LHall wrote:
I have seen this interpretation too often.
No calculation required = no arc flash hazard exists. Completely wrong!
Close. There are dozens of PI's for 2015 addressing this.
No calculation=default hazard.
Defaults hazard does not mean default risk.
Calculated hazard does not mean unacceptable risk (without PPE) either.
An example where there is no appreciable shock hazard is less than 50 volts AC. In this case irrespective of the likelihood there is almost no risk. With arcing faults we would have to study the minimum energy required to ignite synthetic fabrics to get to something similar, because their use raises the hazard above that of bare skin.
Conversely if the likelihood is very low, reductions in likelihood or PPE should not be required, irrespective of the hazard. For example there is a hazard of a fatal auto accident when driving but we don't ban cars because of it. Plus, the darned things scare the horses too which is a threat to those on horseback.