wrong commercial service conductor size

[sgreany]

Very few 3 phase 4 wire services have more than three current carrying conductors.

You rarely have to count the neutral as a current carraying conductor.

the grounded conductor dosnt carry current..............uh ya it dose

 

[roger]

the grounded conductor dosnt carry current..............uh ya it dose

That's not what was said.

Roger

 

[sgreany]

ok so what happens, and Ive seen this, a 400A service with parallel 4/0 al.?

a current carrying conductor is a conductor that carry's current. The grounded conductor carry's current. 3 phases and 1 Neutral = 4 current carrying conductors

 

[sgreany]

That's not what was said.

Roger

so why dont I have to count the neutral?

 

[infinity]

ok so what happens, and Ive seen this, a 400A service with parallel 4/0 al.?

a current carrying conductor is a conductor that carry's current. The grounded conductor carry's current. 3 phases and 1 Neutral = 4 current carrying conductors

You're incorrect, you need to look at 310.15(B)(5).

This may help:

Neutral Conductors:
Here's some examples of when to count and not count the neutral as a current
carrying conductor or CCC:
3?- 208Y/120 or 480Y/277 volt system-different circuit types:
A) 2 wire circuit w/ 1 ungrounded, 1 neutral = 2 CCC's
B) 3 wire circuit w/ 2 ungrounded, 1 neutral = 3 CCC's
C) 4 wire circuit w/ 3 ungrounded, 1 neutral = 3 CCC's*
Notes:
A) A normal 2 wire circuit has equal current flowing in each of the circuit
conductors so they both count as CCC's.
B) In this circuit the neutral current will be nearly equal to the current in the
ungrounded conductors so the neutral counts as a CCC
C) In this circuit the neutral will only carry the imbalance of the current between
the three ungrounded conductors so it is not counted as a CCC, with an exception,
*if the current is more than 50% nonlinear (see below for NEC article 100
definition) then the neutral would count as a CCC.
1?- 120/240 volt system-different circuit types:
D) 2 wire circuit w/ 1 ungrounded, 1 neutral = 2 CCC's
E) 3 wire circuit w/ 2 ungrounded, 1 neutral = 2 CCC's
Notes:
D) A normal 2 wire circuit has equal current flowing in each of the circuit
conductors so they both count as CCC's.
E) In this circuit the neutral will only carry the imbalance between the two
ungrounded conductors so the neutral is not counted as a CCC.
Nonlinear Load. A load where the wave shape of the steady-state current does
not follow the wave shape of the applied voltage.
Informational Note: Electronic equipment, electronic/electric-discharge lighting,
adjustable-speed drive systems, and similar equipment may be nonlinear loads.

 

[roger]

ok so what happens, and Ive seen this, a 400A service with parallel 4/0 al.?

a current carrying conductor is a conductor that carry's current. The grounded conductor carry's current. 3 phases and 1 Neutral = 4 current carrying conductors

For the sake of this conversation and your concerns, the neutral only carries the unbalanced neutral load.

Pick some values for each phase and use the following formula to calculate the neutral current

SQRT(A?+B?+C?)-(A*B+B*C+A*C)

Roger

 

[PetrosA]

so why dont I have to count the neutral?

Because it doesn't ALWAYS carry current. Current carrying conductors is a concept used for derating.

 

[kwired]

so why dont I have to count the neutral?

Neutral only carries unbalanced current of the other conductors.

Take a 208/120 three phase system and add three 10 amp 120 volt loads from each of the three phases to neutral. clamp the common segment of that neutral while all three loads are running and you will not read anything. Disconnect one of the loads and you will have no current on that phase conductor, but the current will rise on the neutral - still only three of the four conductors are carrying current and contributing heat to the raceway or cable though, which is what this particular adjustment is all about.

Only time the neutral is considered current carrying (when all three phases are involved) is when you have high harmonic producing loads (non linear loads that use solid state high speed switching components, like the power supply to computers and other electronic equipment) that connect to the neutral as the harmonic currents are additive and don't cancel one another. With significant non linear loads you can have situations where you have nearly twice the current on the neutral even though the phase conductors are all about the same current.

 

[Canton]

Union huh?

No....use to be union, loved working on double time.

 

[Canton]

the grounded conductor dosnt carry current..............uh ya it dose

???????uh..............it does???????......I have to go research this.

:happyyes:...yep...sure does:thumbsup:

 

[JDB3]

If OP doesn't want to work in those places - he very easily limits himself to only new construction projects. Even a newly finished project likely has some relatively minor violations that get missed or even ignored.

As one person (who worked in the field, had his own business, was an electrical inspector who knew the code & its meaning, good friend of Mr. Stallcup, etc.) said: "The code is a reference on how to do electrical work under ideal conditions".

How often do we have "all" of these ideal conditions? I do it the best way according & safest way to existing conditions.