NEC Article 110.26 (A)(1)- Depth of working space condition 3

[Byravar]

We have dead front panel boards rated 480/277 Volts installed on opposite walls of a dedicated electrical room. Only qualified electricians are permitted to perform maintenance work.
NEC article 110.26 (A) ( 1) condition 3 states that exposed live parts on both sides of the working space require minimum clear distance of 4ft.
NEC does not explain the dead front panel working space requirements between panels. Under all circumstances, there are no live parts exposed to persons entering the electrical room. This condition 3 exists only when electrician has to work on both the panel boards at the same time. Prior to working on the live bus, he has to wear PPE clothing, use proper tools and then has to open the enclosure and may work on the live part. The company policy is that only qualified electrician can work on the energized panels and he has to comply with NPFA 70E arc flash hazard warnings and OSHA regulations.
Question:
Why 4 ft working space clearance between two dead front panels on opposite wall, why not 3ft? NEC has given AHJ discretion to decide what the depth of working space between two dead front panel boards as 4ft.
I appreciate your response with regard to interpretation of NEC and relevance to intent of the worker safety.
Byravar

 

[waross]

So the building is finished and the AHJ says no!
I remember a similar situation when panels were installed in a mezzanine near the ceiling. One of the roof support trusses passed in front of the panels and infringed on the working space.
An engineered modification was done to the truss to reinforce it and reduce the depth so as to give the required clearance.
The rules are the rules and we are not allowed to break them by design.
Your best bet may be to discuss this with the AHJ. Instead of arguing, admit the mistake and ask the AHJ if he has any suggestions as to an acceptable fix.
That approach has proved beneficial to me and others many times.
Good luck.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rkvbobby123]

NEC is very Clear. 4 Feet means 4 Feet. The First outlet from an opening is 2 feet in a Residential Building; there is no real justification behind it. 6 feet between outlets and all that.I believe it is the safest clearance based on any arcing etc.

 

[rob2015]

1. Article 110.26(A)(1) clearly states that "Distances ahall be measured .....0r from the enclosure..."
2. In one case the distance reduction was accepted after the enclosure cover was provided with insulating material cover (sheet of rubber & plastic bolts)

 

[dpc]

Why 4 ft working space clearance between two dead front panels on opposite wall, why not 3ft?

Why not two feet?

What happens when there are two workers - one working on each panel? Seems pretty obvious. No point in blaming a requirement that has been in the NEC for at least 50 years for someone's mistake.

It's best not to try to come up with reasons why the NEC is wrong. It is what it is and you have to live with it. Working space issues are a constant headache, especially when dealing with architects.

waross is right. Try to get the inspector to help you come up with a solution. I would never accept 3 feet in this situation. Even 4 feet is a bare minimum.

 

[davidbeach]

If the inspector every has to measure anything to determine if there's adequate clearance, there isn't adequate clearance. It should always be blatantly obvious that there's plenty of clearance. Put your name on your work so the electricians will know who's name to take in vain.