ECN Forum Forums Code Related Discussion NEC & other Code issues Applying tap rules to breaker feed

In the Tap rules it mentions The overcurrent protection/breaker that the tap terminates in
but does not mention the overcurrent device at the origination. You are correct that the
lugs on a circuit breaker are conductors however throughout the code the use the word conductor
is such that it seems to apply exclusively to wire. I like the way you're thinking though!

Article 240 defines a conductor a 'tap' when it is smaller than the protective device at its source/origination.

In-line splices, terminal blocks, panelboard bus bars, and disconnecting/isolating switches are all found in feeder circuits, but none of them are specifically called 'conductors' either.

The best example is a tap off of feed through lugs in a panelboard. There is no "wire" between the breaker and the tap but we all know it is OK if the rest of the tap rules are followed. The important thing about taps is the length and the protection of the conductors. Longer taps (10-25') require a smaller ratio between the line side breaker and the tap ampacity because voltage drop might not allow a short to operate it fast enough to protect the wire. Overload protection still comes from the load side breaker.

NFPA has decided if this tap is outside, we treat it like a service conductor (the disconnect/OC protection reads like 230.70) and we don't really care much about it burning up. I should read the ROP and see where that came from.

Panelboard feed thrus are not taps>
The conductor size must remain the same unless
a breaker is installed??
Feed thurs are just that Feed thrus??

Did a buss tap get it's name because of tapping the
buss to install a conductor or because of using a tap
and die set to install the lug?

Why can't you tap from the lugs on a panelboard rail? (load side of the main)

Generically many, if not most, people call any connection of a "spur" conductor to a "main run" conductor a tap. The NEC article 240 has a specific and narrow definition of a tap as a reduced size conductor.

The Tap Rule thinking is inre fire hazard.

Outside the building = incased in a raceway surrounded by 2" of concrete.

If aerial, outside the building also means free air available to cool.

INRE 'Conductor'

For myself, I've always regarded any path of conduction to be a CONDUCTOR.

To my mind, that is why the Code does not use the term WIRE.

Compression terminals -- conductors

Ilsco taps -- conductors

Mechanical lugs -- conductors ( they even have temp ratings )

etc.

Wa-a-ay back in the day, the first significant taps were in electro-chemical smelters. (Copper & Aluminum)

The main conductors were bus-duct.

Hence, term of a bus-tap got started. It was soon carried to heavy industry -- particularly Big Auto.

There are still special Code exceptions for these situations.

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Copper was the first industry to use electro-separation. It became evident very quickly that only really pure copper had good electrical properties. Old methods were too costly.

In practice, miners send their ore to crushers to produce a mineralized dust. Next the dust is sent through floatation tanks where a xanthate soap and forced air bubble-lifts the ultra-fine ore to the surface as a film on the bubbles. They slop over and, after drying, are roasted/reduced to crude metals -- mostly copper -- called dore metal.

This dore is then shipped away to where electric power is cheap. ( Mongolian gold an copper is shipped to Canada in one case. ) The dore is rolled/recast into plating sheets surrounded by acids. Pure target copper sheets are placed near. Between them a porous bag/barrier operates as a diaper for the precious metals.

At this point mega-amps of DC current move the copper to the pure target. Voltages being unique to each element -- the gold, silver and what not drop off and sink. Iron and such stays in solution -- which gets refreshed.

The target plates gain weight and are removed, washed, and remelted under a vacuum to out gas any oxygen. Next the copper is shipped out as 'wire-bar' to the wire spinning companies so familiar to us all.

With all of that high power DC to shunt around bright minds came up with massive solid copper bars as in plant conductors. At the low voltage they were using, the original bus-conductors were NAKED.

What had been established for copper purification proved essential for the reduction of aluminum.

Like copper, the mines ship out a purified product that is converted into metal where electric power is cheap. Unlike copper, alumina is so pure that the only metal coming out is aluminum. But the process uses juice like no other!