26401 Load Calculations - Feeders and
Services Study Guide Test.
Load calculated at 2 circuit 1500VA. - CORRECT ANSWER Small Appliance Ciruit
Voltage drop formula 1
VD = (2*L*R*I)/1,000 - CORRECT ANSWER VD = voltage drop (in volts)
L = load center or total length in feet
R = conductor resistance per NEC Chapter 9, Table 8
I = current
The number 1,000 represents 1,000' or less of conductor.
Show window loads should be calculated at _____ per linear foot of show window. - CORRECT ANSWER
200VA
What is the minimum demand required for the portion of a feeder that supplies 30' of show windows?
6,000 VA
5,400 VA
3,000 VA
2,700 VA - CORRECT ANSWER ft x va = va
30ft x 200VA = 6,000VA
NEC 220.14(C)(2)
At 200 Volt-amperes per linear 300 mm (1 ft) of show window
Voltage drop formula 2
VD = (2*L*K*I)/CM - CORRECT ANSWER VD = voltage drop
L = load center or total length in feet
, K= constant (12.9 for copper conductors; 21.2 for aluminum conductors)
I = current
CM= area of the conductor in circular mils (from NEC Chapter 9, Table 8)
Feeder conductor size is adjusted when?
The load supplied is a continuous-duty load.
More than three current-carrying conductors are in a raceway.
The ambient temperature surrounding conductors exceeds temperature ratings.
Voltage drop exceeds 3% for feeders or 5% for the combination of the feeder and branch circuit.
All of the above - CORRECT ANSWER All of those above
In calculating feeder-circuit conductors, if noncontinuous loads equal 450 amperes and continuous loads
equal 550 amperes, what is the total calculated feeder load that the conductors must handle?
A. 1137.50 amperes
B. 1100 amperes
C. 950 amperes
D. 1317.50 amperes - CORRECT ANSWER In order to calculate the total feeder load, you must add 100%
of noncontinuous loads to 125% of continuous loads.
450 + (1.25 × 550) = 1137.50 amperes
Using the 25' tap rule, what is the minimum size copper THWN conductor required for a tap from a
400A, 480V, 3Phase feeder?
1/0
2/0
No. 1
No. 2 - CORRECT ANSWER 1/0
Which of the following factors does not affect conductor ampacity adjustments?
Services Study Guide Test.
Load calculated at 2 circuit 1500VA. - CORRECT ANSWER Small Appliance Ciruit
Voltage drop formula 1
VD = (2*L*R*I)/1,000 - CORRECT ANSWER VD = voltage drop (in volts)
L = load center or total length in feet
R = conductor resistance per NEC Chapter 9, Table 8
I = current
The number 1,000 represents 1,000' or less of conductor.
Show window loads should be calculated at _____ per linear foot of show window. - CORRECT ANSWER
200VA
What is the minimum demand required for the portion of a feeder that supplies 30' of show windows?
6,000 VA
5,400 VA
3,000 VA
2,700 VA - CORRECT ANSWER ft x va = va
30ft x 200VA = 6,000VA
NEC 220.14(C)(2)
At 200 Volt-amperes per linear 300 mm (1 ft) of show window
Voltage drop formula 2
VD = (2*L*K*I)/CM - CORRECT ANSWER VD = voltage drop
L = load center or total length in feet
, K= constant (12.9 for copper conductors; 21.2 for aluminum conductors)
I = current
CM= area of the conductor in circular mils (from NEC Chapter 9, Table 8)
Feeder conductor size is adjusted when?
The load supplied is a continuous-duty load.
More than three current-carrying conductors are in a raceway.
The ambient temperature surrounding conductors exceeds temperature ratings.
Voltage drop exceeds 3% for feeders or 5% for the combination of the feeder and branch circuit.
All of the above - CORRECT ANSWER All of those above
In calculating feeder-circuit conductors, if noncontinuous loads equal 450 amperes and continuous loads
equal 550 amperes, what is the total calculated feeder load that the conductors must handle?
A. 1137.50 amperes
B. 1100 amperes
C. 950 amperes
D. 1317.50 amperes - CORRECT ANSWER In order to calculate the total feeder load, you must add 100%
of noncontinuous loads to 125% of continuous loads.
450 + (1.25 × 550) = 1137.50 amperes
Using the 25' tap rule, what is the minimum size copper THWN conductor required for a tap from a
400A, 480V, 3Phase feeder?
1/0
2/0
No. 1
No. 2 - CORRECT ANSWER 1/0
Which of the following factors does not affect conductor ampacity adjustments?
