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[Class 2 Electrician Skills Examination] Published Problem 7 Strategy Guide [3-way switch/4-way switch circuit]

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(One light can be operated from three locations with three-way, four-way, and three-way switches)

Hello everyone, this is DIY Renova.

The seventh installment of the "Class 2 Electrician Skills Examination Published Question 7 Strategy Guide" series is Published Question 7.
The theme of this problem is "3-way switch + 4-way switch + 3-way switch", and the theme is a circuit that can turn one light on and off from three places. Furthermore, the outlet box joint and electrical material specifications (ring sleeve/plug-in connector) are also involved, making it quite difficult.

Electrician Peko gives the difficulty level a ``4 out of 5'' and explains the reason for this is ``because of the appearance of the outlet box and the 3-way/4-way switch.''
Gamidenki Channel also carefully explains the wiring patterns for 3-way, 4-way, and 3-way, and emphasizes that ``It is recommended that terminal 0 be uniformly colored black.'' (Gamidenki channel)

In this article,
"I don't understand how the 3-way/4-way switch works"
"Double-line diagrams make my head go blank"
I will write down the steps in very detailed steps, with the goal of getting you from that state to the point where you can put this article next to you and go through the process by yourself.

Actually, I am also learning by summarizing things like this lol

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So, here you go.

Basic information

  • Question number: Class 2 electrician skill test published question 7
  • Question theme:
    • 3-way switch, 4-way switch, 3-way switch (so-called "3-way, 4-way, 3-way") switch
    • Joint in the outlet box (A part = ring sleeve, B part = plug-in connector) (Electric shop Peko)
  • Estimated difficulty level: 4 out of 5 points (Electricist Peko standards) (Electricist Peko)

The following points are specifically asked in this exam number:

  • Can I wire each of the 0, 1, and 3 terminals of a three-way switch in a "determined color"?
    (In the construction conditions, it is instructed to use "No. 0 = Black," "No. 1 = White," and "No. 3 = Red.") (Electricist Peko)
  • Can you correctly connect the 2, 4, 1, and 3 terminals of the four-way switch to the 1 and 3 terminals of the left and right three-way switches? (Hozan)
  • Can I use a ring sleeve for the A joint and a plug-in connector for the B joint? (Electricist Peko)

If you know this, you can apply it not only to published problem 7, but also to other problems where three-way and four-way switches appear.

Tools needed for this exam

In addition to basic tools, Published Problem 7 is ``There are a lot of cables and the inside of the outlet box gets crowded,'' so tools that can quickly and uniformly align dimensions and strip are important.

  • electrician knife
    • For making the first cut in the VVF exterior.
  • va stripper
    • Even the electrician Peko says, ``The VA stripper has the performance of a cheat,'' so much so that work efficiency has changed dramatically. (Electricist Peco)
    • We recommend one that allows you to peel the 1.6mm²/2.0mm² sheath and core wire at a fixed length at once.
  • Crimping pliers (for ring sleeves)
    • You can choose the stamp that suits the number of pieces, such as "○" stamp on the small sleeve or "○" stamp on the middle sleeve.
  • nipper
    • Required to cut the core wire from the sleeve with 1mm remaining. (Electricist Peco)
  • Phillips screwdriver number 2
    • For terminal screws of three-way and four-way switches, and fixture screws.
  • Measure (about 3.5m)
  • HOZAN's passing multi-tool system
    • It is especially useful for saving time when dealing with three-way and four-way problems, as it can handle the exterior 5cm/10cm guideline, core wire 10-12mm strips, and loop making with just one tool.
    • If you search for ``HOZAN passed multi-tool Class 2 electrician'' on Amazon or Yahoo! Shopping, you will find several sets for skill exams.

Materials to be prepared for this exam

The actual length and number of pieces may vary slightly depending on the year, but the structure is generally the same.

  • Electric wires
    • VVF 2.0mm²-2 cores (power supply to outlet box, etc.)
    • VVF 1.6mm²-2 cores (between lighting equipment, switches, etc.)
    • VVF 1.6mm²-3 core (crossover wire between 3-way and 4-way switches)
  • switches
    • Three-way switch x 2 (for both ends)
    • Four-way switch x 1 (for center)
  • lighting equipment
    • Lamp receptacle/hook ceiling, etc.
  • joint parts
    • Ring sleeve (small/medium)
    • Plug-in connector (for 2 or 3 wires)
  • Continuous mounting frame (for switch)

The construction conditions include the color of the wires used for the 0, 1, and 3 terminals of the three-way switch, as well as the electrical materials specified for parts A and B, so be sure to check the construction conditions at the same time as checking the supplied materials.

On the actual question paper, the ``distance between cores'' of each cable is indicated in dimensions such as 100 mm, 150 mm, and 200 mm. On the other hand, the idea is to cut the cable by adding the length that will fit inside the device or the length required for the joint (Electrical Shop Peko, 2023).

Main flow

Published problem 7 is a type of problem in which the amount of work itself is not that large once you understand the wiring of the third and fourth routes.
Let's visualize the 40-minute test time roughly divided into the following parts.

  1. Confirmation of construction conditions and supplies (3 to 4 minutes)
  2. Double line diagram (2-3 minutes)
  3. Dimensioning/cable processing (10-12 minutes)
  4. Wiring switches and appliances (10-12 minutes)
  5. Joint in outlet box (5-7 minutes)
  6. Finishing/defect checking (3 to 5 minutes)

Particularly important are "3rd and 4th road switches" and "designation of electrical materials for joints A/B."

(How to use the HOZAN passing multi-tool)

  • Align cable sheaths 5cm/10cm at once
  • Strip the core wire uniformly at 10-12mm
  • Align the rings of 3-way and 4-way switches to a constant diameter

If you use a multi-tool in this area, you won't have to measure with a ruler every time, which will reduce mistakes.

How to draw wiring diagrams and things to be careful about

The most important point in understanding the three routes, four routes, and three routes is to "imagine the internal points of contact."

Image of a three-way switch

  • Terminal: 0, 1, 3
  • Operation:
    • When you raise the lever, "0-1 becomes conductive"
    • When you lower the lever, "0-3 becomes conductive"

Gami Denki Channel describes the three-way switch as a "big selector switch" and explains that it simply distributes electricity from 0 to either 1 or 3. (Gamidenki channel)

Under the construction conditions of published problem 7,
``On a three-way switch, use black for number 0, white for number 1, and red for number 3.'' (Electricist Peco)

Therefore, it is easier to draw on a double-line diagram by fixing it as shown below.

  • 0 terminal of left three-way switch: Power supply L (black)
  • 1 terminal: crossover wire (white)
  • 3 terminals: crossover wire (red)
  • The three-way switch on the right side has the same layout (0 = black, 1 = white, 3 = red)

Image of a four-way switch

A four-way switch, also called a "cross switch," is a component that simply switches two circuits internally.

In HOZAN's explanation, the terminals of the four-way switch are 1, 2, 3, and 4.
This example shows how to connect "terminal 1 of a three-way switch to terminal 2/1 of a four-way switch, and terminal 3 of a three-way switch to terminal 4/3 of a four-way switch." (Hozan)

Specifically, in the HOZAN example, they are connected as follows. (Hozan)

  • Left 3rd road No. 1 → 4th road No. 2
  • No. 3 on the third road on the left → No. 4 on the fourth road
  • No. 1 on the 4th road → No. 1 on the 3rd road on the right
  • No. 3 on the 4th road → No. 3 on the 3rd road on the right

The construction conditions do not specify which number on the fourth road should be connected to the number on the third road.
It is OK to use an easy-to-understand wiring pattern that aligns the wires "top to top" and "bottom to top".

4 steps to draw a double line diagram

  1. Write the symbol as it is
    • Draw the power supply, outlet box, three-way, four-way, and three-way switches, and lighting equipment lined up as per the single-line diagram.
  2. Pull the power supply N side (white) directly to the lighting fixture.
    • As a general rule, draw the N-side white line so that it reaches directly to "all loads (lamps) other than switches."
  3. Power supply L side (black) to left three-way switch 0 terminal
    • As per the construction conditions, the 0 terminal has a black wire. An image of distributing the force from there to the 1 and 3 terminals.
  4. 3rd road on the left → 4th road → 3rd road on the right → Go to lighting equipment
    • Align the 1 and 3 terminals with white and red, and connect to the 3-way on the right side via the 4-way switch.
    • Connect the 0 terminal of the 3rd path on the right side to the L side of the lighting fixture.

In the video on the Gami Denki channel, we explain wiring examples for 3-way, 4-way, and 3-way using only red lines, and then apply the correct colors (black, white, red). (Gamidenki channel)
We recommend that you first create a "temporary double-line diagram drawn entirely in red" and then assign colors.

How to proceed with practical skills and take a breather

From here, we will take a closer look at the steps involved in actually creating the work.
When practicing, repeating this order several times to get your body to memorize it will make it much easier during the actual performance.

1. Loading and marking construction conditions

  • Three-way switch color specification
    • Draw a circle where 0=black, 1=white, and 3=red. (Electricist Peco)
  • Electrical material specification for joint A and B parts
    • Draw a double line where it says Part A = Ring Sleeve, Part B = Plug-in Connector to make it stand out. (Electricist Peco)

It's ok to spend 2-3 minutes here.
The last thing you want to do is skip reading the test center's construction conditions and end up being disqualified, so make a decision that you won't skimp on the time you take to read it.

2. Assemble the switches first (breathing point)

  1. Line up and fix the three-way, four-way, and three-way switches on the continuous frame.
  2. Create a crossover wire connecting the 3rd, 4th, and 3rd routes using a VVF1.6-3 core cable.
    • Use the HOZAN multi tool to peel off the sheath 50mm and core wire 10-12mm on both ends to make it even.
  3. left side three way switch
    • 0 terminal: black
    • 1 terminal: white
    • 3 terminals: red
  4. four way switch
    • Connect the 2 and 4 terminals to the 1 and 3 terminals of the left three paths (example: 1→2, 3→4)
    • Connect the 1 and 3 terminals to the 1 and 3 terminals of the three right paths (Example: 1 → Right 1, 3 → Right 3) (Hozan)
  5. right side three way switch
    • Connect the black wire going to the lighting side to the 0 terminal (later joint with the cable going to the lamp via the outlet box)

This is the first "big mountain".
Once assembled, put down the tools and

  • Are "0=black, 1=white, 3=red" aligned on the left and right three-way switches?
  • Are the crossover wires aligned between the upper and lower tiers?

Try saying it out loud.

3. Cable dimensioning and processing

Electrician Peko recommends cutting the specified 150mm to 290mm, allowing for a little extra dimension. (Electricist Peco)

As a guide,

  • Outlet box side: sheath 100mm, core wire 10mm
  • Switch/appliance side: Sheath 50mm, core wire 10~12mm

By arranging the pieces so that there is enough room in the box, it will be easier to meet the specified dimensions (50% or more).
It is important not to make the sheath too short, as according to the testing center's standards, "less than 50% of the specified length is considered defective." (Electricist Peco)

If you use a HOZAN-approved multi-tool, you can match the sheath length of 100mm/50mm and the core wire of 10 to 12mm just by feeling, so it is especially effective for published problem 7, which has a large number of cables.

4. Construction of lamp receptacle (or sealing)

  1. Prepare the cable for the device
    • Sheath 50mm, core wire 18~20mm
  2. Make a loop on the core wire
    • Using the shaft of a screwdriver or the round part of a multi-tool, make a right-handed ring with a diameter that is large enough to fit the M3 screw.
  3. Attach the white wire to the ground terminal and the black wire to the non-ground terminal.
  4. After tightening the screws firmly,
    • Does the core wire protrude by more than 5 mm?
    • Is it not biting the insulation coating?
      Check visually. (Electricist Peco)

5. Joint inside outlet box

Under construction conditions,
"A part joint = ring sleeve" "B part joint = plug-in connector"
is specified. (Electricist Peco)

  1. A part (ring sleeve)
    • Separate and organize the installation side (white) group and the non-installation side (black, red, etc.) group.
    • Depending on the number of pieces, choose small sleeve/medium sleeve and stamp (○).
    • After crimping, use nippers to cut the core wire by 1mm from the sleeve, and check to see if the insulation is chewed. (Electricist Peco)
  2. Part B (plug-in type connector)
    • Use the specified number of plug-in connectors (for 2 or 3 connectors) and firmly insert them until the core wires are visible through the transparent part.
    • Lift it up and pull it gently to make sure it doesn't fall out.

If the bending radius of the cable is too large relative to its diameter, it will not fit inside the outlet box.
In general, it is said that a bending radius of 4 times or more the outer diameter of the cable will not put stress on the sheath and will ensure long-term safety (general safe values ​​for allowable bending radius for electric wires).
Therefore, it is a good idea to organize the wires inside the box by not forcing them into sharp corners or by bending them into large arcs before pushing them in.

6. Final confirmation (take another breath here)

When construction is complete, be sure to set down tools and visually check using a checklist.

  • three way switch
    • Are 0=black, 1=white, and 3=red on both the left and right sides? (Electricist Peco)
  • four way switch
    • Are the upper rows connected to each other and the lower rows connected? (Check that the left and right sides are not crossed.)
  • lamp receptacle
    • Is the white wire coming to the ground terminal?
  • Joint A/B
    • Is part A a ring sleeve and part B a plug-in connector? (Electricist Peco)
  • sheath length
    • Is it too short? Around 50mm on the instrument side and around 100mm on the box side. (Electricist Peco)

Mr. Peko, an electrician, says that even if the installation itself is completed in about seven minutes and the remaining time is used for ``confirming the construction instructions, double track diagrams, final confirmation, and cleaning up,'' there is still time left. (Electricist Peco)
Even during the actual work, it will be safe if you can check the remaining time with the goal of finishing the construction by 25 minutes.

Items to check for defects and oversights

Finally, I will summarize the flaws and oversights that are particularly likely to occur in Publication Question 7.

  1. Violation of three-way switch color specification
    • Connecting a color other than black to the 0 terminal
    • The white and red of terminals 1 and 3 are different on the left and right.
      → If you forget the construction conditions "0=black, 1=white, 3=red", you will be immediately disqualified. (Electricist Peco)
  2. 4-way switch connection error
    • The upper and lower rows are crossed, and the lamp does not come on when operating a certain switch.
      → If you use a pattern that aligns the upper sides and the lower sides, you will reduce mistakes.
  3. Mix-up of electrical materials in joint A/B
    • Part A is a plug-in connector and part B is a ring sleeve.
      → Be sure to confirm the installation conditions "A = ring sleeve" and "B = plug-in connector" out loud before connecting the wires. (Electricist Peco)
  4. Poor crimping of ring sleeve
    • Wrong marking (sleeve size does not match the number of pieces)
    • After crimping, the core wire is almost invisible/on the contrary, it sticks out for a long time
      → Get in the habit of checking every time to make sure that the cut is aligned so that only 1mm is visible and that the coating is not chewed. (Electricist Peco)
  5. Insufficient sheath length
    • Excessive sheathing on the instrument side or outlet box side results in less than 50% of the specified length
      → If you make the sheath length 50mm/100mm a little longer, it will be on the safe side. (Electricist Peco)
  6. Mistake in polarity/grounding side
    • Connect the black wire to the ground terminal of the lamp receptacle
      → Be sure to repeat the principle that white = N side (ground side) in your head before wiring.

Finally

Publication question 7 is
"Structure of three-way/four-way switch"
"Protect colors and electrical materials according to construction conditions"
If you can do it, it's not as scary as it seems.

First, while reading this article,
"Only around the switch" "Only around the outlet box"
Try practicing this part several times.
Once you get used to it, try timed construction for 40 minutes and aim to be able to assemble it within 25 minutes.

Next time, I will summarize the strategy article for Publication Problem 8.

Videos and materials referenced:

  • Electrician Peko “2023 candidate problem number 7 explanation and construction”
  • HOZAN “Class 2 Electrician Skills Exam Publication Question 7 Construction Method” (Hozan)
  • Gamidenki channel “Publication problem 7 Double line diagram and connection of 3-way, 4-way, 3-way switch” (Gamidenki channel)

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