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[Class 2 Electrician Skills Examination] Published Question 11 [Outlet Box and Threadless Conduit]

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Hello everyone, this is DIY Renova.

Published problem 11 is a problem with the theme of "outlet + 2 lights 2 blinking + metal pipe (screwless conduit) + outlet box".
While the double-line diagram itself is not that difficult, it is known that problems such as ``processing metal pipes,'' ``assembling box connectors and lock nuts,'' and ``routing IV wires'' are easy to stumble upon (according to an explanation on the electrician exam preparation net).Electrician exam preparation net.

In this article, we will explain the process in detail so that even those who are working with metal pipes for the first time can proceed from practice to actual level construction without hesitation just by using this page.

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!

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So, here you go.

Basic information

  • Class 2 Electrician Skill Test Published Question 11 (Candidate Question No. 11)
  • What is the theme of this exam number?
    • ``2 lights, 2 flashes'' with 1 outlet circuit + 2 lights
    • Construction of outlet box + threadless conduit (E19)
    • Wiring configuration using 1.6mm IV wire only in the metal pipe section (from the construction conditions of Candidate Problem No. 11)Hozan.

This problem requires not only simple VVF wiring, but also the ``on-site'' element of passing an IV wire inside a metal tube.
Particularly important is the assembly of the "screwless box connector + lock nut + insulation bushing".

Tools needed for this exam

In addition to the basic set, you will need tools for metal pipes.

  • Electrical knife (for removing the exterior of VVF)
  • VVF stripper or HOZAN passed multitool
    • Convenient for stripping the exterior and keeping the core exposed length constant
  • Pliers (fine adjustment of cutting/bending)
  • Radio pliers (for fine bending, holding terminal screws, etc.)
  • Crimping pliers (for ring sleeves: compatible with E type and P type)
  • Driver (+/-)
  • major (scale)
  • Metal pipe cutter or metal saw (for cutting E19 pipes)
  • Magic pen (dimensions/marking)
  • Insulating tape (marking, etc. as necessary)

If you search for ``VVF stripper'' on Amazon or Yahoo! Shopping for ``Class 2 Electrician Metal Pipe,'' you will find a variety of practice sets.

Materials to be prepared for this exam

Although the dimensions differ slightly depending on the year, the general composition is as follows (refer to the construction conditions of Candidate Problem 11 from 2019 to 2020).eleking.net.

  • power cable
    • VVF 2-core 1.6mm (power supply ~ joint box)
  • Cable for lighting equipment
    • VVF 2-core 1.6mm (for square hook ceiling)
    • VVF 2-core 1.6mm (for lamp receptacle)
  • Switch/outlet side cable
    • VVF 2-core 1.6mm (Joint box to outlet box, combination patterns of VVF + metal tube depending on the year)
  • Electric wire in metal pipe section
    • IV wire 1.6mm (several black, white, red, etc. used for connecting the joint box to the switch and outlet with metal pipes)
  • utensils
    • Square hanging ceiling rosette
    • lamp receptacle
    • Built-in tumbler switch (2 pieces, I and Ro)
    • Recessed electrical outlets (1 or 2)
    • Embedded continuous mounting frame (for switch/outlet)
    • Joint box (for VVF)
    • Outlet box (for metal pipes)
  • metal pipe parts
    • Threadless conduit E19 (1 piece)
    • Screwless box connector (for E19)
    • lock nut
    • insulation bushing
  • connection member
    • Ring sleeve (small/medium)
    • Plug-in connector (for 2 and 3)

The important point here is that only the part that passes through the metal tube becomes an IV wire.
This is based on wiring regulations that generally require single-core insulated wires (IV wires) to be used for reasons such as ``the exterior of the VVF cable is easily damaged in metal pipes'' and ``heat is trapped differently'' (according to the IV wire standard of JIS C 3347 and general construction standards for metal pipe work).Electrician exam preparation net.

Main flow

Here, we will organize the actual work order in rough steps.
I will also write about where you can use HOZAN's "Pass Multi-Tool" (from HOZAN's official explanation).Hozan.

  1. Read the construction conditions of the question paper
    • First, check the grounding side (white) and non-grounding side (black), the IV wire designation of the metal pipe section, the connection method (ring sleeve/connector), the installation position of the box connector, etc.
  2. Draw a double line diagram (wiring diagram)
    • Copy the location of the equipment
    • White line → outlet and each lighting
    • Black wire → to outlet and switch
    • Switch → Corresponding appliance
    • Draw only the metal pipe sections with IV lines.
  3. Determine the cable length and IV wire length
    • Determine the distance between the power supply, J-BOX, and J-BOX, plus the extra length of approximately 100 mm for the joint, while reading the double-track diagram.
    • If you use the scale part of the "passing multi-tool" to note down the basic dimensions such as 100mm and 150mm, you won't get confused during the actual test.
  4. Cutting and stripping the VVF cable
    • Use the strip gauge of the passed multi-tool to maintain a constant value of 10 cm for the exterior peeling and 20 mm for the core wire.
    • This is useful for avoiding defect judgments such as "new line exposure is 10 mm or less" or "20 mm or more" (based on defect judgment criteria).Authorized test center
  5. Dimensioning, cutting, and bending of metal tubes
    • Determine the length of the metal pipe based on the dimensions between the joint box and the outlet box, taking into account the bending allowance.
    • Mark the required length on the scale of the passed multi-tool and cut it with a metal tube cutter.
    • Bend 90 degrees with a bender. The bending radius for E19 is recommended to be approximately 4 times the outside diameter, so if you bend it to the position specified by the vendor, it will meet the standard (based on general metal pipe construction standards).Electrician Examination Preparation Net
  6. Assembly of box connector, lock nut, and insulation bushing
    • Insert the connector into the hole on the side of the outlet box and secure it with a lock nut from inside the box.
    • Insert the metal tube into the threadless connector and tighten.
    • Be sure to install an insulating bushing on the box side to prevent damage to the IV wire.
  7. Cutting and threading IV wire
    • Cut the required number of 1.6mm IV wires, such as black, white, and red, to the same length using the gauge of a passing multitool.
    • Run the wire from the metal tube side to the outlet box, leaving enough room for the tip to come out.
  8. Wiring to each device/Connection inside the joint box
    • While looking at the double-line diagram, connect the white lines to each load and outlet W terminal, the black lines to the outlet/switch, and from the switch to the appliance.
    • The power supply side is connected using a ring sleeve, and the other connections are made using plug-in connectors according to the construction conditions (construction conditions 8 to 9).essence of electricity
  9. Assembling the switch/outlet into the mounting frame
    • Fix the switch and outlet to the continuous mounting frame and screw them to the outlet box.
  10. final check
    • Check the wire type, color, connection point, connection method, and whether you have forgotten to attach any metal pipe parts.

Especially in this case, careful attention to the processing of the metal tube and the configuration of parts around the outlet box will make a big difference.

How to draw wiring diagrams and things to be careful about

The single line diagram in published problem 11 has only the following three components (from the single line diagram explanation in candidate problem 11).eleking.net.

  1. Switch “A” → Flashing circuit of square hook ceiling
  2. Switch "B" → Lamp receptacle flashing circuit
  3. Outlet circuit (always energized)

The basic rules for making this into a double line diagram are the same as for other problems.

  1. Place the equipment
    • Draw the power supply, joint box, outlet box, square hook ceiling, lamp receptacle, switch (I and B), and outlet in the same layout as the problem diagram.
    • Be sure to write "i" and "b" on the switch so that you can see at a glance which device it is compatible with.
  2. Connect the ground side (white)
    • Connect in order from the ground side (white circle) of the power supply to the "W display terminal" of the outlet, the ground side terminal of the square hook ceiling, and the screw part of the lamp receptacle's holder (installation conditions 2, 4, 5, 6).essence of electricity
    • Marking the connection points in the joint box with a black circle (・) will help you avoid misunderstanding the location of the ring sleeve/connector later.
  3. Connect the non-grounded side (black) to the switch and outlet
    • Connect the non-grounded side (black circle) of the power supply to the outlet and switches "A" and "B" (Construction condition 3).essence of electricity
    • Up to this point, you can draw "power supply → outlet" and "power supply → switch."
  4. From switch to fixture
    • From switch “I” to square hook ceiling
    • From switch “ro” to lamp receptacle
    • The color of this part is often not specified in the construction conditions, so you can choose it from red, white, black, etc. (however, choose a color that you are unlikely to make a mistake with).
  5. Draw different metal pipe sections (IV lines)
    • Draw the "IV line" between the joint box and the outlet box as a metal pipe section.
    • If you clarify the location where VVF changes to IV and the number of pieces, you will not get confused when checking the materials.
    • For example, write the color and number of wires in the form of "1 white wire (ground side)," "1 black wire (non-ground side)," "1 red wire (for switch)," etc.
  6. Add cable/wire type/thickness
    • Make a small note of VVF1.6-2C, VVF1.6-3C, IV1.6, etc. next to the line.
    • Don't forget to write the IV wire inside the metal tube (this is emphasized as a key point in the official HOZAN explanation).Ho-zan.
  7. Connection method and crimp mark
    • Write on the double-track diagram the information specified in the construction conditions, such as "A part is a ring sleeve" and "B part is a plug-in connector."
    • For the ring sleeve part, decide on the markings such as "〇・Small" or "Medium" based on the thickness of the core wire (1.6 mm = equivalent to "Small") and the number of wires, and write "Small" etc. next to the connection point on the double-track diagram to make installation smoother (according to the ring sleeve marking standards).Qualified person

The key is to "determine all the white line routes first."
If you connect the white lines with the image of "power supply → outlet → lighting equipment" in one stroke, and then draw the black line and switch line, the double-line diagram will look more organized.

How to proceed with practical skills and take a breather

From here, I will write down the actual procedure keeping in mind the 40-minute exam time and a guideline for where to take a break.

  1. Confirmation of supplied materials (target: 5 minutes)
    • While looking at the list of materials provided for the question paper, check whether each item is ``Yes'' or ``No.''
    • Be sure to check that the metal tube, outlet box, box connector, lock nut, and insulating bushing are included.
    • If there is a shortage here, please raise your hand and report it. Before you rush into wiring, take a deep breath and clear your head.
  2. Draw a double-line diagram (goal: 7-10 minutes)
    • Equipment arrangement → white line → black line → switch wire → line type/crimping mark.
    • When you have finished writing, be sure to check out loud whether the words are "switchy → square hook" or "switchro → lampre" to make it easier to notice mistakes.
    • Where this ends is the first "breathing point".
  3. Dimensioning and cutting of cable/IV wire (target: 5-7 minutes)
    • Quickly mark 100mm and 150mm using a passed multi-tool.
    • For each section, determine the length based on the "distance between devices + approximately 100 mm of extra length inside the joint box".
    • For example, if the power supply ~ J-BOX is 150 mm, and the extra length inside the J-BOX is 100 mm, the format would be "250 mm."
    • While cutting, lightly write ``power'', ``sealing'', ``lamp'', etc. on the cut cable with a marker to avoid confusion.
  4. Machining metal tubes (target: 7-10 minutes)
    • Measure and mark the required length of the metal tube.
    • Cut with a metal tube cutter and "deburr" the cut surface with a reamer or file.
      • If any burrs remain, they will damage the vinyl sheathing of the IV wire, leading to future insulation failures (because the withstand voltage of wire insulation tends to drop below the breakdown electric field strength when there are scratches, as the electric field concentrates locally).
    • Bend 90 degrees with a bender.
      • The outer diameter of E19 is approximately 19 mm, so keeping the bending radius at least four times that radius (approximately 80 mm) will reduce the possibility of tube collapse and make wire threading easier (recommended value for general metal tube bending).Electrician Examination Preparation Net
    • Attach the connector + lock nut + insulation bushing to secure the metal tube.
  5. IV line running (target: 3-5 minutes)
    • Cut the IV wires of the number and color determined on the double line diagram to the specified length.
    • It will be faster if you pass all three of them at once from the metal pipe side towards the outlet box.
    • You can leave the tip about 100mm out with plenty of room and trim it later to match the length of the instrument.
  6. Wire connection to equipment/connection inside joint box (target: 10-12 minutes)
    • First, connect the white wire and black wire inside the joint box using a ring sleeve/connector.
    • Next, connect the lighting equipment, outlet, and switch side in order.
    • Around the switch, be careful not to confuse the common feed of the black wire (power supply → A → B) with the switch wire output from I and R.
    • Once you visualize in your head what the circuit will look like when all the switches are operated, it will be easier to notice incorrect wiring.
  7. Installation of equipment and final confirmation (goal: all remaining time)
    • Fix the switch/outlet to the mounting frame and screw it to the outlet box.
    • Install the square hook ceiling/lamp receptacle in the specified direction and cable lead-in method.
    • Finally, check the 4-item set of ``color,'' ``wire type,'' ``connection method,'' and ``metal pipe parts'' before submitting.

As for time allocation, practicing with the idea that you should leave 25 minutes for ``double line diagram + cable/metal tube processing'' and 15 minutes for ``wiring + final confirmation'', so you will have more time during the actual session.

Items to check for defects and oversights

The ``common defects'' unique to Publication Question 11 are summarized in a checklist format.
After practicing before the actual performance, it is a good idea to self-check with this list (organized based on the Electrical Engineer Examination Center's defect criteria and explanation of construction conditions for Candidate Question 11).Authorized test center

  1. Around metal pipes and outlet boxes
    • Is the direction of the screwless box connector reversed?
    • Is the lock nut firmly tightened from the inside?
    • Is an insulating bushing installed?
    • Is the metal tube fully inserted into the connector and is there no looseness?
    • Are there any burrs left on the cut surface of the metal pipe (it is dangerous if it is sharp and visible to the naked eye)?
  2. Incorrect line type/color of IV line/VVF
    • Is VVF not passed through the metal pipe section (must be IV wire)?
    • Are all the grounding sides marked with white lines?
    • Is the white wire connected to the W terminal of the outlet?
    • Is the white wire connected to the screw part of the lamp receptacle?
    • Is the white wire connected to the ground terminal of the hook ceiling?
  3. Wiring error in switch/outlet
    • Is the switch "A" → square hook ceiling, "B" → lamp receptacle?
    • Does the black wire of the power supply come to the common side of the switch (does it not go from the switch to the power supply side)?
    • Is there a black wire that is always energized on one side of the outlet (is it connected through a switch)?
  4. Incorrect connection method
    • Even though the connection to the power supply is specified with a ring sleeve, are you connecting it with a plug-in connector?
    • Is the plug-in connector used in a ring sleeve?
    • Is the marking on the ring sleeve (small, medium, etc.) correct for the thickness and number of core wires?
    • Is the exposed core length extremely short (less than 5 mm)/too long so that the copper is completely exposed?
  5. Poor installation of equipment
    • Is the cable lead-in direction of the lamp receptacle from the bottom as specified? (Is the pedestal missing?)
    • Is the length of the square ceiling ceiling with the exterior peeled off appropriate? (Almost no exterior remains/On the other hand, is it too long and unsightly?)
    • Is the switch/outlet firmly fixed to the mounting frame (no wobbling)?
  6. Mismatch with wiring diagram
    • Is construction carried out according to the double-track diagram? (Are there any improvisational changes made during construction?)
    • Are there any errors in the number and thickness of VVF/IV to be used?
    • If the construction conditions state that all wires passing through the joint box must have connection points, are there any wires that are passed through?

Finally, although this problem may seem difficult because there is a metal tube, the structure itself is quite simple.
Rather, it is a type of problem where wiring mistakes and forgetting to attach parts around metal pipes become more noticeable because the double-track diagram is clear.

Try practicing it several times,

  • "Write a double line diagram"
  • "Processing cables, metal tubes, and IVs"
  • "Connect"

If you measure your time every three blocks, you will be able to work calmly during the actual performance.

Main materials/videos used for reference (for transparency of learning)

  • HOZAN “Class 2 Electrician Examination Tiger Candidate Question No. 11 Explanation Page” (Key points for outlet boxes and screwless conduit)Hozan.
  • Electrician Examination Preparation Net “Candidate Question No. 11 Double Line Diagram” (Overview of circuit configuration and metal pipe work)Electrician Examination Preparation Net
  • Eleking.net “Reiwa 5/Reiwa 6 Candidate Question No. 11 Single Line Diagram and Construction Condition Explanation” (Used to organize construction conditions)eleking.net.
  • Various qualification information sites "Candidate Question No. 11 Explanation of how to draw a double-track diagram" (confirmation of general double-track diagram procedure of 2 lights, 2 blinks + outlet)electrical-worklife.com.
  • Provided by users
    • Gamidenki Channel Publication Problem Series
    • Electrician Peko's skill test explanation video
    • HOZAN official video “Second class electrician skill test construction method”
      (Used as a reference to supplement the nuances of how to draw double-line diagrams, work procedures, and precautions)

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