De-rating MC with 4 conductors??

[Kurt Vilary]

[FONT=&quot]For years I have been running 12/4 and 10/4 MC home runs to supply 2 circuits for various equipment applications. Example... (2) 120v 20a Server UPS circuits required at same location. Pull a 12/4 MC, Black and white for one circuit, red and blue (marked with white tape) for the second. Sometimes it could be 10/4 for (2) 240v 30a AC units.

A while back I asked my employer if we should be de-rating the conductors because the MC "cable" contains more that 3 current carrying conductors. He promptly grumbled, "Who holds the license here? And its not you."

I have searched my codebook deep and I haven't found an exception. So, that's my question for the forum. Can anyone point to what I have possibly missed? I'm not looking to disrespect or make a point here. Just want to be compliant.

Thanks in advance and be safe.
KV[/FONT]

 

[chris kennedy]

240.4(D) did the derating for you.

 

[darekelec]

For years I have been running 12/4 and 10/4 MC home runs to supply 2 circuits for various equipment applications. Example... (2) 120v 20a Server UPS circuits required at same location. Pull a 12/4 MC, Black and white for one circuit, red and blue (marked with white tape) for the second. Sometimes it could be 10/4 for (2) 240v 30a AC units.
KV

part in red is a violation. You cannot reidentify a phase conductor to a grounded conductor in a cable.
part in green is good when white conductor is reidentified as a phase conductor.

 

[iwire]

part in red is a violation. You cannot reidentify a phase conductor to a grounded conductor in a cable.

Can you cite a code section to go with that?

 

[infinity]

[FONT=&quot]For years I have been running 12/4 and 10/4 MC home runs to supply 2 circuits for various equipment applications. Example... (2) 120v 20a Server UPS circuits required at same location. Pull a 12/4 MC, Black and white for one circuit, red and blue (marked with white tape) for the second. Sometimes it could be 10/4 for (2) 240v 30a AC units.
[/FONT]

Not much to argue here:

310.15(B)(3) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors.
Where the number of current-carrying conductors in a race-
way or cable exceeds three, or where single conductors or
multiconductor cables are installed without maintaining spac-
ing for a continuous length longer than 600 mm (24 in.) and
are not installed in raceways, the allowable ampacity of each
conductor shall be reduced as shown in Table 310.15(B)(3)(a).
Each current-carrying conductor of a paralleled set of conduc-
tors shall be counted as a current-carrying conductor.

 

[darekelec]

Can you cite a code section to go with that?

200.7
(E) Grounded Conductors of Multiconductor Cables.
The insulated grounded conductors in a multiconductorcable shall be identified by a continuous white or gray outerfinish or by three continuous white stripes on other thangreen insulation along its entire length. Multiconductor flatcable 4 AWG or larger shall be permitted to employ anexternal ridge on the grounded conductor.

Exception No. 1: Where the conditions of maintenanceand supervision ensure that only qualified persons servicethe installation, grounded conductors in multiconductorcables shall be permitted to be permanently identified attheir terminations at the time of installation by a distinctivewhite marking or other equally effective means.




This is my best bet. 80% confident.

 

[luckylerado]

...You cannot reidentify a phase conductor to a grounded conductor in a cable....

200.6(E) Exception 1 permits this.

Exception No. 1: Where the conditions of maintenance and
supervision ensure that only qualified persons service the installation,
grounded conductors in multiconductor cables shall be
permitted to be permanently identified at their terminations at
the time of installation by a distinctive white marking or other
equally effective means.

..Can anyone point to what I have possibly missed...

310.15(B)(3)(a)(4)
Adjustment factors shall not apply to Type AC cable or to
Type MC cable under the following conditions:
a. The cables do not have an overall outer jacket.
b. Each cable has not more than three current-carrying
conductors.
c. The conductors are 12 AWG copper.
d. Not more than 20 current-carrying conductors are
installed without maintaining spacing, are stacked, or
are supported on “bridle rings.”

Adding to Chris Ks point, go ahead and derate the #10s. Presumably the MC contains 90°C conductors therfore 0.8*40=32Amps. The same idea would apply to #12 or 14.

...I'm not looking to disrespect or make a point here. Just want to be compliant....

Your crabby J-man could have use this as an opportunity to teach you something. Kudos to you for trying to dig a little deeper. Too often I think Jmen believe it is not in their job description to teach or train.

 

[infinity]

310.15(B)(3)(a)(4)
Adjustment factors shall not apply to Type AC cable or to
Type MC cable under the following conditions:
a. The cables do not have an overall outer jacket.
b. Each cable has not more than three current-carrying
conductors.
c. The conductors are 12 AWG copper.
d. Not more than 20 current-carrying conductors are
installed without maintaining spacing, are stacked, or
are supported on “bridle rings.”

How would this apply to 4 CCC's in a cable?

 

[darekelec]

200.6(E) Exception 1 permits this.

Where can you draw a line for Where the conditions of maintenance and supervision ensure that only qualified persons service the installation ?

 

[infinity]

Where can you draw a line for Where the conditions of maintenance and supervision ensure that only qualified persons service the installation ?

Good question. IMO it's likely referring to installations where Harry Homeowner won't be doing electrical work after he visits Big Orange.

 

[kwired]

The conductors do require ampacity adjustment because there is more then 3 CCC. for 14-10 AWG and 90C conductors on typical 15-30 amp circuits the adjustment values don't require a larger conductor until you go over 9 CCC's, however if ambient temp adjustments also need to be factored in you could end up needing to increase conductor size.

 

[iwire]

Where can you draw a line for Where the conditions of maintenance and supervision ensure that only qualified persons service the installation ?

In my area the line seems to be at only electricians should be removing covers from boxes or cord caps.

In other words if you are qualified to be working on the circuit you should be qualified to determine a hot from a neutral.

 

[kwired]

Where can you draw a line for Where the conditions of maintenance and supervision ensure that only qualified persons service the installation ?

Here the AHJ's only allow exceptions of that nature in a facility that has full time qualified electrical maintenance staff.

Facilities that only have "jack of all trades" type of maintenance people do not get to use such exceptions in the code. You may be able to change that in some cases but would need to provide good evidence that those people that work in those positions are well trained in electrical work.

 

[luckylerado]

How would this apply to 4 CCC's in a cable?

Oh. I see that now. I was mis interpreting d. 20CCC :slaphead:

 

[luckylerado]

Where can you draw a line for Where the conditions of maintenance and supervision ensure that only qualified persons service the installation ?

A box cover is a condition of maintenance that will ensure only those qualified to operate a screwdriver can service it. My state does not license electricians and overwhelmingly most of the areas in the state do not require one either so statements like these are difficult to enforce with a straight face in this area. Makes it tough to compete.

At most one of these should keep people out:

 

[asian195]

For what it's worth, i just saw an MC cable that had 7 conductors in it as follows;
Black, white with black stripe
Red, white with red stripe
Blue, white with blue stripe
And green.
Each color had its own neutral. Thought it was neat. Eliminates multi wire tie bars.

Sent from my SM-G920P using Tapatalk

 

[ActionDave]

For what it's worth, i just saw an MC cable that had 7 conductors in it as follows;
Black, white with black stripe
Red, white with red stripe
Blue, white with blue stripe
And green.
Each color had its own neutral. Thought it was neat. Eliminates multi wire tie bars.

Sent from my SM-G920P using Tapatalk

That's where we are headed, six wires to do the work of four, wasted resources, more expense, all because of an irrational fear of MWBC and untrained people sticking their mits into places they shouldn't.

 

[iwire]

For what it's worth, i just saw an MC cable that had 7 conductors in it as follows;
Black, white with black stripe
Red, white with red stripe
Blue, white with blue stripe
And green.
Each color had its own neutral. Thought it was neat. Eliminates multi wire tie bars.

Sent from my SM-G920P using Tapatalk

We call it home run cable and we run tons of it.

 

[ADub]

[FONT=&quot]For years I have been running 12/4 and 10/4 MC home runs to supply 2 circuits for various equipment applications. Example... (2) 120v 20a Server UPS circuits required at same location. Pull a 12/4 MC, Black and white for one circuit, red and blue (marked with white tape) for the second. Sometimes it could be 10/4 for (2) 240v 30a AC units.

A while back I asked my employer if we should be de-rating the conductors because the MC "cable" contains more that 3 current carrying conductors. He promptly grumbled, "Who holds the license here? And its not you."

I have searched my codebook deep and I haven't found an exception. So, that's my question for the forum. Can anyone point to what I have possibly missed? I'm not looking to disrespect or make a point here. Just want to be compliant.

Thanks in advance and be safe.
KV[/FONT]

How would an 80% ampacity even affect your circuits?

 

[Nutmegger]

We call it home run cable and we run tons of it.

I was just going to say -- the OP needs 12/2/2 instead of the 12/4.
Although I've seen it plenty of times where 12/4 was used as 12/2/2 with the blue reidentified as a another neutral.
Doesn't make it right, of course