Two Minute Drill: Raceways and Boxes 2017

Two Minute Drill: Raceways and Boxes 2017
©Ted “Smitty” Smith 2008, 2011, 2014, 2017

Instructions This speed drill is designed to help you practice calculations. The slides will transition in three and one half minutes instead of two minutes. Attempt to answer the questions and then when the slide show completes, Check your answer. When you reach the end of the drill all of the slides will be repeated without the timer so you will have time to check and verify your answers at that time. Click on the left mouse button to begin.

BOX FILL REMINDERS Junction Boxes with Conductors 6 AWG or Smaller
Important Things to Remember USE (B) The steps to the calculation are laid out step by step in the NEC Use the volume allowances found in Table (B) and apply them as required Count all the conductors entering the box and any conductor passing through the box Any conductor that passes through the box and has a loop that is 12” is or greater has to be counted as two conductors because later on it could be cut to make two conductors Does the box have any internal cable clamps If it does, count 1 volume allowance for each TYPE of internal cable clamp based on the largest conductor in the box Does the box have any fixture studs or fixture hickeys If it does, count 1 volume allowance for each type in the box based on the largest conductor in the box Does the box have any devices If it does, count 2 volume allowance for each yoke based on the largest conductor connected to the device. Now count 1 volume allowance for the equipment grounds based on the largest equipment ground in the box. These conductors do not carry current so it doesn’t matter how many you have. You only count 1 volume allowance. Any box that has a barrier installed for the purposes of separating systems or to meet code requirements. Each space separated by the barrier shall be calculated as if it was a separate box. Also the barrier has to be taken into account as space used in both spaces on either side of it. If it is not marked with its volume allowance, it is calculated at ½” if metal and 1” if non-metallic. IF A BOX CONTAINS A CONDUCTOR WHICH IS 4 AWG OR LARGER. The box fill rules of (B) do not apply. These boxes must be calculated using the Pull Box rules in Based on the raceways sizes entering the box Straight Pulls Must be at least 8 times the largest raceway entering the box Angle or U Pull Must be 6 times the largest conductor on one side then add the raceway sizes of all the other conduits on the same side. Do this this for any side that has raceways entering it. Raceways have to be installed in rows. So it there is more than one row raceways entering a side, then you only account for the row which gives you the highest result Any time two conduits in a box encircle the same conductor, the two conduits must be at least 6 times the largest diameter of the raceways apart.

Raceway Calculations Table 4 Table 5
Be sure to use the correct table for the type of raceway you are using Be sure to use the correct column 60% if the raceway is a nipple (24” or shorter) 40% if the raceway contains more than 2 conductors 31% of the raceway contains only two conductors 53% if the raceway contains only 1 conductor Be sure to use the area of the conductor, not the diameter Be sure to use the correct insulation Only use Table 5A if you are sizing for Compact Aluminum Conductors Notice the * at the end of the Table Rubber insulated conductors can be ordered with a nylon outer covering to help them pull through raceways. If the conductors you are using have the outer covering then use the values for RHH, RHW or RHW-2 that do not have an * If they do not have an outer covering use the values with the *

Metric versus Imperial
When doing the calculation simply use the values that are listed. If the question is asking for the Trade Size then use the Imperial values on Table 5 and the Imperial Values on Table 4 If the question is asking for the Metric Designator then use the Metric values on Table 5 and the Metric Values on Table 4 Don’t let this throw you off if the question is asked using Metric designators. The code book specifically tells us to not covert measurements. This is because the code book uses two different methods to do conversion depending on the application. SO……the code book gives us the conversions for us. Every measurement in the NEC is listed in both Metric (Standard) and Imperial ( What we Americans call Standard.)

Step 1: Determine the area used by the conductors.
Wireways, Gutters, ETC Step 1: Determine the area used by the conductors. Use the values in Table 5 for the size and insulation of the conductors. Get the total of all the conductors Step 2: Divide the total in step 1 by .20 (20%) or .40(40%) depending on the applicable Article to the right. Step 3: The answer to two will be the minimum area gutter or wireway you will need. Find the area of your box Multiply the width by the length Often times questions about wireway and gutter fill throw people off on the test. These calculations are actually fairly simple once you learn the process. The following articles use the formula to the right: Auxiliary Gutters % Cellular Concrete Floor Raceways % Cellular Metal Floor Raceways % Metal Wireways % Nonmetallic Wireways %

Question 1 A 4” x 1 ½” octagon junction box with a flat blank cover may contain no more than _____________ size 14 AWG conductors? A. 6 B. 7 C. 9 D. 10

Question 2 Two (2) size 12 AWG conductors are looped inside a junction box so that there is more than 12” of free conductor. The conductors are not spliced and do not terminate on devices. What volume allowance, in cubic inches, must be counted for the looped conductors? A cubic inches B cubic inches C. 4.5 cubic inches D. 9.0 cubic inches

Question 3 Which of the following auxiliary gutters can NOT be used to contain nine (9) 300 kcmil THHN aluminum conductors, three (3) 500 kcmil THHN Aluminum conductors and three (3) 2 AWG THHN copper conductors? A. 12” x 24” B. 6” x 12” C. 3” x 8” D. 4” x 10”

C. 3” x 8” 366.22 A minimum 30.6525” is required 3” x 8” is only 24”
Answer 3 Copyright 2005 Ted "Smitty" Smith

Question 4 A two gang device box is to contain two (2) size 12/2 AWG with ground nonmetallic sheathed cables connected to a duplex receptacle and two (2), size 14/2 AWG with ground nonmetallic sheathed cables connected to a single pole switch. The device box will contain four (4) internal clamps. The two gang box is required to have a volume of at least ________. A. 36 cubic inches B. 34 cubic inches C. 30 cubic inches D. 28 cubic inches

Answer 4 C. 30 cubic inches 314.16(B)(1-5) Table 314.16(B)
Copyright 2005 Ted "Smitty" Smith

Question 5 What is the minimum sized EMT conduit which can be used for the following conductors: Six (6) THHN Size 10 AWG Four (4) RHH with outercovering Size 8 One (1) THHN size 12 AWG A. ¾” B. 1” C. 1 ¼” D. 2”

Question 6 What is the minimum metric designator Rigid Metal Conduit which can be used for a conduit nipple which is 8” in length for the following conductors: Sixteen (16) THHN 10 AWG Eight (8) THW 6 AWG Ten (10) THHN 12 AWG A. 2” B. 1 ½” C. 1 ¾” D. 3”

Question 7 When a junction box will contain conductors of size 4 AWG or larger and all of the conduits enter on side and exit on the opposite side only , the length of the box shall not less than __________________ times the trade size of the largest raceway entering the box. A. 4 B. 6 C. 8 D. 24

Question 8 A two gang device box will contain two single switches. A permanent device barrier will be installed between the switches because they are switching two different phases of 277V lighting circuits. Each side of the barrier will contain a single pole switch and a 12/3 MC cable with ground. The barrier is nonmetallic and no volume allowance is marked on the barrier. What is the minimum volume required for each side of the barrier? A. 20 B. 29 C. 20 D. 14.5

Question 9 Determine the Maximum number of size 250 kcmil XHHW compact aluminum conductors permitted to be installed in a 4” x 4” x 6’ long metal wireway. A. Twenty B. Ten C. Eight D. nine

D. Nine 376. 22(A) 4 x 4 = 16 inches at any cross section 16 x. 20= 3
D. Nine (A) 4 x 4 = 16 inches at any cross section 16 x .20= 3.2 sq inches of fill permitted 3.2/.3421 for one conductor from Table 5A= 9.3 Answer 9 Copyright 2005 Ted "Smitty" Smith

Question 10 A fifty foot run of Schedule 40 PVC conduit is to contain the following copper conductors: Four (4) size 1 AWG XHHW One (1) size 6 AWG bare Determine the minimum trade size PVC required. A. 2 inches B. 1.5 inches C inches D. 1 inch

Answer 10 1.5 inches Table 1, Note 8 Table 4 Table 5 Table 8

Question 11 A metal wireway is to contain the following listed copper conductors: Eight (8) size 500 kcmil THWN Twenty four (24) size 2 AWG THWN Which one of the following listed wireways is the MINIMUM size to house the conductors? A. 10” x 10” B. 6” x 6” C. 8” x 8” D. 12” x 12”

C. 8” x 8” Table 5 376. 22(A) 500 kcmil=. 7073 x 8= 5. 6584 2 AWG =
C. 8” x 8” Table (A) 500 kcmil= x 8= AWG = x 24= Total= square inches /.20= square inches required An 8” x 8” = 64 square inches A 12” x 12” would also work but the questions asked which one is the MINIMUM size. Answer 11 Copyright 2005 Ted "Smitty" Smith

Question 12 Determine the MAXIMUM number of size 300 kcmil RHW copper conductors, without outer covering, permitted to be installed in an 18 inch long, trade size 4”, electrical metallic tubing. A. 14 B. 15 C. 16 D. 17

Question 13 A junction box contains THHN conductors which are feeding 208V three phase circuits, 120 V single phase circuits and 480 V three phase circuits. Is this an acceptable installation according the NEC? A. Yes B. No

Question 14 How many 12/2 AWG with ground, nonmetallic sheathed cables, are permitted to be installed in a device box having a total volume of 18 cubic inches where a duplex receptacle outlet is in the box? A. 1 B. 2 C. 3 D. 4

Answer 14 B. 2 314.16(B)(1-5) Table 314.16(B)

Question 15 A single gang FS box with single cover will have two ½” raceways entering the box from opposite sides. The box will contain four (4) THNN size 12 AWG conductors and three (3) THHN size 12 equipment grounding conductors and one duplex receptacle. Is this an acceptable installation according the NEC? A. Yes B. No

B. No Table 314. 16(A) 314. 16(B)(1-5) The total fill is 15
B. No Table (A) (B)(1-5) The total fill is and a FS single cover is only 13.5 Answer 15 Copyright 2005 Ted "Smitty" Smith

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Question 1 A 4” x 1 ½” octagon junction box with a flat blank cover may contain no more than _____________ size 14 AWG conductors? A. 6 B. 7 C. 9 D. 10

Question 2 Two (2) size 12 AWG conductors are looped inside a junction box so that there is more than 12” of free conductor. The conductors are not spliced and do not terminate on devices. What volume allowance, in cubic inches, must be counted for the looped conductors? A cubic inches B cubic inches C. 4.5 cubic inches D. 9.0 cubic inches

Question 3 Which of the following auxiliary gutters can NOT be used to contain nine (9) 300 kcmil THHN aluminum conductors, three (3) 500 kcmil THHN Aluminum conductors and three (3) 2 AWG THHN copper conductors? A. 12” x 24” B. 6” x 12” C. 3” x 8” D. 4” x 10”

C. 3” x 8” 366.22 A minimum 30.6525” is required 3” x 8” is only 24”
Answer 3 Copyright 2005 Ted "Smitty" Smith

Question 4 A two gang device box is to contain two (2) size 12/2 AWG with ground nonmetallic sheathed cables connected to a duplex receptacle and two (2), size 14/2 AWG with ground nonmetallic sheathed cables connected to a single pole switch. The device box will contain four (4) internal clamps. The two gang box is required to have a volume of at least ________. A. 36 cubic inches B. 34 cubic inches C. 30 cubic inches D. 28 cubic inches

Answer 4 C. 30 cubic inches 314.16(B)(1-5) Table 314.16(B)