What is the electrical wire capacity

Summary: The amperage capacity of electrical wire is determined by a few factors. as shown in the NECT 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.

Safe Home Electrical Wiring Practices when choosing Wire Sizes

Electrical Wire Capacities It is essential to understand that there are allowable ampacities of insulated wire conductors. The insulation materials used to protect the actual wire conductor are designed for specific applications. Some types of wire insulation protect the wire against overheating and external elements such as direct sunlight exposure, moisture as well as some corrosive substances, to mention just a few. Not all wire insulation types are designed the same, therefore they have specific amperage capacities.

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