TMAG 4005 – Chapter 2 Review Questions
Part 1—Electrical Features
1. What does a plan show about electrical outlets?
(Pg. 33) Electrical symbols used on an architectural plan show the location and type of electrical
device required.
2. What is an outlet?
(Pg. 33) Outlet is a point on the wiring system at which current is taken to supply utilization
equipment.
3. Match the following switch types with the proper symbol. (Pg. 37)
a. single-pole
d___ Sp
b. three-way
c___ S4
c. four-way
a___ S
d. single-pole with pilot light
b___ S3
4. The plans show curved lines running between switches and various outlets. What do these lines
indicate?
(Pg. 37, Figure 2-9) Switch leg; connects switched outlets with control points
5. Why are the lines referred to in problem 4 usually curved?
(Pg. 34) Curved lines are used to differentiate the electrical circuitry from the building construction
drawing lines.
6.
a. What are junction boxes used for?
Junction boxes are used as support for devices and lighting fixtures as well as protection wires and
terminals. The boxes will contain the arch blast that could occur during a fault.
b. Are junction boxes normally used in wiring the first floor? Explain.
When you have electrical outlets, appliance attachment or just the joining of wires together you must
have a junction box that must be accessible, whether it is on the first floor or any where else.
c. Are junction boxes normally used to wire exposed portions of the basement? Explain.
Yes, because exposed portion of the wiring below 8 feet are required to be protected from physical
damage and boxes are required anywhere you have wires spliced.
7. How are standard sectional switch (device) boxes mounted?
NEC 314.20 states that boxes must be mounted so that they will be set back not more than 1/4in.
(6mm) in noncombustible walls or ceilings and flush when installed in combustible. (pg.-43)
8.
a. What is an offset bar hanger?
A bar that is offset to allow the box to set out a determined amount, the hanger also allows the box to
be located away from the stud (pg.-41; Figure 2-13)
b. What types of boxes may be used with offset bar hangers?
Boxes that are designed to be used with the rated hanger, which means that they must be able to be
attached to the offset bar hanger. The book shows a round fixture box but most any type of steel box
could be used, but the set back may not be correct or may have to be adjusted for. (pg.-41; Figure 213)
9. What methods may be used to mount luminaires to an outlet box fastened to an offset bar hanger?
The luminaries that weight less than 6-lbs maybe installed with 6-32 screws if it is wall mount and 832’s most any where else up to 50-lbs. Then special support is needed for the box. (pg. 43)—NEC
314.27(A) and (B)
10. What advantage does a 4 in. octagon box have over a 3 ¼ in. octagon box?
The additional size will allow a greater number of conductors to enter and exit the box. The depth of
the box can also be greater with a 4-in. octagon box than a 3 ¼-in.
11. What is the size of the opening of a switch (device) box for a single device?
The dimensions of a standard switch box is 2 in. x 3 in. (pg. 46)
12. The space between a door casing and a window casing is 3 ½ in. (88.9 mm). Two switches are to be
installed at this location. What type of switches will be used?
A piggy-back switch, which means the switches are stacked in the same area as a single switch. A
standard 2-gang square box requires 4 inches so you can only use a single-gang box. (pg. 47)
13. Three switches are mounted in a 3-gang switch (device) box. The wall plate for this assembly is called
a three-ganged cover plate.
14. The mounting holes in a device (switch) box are tapped for No. 6-32 screws. The mounting holes in
an outlet box are tapped for No. 8-32 screws. The mounting holes in metal boxes for attaching
equipment grounding conductors are tapped for 10-32 screws.
15.
a. How high above the finished floor in the living room are switches located? 46 in. (pg. 64;
Tabla 2-2)
b. How high above the garage floor are switches located? 46in. (pg. 64; Tabla 2-2)
16.
a. How high above the finished floor in the living room are receptacles located? 12in (pg. 64;
Tabla 2-2)
b. How high above the garage floor are receptacles located? 46 in (pg. 64; Tabla 2-2)
17. Outdoor receptacle outlets in this dwelling are located 18 in. above grade. (pg. 52)
18. In the spaces provided, draw the correct symbol for each of the descriptions listed in (a) through (r).
a.
_________ Lighting panel
b.
_________ Clock outlet
c.
_________ Duplex outlet
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
_________ Outside telephone
_________ Single-pole switch
_________ Motor
_________ Duplex outlet, split-wired
_________ Lampholder with pull switch
_________ Weatherproof outlet
_________ Special-purpose outlet
_________ Fan outlet
_________ Range outlet
_________ Power panel
_________ 3-way switch
_________ Push button
_________ Thermostat
_________ Electric door opener
_________ Multioutlet assembly
19. The front edge of a box installed in a combustible wall must be flush with the finished surface. (pg.
48)
20. List the maximum number of 12 AWG conductors permitted in the following metal boxes: (pg 60)
a. 4 in. x 1 ½ in. octagon box. 6
b. 4 11⁄16 in. x 1 ½ in. square box. (4 11⁄16 in. x 4 11⁄16 in. x 1 ½ in)/2.25 = 14
c. 3 in. x 2 in. x 3 ½ in. device box. 8
21. When a switch (device) box is nailed to a stud, and the nail runs through the box, the nails must not
interfere with the wiring space. To accomplish this, keep the nail: C (pg 49; NEC 314.23)
a. halfway between the front and rear of the box.
b. a maximum of ¼ in. (6 mm) from the front edge of the box.
c. a maximum of ¼ in. (6 mm) from the rear of the box.
22. Hanging a ceiling luminaire directly from a plastic outlet box is permitted only if the box is rated for
a luminaire and if it weighs less than 6 lbs. then 6-32 screws can be used.
23. It is necessary to count luminaire wires when counting the permitted number of conductors in a box
according to 314.16. True or false? FALSE
24. Table 314.16(A) allows a maximum 10 ten wires in a certain box. However, the box will have two
cable clamps and one fixture stud in it. What is the maximum number of wires allowed in this box? 8
25. When laying out a job, the electrician will usually make a layout of the circuit, taking into
consideration the best way to run the cables and/or conduits and how to make up the electrical
connections. Doing this ahead of time, the electrician determines exactly how many conductors will be
fed into each box. With experience, the electrician will probably select two or three sizes and types of
boxes that will provide adequate space to“Meet Code.”Table 314.16(A) of the Code shows the
maximum number of conductors permitted in a given size metal box. In addition to counting the number
of conductors that will be in the box, what is the additional volume that must be provided for the
following items? Enter single or double volume allowance in the blank provided. (Pg. 58; Table 2-1)
a. one or more internal cable clamps: single-volume allowance.
b. for a fixture stud: single-volume allowance.
c. for one or more wiring devices on one yoke: double-volume allowance.
d. for one or more equipment grounding conductors: single-volume allowance.
26. Is it permissible to install a receptacle outlet above an electric baseboard heater?
No, page 63 states that receptacles are not permitted to be located above an electric baseboard
heating unit.
27. What is the maximum weight of a luminaire permitted to be hung directly from an outlet box in a
ceiling? 50 lb.
28. Two 12-2 AWG and two 14-2 AWG nonmetallic-sheathed cables enter a box. Each cable has an
equipment grounding conductor. The 12 AWG conductors are connected to a receptacle. Two of the 14
AWG conductors are connected to a toggle switch. The other two 14 AWG conductors are spliced
together because they serve as a switch loop. The box contains two cable clamps. Calculate the
minimum cubic-inch volume required for the box.
Ground Wire----#12 (2.25cu. in.)—1 x 2.25----------2.25 cu. in.
Conductors:
2—#12/2 ---- 2 x 2 x 2.25 ------------------------------9.00 cu. in.
2—#14/2 ---- 2 x 2 x 2.00 ------------------------------8.00 cu. in.
Devices:
1—toggle switch –1 x 2 x 2.25 ------------------------4.50 cu. in.
1—receptacle –1 x 2 x 2.25 ----------------------------4.50 cu. in.
Fittings (clamps)
2—cable clamps—1 x 2.25 ----------------------------2.25 cu. in.
------------------------------------------------------------- 31.50 cu. in.
29. Using the same number and size of conductors as in problem 28, but using electrical metallic tubing,
calculate the minimum cubic-inch volume required for the box. There will be no separate equipment
grounding conductors, nor will there be any clamps in the box.
Ground Wire—must figure on one ground wire due to the LOCAL CODE requirement of all conduit
systems requiring a ground wire.
(The answers will be the same because the electrical metallic tubing will require the use of metallic
connectors that must enter the box, you would count them as fittings, which means that no matter how
many fittings are coming into the box the you will figure it at (1-times the cubic inch of the largest
conductor that enters the box. But…)
Ground Wire----#12 (2.25cu. in.)—1 x 2.25----------2.25 cu. in.
Conductors:
2—#12/2 ---- 2 x 2 x 2.25 ------------------------------9.00 cu. in.
2—#14/2 ---- 2 x 2 x 2.00 ------------------------------8.00 cu. in.
Devices:
1—toggle switch –1 x 2 x 2.25 ------------------------4.50 cu. in.
1—receptacle –1 x 2 x 2.25 ----------------------------4.50 cu. in.
Fittings (clamps)
None
------------------------------------------------------------- 29.25 cu. in.
30. To allow for adequate conductor length at electrical outlet and device boxes to make up
connections, 300.14 requires that not less than [3 in. (75 mm), 6 in. (150 mm), 9 in. (225 mm)] of
conductor length be provided. This length is measured from where the conductor emerges from the
cable or raceway to the end of the conductor. For box openings having any dimension less than 8 in.
(200 mm), the minimum length of conductor measured from the box opening in the wall to the end of
the conductor is [3 in. (75 mm), 6 in. (150 mm), 9 in. (225 mm)]. (Circle the correct answers.)
31. When wiring a residence, what must be considered when installing wall boxes on both sides of a
common partition that separates the garage and a habitable room?
The fire rating of the walls must be maintained which means that boxes may not be mounted “back to
back” or in the same air void. A separation of 24 inches horizontal must be maintained unless the
boxes are listed as being fire resistant. The boxes that are on the fire rated wall must be properly
protected or encased with a fire puddy.
32. Does the NEC allow metal raceways to be used with nonmetallic boxes?
Yes _XX_ No ____, NEC _ NEC 314.3_
Part 2—structural features
1. To what scale is the basement plan drawn?
¼” = 1’-0”
2. What is the size of the footing for the steel Lally columns in the basement? Refer to Plan 1 of 10. (Lally
is the trademark used for a concrete-filled steel cylinder used as a supporting member for wood or steel
girders and beams. The Lally column was named after John Lally, born in Ireland in 1859. The term lolly
is also used.) 24”*24”*12”
3. To what kind of material will the front porch lighting bracket luminaire be attached? Wood sidings
4. Give the size, spacing, and direction of the ceiling joists in the workshop. 2”*10” @ 16” OC – front to
back
5. What is the size of the lot on which this residence is located? 150.5’ * 99.0’
6. The front of the house is facing which compass direction? South-South West
7. How far is the front garage wall from the curb? 20.916’
8. How far is the side garage wall from the property lot line? 25’
9. How many steel Lally columns are in the basement and what size are they? Six columns, 3” diameter
10. What is the purpose of the I-beams that rest on top of the steel Lally columns? Support the 2”*10”
joists
11. To make sure that switch boxes and outlet boxes are set properly in the garage walls and ceilings, we
need to know the thickness of the gypsum wallboard used in these locations. In the garage, what is the
thickness and type of the gypsum wallboard?
a. On the“warm walls”of the garage? 5/8”
b. On the“cold walls”of the garage? ½”
c. On the ceiling of the garage? 5/8”
12. Where is access to the attic provided? Garage
13. Give the thickness of the outer basement walls. 12”
14. What material is indicated for the foundation walls? 12”*8”*16” concrete blocks
15. Where are the smoke detectors located in the basement? Only one in front of the stairs
What is the ceiling height in the basement workshop from the bottom of the joists to the floor? 8’
16. Give the size and type of the front door. Double door, 2’8” x 6’8”x 1 ¾” decorative w/Lite
17. What is the stud size for the partitions between the bathrooms in the bedroom area where
substantial plumbing is to be installed? 6”
18. Who is to furnish the range hood? Owner
19. Who is to install the range hood? Electrical Contractor
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TMAG 4005 – Chapter 2 Review Questions Part 1—Electrical