Let's conquer published problem 6 "3-way switch + exposed outlet" [Class 2 Electrician Skills Examination]

12/09/2025

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The 6th installment of the series is Publication Problem 6.
It's a very ``exam-like'' problem, with a 3-way switch and an exposed outlet appearing at the same time. In the videos of Gamidenki Channel and Denkiya Peko, it is also treated as an episode that many examinees are weak at.

In this article, I will write down the steps in very detailed steps, with the goal that even people who are practicing at home with a DIY feel can make it all by themselves while reading this article.

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So, here you go.

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Table of Contents

Basic information

Question number: Publication question 6 (candidate question 6)
The theme of this exam number:
This question asks whether you can correctly understand ``control of multiple lights using a 3-way switch'' and ``how to install and connect exposed electrical outlets,'' and whether you can reliably follow the color-based wiring rules and joint methods (distinguishing the use of plug-in connectors and ring sleeves) (Gamidenki ``Published Question 6'' (Gamidenki channel), Denkiya Peko ``Candidate Question 6'' (Electric Shop Peco)).

The difficulty level is 4 out of 5 based on Denkiya Peko's standards, and the key points are the exposed electrical outlet, which is rarely asked, and the complicated three-way switch connection (English Shop Peko ``2023 Candidate Question 6 Explanation'' (Electric Shop Peko)).

Tools needed for this exam

Here, we will summarize the minimum + tools that are easy to have, assuming Publication Problem 6.

Crimping pliers (for ring sleeves: those with medium and small markings)
va stripper
- A device that safely peels the outer sheath and core wire of VVF1.6/2.0 to a certain length.
- Denkiya Peko also introduces that ``A VA stripper will vastly improve work efficiency'' (Electric Shop Peko "Candidate Question 6" (Electric Shop Peko)).
Nippers/pliers
- Used for cutting excess length and leaving 1 mm of core wire protruding from the ring sleeve.
Screwdriver (No. 2 Phillips, sometimes flathead as well)
- The screws on exposed electrical outlets are generally M4, so a screwdriver that can apply a firm torque is essential (Electric Shop Peko's ``Ring part of exposed electrical outlets'' (Electric Shop Peko)).
Measure (about 3.5m made of steel)
Passed multi-tool with cable stripper (Hozan)
- You can quickly measure sheath lengths of 100mm/50mm, strip 12mm of core wire, make loops, etc. all in one operation, so it is very advantageous in saving time (Hozan "Candidate Problem 6" (Hozan)).
Voltage detector or simple checker (for final self-check practice)
Pencil/Eraser (for double-line drawings)

"VA Stripper" and "Class 2 Electrician Skill Test Tool Set" are sold in large numbers on Amazon and Yahoo! Shopping.
If you search for keywords such as "VA stripper compatible with VVF 1.6 2.0" and prepare one that fits your hands, your practice efficiency will instantly increase.

Materials to be prepared for this exam

In the actual exam, you will use the materials distributed by the Electrical Engineer Examination Center as they are, but here we will organize the materials that typically appear in published question 6 (Hozan "Candidate Question 6 Confirmation of Supplied Materials").

Electric wires
- VVF 2.0mm²-2 cores (for power supply: length 250mm, etc.)
- VVF 1.6mm²-2 core (for lighting/outlet)
- VVF 1.6mm²-3 core (crossover wire for 3-way switch)
utensil
- 3-way switch (3-way switch) x 2
  - Terminal display: 0, 1, 3 (notation may be omitted depending on the manufacturer)
- Hanging ceiling (or exposed type ceiling) x multiple
- Lamp receptacle (screw-in lamp base)
- exposed outlet
  - There is a "W (white)" mark on the terminal, and the rule is to connect the white wire (ground side) here (Gamidenki "Checking the outlet" (Gamidenki channel)).
Joint related
- Plug-in type connector (designated part A or B)
- Ring sleeve (medium/small)
Continuous use frame (for 3-way switch)
Insulating tape (may be provided: bending reinforcement, etc.)

The actual length and quantity may vary slightly depending on the year and past questions, so be sure to check the ``Construction Conditions'' and ``List of Supplied Materials'' first, both during practice and in the actual exam (Hozan "Candidate Question 6 Confirmation of 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).

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Main flow

Here, we will organize the "time allocation" and "work order" based on the image of a 40-minute performance.
Once you get used to it, the installation itself will be completed in 15 to 20 minutes, and you will be able to check the remaining time (At Denkiya Peko, the installation is completed in less than 10 minutes (Electric Shop Peko)).

Confirm construction conditions (about 2 minutes)
- Circle the designation to use black for terminal 0 of the 3-way switch, white for terminal 1, and red for terminal 3.
- Part A is a plug-in connector, part B is a ring sleeve, and other joint designations are highlighted with lines.
- Check the connection conditions of the exposed outlet (connection near the terminal on the side where the cable enters, white for W, etc.) (Gamidenki ``Confirmation of installation conditions'' (Gamidenki channel)).
Temporary placement of equipment (about 2 minutes)
- Arrange the appliances on the board according to the wiring diagram and visually understand where the A joint, B joint, switch, and exposed outlet are.
Double track diagram (about 2-3 minutes)
- Problem 6 involves a 3-way switch + multiple lights + an exposed outlet, so be especially careful to draw the polarity around the 3-way switch and the exposed outlet, which can be easily confused (Gamidenki ``Explanation of 3-way switch double-line diagram'' (Gamidenki channel)).
Dimensioning, cable cutting, and sheath stripping (about 10 to 12 minutes)
- For the part specified as 150mm, it is safe to cut it at 250 to 300mm, and Peko standardizes it at 290mm (Electric Shop Peko's "Dimension Cutting Guidelines" (Electric Shop Peko)).
- When stripping the sheath, use a guideline of 100 mm on the joint side and 50 mm on the instrument side, and it is said that ``it is OK to peel it all at once by feeling (it will not be a defect if it is less than half of the specified length)'' (Denkiya Peko ``How to think about peeling length'' (Denkiya Peko)).
- For the wire that goes into an exposed outlet, strip the core wire to about 12 mm for the loop at the end (Gamidenki ``Length to peel for exposed outlets'').
Wire connection/installation to equipment (about 10 minutes)
- Assemble a 3-way switch in the continuous frame
- Make a loop in the lamp receptacle/hanging ceiling and connect the wires.
- Connect to the exposed outlet with a loop (white on W, black on the non-grounded side, right-handed) (Electricist Peco).
Wiring inside the joint box (about 8 minutes)
- Part A: Using the plug-in connector, first connect all the white (N side) → then put together the black/red in that order.
- Part B: Organize the ring sleeves into installed and non-installed sides, and be sure to check the engraving and number (Gamidenki ``Publication Problem 6 Checking the Joint Part'' (Gamidenki channel)).
Adjust the shape and check for defects (all remaining time)
- Each item was checked for the exposed core length, sheath length, whether published conditions were met, and the coloring of the terminals.

(If you use HHOZAN's approved multi-tool, please refer to "4. Dimensioning, cable cutting, and sheath stripping" above and "5. You can quickly measure 100mm/50mm sheaths without any jigs, strip 12mm core wires to a uniform diameter, and make loops with uniform diameters. HOZAN's video also introduces the process of aligning the sheath length and core wire length immediately after checking the supplied materials (Hozan).

How to draw wiring diagrams and things to be careful about

The key points in published question 6 are "understanding 3-way switches" and "polarity of exposed outlets."
Before drawing a double-track diagram, it will be much easier if you organize it in your head as follows (Gamidenki "3-way switch concept" (Gamidenki channel)).

Think of a 3-way switch as "three big switches"
- Power supply L (black) → 3-way switch 0 terminal → internal contact → 1 or 3 terminal → to each lamp
- Gamidenki channel explains that it is ``same as one big switch, it just switches electricity from 0 to 1.3'' (Gamidenki Publication Problem 6 Explanation (Gamidenki channel)).
- So, on the double track diagram, just imagine that ``the L side is in the 3-way switch 0, and the return lines are coming out from 1 and 3 to each lamp.''
Follow the basic rules of wiring diagrams
- On the ground side of all appliances (lights, outlets) other than switches, draw a white line so that it goes directly from the branch point (Electricalist Peko's "Common Rules for Double-Line Diagrams" (Electricalist Peko)).
- Draw a black line directly from the L side to the non-grounded side of the non-lighting equipment (in this case, the exposed outlet).
- Make it clear that the outlet returns from the "white = W terminal" side to the N side (Gamidenki "Checking the outlet section" (Gamidenki channel)).
Fix the color and terminal on the diagram
- 3 way switch
  - 0 terminal: Power supply L (black)
  - 1 terminal: White (crossover wire)
  - 3 terminals: Red (crossover wire)
    This designation is specified in the construction conditions, and if it is incorrect, it will be an immediate defect (Electrical Shop Peco, "Candidate Question 6 Explanation of Construction Procedure No. 2" (Electric Shop Peco)).
- exposed outlet
  - W terminal: White (N side)
  - The other side: black (L side)
Complete the double-line diagram while writing the cable type
- Power supply ~ Joint: VVF2.0-2C (black/white)
- Joint ~ Lighting: VVF1.6-2C
- Between 3-way switches/3-way switch to joint: VVF1.6-3C
  If you write "2C" and "3C" next to the line, you won't get confused when cutting to size.

The ideal time to spend on a double-line diagram is between 30 seconds and 3 minutes. If you follow the same steps for what you write each time, your speed will naturally increase.

How to proceed with practical skills and take a breather

From here, I will write down the ``super specific steps'' when actually moving my hands.
When practicing, repeat this sequence several times to let it sink into your body.

1. Assemble the 3-way switch first

Attach two 3-way switches to the continuous frame.
About each 3-way switch
- Black wire to 0 terminal (power supply side or crossing source)
- White wire on 1 terminal
- Red wire to 3 terminals
  Insert the core wire in this way (Denkiya Peko's ``Connection of a 3-way switch'' (Denkiya Peko)).
Use VVF1.6-3C for the crossover wire, and connect the 3-way switch by stripping the sheath 50mm from both ends and stripping the core wire by 12mm (Electric Shop Peco).

Here is a ``breathing point''.
Stopping around the 3-way switch,
"0 is black, 1 is white, 3 is red. Are the two 3-way switches arranged in the same color?"
Please review. If you make a mistake here, it will be really troublesome to correct it later.

2. Making a loop and connecting the exposed outlet

Strip the core wire at the end of the cable by about 12mm to 15mm.
Make a ring with round pliers or an approved multi-tool with a diameter that is one size larger than the ring of the lamp receptacle (the screw for the exposed outlet is M4, so it needs to be one size larger than the M3 screw for the lamp receptacle (Electric Shop Peco's ``Creating a Ring for an Exposed Outlet'' (Electric Shop Peko)).
Attach the white wire to the W terminal side and the black wire to the other terminal in a right-handed manner.
- By winding it to the right, when you tighten the screw, the wire gets caught up in the screw and tightens, making it less likely to come loose (Gamidenki ``Checking Exposed Outlets'' (Gamidenki channel)).
After tightening the screws,
- Core wire protrusion is within 5mm
- Insulation coating is not bitten
- There is definitely a white line on the W side.
  Check it out (Gamidenki channel).

This is where the test center's defect standards are checked, so be sure to get into the habit of checking after tightening.

3. Connection of lighting equipment (lamp receptacle/ceiling)

Cable for lamp receptacle
- Instrument side: sheath 50mm, core wire 18~20mm
- Joint side: sheath 100mm, core wire 12mm
  If you peel it to this length, it will fit just right in most cases (Electrical Shop Peko's "Dimensions for Lamp Receptacles" (Electrical Shop Peko)).
Make a loop first and then bend it to fit the device.
- If you make a loop and then bend it into a U-shape or L-shape to match the terminal position of the device, it will be easier to insert it into the screw (Electrical Shop Peko).
protect polarity
- Lamp receptacle: connect the white wire to the "outside" ground terminal
- Sealing: Follow the instructions and move the white line to the N side.

4. Wiring inside the joint box (Part A: Plug-in connector, Part B: Ring sleeve)

Part A (plug-in connector)
- First, collect all the white wires (N side) and insert them firmly into the plug-in connector as far as they will go (Gamidenki "Procedure for assembling the N side" (Gamidenki channel)).
- Next, collect the non-grounded sides such as the black wire and red wire.
- For plug-in connectors, check whether the core wires are visible through the transparent part and whether they are inserted all the way (Gamidenki channel).
Part B (ring sleeve)
- The installation side (white) and non-installation side (black/red) must be grouped together in separate groups.
- Select the "small" or "medium" stamp depending on the number of crimping pliers, and match it with the stamp on the crimping pliers (for example, if 1.6mm² x 2 + 2.0mm² x 1, small = ○ sleeve, etc.).
- After crimping,
  - Cut so that only about 1mm of core wire protrudes from the base of the sleeve.
  - Check that the sheath or coating is not bitten.
  - Spread the sleeves apart a little so they don't stick together.
    (Gamidenki "How to finish a ring sleeve" (Gamidenki channel)).

5. Last “breathing” time: shaping and looking for flaws

Once the construction is complete, put down your tools and take a deep breath.
Then, perform a visual inspection in the following order.

3 way switch
- Are both 0=black, 1=white, and 3=red?
- Are the white and red of the crossover wire in the same position on both the left and right?
exposed outlet
- White on W, black on the other
- The ring is right-handed
- Visibility of core wire is within 5mm
Ceiling lamp receptacle
- Is the white wire coming to the ground terminal?
- Ring direction/tightness
joint part
- Is part A a plug-in connector and part B a ring sleeve?
- Are the stamps and numbers correct?
- Is the exposed length of the core wire around 1mm?
sheath length
- Inside the joint box: around 100mm
- Instrument side: around 50mm
  According to the test center's standards, if it is "less than 50% of the specified dimensions" it will be treated as a defect, so check to see if it is extremely short (Electrical Shop Peco, "Explanation of Sheath Length and Defect Criteria" (Electric Shop Peko)).

Items to check for defects and oversights

Finally, I will list the flaws and oversights that are particularly likely to occur in Publication Question 6.
Please use it as a "checklist" when checking your completed work.

3 way switch related
- A wire other than the black wire is inserted into the 0 terminal.
- The white and red of 1 and 3 are different depending on the left and right switches (lighting becomes strange)
- The crossover wire is forced to use a 2-core cable instead of VVF1.6-3C.
Exposed outlet related
- Connecting black instead of white to the W terminal
- The loop is wound to the left so it loosens when tightening.
- The peeling length is too long and the core wire is exposed (more than 5mm)
- The insulation sheathing is screwed in (Gamidenki "Exposed Outlet Finish Check" (Gamidenki channel)).
Joint part related
- Electrical materials in parts A and B are reversed (mixture of plug-in connector and ring sleeve)
- Wrong engraving on ring sleeve (wrong size for number)
- The core wire protrudes more than 1mm from the sleeve too much/hardly protrudes.
Polarity/grounding related
- White lines do not reach all lighting equipment
- The N side (W) and L side (non-grounded side) of the outlet are installed oppositely.
- The 3-way switch works, but the polarity of the outlet is reversed.
Dimensions/appearance related
- The sheath is too short, leaving too much core wire exposed inside the box.
- On the other hand, it is too long, and the core wire cannot reach inside the box, so you are pulling it forcibly.
- The bending radius of the cable is extremely small, and wrinkles and cracks are visible in the coating.

These points are a compilation of the points that Gamidenki Channel, Denkiya Peko, and HOZAN each point out as points to note while actually performing construction in their videos (Gamidenki Publication Problem 6 Explanation (Gamidenki channel), Denkiya Peko Candidate Question 6 Explanation (Electricist Peko), Hozan Candidate Question 6 Explanation (Hozan)).

Summary

Publication question 6 is

Wire the 3-way switch according to the color specifications: 0 = black, 1 = white, 3 = red.
Observe "W = white", "right-handed loop", and "core wire exposure within 5 mm" with exposed outlets.
Strictly adhere to the electrical material specifications for the joint (A = plug-in connector, B = ring sleeve)

As long as you keep these three things in mind, it's not as difficult as it looks.

It may take some time at first, so
"A level at which you can wire the same wiring diagram three times in a row without looking at the diagram."
If you practice until then, you will feel much more relaxed during the actual performance.