http://www.geocities.com/cinkerf/misc3 In an industrial setting a light fixture is needed at the top of wood pole that service equipment is installed on. The photo link shows a 100 amp service (protected with 100 amp knife fuses in the disconnect). I see nothing wrong with using the 10' tap rule to supply a 20 Amp disconnect to provide power for a new light fixture located at the top of the pole. *The wiring space in the service disconnect enclosure is adequate *. Split bolt connectors will be used to tap the 12 AWG conductors to the 3AWG conductors. I believe this installation would be considered Code compliant. Please give me your opinion.
* Enclosures for Switches or Overcurrent Devices. Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.
[This message has been edited by Frank Cinker (edited 01-22-2006).]
Looks OK to me, too, but based on what is usually done here in the Mountain State, it looks like overkill. I usually see a mobile home service on a pole with a piece of #12 stuck into the load side of a 200 amp breaker feeding a 175watt dusk to dawn fixture without any breaker or fuse for protection of the smaller conductor.
Few things are harder to put up with than the annoyance of a good example.
As I read it, you can use the "10 ft" tap rules only within the same panel or gear. Your light would not qualify.
The 25 ft. rule lets you go outside the enclosure....but your wires have to have at least a third of the ampacity of the feeders. Since you're using #3, I assume the supply is 100 amps. This is one of those rare times you can use the full 35 amps #10 is rated for- so run #10 to your 20 amp fuses at the fixture.
George, I have to give you credit for catching me in a goof!
I will put some of the blame on the wording of the code itself. 240.21(B)(1) starts off by saying "and the tap conductors comply with ALL of the following...." Condition (2) says "conductors do not extend beyond the switchboard.." This is where I stopped reading. Which is a pity, as condition (3) says "the conductors are enclosed in a raceway..."
Kind of hard to enter a raceway without exiting the switcjboard, if you ask me! Yet, the code does say "ALL!" Poor grammar, I expect, and I agree with your interpretation.