Breaker selection for wiring protection in North America.

Makes it easy to select a breaker type based on the wire size for the North American market and the short-circuit current of the electrical system.

Model selection for wiring protection

G-TWIN Series G-TWIN Series Fuji Electric FA Components & Systems Co.,Ltd.

V20210329

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Model selection
for North America

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Select a UL489 certified MCCB or ELCB type when applying the AWG (American Wire Gauge) system.

The AWG size resistance corresponds to the 20℃ value in the UL83 Table 15, and the reactance corresponds to the value when IV (or VV) wires are formed into three-wire strands.

The allowable current-carrying capacity indicates the allowable current value for the types (RHW, THHW, THW, THWN, XHHW, USE, ZW: 30°C to 75°C) in NFPA 70 Table 310.15(B)(16).

The short-circuit current is obtained using a simple calculation based on the 3-phase transformer capacity, short-circuit impedance, and the resistance for the AWG size.

Three-phase transformer capacity [kVA]

Secondary rated voltage [V]

Short-circuit impedance Cross reference of transformer capacity [kVA] and short-circuit impedance [%]

X / R ratio

Secondary rated current [A]

A1-point short-circuit current [kA]

Selection method

[CB1]

Rated current [A]

Molded case circuit breaker (MCCB) selection type

Earth leakage circuit breaker (ELCB) selection type

* () Indicates the breaking capacity [kA].

[Connection wire]

AWG, kcmil size

(mm²)

Allowable current [A]

No. / phase [pcs.]

Length [m]

A2-point short-circuit current [kA]

[CB2]

Rated current [A]

Molded case circuit breaker (MCCB) selection type

Earth leakage circuit breaker (ELCB) selection type

* () Indicates the breaking capacity [kA].

Short-circuit impedance at rated current

Rated power [kVA]			Minimum short-circuit impedance [%]
25	to	630	4.0
631	to	1,250	5.0
1,251	to	2,500	6.0
2,501	to	6,300	7.0
6,301	to	25,000	8.0
25,001	to	40,000	10.0
40,001	to	63,000	11.0
63,001	to	100,000	12.5
100,001	to		> 12.5

AWG number (reference values in kcmil) and mm²

AWG number	kcmil	(mm²)	Allowable current [A]
Not applicable size.	800	405.4	490
	750	380.0	475
	700	354.7	460
	600	304.0	420
Red letters are the numbers when specifying the size.	500	253.4	380
	400	202.7	335
	350	177.3	310
	300	152.0	285
	250	126.7	255
4/0	211.600	107.2	230
3/0	167.772	85.03	200
2/0	133.079	67.42	175
1/0	105.560	53.49	150
1	83.694	42.41	130
2	66.358	33.62	115
3	52.624	26.66	100
4	41.738	21.15	85
6	26.244	13.80	65
8	16.152	8.368	50
10	10.384	5.262	35
12	6.530	3.309	25
14	4.107	2.082	20