Billfred cited the rule correctly. However, I would still heed Al's suggestions above. He has many a grey hair and he earned them all the old-fashioned way.
The UL Safety Advisors are, well, UL people. Their professional responsibility is looking out for safety hazards, and they
literally set the standards for that. I would expect them to look for UL labels on any electrical device that is connected to the AC power system, and for any such device to be properly connected to an earth terminal (aka "ground") when it is in use.
__________________
Richard Wallace
Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003
I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)