Chapter 12 Branch Circuits and Feeders 159
Copyright Goodheart-Willcox Co., Inc.
Sample Problem 12-15 Continued
The total reduced lighting load is determined:
Lighting load = 10,000 VA + 32,000 VA + 8000 VA
= 50,000 VA
The air-conditioning load must be calculated. The voltage
is 208 V × 1.732 (360 volts) due to the three-phase supply:
Air-conditioning load = 360 V × 30 A
= 10,800 VA
This is larger than the heating load, so the air-conditioning
load is used in the total load. The load per room is
10,800 VA, so it must be multiplied by 200 to determine
the total load:
Total air-conditioning load = 10,800 VA × 200
= 2,160,000 VA
General equipment load = 30,000 VA × 1.25
= 37,500 VA
All loads are added to determine the total load:
Total load = 50,000 VA + 2,160,000 VA + 37,500 VA
= 2,247,500 VA
The total current can be calculated:
I =
P
E
=
=
2,247,500 VA
6243 A
360 V
The total current is 6243 A.
Review Questions
Answer the following questions using the information
provided in this chapter.
1. What type of conductors extend beyond the final
overcurrent device?
2. What type of conductors originate at the main disconnect
device and terminate at panelboards and load centers?
3. How is the rating of a branch circuit determined?
4. What is the smallest conductor permitted for use in a
branch circuit?
5. What color insulation is used on equipment grounding
conductors?
6. Define continuous load.
7. What are the five general types of branch-circuit loads?
8. If the exact number of receptacles is unknown, how
can the receptacle load be calculated?
9. How is the show-window lighting load determined?
10. How many receptacles must be installed for the
nondwelling receptacle loads derating to reduce the
total receptacle load?
11. A large hotel has 2500 ft2 of hallway space. Assuming
continuous load, how many volt-amperes should be
allowed for this load for service computation?
12. Calculate the general lighting load for a commercial
warehouse having an area of 90,000 ft2. Assume
continuous duty.
13. What is the demand factor used for four kitchen
equipment loads in a commercial cafeteria?
14. Compute the receptacle load for a department store
having 165 duplex receptacles.
15. A furniture store has 60 linear feet of show window.
Calculate this continuous load.
16. What is the minimum outside sign lighting load
required by the Code?
17. What is the general lighting load for a 50-room motel
where each room is 12′ × 20′?
18. A 24-hour service restaurant has 75 duplex recepta-
cles. Calculate the total load for feeder calculations.
19. What is the service demand for a small bank mea-
suring 2500 ft2 and supplied with 208/120-volt,
three-phase service? Assume lighting as continuous.
The bank has the following loads:
15 kW heating (208-volt)
7.5 hp air conditioning
50 linear feet of show window
25 duplex receptacles
20. A new high school is to be erected, supplied with
208/120-volt, single-phase power. The school has the
following dimensions and loads. Calculate the total
feeder conductor and feeder neutral loads. Assume
all lighting loads are continuous.
30,000 ft2 classroom space
6000 ft2 auditorium
5000 ft2 cafeteria (use restaurant load)
10 kW outside lighting (120-volt)
225 duplex receptacles (120-volt)
(Continued on the following page.)