Question, because it's really hard to actually read that document. Is the
arc-flash incident potential when hot swapping a
dimmer module similar to the
arc flash potential when unplugging a
stage pin under load? i.e., are these recommendations that
etc makes driven by the need for legal
safety? Or because of a likelyness of something happening.
The
arc flash potential when swapping a module might be much larger than when unplugging a
stage pin under load. Unfortunately,
ETC doesn't know what the incident energy available at the
phase bars in the rack might be as that is specific to each installation. When removing a module from a rack, you are exposing potential to both
electric shock and
arc flash and we would like everyone to know that doing any electrical work live is neither safe nor recommended unless you have been trained to do so.
Let's be
clear, because these questions have come up before. Sensor rack
dimmer and control modules are designed to be hot swapped. You can either swap the modules while wearing the appropriate
PPE and following your facility's
electrical safety practices as designated by
NFPA 70E, or you may simple choose to
Lock-Out/Tag-Out the rack.
Also, while no incidents of swapping modules have created an electrically unsafe situation for a
system owner, the likeliness of something happening cannot be predicted. Simply think about the possibility that someone has previously dropped a
dimmer module which cracked the casting and then placed it back into the rack. The next person comes along to remove the module and that casting piece breaks off the module into the
dimmer below or falls next to the
phase bar. That's all it would take to potentially be a problem.
I do have stories of other
electrical safety issues that have occurred over the years, but fortunately no one has been hurt. So to answer the last question....
ETC is spreading this information, and training all their internal and contract technicians, because of legal issues AND our desire to keep everyone educated and SAFE.
Dimmer racks are high
current power distribution devices. We need to respect them as such.
If there are additional questions about
electrical safety, since I spend a good amount of time on this area, I would be glad to provide answers.
David