rpoet
Member
All,
I was recently told by a colleague who works for a UL508A panel shop that DIN rail can't be considered bonded to the ground plane because the screws are "mounting screws" and not "bonding screws." His interpretation is that one must have at least (2) screws for physical mounting, and (1) screw, marked green, for bonding. The Bonding screw can be right next to the "mounting screw, but can't be used for mounting (WHAT???).
He also stated that the grounding-style terminal blocks that clamp to the DIN rail and form an electrical connection are not considered a bonding means, and that a jumper needs to be run from the block to a ground screw on the back plane.
Further, even when using star or split lock washers under the manufacturer-supplied nuts, the subpanel mounting studs can't be considered a bonding means because they're a "mechanical mounting means."
This all seams a bit ridiculous. Why would the electrons care? Is this a misinterpretation, or has UL really gone off the deep end? Admittedly, I don't have a copy of UL508A in front of me right now, but when reading over it previously, I remember nothing like this anywhere.
Thanks,
-rpoet
I was recently told by a colleague who works for a UL508A panel shop that DIN rail can't be considered bonded to the ground plane because the screws are "mounting screws" and not "bonding screws." His interpretation is that one must have at least (2) screws for physical mounting, and (1) screw, marked green, for bonding. The Bonding screw can be right next to the "mounting screw, but can't be used for mounting (WHAT???).
He also stated that the grounding-style terminal blocks that clamp to the DIN rail and form an electrical connection are not considered a bonding means, and that a jumper needs to be run from the block to a ground screw on the back plane.
Further, even when using star or split lock washers under the manufacturer-supplied nuts, the subpanel mounting studs can't be considered a bonding means because they're a "mechanical mounting means."
This all seams a bit ridiculous. Why would the electrons care? Is this a misinterpretation, or has UL really gone off the deep end? Admittedly, I don't have a copy of UL508A in front of me right now, but when reading over it previously, I remember nothing like this anywhere.
Thanks,
-rpoet