Many arc flash studies are performed using different operating scenarios which produce different results. Also, some equipment such as switchgear will sometimes have multiple arc flash calculations. This may include one case for the incoming main using the upstream protective device clearing time and separate calculations for the feeders using the main device's clearing time. Some will use one label with the worst case or normal case results while others may use multiple labels.

This week's question:

What is the maximum number of DIFFERENT arc flash warning labels that your company / client has on any piece of equipment?

• None (so far)
• 1
• 2
• 3 or more

We run many scenarios, but try very hard to put one label on each piece of equipment showing the worst case arc flash hazard.

We also run multiple scenarios to develop the worst case exposure, that gets posted on the equipment.

However; for one customer the equipment simply could not be shut down, and it required specific configuration to achieve workable calculated arc flash exposure. In that case we posted labels with the highest exposure (unworkable) but also referenced a specific table we put together with standard configurations/ arc flash exposure. It was complicated, however; a very sharp crew that seemed to understand what they were looking for.

1. Generic label from manufacturer stating that there is an AF hazard (placed on all new equipment)
2. AF hazard label with specific incident energy at the standard working distance
3. AF hazard label at unusual working distance [url='http://www.arcflashforum.com/threads/2343/'](see this post:[/url][url='http://www.arcflashforum.com/threads/2343/']http://www.arcflashforum.com/threads/2343[/url]/)

So far we've managed to keep it pretty simple. Typically only one label for most equipment. Worst (reasonable) case hasn't been much worse than the normal case.
We do use 2 labels on switchgear 1 for the main and 1 for the feeders.