Example Problem: Level 3
from Problems: A Key Factor in PBL Barbara Duch,

(page 1)

Sharon and Stanley are building their dreamhouse. They have already designed the layout of all the rooms, with the help of Stan's father who is an architect. You are good friends with Sharon and Stan and since you've just studied circuits in your physics class, you are interested in the wiring plans for the new home. Sharon tells you that the house will have 4 bedrooms, a family room, living room, dining room, 2 bathrooms, a utility/wash room, and a combination kitchen/breakfast area. Stan tells you that he doesn't know how many circuits his house needs in order to be safe. In fact, Stan isn't even sure he knows what a circuit is, or how a circuit breaker works. Does he need some 240 V lines as well as 120 V ? What voltage are the electrical lines coming into the house? How are the ratings on the circuit breakers determined? How are houses wired?

Using your knowledge of physics, answer Stan's questions. If you don't know the answer, where can you find the information you need? What questions should you ask Sharon and Stan in order to determine their wiring needs?

(page 2)

Sharon tells you that they will have many appliances in the kitchen. A microwave, refrigerator, blender, toaster oven, toaster, can opener, electric fry pan, electric wok, mixer, clock radio, clock, crock pot, and dishwasher. Stan says that his computer and printer, and Sharon's ironing and sewing "stuff" will be in the same bedroom. Stan uses an electric razor, while Sharon uses a blow dryer and curling iron in the main bath.

They also inform you that in the morning, Stan cooks breakfast while Sharon does her hair in the bathroom. And in the evening, while Sharon cooks dinner, Stan works on his computer or watches TV in the living room. Sharon likes to sew or iron while Stan does the budget on the computer.

They show you a sketch of the floor plans for the house. The dimensions of the rooms are as follows: kitchen: 12'x15', living room: 15'x25', spare bedroom: 10'x12'.

Is there a minimum number of outlets that must be wired for each room? How are overhead light switches wired into the circuit?

Sketch the wiring diagram for the kitchen. Do you need more than one circuit breaker for the kitchen? Design the wiring so that no circuit breaker opens while Sharon is using several of her appliances cooking dinner. Be sure to give several examples of multiple appliance use.

When you have answered these questions and sketched the wiring diagram, check with your instructor before doing the final activity.

Construct a wiring plan for the kitchen, main bathroom, spare bedroom, and living room in the new house with the minimum number of circuits which will still suit Stan's and Sharon's mode of living. Your design should insure that no circuit breakers will trip during the busy mornings or evenings. Be sure to include the normal items in rooms (lights, stereo, VCR, etc.) as you plan your wiring diagram.

Written by Barbara J. Duch
May, 1995; Revised January 1996

 "http://www.udel.edu/pbl/overload.html" Last updated Feb. 20, 1997. Copyright Barbara Duch, Univ. of Delaware, 1996.