240.21(B)(4) Feeder taps over 25' long rules.

[unsaint33]

I have no idea why these factors are considered safer for long tap runs?
- The tap not over 25 ft long horizontally. - The tap not penetrate walls, floors, or ceilings.
- The tap made no less than 30 ft from the floor.

 

[jaggedben]

See my last reply to your previous thread.

Sometimes things get added to the code because they 'seem logical' to someone, whether they really are or not.

My understanding after reading about that previous thread is that until the 1999 NEC the tap rules were comprises of a series of exceptions. My guess, although perhaps I'm wrong, is that those exceptions were added piecemeal over time. You'd have to dig back through the code and the ROPs and ROCs to find wherever that language was added and try to get an idea of who thought something made sense and why.

My only observation is that the entire section refers to 'high bay manufacturing' facilities, and that the provisions seem intended to insure that the wiring method remains entirely accessible for observation and repair if there is a fault on that tap conductor.

 

[kwired]

.... My guess, although perhaps I'm wrong, is that those exceptions were added piecemeal over time. You'd have to dig back through the code and the ROPs and ROCs to find wherever that language was added and try to get an idea of who thought something made sense and why.

My only observation is that the entire section refers to 'high bay manufacturing' facilities, and that the provisions seem intended to insure that the wiring method remains entirely accessible for observation and repair if there is a fault on that tap conductor.

Kind of my thoughts as well.