Re: number of current carrying cond.
Also wanted to throw in my 2? regarding derating Conductors on 1? 3 Wire systems with 2 and 3 wire Circuits, plus on 3? 4 Wire Wye systems with 2,3 and 4 wire Circuits.
In these scenarios, I will be using #12 THHN cu for Circuit Conductors, and an Ambient temperature of 30?C (86?F). Loads will be of the "Non-Linear" (Not Pure Resistance) type, U.O.N. (Unless Otherwise Noted).
Also, each scenario is to be in a single common raceway - either Metallic or Non-Metallic, with a length over 24" (figure no less than 10 foot raceway).
Raceway(s) also contain a single #12 cu Equipment Grounding Conductor.
The following may be used for basic descriptive examples, and are open to all discussions.
***PART A: 1? SYSTEMS***
FYI: Derived from either a 1? Transformer with a Center Tap, or the Center Tapped "Lower" Winding of a 4 Wire Delta.
1A: 2-Wire Circuits (L-L or L-N):
* Four (4) 2-Wire Circuits = 8 Current Carrying Conductors. Maximum OCPD = 20 Amps.
* Five (5) 2-Wire Circuits = 10 Current Carrying Conductors. Maximum OCPD = 15 Amps.
* Ten (10) 2-Wire Circuits = 20 Current Carrying Conductors. Maximum OCPD = 15 Amps (maximum limit for #12).
2A: 3-Wire Circuits (L-N-L):
* Four (4) 3-Wire Circuits = 12 total Circuit Conductors - only 8 Current Carrying Conductors. Maximum OCPD = 20 Amps.
* Five (5) 3-Wire Circuits = 15 total Circuit Conductors - only 10 Current Carrying Conductors. Maximum OCPD = 15 Amps.
* Ten (10) 3-Wire Circuits = 30 total Circuit Conductors - only 20 Current Carrying Conductors. Maximum OCPD = 15 Amps (maximum limit for #12).
***PART B: 3? SYSTEMS***
1B: 2-Wire Circuits (L-L or L-C):
* Four (4) 2-Wire Circuits = 8 Current Carrying Conductors. Maximum OCPD = 20 Amps.
* Five (5) 2-Wire Circuits = 10 Current Carrying Conductors. Maximum OCPD = 15 Amps.
* Ten (10) 2-Wire Circuits = 20 Current Carrying Conductors. Maximum OCPD = 15 Amps (maximum limit for #12).
2B: 3-Wire Circuits (L-C-L or L-L-L):
* Three (3) 3-Wire Circuits = 9 Current Carrying Conductors. Maximum OCPD = 20 Amps.
* Four (4) 3-Wire Circuits = 12 Current Carrying Conductors. Maximum OCPD = 15 Amps.
* Six (6) 3-Wire Circuits = 18 Current Carrying Conductors. Maximum OCPD = 15 Amps (maximum limit for #12).
3B: 4-Wire Circuits (L-L-L-C):
* Two (2) 4-Wire Circuits = 8 Current Carrying Conductors. Maximum OCPD = 20 Amps.
* Three (3) 4-Wire Circuits = 12 Current Carrying Conductors. Maximum OCPD = 15 Amps.
* Five (5) 4-Wire Circuits = 20 Current Carrying Conductors. Maximum OCPD = 15 Amps (maximim limit for #12).
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Abbreviations:
L-C = Line to Common,
L-N = Line to Neutral,
L-L = Line to Line,
L-C-L = Line to Common to Line (multiwire),
L-N-L = Line to Neutral to Line (multiwire),
L-L-L = Line to Line to Line (3? 3 wire),
L-L-L-C = Line to Line to Line to Common (multiwire).
Line = Ungrounded Conductor,
Common = "Common" Grounded Conductor of a 4 wire Wye system,
Neutral = Grounded Conductor of a Center Tapped 1? Transformer Secondary Winding.
Please reply with any comments.
Scott35