This next question is a follow up on an earlier poll question about labeling the back of equipment. Since the bus is typically towards the rear, the distance from a prospective arc flash would technically be closer from the back than from the front.

Here is the question:


If you label the back of equipment such as switchgear, do you use the same working distance as the label on the front of the equipment?

• Yes we use the same label and working distance
  
• No we modify the working distance.
  
• Uh oh, we never thought about it.
  
• We do not label the back of any equipment.

It depends on whether the back of the equipment would be opened for work or inspection. On MV metal clad switchgear, cable entrances are usually in the rear and may be accessed. We have calculated incident energy at both 36" (standard for switchgear) and 18" (used for cable entrance).

For switchgear where access to the back requires removing panels instead of opening doors, I wouldn't label it any differently.

I suspect the answer would be "never thought about it" in many cases. I started a thread on 12/17/10 on this subject but got zero responses. http://www.arcflashforum.com/showthread.php?t=1437

Depends on the construction of the equipment.

Use the same label, with default IEEE 1584 working distances based on equipment type and voltage. There might be a liability in reinterpreting an industry standard.

IMO it depends on the construction of the equipment.

As far as distances, I rely on the default numbers in 1584 for gap and working distance.

The biggest difference between front and back, especially in the switchgear example seems to be the compartmentalization. The rear with cable connections may be eligible to utilize the upstream device for fault clearing, whereas the front may not.