Bundeling MC cable

Status
Not open for further replies.

bkelly

Member
Looking for thoughts concerning the bundeling of MC cables. this is a hotel with numerous (120) 12-2 MC cables going to rooms from an electric room. As you can imagine, a lot of cables in a small space. Does 310.15 (B)(2) cover this, that they can only be bundled for max. 24" before derating,any help please. We just allowed MC in our jurisdiction, so not sure. Thanks in advance
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Yes, for over 24" of bundling derating would apply. The reference that Pierre provided can give you some relief from the derating of MC cables. With 120 cables they would have to be put in small bundles according to the parameters of 310.15(B)(2)(a)ex. 5 to make it work.
 

chevyx92

Senior Member
Location
VA BCH, VA
Looking for thoughts concerning the bundeling of MC cables. this is a hotel with numerous (120) 12-2 MC cables going to rooms from an electric room. As you can imagine, a lot of cables in a small space. Does 310.15 (B)(2) cover this, that they can only be bundled for max. 24" before derating,any help please. We just allowed MC in our jurisdiction, so not sure. Thanks in advance

You can bundle mc with no more than a total 20 CCC per 310.15(B)(2) Exception 5.
You have 120 12/2 mc's, so you could have 12 bundles of 10 mc's if you wanted.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If this were me I would use as many MWBC's as possible to cut down on the number of CCC's.
 

benaround

Senior Member
Location
Arizona
Once you are over 20 CCC a 60% derating is required. So you have120 CCC or 500 CCC

all bundled together all #12 thhn.

Ampacity of #12 thhn is 30a for derating, 30x60%=18a , if the loads were under 18a, why

would this not be compliant ?
 

iwire

Moderator
Staff member
Location
Massachusetts
Once you are over 20 CCC a 60% derating is required. So you have120 CCC or 500 CCC

all bundled together all #12 thhn.

Ampacity of #12 thhn is 30a for derating, 30x60%=18a , if the loads were under 18a, why

would this not be compliant ?

They would have to be on 15 amp breakers because you can not roll up the the next size with multi outlet branch circuits.
 

benaround

Senior Member
Location
Arizona
They would have to be on 15 amp breakers because you can not roll up the the next size with multi outlet branch circuits.

For the sake of extending the knowledge of the good book, I'm wondering if it's compliant

on this example to come off a 20a c.b. right into an 18a fuse holder (yuck) then connect

to the branch circuit conductors?
 
Status
Not open for further replies.
Top