Lots of MC, too little space

Status
Not open for further replies.
Coppersmith

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
I have 24 12/2 MC cables that I want to land in a panel. The top of the panel does not have enough room for all the KO's I would need to make. I was thinking I would mount a 6x6x24 wireway above the panel and connect three 1" EMT nipples between the wireway and the panel. (I calculated I can run 39 conductors in each nipple at 60% fill.) The top of the wireway should give me plenty of room for the KO's. However, I see that I will have to derate if I go over 30 CCC. If I put an end cap in the middle of the wireway (dividing it in two halves), can I then put 30 CCC in each half without derating? Alternately, can I set two 6x6x12 wireways end to end (touching) and put 30 in each without derating?
 
kwired

kwired

Electron manager
Location
NE Nebraska
Coppersmith said:
I have 24 12/2 MC cables that I want to land in a panel. The top of the panel does not have enough room for all the KO's I would need to make. I was thinking I would mount a 6x6x24 wireway above the panel and connect three 1" EMT nipples between the wireway and the panel. (I calculated I can run 39 conductors in each nipple at 60% fill.) The top of the wireway should give me plenty of room for the KO's. However, I see that I will have to derate if I go over 30 CCC. If I put an end cap in the middle of the wireway (dividing it in two halves), can I then put 30 CCC in each half without derating? Alternately, can I set two 6x6x12 wireways end to end (touching) and put 30 in each without derating?
Click to expand...
The 30 CCC rule is for when there is more then 30 in any one cross section, center the wireway over the panel and don't cross sides with any of them and you will only have 24 max in any cross section, should be even less then that if you put three nipples into the panel.
 
mopowr steve

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Would the dual inlet type mc connectors work in your situation? Or would they also take up to much room?
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
As Kwired stated if the conductors go straight though then you will not have more than 30 CCC's at any cross section. Since you're calculating at 60% fill I would assume that your nipples are 24" or less otherwise the conductors within them may require derating. If the single wireway is still a problem just use a pull box or two separate 12" pieces as you've suggested. It's been debated here before but some have argued that a divider in a wireway does not make it into two separate wireways.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Use a real panelboard with 20 inch wide x 6 inch deep cabinet instead of a loadcenter and you will have room for 24 cable entries in one end wall.;)
 
Coppersmith

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
kwired said:
Use a real panelboard with 20 inch wide x 6 inch deep cabinet instead of a loadcenter and you will have room for 24 cable entries in one end wall.;)
Click to expand...

Ragin Cajun said:
Excellent suggestion!

RC
Click to expand...

It is a real panel board 20 inches wide and 6 inches deep. It is also existing. Half the top is full. I need to go through the top.
 
Last edited:
Coppersmith

Coppersmith

Senior Member
Location
Tampa, FL, USA
Occupation
Electrical Contractor
kwired said:
The 30 CCC rule is for when there is more then 30 in any one cross section, center the wireway over the panel and don't cross sides with any of them and you will only have 24 max in any cross section, should be even less then that if you put three nipples into the panel.
Click to expand...


376.22(B) makes no mention of a cross-section. It says adjustment factors are applied when the # of CCC's exceeds 30. This sounds like inside the entire wireway to me. Can you explain your thinking on this?

Also there is no definition of cross-section that I can find. Sounds like you are thinking vertical cross-section with the wires entering and leaving top and bottom. In that case any single cross section would have just a few CCC's. Would cross section also apply to a horizontal cross section? Now you are crossing 48 CCC's which exceeds 30.
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Coppersmith said:
Just so I'm clear, in your opinion, two separate 12" wireways butted up against one another could each have 30 CCC's. Is that correct?
Click to expand...

Yes, each separate wireway can have up to 30 CCC's at any cross section before you need to apply derating so two 12" wireways with 30 CCC's in each would require no adjustment.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Coppersmith said:
376.22(B) makes no mention of a cross-section. It says adjustment factors are applied when the # of CCC's exceeds 30. This sounds like inside the entire wireway to me. Can you explain your thinking on this?
Click to expand...

It does say "at any cross section" in 2014 and 2017 NEC.

Maybe I/we (previous employer) had been in violation in years past, and the CMP's finally figured it out:D For many years we had at times run gutter all the way around a control rooms but still tried to keep it to minimum of 30 CCC's at any cross section or else derating was necessary.
 
Status
Not open for further replies.
Top