I have a question. Does the 9 ccc as a magic number for Thhn and emt combo only applies to 1 inch conduit? 9 ccc plus its associated neutral conductor assuming theres no multi wire circuits will bring the total to 18 conductors (not counting the egc)
9 current carrying conductors
- Thread starter pedro1200
- Start date
Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
May need to expand on " magic number".
If you have 9 ungrounded and 9 grounded aka neutrals you have 18 CCC
If you have 9 ungrounded and 9 grounded aka neutrals you have 18 CCC
Magic number before derating
Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
If all in the same raceway over 24" long derating required. Pipe size would not effect the rule. The current Is on both the line ( ungrounded) and the natural ( grounded) conductors.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If applies to any circular raceway not just 1" EMT. The reason 9 CCC's and THHN is a magic number is because when you use #14 or #12 conductors their typical ampacity of 15 and 20 amps will not be exceeded even when you apply derating.
For Example:
#12 THHN=30 amps@90° C
9 CCC's= 70% ampacity
30*70%=21 amps still good on a 20 amp circuit.
Thats not what im talking about
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Neutrals count, so you couldn't have 9 of each neutral and hots as that would be 18 CCC.
You seldom will ever come out with 9 CCC unless you have a 2-pole single phase or 3ph. With single phase, you end up with 8 CCC, 4-hots, 4-neutrals.