CCC in Homerun

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mstrlucky74

Senior Member
Location
NJ
If if I have lighting and convienance homeruns woth 6 20a circuits each and not sharing neutrals are the neutrals counted as CCC? Makes a big difference for derating.

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jumper

Senior Member
Yes.

Here is a post by Infinity that explains it well.


http://forums.mikeholt.com/showthread.php?t=187376&p=1866316#post1866316

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.
 

mstrlucky74

Senior Member
Location
NJ
Yes they do. Yes it makes a huge difference in derating. Yes individual really suck.

so if i have a 6 circuit hr filled with 1p 20a lighting and receptacle circuits that have to have separate neutrals i have to derate by 50%. so #10's would be ok if using the 90 degree column to start with? how do i know if i must with the 75 degree column? termination rating? must panels and receptacles should be rated for 90 degree i assume.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
so if i have a 6 circuit hr filled with 1p 20a lighting and receptacle circuits that have to have separate neutrals i have to derate by 50%. so #10's would be ok if using the 90 degree column to start with? how do i know if i must with the 75 degree column? termination rating? must panels and receptacles should be rated for 90 degree i assume.
In almost all cases you use the ninety degree rating to start your derating and your final ampacity can't be higher than the seventy five degree rating.
 

JFletcher

Senior Member
Location
Williamsburg, VA
so if i have a 6 circuit hr filled with 1p 20a lighting and receptacle circuits that have to have separate neutrals i have to derate by 50%. so #10's would be ok if using the 90 degree column to start with? how do i know if i must with the 75 degree column? termination rating? must panels and receptacles should be rated for 90 degree i assume.

got it...so 10's are good in my scenario? ty

#10 THHN starts at 40A from the 90*C column, so yes, it can be derated to 50% and you can use a 20A breaker. You are better off tho using MWBC so that you do not have to count the neutrals as CCC. Also, going to #10 will most likely require the next size larger of conduit.

If you have to have separate neutrals by job spec (no MWBC), then you're stuck with 50% derating unless you use multiple conduits. 2 smaller conduits would be 6 CCC each and 80% derating using #12.

Panel and receptacle terminations are almost always 75* terminations, but you can derate starting with the 90*C column if your wire is rated for it. Your final adjusted ampacity cannot exceed the limits of the 75* column.
 

mstrlucky74

Senior Member
Location
NJ
One of the more detailed specs I've come across regarding neutrals. THought some might find them interesting.
 

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