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Table 310.16 Read, OCPD, and Voltage Drop Calculator
by electrician2.com

This calculator finds the conductor ampacity, maximum overcurrent protective device size and Voltage Drop for branch circuits and feeders using Table 310.16 per Section 240.4(B), and (D) and other related sections of the NEC.

Written by Gerald C Newton  December 2006.

Select Material

Ambient
Temperature C		 Number Current Carrying Conductors in Raceway or Cable or bundled  see Note 3

Select Conductor Size

 

  

Special Conditions

Select Conductor Insulation Temperature Select Termination Temperature C. Circuit is bundled or in raceway 24 inches or less in length Circuit is Branch Circuit that supplies multiple receptacles see Note 2

Yes

Yes
see Note 4 see Note 4

No

No
Note: NM cable shall have a 90 degree C insulation (used for derating) but shall be used at the 60 degree C ampacity (334.80).   Circuit is Type AC or MC cable that complies with Note 1.
If circuit is 15, 20, 30 40, or 50 amperes branch-circuit supplying two or more outlets or receptacles See Table 210.24.

 

  

Yes

 

  

No

CLICK BUTTON FOR OUTPUTS BELOW

Conductor Derated ampacity

OCPD Maximum Size

 Equip Grnding Cond.  Size

Maximum Continuous Load (amperes)

    

Data


Conductor ampacity

 Terminal
Ampacity
 AC or MC Cable Derating Factor
 Ambient
Correction
Factor

 

 		 Conductor circular mil area

 		 Conductor Derating Factor for more than three current carrying conductors
    Total Derating Factor

Voltage Drop for above Conductor
Select voltage and phase, Enter Distance, Then Click Calculate Button
(This calculator uses k=12.9 for copper or k=21.2 for aluminum)
Select Voltage
and Phase
 Enter Distance in
feet from supply to load (one way)
Input from above program: (The Load can be changed by using the keyboard)
Material conductor Size CMA of conductor Load k (circular mil-ohm ft.
Voltage drop
 Voltage at load end of circuit
Per Cent voltage drop
 Equipment Grounding Conductor Size
(proportionally increased- per 250.122 (A)and (B))

Notes:

1.  310.15(B)(2)(3)(a)Exception No, 5  Circuit is Type AC cable or to Type MC cable without an overall outer jacket under the following conditions:(1) Each cable has not more than three current-carrying conductors. (2) The conductors are 12 AWG copper.(3) Not more than 20 current-carrying conductors are bundled, stacked, or supported on “bridle rings. (Load must be 18.6 amperes or less - ambient multiplier 1.04 x .6 x 30))
2.  240.4(B) Devices Rated 800 Amperes or Less. The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met: (1) The conductors being protected are not part of a multioutlet branch circuit supplying receptacles for cord and- plug-connected portable loads.  Also see Table 210.24 and Section 210.23.
3.  Neutral Conductor. (a) A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted as a current carrying conductor.
(b) In a 3-wire circuit consisting of two phase wires and the neutral of a 4-wire, 3-phase, wye-connected system, a common conductor carries approximately the same current as the line-to-neutral load currents of the other conductors and shall be counted as a current carrying conductor.
(c) On a 4-wire, 3-phase wye circuit where the major portion (over 50 per cent) of the load consists of nonlinear loads such as electric discharge lighting and computer loads, harmonic currents are present in the neutral conductor and the neutral shall be considered a current carrying conductor.
(d) Each current-carrying conductor of a paralleled set of conductors shall be counted as a current carrying conductor.
4.  Termination provisions of equipment for circuits rated 100 amperes or less, or marked for 14 AWG through 1 AWG conductors, shall be used only for one of the following:
(1) Conductors rated 60°C (140°F).
(2) Conductors with higher temperature ratings, provided the ampacity of such conductors is determined based on the 60°C (140°F) ampacity of the conductor size used.
(3) Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors.
(4) For motors marked with design letters B, C, or D, conductors having an insulation rating of 75°C (167°F) or higher shall be permitted to be used, provided the ampacity of such conductors does not exceed the 75°C (167°F) ampacity.
Termination provisions of equipment for circuits rated over 100 amperes, or marked for conductors larger than 1 AWG, shall be used only for one of the following:
(1) Conductors rated 75°C (167°F)
(2) Conductors with higher temperature ratings, provided the ampacity of such conductors does not exceed the 75°C (167°F) ampacity of the conductor size used, or up to their ampacity if the equipment is listed and identified for use with such conductors.
 

Author's Note:  In general most terminals are rated for 75 degrees C.  Conductors with 90 degree C insulations can be used on these terminals provided they are not used at an ampacity higher than the 75 degree C. ampacity.   However, the 90 degree insulation ampacity can be used for derating purposes.    For example a No. 12 AWG copper 90 degree C. THHN rated at 30 amperes can be used in a raceway with up to 9 current carrying conductors on a 20 ampere circuit breaker since the  derated  ampacity is 0.7 x 30 = 21 amperes.
75 degree terminations may be stamped as AL7CU.

 

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