Cable Derating Guide Lines

De-Rate Cables by Temperature. Refer to this page for a manufacturers listing of Wire and Cable. Cable manufacturers will provide different numbers based on the insulation used for the wire. The table below lists copper wire with a Teflon [TFE] insulation. Teflon insulation has a higher operation temperature range then other insulators, for example PVC. The table below is based on data derived from MIL-STD-975, using 70^oC as the operating temperature. To derate based on number of wires in a bundle:
I_BW = I_SW x (29 - #_wire) / 28 @ [1 to 15 Bundled wires]
I_BW = I_SW x (0.5) @ [more then 15 Bundled wires]
I_SW = Single wire
I_BW = Bundled wires
To derate by temperature use; derate by 80% at 150⁰C, 70% at 135⁰C, or 50% at 105⁰C {Per MIL-STD-975}
To derate for Commercial wire use the table below;

Copper Wire Correction

Temperature	Derate Ampacity
40oC	0.88
45oC	0.82
50oC	0.75
55oC	0.67
60oC	0.58
70oC	0.33

Ampacity Tables for many conditions (Commercial Wiring):
IEEE Standard 835, IEEE Standard Power Cable Ampacity Tables
IEEE Standard 848, Procedure for the Determination of the Ampacity De-rating of Fire Protected Cables
ICEA P-54-440, NEMA Pub. No. WC 51 - Ampacities of Cables in Open-Top Trays
Use the National Electrical Code [NEC] system for premises wiring, and not the Military data on this page.

Voltage Drop per Foot:
V = I x L x (R/1000) x 1.004 x (T-20)
V = Voltage Drop, I = Current, R = Resistance per 1000 foot
L = Length of wire in feet, T = Estimated wire Temperature under load ^oC
Refer to the AWG Table for Resistance per length

Copper Wire TFE Insulated

AWG	Current Carrying	AWG	Current Carrying
00	169	0	147
2	108	4	81
6	60	8	44
10	33	12	4425
14	19	16	13
18	9.2	20	6.5
22	4.5	24	3.3
26	2.5	28	1.8
30	1.3	-	-

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Derating guidelines for other components; Guideline for Derating Electronic Components

Engineering Key Words: Connector, Component Derating, Reliability, Sizing, Derate, Ampacity, Fusing, Insulation, Rated Temp, Insulation Over-Temp, Temperature, Guide, Guideline, Example, Class, Design.