Concept explainers
Determine the ohms-per-mil-foot of an aluminum conductor located in an area with a temperature of 104°F (40°C).
Use the NEC to determine the ampacity of the following conductors.
To find:
The ohms-per-mil-foot of an aluminum conductor located in an area with a temperature of 104°F (40°C). Also, use the NEC to determine the ampacity of the following conductors.
Answer to Problem 10PP
The resistance of a 16 AWG copper conductor is 1.27 ohms.
Explanation of Solution
The resistivity, K of the conductor at temperature T is
where, Rref is the resistance at 20°C
From Figure 10-16, the value of Rref can be obtained
Tref is the reference temperature (20°C)
Substituting the values, we get
(a) From Table 310.15(B)(16), we know that the maximum ampacity of a 10 AWG copper conductor of Type RHW insulation is 35A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
(b) From Table 310.15(B)(16), we know that the maximum ampacity of a 350 kcmil copper conductor of Type XHH insulation is 350A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
If a raceway is to contain more than three conductors, the ampacity of the conductors must be de-rated. The correction factors for six copper conductors is 80%. Thus, after correction, the ampacity will be
(c) From Table 310.15(B)(16), we know that the maximum ampacity of a 2 AWG aluminum conductor of Type TW insulation is 75A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
(d) From Table 310.15(B)(16), we know that the maximum ampacity of a 3/0 AWG aluminum conductor of Type XHHW-2 insulation is 175A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
If a raceway is to contain more than three conductors, the ampacity of the conductors must be de-rated. The correction factors for nine aluminum conductors is 70%. Thus, after correction, the ampacity will be
(e) From Table 310.15(B)(16), we know that the maximum ampacity of a 500 kcmil copper conductor of Type THWN insulation is 380A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
If a raceway is to contain more than three conductors, the ampacity of the conductors must be de-rated. The correction factors for six copper conductors is 80%. Thus, after correction, the ampacity will be
(f) From Table 310.15(B)(16), we know that the maximum ampacity of a 6 AWG copper conductor of Type THW-2 insulation is 75A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
(g) From Table 310.15(B)(16), we know that the maximum ampacity of a 2/0 AWG aluminum conductor of Type UF insulation is 115A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
If a raceway is to contain more than three conductors, the ampacity of the conductors must be de-rated. The correction factors for 12 aluminum conductors is 50%. Thus, after correction, the ampacity will be
(h) From Table 310.15(B)(16), we know that the maximum ampacity of a 750 kcmil aluminum conductor of Type RHW-2 insulation is 435A and the rated temperature is
Thus, from Table 310.15(B)(2)(a), the correction factor of the ambient air temperature at
Thus, after correction, the ampacity will be
If a raceway is to contain more than three conductors, the ampacity of the conductors must be de-rated. The correction factors for 6 aluminum conductors is 80%. Thus, after correction, the ampacity will be
Thus, the table will be:
Want to see more full solutions like this?
Chapter 10 Solutions
EBK MINDTAP FOR HERMAN'S DELMAR'S STAND
- 3. The resistance of a conductor having length 1 area of cross section a and resistivity p is given as: a. pa/l b. pl/a c. pla d. /parrow_forwardWhat size ungrounded conductors do we need for the 60 amp load? All conductors have typeTHHN insulation.arrow_forwardHow many holes are there in a conductor?Please select one:a.Same number as free electronicsb.Only those produced with thermal energyc.Manyd.Nonearrow_forward
- Consider a three-core, three-phase, 50 Hz, 11 kV cable whose conductors are denoted as R, Y and B in the figure. The inter-phase capacitance (C₁) between each pair of conductors is 0.2 µF and the capacitance between each line conductor and the sheath is 0.4 µF. The per-phase charging current is C₂ HE C₁ ,C₁ Outer Sheatharrow_forwardThe resistance of the wire increases from 40 ohms at 10°C to 48.25 ohms at 60°C. Find the temperature coefficient of resistance at 0°C of the conductor material.arrow_forwardIf the cross sectional area of a conductor is doubled, then the resistance of the conductor remains the same. becomes half of the initial value. becomes double the initial value. becomes four times the initial value.arrow_forward
- Two conductors, one of copper and the other of iron, are connected in parallel and carry equalcurrents at 25°C. How many percent of the total current will the copper conductor carry if thetemperature is raised to 100°C? The temperature coefficients of resistance at 0 °C are 0.0043 /°Cand 0.0063 /°C for copper and iron, respectively.arrow_forwardA certain conductor is composed of strands that are arrangend in 6 layers. Each strand of this conductor has a diameter of 3.157 mm. Its resistivity is 22.17 nano-ohm-meter at 20 deg. celsius. What is the dc resistance of this conductor in milli-ohm/km at 54.1 deg. celsius if its inferred zero resistance temperature -151 celsius? Assume 1.25 % increase in resistance due to spiraling. (Hint: The number of strands = 3x2-3x+1, where x = no. of layers)arrow_forwardThe diameter of a cylindrical conductor A is 6 mm, and its length is 2 m. The diameter and length of a cylindrical conductor B of the same material as A arel3 mm and 1 m. The resistance of conductor B is 0.02 Determine resistance of conductor A, its temperature being the same as that of B.arrow_forward
- A 5 meter long conductor with diameter of 5 mm is connected to a source and an external resistance. The temperature of the conductor changes from 25 degrees to 35 degrees. Determine the resistivities and resistances at each temperature. Thermal coefficient of the conductor is 40 x 10^-3 and the conductivity at 20 degrees Celcius is 2.5465 x 10^4 per ohm-meterarrow_forwardtemperature rating that a conductor must have and still have 69 Ambient Tempere 4. The ampacity of 15 current-carrying 10 RHW aluminum conduc- tors in a raceway in an ambient temperature of 75'F is 1. gon factor for conductor ampacity in this location is (a) 12A (b) 15A (c) 22A (d) 30A 0.71 b0.82 0.88 0.96 5. Ain) uous load if the ambient temperature is 75°F and there are nine THHN conductor is required for a 19.70A noncontin- ne ambient temperature is 71"C, the minimum insulation current-carrying conductors in the raceway in a dry location. he capacity to carry current is (a) 14 (b) 12 (c) 10 A 60°C AI 90°C 105°C (d) 8 0 120°C 6. 6.11 Ampacity Adjustment [310.15(B)(3)(a)] The ampacity for each of nine current-carrying 10 THW conduc- tors installed in a 20 in. long raceway is 1 The ampacity of six current-carrying 4/0 XHHW aluminum con- ductors installed in a ground floor slab (wet location) is (a) 25A (b) 30A (c) 35A (d) 40A a) 135A 0) 144A (e) 185A 4 210Aarrow_forward38 docs.google.com/forms/d/e, resistor with a temperature coefficient at (20°C) 0.00393, determine the resistance at (80°C) ? * 1.24 Q O 1.42 Q 1.44 Q 7-What is the relative increase or decrease in conductivity of a conductor if the area is increasing by (30%) and the length is decreasing by (40%) ? The resistivity is fixed. * G2 =2.1667 G, 1 --arrow_forward
- Delmar's Standard Textbook Of ElectricityElectrical EngineeringISBN:9781337900348Author:Stephen L. HermanPublisher:Cengage LearningPower System Analysis and Design (MindTap Course ...Electrical EngineeringISBN:9781305632134Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. SarmaPublisher:Cengage Learning