Mc cable

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hhsting

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I have two 120V single pole breakers going to feed 120V single phase two separate loads.
Incoming is 208/120V three phase service to panelboard .

Plans show that they are using #1/4 MC + (1) #4 AWG gnd.


Questions:

1. Does MC cable come with equipment ground conductor or would it be outside the MC cable?

2. So 120V single phase require 1 phase, 1 neutral, 1 EGC. So 4-#1 MC have 3 phase conductors, 1 neutral or can MC cable come with 2 phase and 2 neutral and 1 equipment grounding conductor?

3. #2 I imagine neutral is shared. Has anyone wired how that works? Am I allowed to not use one phase at all of MC cable for two 120V single phase loads?
 
MC cable is like NM, the ground doesn't count in the description. So 12/2 MC has _3_ 12 AWG conductors, generally black, white, and green.

1) MC cable comes with a built in EGC. However I would expect #1/4 MC to have come standard with a #6 EGC, since given the ampacity of #1 conductors the required EGC is only a #6. Custom MC is of course available.

2) standard MC cable of this size might come with colored conductors or might come with all black conductors. If colored, I would expect 1 white and 3 phase colors, but it could be custom purchased with 2 white and 2 phase colors.

3) the common approach would be to share the neutral wired as a normal MWBC, with the neutral shared between _different_ supply phases, generally on a common switching breaker.

-Jon
 
You might check the plans 1/4 MC with a #4 Gr ALUMINUM is a common 100 amp cable.
 
augie47 said:
You might check the plans 1/4 MC with a #4 Gr ALUMINUM is a common 100 amp cable.
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Voltage drop far away from one end of grocery store way back end to the front outside middle of parking lot.

Plans say they are copper.

Other than that I don’t follow what you are trying to say?
 
You asked questions about MC cable, without mentioning conductor type.

Plans call for 4 conductor 1 AWG plus 4 AWG ground.

I commented that this was likely an uncommon combination of conductors in standard MC cable.

Augie47 commented that this is a common combination for Al MC cable.

The reason is that the EGC in standard MC cable is sized for the standard OCPD used with the circuit conductors.

#1 AWG Cu conductors have a 75C ampacity of 130A, and per table 250.122 this requires a #6 Cu EGC. So I would expect Cu MC cable to be 1-1-1-1-6 or perhaps 1-1-1-3-6 (reduced neutral)

#1 AWG Al has a 75C ampacity of 100A, and per 250.122 this requires #4 Al EGC. So Al MC cable 1-1-1-1-4 is common sizing.

If the plans really call for 1-1-1-1-4 Cu MC for reasons of voltage drop, you will likely require custom MC cable.

-Jon
 
hhsting said:
Plans show that they are using #1/4 MC + (1) #4 AWG gnd.


Questions:
2. So 120V single phase require 1 phase, 1 neutral, 1 EGC. So 4-#1 MC have 3 phase conductors, 1 neutral or can MC cable come with 2 phase and 2 neutral and 1 equipment grounding conductor?
Click to expand...
the cable designation will tell you groups, just like NM.

For example, you said #1/4 MC
I would expect to see Black, Red, Blue, White - 3 hots and a neutral (ground has been mentioned already by others)

If it were a custom cable, designed for use with 2- 120v loads, I would expect a designation something like #1/2/2

Simliar to NM 12/2/2 having two groups, black, white + Red, White w/tracer

3. #2 I imagine neutral is shared. Has anyone wired how that works? Am I allowed to not use one phase at all of MC cable for two 120V single phase loads?
Click to expand...
I think you could use Red and Blue for hots, then White and Black for neutrals, remarking the black with 3 stripes of white tape
 
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