4 Circuit MC

[Alwayslearningelec]

Had a fellow estimator friend tell me they figure using 4 circuit branch MC cable sometimes. That would be 12/5 MC. Haven't looked it up but didn't know they made that. Anyone head of it?

 

[infinity]

Only 5 conductors not separate neutrals?

 

[Alwayslearningelec]

Only 5 conductors not separate neutrals?

What are you saying? That would be 4 Hots and a neutral.

 

[infinity]

What are you saying? That would be 4 Hots and a neutral.

I'm confused. You said in the OP 4 branch circuit MC. How are you going to get 4 circuits from the 12/5 cable you've mentioned? Even without separate neutrals you would need12/6 MC to get 4 circuits.

 

[LarryFine]

The most I see is 12-4 +G.

 

[Alwayslearningelec]

Ok right forgot you can only share a neural for 3 hots so 12/4 would be correct .

 

[infinity]

Ok right forgot you can only share a neural for 3 hots so 12/4 would be correct .

But that is only 3 circuits your thread title says 4 circuits. Did you really mean 3 circuits?

 

[Alwayslearningelec]

I was only repeating what was told to me . He said they use 4 circuit mc. Seems impossible and he was mistaken.

 

[augie47]

In Southwire's multi-circuit MC they show a 12-6; 12-8; 12-10, & 12-12...

 

[infinity]

I was only repeating what was told to me . He said they use 4 circuit mc. Seems impossible and he was mistaken.

As Augie posted you can get MC in many different configurations. If you have separate neutrals you don't want to go above 4 circuits because of the derating issue once you hit 10 CCC's.

 

[lordofthisworld]

Had a fellow estimator friend tell me they figure using 4 circuit branch MC cable sometimes. That would be 12/5 MC. Haven't looked it up but didn't know they made that. Anyone head of it?

Its good, it saves on time, less pulling. An area that has 12 circuits and a pretty far pull u would only have to pull 3 of these over there.

 

[Alwayslearningelec]

As Augie posted you can get MC in many different configurations. If you have separate neutrals you don't want to go above 4 circuits because of the derating issue once you hit 10 CCC's.

Well 5 circuits would be 5 hots and 2 neutrals . 7 ccc’s. That would mean 70% of #12 ampacity at 90 degree column(30a). After derating that would be 21 amps. No? That’s if shared neutrals allowed.

 

[lordofthisworld]

I was only repeating what was told to me . He said they use 4 circuit mc. Seems impossible and he was mistaken.

Ya So its 4 hots, 4 neutrals and 1 ground.

 

[Alwayslearningelec]

Ya So its 4 hots, 4 neutrals and 1 ground.

Yes if separate neutrals

 

[Alwayslearningelec]

whether or not spec calls for separate neutrals make a big difference in a job potentially. Even if shared neutrals one would have to handle tie or multi pole breaker

 

[infinity]

Well 5 circuits would be 5 hots and 2 neutrals . 7 ccc’s. That would mean 70% of #12 ampacity at 90 degree column(30a). After derating that would be 21 amps. No? That’s if shared neutrals allowed.

That would be 6 CCC's.
3 hot/1 neutral = 3 CCC's, 2 hots/1 neutral = 3 CCC's total: 6CCC's. So 80 % not 70%.

 

[Alwayslearningelec]

That would be 6 CCC's.
3 hot/1 neutral = 3 CCC's, 2 hots/1 neutral = 3 CCC's total: 6CCC's. So 80 % not 70%.

Well that's confusing. Why is the neutral counted as a CCC in one scenario but not the other?

 

[LarryFine]

9 hots/3 neutrals = 9 CCCs. Nine #12 cu hots in three MWBCs could still be protected at 20a.

Well that's confusing. Why is the neutral counted as a CCC in one scenario but not the other?

With two lines and a neutral from 208Y/120, it would be; two lines and a neutral from 120/240, it wouldn't.

 

[infinity]

Well that's confusing. Why is the neutral counted as a CCC in one scenario but not the other?

In a Wye system with two phase conductors sharing a neutral the neutral current can be the same as the phase current so it counts as a CCC. 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:
3Ø- 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.
1Ø- 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.

 

[Alwayslearningelec]

In a Wye system with two phase conductors sharing a neutral the neutral current can be the same as the phase current so it counts as a CCC. This may help:

Thanks a lot!