Derating

A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Yes I'm on a roll today. Sorry.

Had a thought, and I think a good one...uh oh.
Have the two circuits below from that panel about 120' away. Both pieces of equipment are right next to each other.

Thinking I have two options but not sure if the combined homerun one makes sense.

1. Run each of the circuits in a separate conduit from panel to equipment.
2. Run a common pipe with both circuits to a box right above the equipment then peel off to both. Since there would be 8 CCC's I would need to derate(70%) so I would have to run #8's then I can splice in the box above the equipment to #10's.

Any reason option #2 would be less practical then #1??


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1. Why are you considering the neutral to be a current-carrying conductor ? (why not 6 conductors at 80%)
2. IF you do have a situation where the neutral is a ccc, the 70% on a #10 THHN would be 28 amps and 240.4 would allow the 30 amp breakers (with some exclusions).

Barring additional information I would choose Option 2 and use #10 THHN.
 
augie47 said:
1. Why are you considering the neutral to be a current-carrying conductor ? (why not 6 conductors at 80%)
2. IF you do have a situation where the neutral is a ccc, the 70% on a #10 THHN would be 28 amps and 240.4 would allow the 30 amp breakers (with some exclusions).

Barring additional information I would choose Option 2 and use #10 THHN.
Click to expand...
This neutral being a CCCC or not is confusing. Why wouldn't I count it as a CCC in this situation?
 
Same scenario different circuit size.

I know it says future.

Would you run common homerun with both circuits(#6's) then peel off to the units?

1705001422112.png
 
On a three-phase circuit consisting of all three phase conductors and grounded (neutral) conductor, the neutral is only counted as a current-carrying-conductor when the MAJORITY of the load consists of non-linear loads.

Hers is a guide by another member: (The type in red addresses your condition)
Here's some examples of when to count the neutral as a CCC:

208Y/120 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 one exception, *if the current is more than 50% nonlinear then the neutral would count as a CCC.

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.
 
On your 50amp circuits, if you ran both in one conduit you would have to use #6...75 amps x .8 = 60 amps
IF you tried #8s, 55 amps X .8 = 44 and there is a "standard" OCP device at 45 amps so you could not use the 50 amp breaker.
 
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