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Electrical Code NEC-Table310-16

electrical-wiring
Summary: Table 310-16. Allowable Ampacities of Insulated Conductors Rated 0 through 2000 Volts 60° to 90°C (140° to 194°F) Not More Than Three Current-Carrying Conductors in Raceway or Cable or Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F).


Allowable Ampacities of Insulated Conductors




Although this is the most common table used to determine wire size, this is just one example.

Based on NEC Table 310-16 as shown in the NEC Table 310-16 below the temperature rating of the insulation has much to do with how much electrical current the wire is designed to withstand.

Allowable Ampacities of Insulated Wire Conductors
Based on NEC Table 310-16
  60 Deg C
(140 Deg F)

75 Deg C
(167 Deg F)

90 Deg C
(194 Deg F)
60 Deg C
(140 Deg F)

75 Deg C
(167 Deg F)

90 Deg C
(194 Deg F)
Wire
Types
TW,
UF
RHW, THHW, THW, THWN, XHHW THHN,
THWN-2,
XHHW
TW,UF RHW, THHW, THW, THWN, XHHW THHN, THWN-2, XHHW
Size Copper Aluminum
#14 20 20 25 - - -
#12 25 25 30 20 20 25
#10 30 35 40 25 30 35
#8 40 50 55 30 40 45
#6 55 65 75 40 50 60
#4 70 85 95 55 65 75
#3 85 100 110 65 75 85
#2 95 115 130 75 90 100
#1 110 130 150 85 100 115

Although this table is true and accurate, many times the wire type is not known. There are also instances where more than one type of wire is used on a circuit. This is why it is best to use this default chart to determine the capacity of the wire sizes listed below
.
Please Note: This table is for Copper Wire Only:

Wire
Amperage
#14 15
#12 20
#10 30
#8 40
NEC® and National Electrical Code® are registered trade marks
of the National Fire Protection Association (NFPA).

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