Overcurrent Protection Size
15 20 25 30 35 40 45 50 60 70 80 90 100 110 125 150 175 200 225 250 300 350 400 400
Copper (1) Wire 75ºC Terminal
14 12 10 10 8 8 8 8 6 4 4 3 3 2 1 1/0 2/0 3/0 4/0 250 kcmil 350 kcmil 400 kcmil 500 kcmil 600 kcmil
Maximum (2) Continuous Ampe Ampere re Load Load
12 16 20 24 28 32 36 40 48 56 64 72 80 88 100 120 140 160 180 200 240 268(5) 304(5) 320
Race Racewa wayy
(3)
Equipment (4) Ground Wire
½” ½” ¾” ¾” 1” 1” 1” 1” 1” 1¼” 1¼” 1¼” 1¼” 1½” 2” 2” 2” 2½” 2½” 3” 3½” 3½” 4” 4”
14 12 10 10 10 10 10 10 10 8 8 8 8 6 6 6 6 6 4 4 4 3 3 3
120V
208V
240V
277V
480V
208V
240V
48 0 V
1,440 1,920 2,400 2,880 3,360 3,840 4,320 4,800 5,760 6,720 7,680 8,640 9,600 10,560 12,000 14,400 16,800 19,200 21,600 24,000 28,800 32,160 36,480
2,496 3,328 4,160 4,992 5,824 6,656 7,488 8,320 9,984 11,648 13,312 14,976 16,640 18,304 20,800 24,960 29,120 33,280 37,440 41,600 49,920 55,744 63,232
2,880 3,840 4,800 5,760 6,720 7,680 8,640 9,600 11,520 13,440 15,360 17,280 19,200 21,120 24,000 28,800 33,600 38,400 43,200 48,000 57,600 64,320 72,960
3,324 4,432 5,540 6,648 7,756 8,864 9,972 11,080 13,296 15,512 17,728 19,944 22,160 24,376 27,700 33,240 38,780 44,320 49,860 55,400 66,480 74,236 84,208
5,760 7,680 9,600 11,520 13,440 15,360 17,280 19,200 23,040 26,880 30,720 34,560 38,400 42,240 48,000 57,600 67,200 76,800 86,400 96,000 115,200 128,640 145,920
4,323 5,764 7,205 8,646 10,087 11,528 12,969 14,410 17,292 20,174 23,056 25,938 28,820 31,703 36,026 43,231 50,436 57,641 64,846 72,051 86,461 96,549 109,518
4,988 6,651 8,314 9,976 11,639 13,302 14,964 16,627 19,953 23,278 26,604 29,929 33,254 36,580 41,568 49,882 58,195 66,509 74,822 83,136 99,763 111,402 126,367
9,976 13,302 16,627 19,953 23,278 26,604 29,929 33,254 39,905 46,556 53,207 59,858 66,509 73,160 83,136 99,763 116,390 133,018 149,645 166,272 199,526 222,804 252,733
38,400
66,560
76,800
88,640
Conductor size based on 75°C terminal rating [110.14(C)(1)]. Ampacity based on our 90°C current-carrying conductors [Table 310.15(B)(3)(a) and Table 310.15(B)(16)]. (2) Maximum continuous nonlinear load in an ambient temperature o 30°C limited to 80 percent o the overcurrent device rating or the c onductor ampacity, which ever is less [210.19(A), 240.6(A), 215.2(A)(1)]. (1)
Conversion Formulas
Area o Circle = πr2 Break-even Dollars = Overhead Cost $/Gross Prot % Busbar Ampacity AL = 700A sq. in. and CU = 1,000A sq. in. Centimeters = Inches/2.54 Inch = 0.0254 Meters Inch = 2.54 Centimeters Inch = 25.40 Millimeters Kilometer = 0.6213 Miles Length o Coiled Wire = Diameter o Coil (average) x Number o Coils x π Lightning Distance in Miles = Seconds between fash and thunder/4.68 Meter = 39.37 Inches Mile = 5,280 t, 1,760 yards, 1,609 meters, 1.609 km Millimeter = 0.03937 Inch Selling Price = Estimated Cost $/(1 - Gross Prot %) Speed o Sound (Sea Level) = 1,128 ps or 769 mph Temp C = (Temp F - 32)/1.80 Temp F = (Temp C x 1.80) + 32 Yardd = 0.9144 Yar 0.9144 Meters Meters Electrical Formulas Based on 60 Hz
Capacitive Reactance (XC) in Ohms = 1/(2 C) Eective (RMS) ac Amperes = Peak Amperes x 0.707 Eective (RMS) ac Volts = Peak Volts x 0.707 Eciency (percent) = Output/Input x 100 Eciency = Output/Input Horsepower = Output Watts/746 Inductive Reactance (XL) in Ohms = 2 L Input = Output/Eciency
115,282
133,108
266,035
To ensure ease o installation, raceways are sized to six THHN conductors in PVC conduit [Annex C.10]. Copper equipment grounding conductor is sized in accordance with Table 250.122. (5) Maximum continuous load is limited to 80 percent o 75°C conductor ampacity because the conductor ampacity is lower than the overcurrent protection device rating. (4)
Parallel Circuits
Note 1: Total resistance is always less than the smallest resistor RT = 1/(1/R1 + 1/R2 + 1/R3 +...) Note 2: Total current is equal to the sum o the currents o all parallel resistors Note 3: Total power is equal to the sum o power o all parallel resistors Note 4: Voltage is the same across each o the parallel resistors Series Circuits
Note 1: Total resistance is equal to the sum o all the resistors Note 2: Current in the circuit remains the same through all the resistors Note 3: Voltage source is equal to the sum o voltage drops o all resistors Note 4: Power o the circuit is equal to the sum o the power o all resistors Secondary Amperes single-Phase = VA/Volts
153,600
(3)
Neutral Current (Wye) = √[(L12 + L22 + L32 ) – [(L1 x L2 ) + (L2 x L3 ) + (L1 x L3 )]] Output = Input x Eciency Peak AC Volts = Eective (RMS) AC Volts x √2 Peak Amperes = Eective (RMS) Amperes x √2 Power Factor (PF) = Watts/VA VA (apparent (apparent power) = Volts ts x Ampere or Watts/Power ts/Power Factor Factor VA single-Phase ngle-Phase = Volts x Amperes Amperes VA three-Ph three-Phase ase = Volts x Amperes Amperes x √3 Watts (real power) Single-Phase = Volts x Amperes x Power Factor Watts (real power) Three-Phase = Volts x Amperes x Power Factor x √3
Transformer Amperes Amperes
Maximum Continuous Three-Phase VA Load (2)
Maximum Continuous Single-Phase VA Load (2)
Secondary Amperes three-Phase = VA/(Volts x √3) Secondary Available Fault single-Phase = VA/(Volt VA/ (Volts x %impedance) mpedance) Transformer Amperes (continued)
Secondary Available Fault three-Phase = VA/(Volts Volts x √3 x %Impedance) %Impedance) Delta 4-Wire: Line Amperes = Phase (one winding) Amperes x √3 Delta 4-Wire: Line Volts = Phase (one Winding) Volts Delta 4-Wire: High-Leg Voltage (L-to-G) = Phase (one winding) Volts x 0.50 x √3 Wye: Line Volts = Phase (one winding) Volts x √3 Wye: Line Amperes = Phase (one winding) Amperes Voltage Drop
VD (single-Phase) ngle-Phase) = 2KID/Cmil 2KID/Cmil VD (three-Pha (three-Phase) se) = √3 √3 KID/Cmil Cmil Cmil (single-Phase) = 2KID/VD Cmil (three-Phase) = √3 KID/VD Code Rules
Breaker/Fuse Ratings – 240.6(A) Conductor Ampacity – 310.15 and Table 310.15(B)16 Equipment Grounding Conductor – 250.122 Grounding Electrode Conductor – 250.66 Motor Conductor Size – 430.22 (Single) 430.24 (Multiple) Motor Short-Circuit Protection – 430.52 Transormer Overcurrent Protection – 450.3
Legend π(Pi) = 3.142 (approximately) √2 = 1.414 (approximately) √3 = 1.732 (approximately) = requency r = radius d = diameter C = Capacitance (arads) L = Inductance (henrys) Cmil = Circular Mils VD = Volts Drop I = Amperes o load D = Distance one way K75°C = (12.90 ohms CU) (21.20 ohms AL)
