Estimation of current carrying capacity of insulated conductors

Conductor cross section (mm 2 )	1	1.5	2.5	4	6	10	16	25	35	50	70	95	120
Current carrying is cross section multiple	9			8	7	6	5	4	3.5	3		2.5
Current carrying capacity (A)	9	14	twenty three	32	48	60	90	100	123	150	210	238	300

Estimation formula:
2.5 times nine, minus one sign upward.
35 times 3.5, minus one sign upward in pairs.
Add discounts when conditions change, 90% discount for high temperature copper upgrade.
234 for the number of pipes, 876% discount for full load current.
Note:
(1) The formula in this section does not directly indicate the current carrying capacity (safety current) of various insulated wires (rubber and plastic insulated wires), but rather expresses it by "multiplying the cross section by a certain multiple" and obtains it through mental calculation. It can be seen from Table 5.3 that the multiple decreases as the cross section increases.
"2.5 times nine, minus one sign upward" refers to various cross-section aluminum core insulated wires of 2.5mm' and below, whose current carrying capacity is about 9 times the number of cross sections. For example, the current carrying capacity of a 2.5mm' conductor is 2.5×9＝22.5(A). The relationship between the current carrying capacity and the number of cross-sections of conductors of 4mm' and above is arranged in ascending order from the wire number, and the multiples are reduced by 1, that is, 4×8, 6×7, 10×6, 16×5, 25×4.
"Thirty-five times three and a half, minus five in pairs", means that the current carrying capacity of a 35mm' conductor is 3.5 times the number of cross-sections, that is, 35×3.5＝122.5(A). For conductors of 50mm' and above, the relationship between the current carrying capacity and the number of cross-sections changes to two wire numbers in a group, and the multiples are reduced by 0.5. That is, the current carrying capacity of 50 and 70mm' conductors is 3 times the number of cross-sections; the current carrying capacity of 95 and 120mm' conductors is 2.5 times the number of their cross-sectional areas, and so on.
"Conditions change and discounts are added, and high temperature copper is upgraded with a 90% discount". The above formula is based on aluminum core insulated wires and exposed laying at an ambient temperature of 25℃. If the aluminum core insulated wire is laid in the open in an area where the ambient temperature is higher than 25℃ for a long time, the current carrying capacity of the wire can be calculated according to the above formula, and then 10% discount can be applied; when the current carrying capacity of the copper core insulated wire is slightly larger than that of the aluminum wire of the same specification, the current carrying capacity of the wire with one wire size larger than that of the aluminum wire can be calculated according to the above formula. For example, the current carrying capacity of a 16mm' copper wire can be calculated according to the 25mm2 aluminum wire.