles Miller NEC Expert, & Bhanu Srilla CESP CMRP.
Charles Miller: Let's say we've got up to 120 volts. We have several things to discuss: What is the shock hazard? What is the arc flash hazard? The limited approach boundary is three and a half feet. The restricted approach boundary is avoiding contact, don't touch it. So, there's no distance away from it like it would be for a 208-volt.
We don't get 120 volts by measuring phase to phase. We get 120 volts by measuring phase to ground. But there is a footnote that references us to that row. Once we go over, if we're going to be 208 up to 750 volts, the limited approach boundary is still three and a half feet. However, the restricted approach boundary is one foot. We also have in the arc flash table, that talks about that if it's only 120 volts, then you're going to have to do a risk assessment to make sure there are no other underlying problems. Otherwise, there is a section at the top of the arc flash table for tasks about the third one down or so that lets us know, if it's only 120 volts then there is no arc flash hazard. You don't have to wear arc-rated PPE.
View the complete electrical safety panel discussion below: