From a safety standpoint, when using AC power in or near water or other potentially wet locations, it is essential (and in most cases, mandatory) to use a Class “A” UL approved GFCI (Ground Fault Circuit Interrupter) for actor and film crew protection.
The purpose of a GFCI is to interrupt current flow to a circuit or load when excessive fault current (or shock current) flows to ground or along any other unintentional current return path. The standard level of current needed to trip a “people” protection Class “A” GFCI is 5mA.
Class “A” GFCIs are designed for “people” protection. Other GFCIs are designed for various levels of “equipment” and “distribution” protection. In general, if you can’t readily see the Class “A” marking on a GFCI, the device is probably not designed for “people” protection. To make sure that the GFCI being used is a Class “A” device, Section 38 of UL 943 (the standard for GFCIs) requires that the “Class” of the GFCI is clearly marked on the device in letters that are clearly visible to the user.
Today, Class “A” GFCIs are readily available for loads up to 100-Amps, single and three-phase, for both 120v and 208/240v fixed voltage applications.
Certain special GFCIs can also operate on variable voltage power supplies (behind dimmers). If the device’s label does not clearly state the working voltage range of the unit, check with the device’s manufacturer before using the unit on dimmers (or other variable voltage applications), since conventional GFCIs may not operate correctly below their rated voltage.
Specialty GFCI manufacturers produce advanced GFCI devices that offer other important safety features, such as monitoring predictive maintenance, power supply phase and ground correctness. Choose your GFCIs carefully, because if misapplied, these important safety devices may unknowingly fail to function and render your installation with a false sense of security.