Basic information

• Class 2 electrician skill test published question 12
• What is the theme of this exam number?
  • Construction of synthetic resin flexible conduit "PF pipe" and outlet box
  • Wiring the inside of the PF pipe with single core electric wire (IV wire) instead of cable
  • Application problem of basic pattern + PF tube including wiring around switches and outlets (from HOZAN candidate problem explanation) (Hozan)

Published problem 12 looks simple, but the key issue is ``how to handle the PF tube.'' Insufficiently fixing the PF tube or forgetting to tighten the lock nut will directly lead to a defect, so if you keep these things in mind, you will quickly get closer to passing the test (a common point in the videos of HOZAN, Gamidenki, and Denkiya Peco). (Gamidenki channel)

I've written it in a lot of detail because I'm assuming there are people who say, ``Even after looking at the official text, I don't know where to start...'' I would be happy if you could actually practice using your hands while reading the article.

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

If you're wondering "How much renovation or remodeling can I actually do on my own home?" or "Where should I even start?", please visit this page. If you're looking to learn more about specific renovation processes or construction details, don't miss this page as well!

Information on updates to this website will be delivered to you once a month.NewsletterIf you are interested, please register.

So, here you go.

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Tools needed for this exam

For Publication Question 12, organize the minimum number of tools you want to have, keeping in mind the area around the PF pipe.

• electrician knife
  • Make a cross cut in the rubber bushing (Jet Black 680 is used in the HOZAN video)
• Electrician pliers (crimping pliers)
  • For crimping ring sleeves (ensures medium and small markings)
• wire stripper
  • Accurately align the sheath stripping dimensions of VVF cables and IV wires
• Nippers
  • Finish adjustment for cutting cables, wires, and PF pipes
• Driver (+/-)
  • Tightening screws for switches, outlets, and terminal blocks
• Water pump pliers (Deiken 200 class recommended)
  • Used for retightening lock nuts of box connectors for PF pipes (HOZAN explanation)
• Measure/Ruler
  • Measure the length of PF pipes and wires
• Passed multi-tool (HOZAN)
  • Convenient for tightening lock nuts and retightening bushings (Gamidenki channel also explains that it can be used to tighten PF pipes) (Gamidenki channel)

You can tighten the PF tube with just your fingers, but if you're under tension during the actual test, you won't be able to tighten it just a little more and it will likely loosen. For peace of mind, be sure to retighten the lock nut and hexagonal part of the PF connector using water pump pliers or an approved multi-tool.

The tools are available at home centers, but if you search for ``Class 2 Electrician Skill Test Tool Set'' on online shopping sites (Amazon, Yahoo Shopping, etc.), you can also find sets that include all the tools you need.

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Materials to be prepared for this exam

What is distinctive about published problem 12 is the combination of the PF pipe and outlet box. Although detailed dimensions may change from year to year, the general structure is as follows (combining official construction conditions and various explanations).eleking.net.

• VVF cable
  • 2-core/3-core VVF (1.6mm or 2.0mm)
  • The required length will be provided according to the construction conditions.
• Single core electric wire (IV wire)
  • Black, white, etc. for passing inside the PF tube
  • A little extra black wire is provided, and there are many patterns where it is used as a crossover wire from the switch to the outlet (Shima-chan blog)Shima-chan's blog, Shima-bro
• PF pipe (synthetic resin flexible conduit)
  • One PF tube of specified length is provided.
  • The basic pattern is to attach box connectors at both ends.
• PF pipe box connector + lock nut
  • Metal fittings for fixing the PF pipe and outlet box
  • Many types have a "Connect/Disconnect" display (Gamidenki channel)
• Rubber bushing (19mm)
  • Used to protect the remaining three holes in the outlet box (HOZAN explanation)
• Lamp receptacle or hook ceiling
• Embedded switch (single cut)
• recessed electrical outlet
• Terminal block (power supply side)
• Ring sleeve (small/medium)
• Plug-in connector

Another important point of this problem is that the wires running inside the PF pipe are not cables but single-core wires (article explaining the published problem).Shima-chan's blog, Shima-bro. If you make a mistake here and pass it through as VVF, it will instantly become defective, so be careful.

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Main flow

Here, we will summarize the actual flow, focusing on ``time allocation'' and ``handling of PF tubes.''

1. Double track diagram confirmation/check (5 minutes)
2. Preparation of outlet box and PF tube (5-7 minutes)
3. Dimensioning and cutting of cables and wires (5 to 7 minutes)
4. Wire connection to equipment and construction of joint parts (10 to 12 minutes)
5. Wiring the PF pipe route (passing the IV line)
6. Final defect check (more than 5 minutes)

The duration is 40 minutes, but in the video of Electrician Peko, it is strongly recommended that ``the construction work itself be completed within 25 minutes, and the remaining time be used for confirmation'' (from the explanation for skill test No. 13) (Electricalist Peko). Publication question 12 has the same feeling, and it is safe to aim for ``25 minutes to complete + 15 minutes to check''.

There are two practical ways to use a successful multi-tool here:

• Tightening the lock nut of the PF pipe box connector
• Retighten the rubber bushing (to prevent it from coming off)

If you tighten the area around the PF pipe by hand, it is surprisingly easy to loosen, so if you take the time to tighten it with a passing multi-tool, the risk of defects will be significantly reduced (Gamidenki channel recommends using a tool to tighten the PF pipe) (Gamidenki channel).

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How to draw wiring diagrams and things to be careful about

The double line diagram in Publication Problem 12 is not in itself very special. Other than the PF tube section, it is a combination of the same basic patterns as other problems (Shima-chan blog / double line diagram explanation)Shima-chan's blog, Shima-bro.

I'll just sort out the points.

1. From power supply to terminal block, switch, outlet, and lighting
   • Power supply → terminal block → branch to each load
   • The switch basically controls the "non-grounded side (black) of the lighting."
2. The PF pipe section first encloses "from where to where"
   • If you look at the construction conditions and clearly indicate "PF pipe + IV line in this section", surround it with a square or marker on the double track diagram to avoid confusion.
   • Clearly write the color and number of wires inside the PF tube on the diagram (e.g. "IV black x 1, IV white x 1", etc.).
3. Switch/outlet side crossover wire
   • There are many cases where an extra 100mm of black wire is provided, and this is used for crossing from the switch to the outlet (Shima-chan Blog)Shima-chan's blog, Shima-bro
   • By clearly indicating the color of the crossover wires on the double-track diagram, wiring errors during construction will be reduced.
4. Write a memo of the peeling dimensions
   • Ring sleeve connection: Sheath approx. 100mm, insulation coating approx. 20mm
   • Plug-in connector: Sheath approx. 100mm, insulation coating approx. 12mm
   • Terminal block: sheath 50mm, insulation coating 10mm
     If you make a small note of the approximate values ​​such as in the margin of the double line diagram, you will not get confused during work (reference values ​​for cable sheath dimensions)
5. Put a check mark on important routes
   • Number and color of lines in the PF tube
   • Grounding side (white) handling
   • Make sure that one side of the lamp receptacle is the ground side.
     By double-circling and checking these on the double-track diagram, you can reduce the number of times you wonder where they are during construction.

When drawing a double-line diagram, it's OK to keep in mind that just because it's a PF tube, there's no special way to draw it. You can draw it calmly by thinking that the middle of the exposed wiring is just a PF tube (a similar explanation is given in the explanation video by Japan Energy Management Center).youtube.com.

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How to proceed with practical skills and take a breather

This is the most important part of the actual image. I will write step by step, mainly around the PF tube.

1. Preparation of outlet box and PF pipe

1. Cross cut on rubber bushing
   • A rubber bushing is provided to attach to the small hole (19mm) of the outlet box.
   • Make a cross-shaped cut in the center with an electrician's knife or scissors.
   • A HOZAN video explains that rather than rubbing the knife back and forth, ``pushing it from top to bottom'' will result in a cleaner finish (be careful not to put your finger on the blade) (Hozan) (Gamidenki channel)
2. Attach the rubber bushing to the box
   • Excluding one hole for connecting the PF pipe, fit rubber bushings in the remaining three holes.
   • Rubber bushings have almost no front and back sides, so you don't have to worry about the orientation (HOZAN video)
3. Connection of PF pipe connector and PF pipe
   • Check the "Connect/Release" display on the PF pipe box connector and turn it to the "Release" position (Gamidenki channel)
   • Insert the PF pipe all the way and return it to the "Connect" position to lock it.
   • At this time, check to see if it comes out by pulling it gently.
4. Fixing to outlet box
   • Insert the connector with PF pipe into the designated hole of the outlet box, insert the lock nut from inside with the flat side facing the box, and tighten it with your fingers (HOZAN video)
   • Then, while holding the box with one hand, tighten the lock nut firmly using water pump pliers or the wrench part of an approved multi-tool with the other hand.
   • If there is a visible gap between the PF pipe and the box, it is a defect, so visually confirm that there is "zero gap" (HOZAN explanation) (Hozan)

These are the steps for "mechanically fixing" the PF tube. If you solidify this area first, it will make wiring work much easier later.

2. Dimensioning and cutting of cables and wires

First, measure and cut all cables, including cables other than the PF tube.

• Calculated by adding the dimensions of the construction conditions + the extra length to be removed inside the fixture (approximately 50 to 100 mm)
• The IV line of the PF pipe section is basically "PF pipe length + extra length inside the box at both ends (100mm each)". For example, if the distance between the centers of the PF tubes is 500mm,
  • 500mm+100mm+100mm=about 700mm
    (The idea of ​​calculating wire length is introduced in the HOZAN video as a way to memorize in 50 mm increments) (Hozan)

When stripping the cable insulation, you can reduce damage to the insulation insulation by cutting only the sheath with a stripper and tearing it off by hand, while keeping the above-mentioned guideline dimensions in mind. There is also a report that if you pull it all at once with a stripper, the inner insulation coating may be scraped (Notes on Shima-chan's blog)Shima-chan's blog, Shima-bro.

3. Connection to equipment and joint parts

This area is almost the same as published questions 1 to 11, but I will clarify it.

• Terminal block: Connect the power supply side and load side according to the construction conditions.
• Switch: Be aware of passing only the non-grounded side (black)
• Outlet: Be sure to connect the ground side (white) to the long side terminal
• Lamp receptacle: Do not confuse ground side/non-ground side

Inside the joint box, visually check the crimped position of the ring sleeve to make sure that the sheathing is not caught and that all the core wires are firmly coming out of the sleeve (emphasized by both Gamidenki and Electric Shop Peko) (Gamidenki channel).

4. Routing of PF pipe section

1. First, gather the IV wires that will be passed into the PF tube.
   • If you have two pieces, just twist them slightly and bundle them together.
   • Even if you don't have a wiring wire, it's short enough that you can reach it by pushing it in.
2. Push the IV wire from one side of the PF tube.
   • If you feel that it gets stuck in the middle, do not force it in, but move it back a little and change the angle.
   • If the bend in the PF pipe is too tight, it will be difficult to pass the wire through, so be aware of the bending radius specified in the construction conditions (a general guideline is that the minimum bending radius for a PF pipe is approximately 4 to 6 times the outside diameter).Hozan.
3. Pull the IV wire out of the box on the other side
   • Secure the necessary extra length (approximately 100 mm each) and then connect the wires using a ring sleeve or plug-in connector as you would for a normal connection.

Many test reports say that the construction of PF pipes is easier than that of metal pipes (Shima-chan blog and various explanations).Shima-chan's blog, Shima-broIf you skip "Preventing disconnection" and "Checking the connection part", it will immediately become a defect, so proceed with caution here.

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How to proceed with practical skills and take a breather

It's easy to get nervous during the actual exam. In the explanation of Denkiya Peko, a guideline of ``25 minutes for construction + 15 minutes for confirmation'' is presented, and it is said that it is important not to rush the work itself (Dekiya Peko).

There are three recommended places to take a breather:

1. When PF pipe + outlet box is attached
   • This is the point where you can take a breather and say, “Okay, the PF tube is physically OK.”
   • At this point, check again to make sure that the PF tube does not come off and that there is no gap between it and the box.
2. When all the equipment has been connected
   • Take a deep breath while checking that the screws on switches, outlets, terminal blocks, and lamp receptacles are fully tightened, not temporarily tightened.
3. last 5-10 minutes
   • Never mess with the wiring during this time, and use it as a "check-only time."
   • We simply go through the checklist and check whether the plug-in connector is inserted all the way, whether the markings on the ring sleeve are correct, whether the area around the PF tube is loose, etc.

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Items to check for defects and oversights

Finally, we will list the flaws that are particularly common in Publication Question 12 and check points for them. You can also use this as a "checklist" for your blog.

1. Around PF pipe/box connector
   • Is the PF tube starting to come loose from the connector? (Does it not move even if you pull it lightly?) (Gamidenki channel)
   • Is there a gap between the connector and the box? (If there is enough space that you can see the light, it's out) (Hozan)
   • Is the lock nut finger-tight? (Has it been tightened further with a tool?)
2. rubber bushing
   • Are all holes inserted correctly (except the hole for passing the PF pipe)? (Hozan)
   • Does it have a cross-shaped notch (otherwise there is a risk of damaging the cable with sharp edges)?
3. Wiring/connection
   • Is the PF pipe wired with an IV wire instead of a cable? (Isn't the VVF passed through as is?)Shima-chan's blog, Shima-bro
   • Are you confusing black and white around switches and outlets?
   • Are the grounded and non-grounded sides of the lamp receptacle or terminal block reversed?
   • Is the marking (small/medium) on the ring sleeve correct for the total cross-sectional area of ​​the wire?
   • Isn't the insulation coating bitten by the ring sleeve? (Is the insulation getting into the sleeve?)
4. Plug-in connector
   • Is the core wire firmly inserted all the way? (The copper wire is barely visible when viewed from below) (Gamidenki channel)
   • Is the length of the stripping too short so that the copper wire is barely visible?
5. time management
   • Is construction completed within 40 minutes?
   • Have you secured at least 5 minutes or more, preferably 10 minutes or more to confirm (Electricalist Peko's guideline) (Electricalist Peko)

If you're wondering "How much renovation or remodeling can I actually do on my own home?" or "Where should I even start?", please visit this page. If you're looking to learn more about specific renovation processes or construction details, don't miss this page as well!

Information on updates to this website will be delivered to you once a month.NewsletterIf you are interested, please register.

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References and Videos

I have summarized the materials and videos referenced in this text.

• HOZAN Co., Ltd. “Class 2 Electrician Examination Tiger Candidate Question No. 12 Construction Explanation of PF Pipe and Outlet Box” (Hozan)
• Gamidenki Channel “[Compatible with R7] PF pipe construction! Now is the time to recheck the double track diagram, explanation of published problem 12” (Gamidenki channel)youtube.com
• Electrician Peko "Class 2 Electrician Skills Examination Published Questions Explanation Series (Time Allocation/Confirmation Method)" (Electricist Peko)
• Shima-chan's blog "Class 2 Electrician Skills Exam Candidate Question No. 12 PF Pipe Construction"Shima-chan's blog, Shima-bro
• Japan Energy Management Center “Publication Problem No. 12 Double-track diagram/work explanation video”

If you watch all the videos and blogs about this area and then practice 2-3 times by following the steps in this article, I think you will be able to approach Publication Question 12 with a lot of confidence. If you have the PF pipe on your side, this problem is close to a service problem that can be solved if you calmly and carefully do it, so relax and practice.