Summary of remote control relay (terminal block) concepts and construction procedures
First of all, I'm sorry for the strong gamiden color that came out last time. From now on, as originally requested, I will rewrite it properly as a "blog article" as part of the series of published questions 1 to 13. This time, we will focus on "Published Problem 8" and will cover everything from wiring diagrams to installation and defect checking all at once.
Actually, I am also learning by summarizing things like this lol
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So, here you go.
Basic information
- Class 2 Electrician Skills Test Published Question 8 (assuming the same type of questions as 2021-2020) (organized HOZAN official commentary and various web explanations)Hozan Co., Ltd.）
- What is the theme of this exam number?
- Circuit configuration in which a “terminal block” is used instead of a remote control relay
- How to use VVR cable (1.6mm 2-core)
- Ability to organize wiring to control three loads (lighting) with separate switches
- Power to correctly separate connections between joint box and terminal block
Many people say that ``It looks messy and I don't like it...'' regarding Publication Problem 8, but the mechanism itself is simple, just ``branch the phase (black) with a terminal block and connect it to each switch/load.'' If you understand this at a verbal level and then draw a double-line diagram, you will be able to understand it much more clearly (the explanations for electrical qualification labs etc. are also explained along the same principle)essence of electricity）。
Tools needed for this exam
In addition to the general skills test set, we will list tools that you should be especially aware of in Publication Question 8.
- Crimping tool (for ring sleeve)
- Electrical knife or stripper (for stripping the exterior and core wires of VVF/VVR)
- Phillips screwdriver (No. 2)
- Flat head screwdriver (tightening/loosening terminal block screws)
- pliers
- Measure (about 300mm is enough)
- Pliers with cable stripper/HOZAN certified multi-tool
- Useful for assisting insertion into ring sleeves and tightening lock nuts, etc. (From HOZAN video manuscript (Hozan))
Materials to be prepared for this exam
Although there are detailed differences depending on the year, we will organize the typical patterns (standard structure of candidate question 8).Denbro｜Specialized site for electrical work）。
- cable
- VVF 1.6mm 2 cores
- VVF 1.6mm 3-core (between switch and joint box, etc.)
- VVR 1.6mm 2-core (wiring around the terminal block. Cable with rounded sheath and slightly hard)
- utensils
- One-way switch (3 pieces)
- lamp receptacle
- Hanging ceiling (may include installation omitted)
- Terminal block (replacement of remote control relay)
- Joint box/outlet box
- connection member
- Ring sleeve (small)
- Plug-in connector (for 2 and 3)
- insulation tape
- others
- VVR imitating vinyl cabtyre round cable
- Instrument screws, mounting frames, etc.
Since the thickness of all core wires is 1.6 mm, only the "small" size ring sleeve is sufficient (according to the conditions in Denkishoin's test preparation book and online commentary).
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
From here, we will briefly outline the flow from "starting the exam to completing the work" and then move on to detailed steps.
- Take a quick look at the question paper and check the characteristics of the wiring diagram (single line diagram)
- The symbol for the terminal block is displayed.
- 3 lights blinking individually with each switch
- Copy the fixture symbols in the same layout as the wiring diagram
- Create a multi-line diagram in 5 steps, focusing on the terminal block
- Determine the length of the cable and cut it out at once
- Strip the exterior and core wires, temporarily connect the wires → compare them with the double track diagram
- Terminal block screw fixing, joint box crimping and connector processing
- Finally, install the switches and equipment and check the continuity image in your head.
- Visual check according to defect checklist
Here, the ``HOZAN Pass Multi-Tool'' clearly comes into play in the following two places (organizing HOZAN/Gamidenki video manuscripts).
- When pushing the core wire all the way into the ring sleeve
- Aligning the small hole at the tip of the multi-tool with the ring sleeve and pressing firmly will help prevent core wire exposure defects of 1 cm or more.
- Attaching and detaching the mounting frame
- You can quickly insert and remove the switch by inserting the tip of the multi-tool into the groove and twisting it.
Although it is not a "must" tool, Problem 8 has many connection points and "speed and reliability" are important, so it is a very compatible problem in terms of saving time.
How to draw wiring diagrams and things to be careful about
From here on, we will break down how to draw double-line diagrams into the simplest possible rules.
It is easy to remember a double-line diagram if you write it in the following 5 steps (similar to the explanation of double-line diagrams by Ohara of Qualification and Eleking).
1. Place the equipment as is.
- In the same positional relationship as the single line diagram on the question paper.
- power supply
- terminal block
- joint box
- 3 lights (the only part omitted is the dotted frame)
- three switches
Arrange them as they are on graph paper or in the memo space.
This is the work of "aligning shapes", so you can just copy without thinking anything.
2. Connect only the ground side (white) at once
- Starting from the ground side (white) of the power supply
- all light fixtures white
- If necessary, use the W side of the outlet.
Connect them in a straight line.
In published problem 8, the theme of the terminal block is "branching on the phase (black) side," so in most cases the ground side is grouped together in a joint box without going through a terminal block (according to Eleking's explanatory diagram).
The key is to use one stroke of white as much as possible. If you connect all the white lines first and then the black lines, the visibility of the double-line diagram will improve at once.
3. Organize the black (phase) around the terminal block
This is the ``cruel'' of Publication Question 8.
- Black power supply → common terminal on terminal block
- Each output terminal on the terminal block → to each switch
- Switch return line (line coming out of the switch) → black of each light
At this time, the concept of cable type is as follows.
- Power supply to terminal block: VVF 2-core OK (black/white)
- Terminal block to switch group: Pattern where VVR 2-core is specified
- Because the covering is round, it often appears "roundish" in illustrations.
- Switch ~ Lighting: VVF 2 cores
It is easier to remember if you think of the terminal block as a ``remote control relay box'' with only the black wires going in and out.
4. Complete the control lines (switches to lights)
- Check the combination of each switch and the corresponding lighting
- Example: Switch A → Fixture A, Switch B → Fixture B...
- Draw black as the "switch return line" for each.
Once you've written this far, you should be able to see "All Black Routes."
Finally, if necessary, make an auxiliary note of where to use the "red" part of the 3-core cable (this time, most of the patterns are based on VVR 2-core cables, so red appears less frequently, but depending on the year, there are variations that combine with 3-core VVF)Eleking）。
5. Write down the wire color and connection method (if necessary)
- Add color symbols such as "W", "B", and "R" to each of the white, black, and red lines.
- Write crimp marks such as "small" and "○" where the ring sleeve will be used.
- For 1.6mm x 3 pieces, "small sleeve/small mark" etc. (see list of qualified shops)
At this stage, when you look back at the double-track diagram during actual construction, you can instantly determine that this is a small sleeve or small mark, which reduces the amount of time you spend getting lost during construction.
How to proceed with practical skills and take a breather
From here, I'll break it down into steps along the timeline, including where to take a break.
Step 1: Finish the double line diagram within 5 minutes of starting
- The exam time is 40 minutes. Of that time, you can use ``at most 5 minutes'' for double-track diagrams.
- Once you get used to it, you will be able to draw it in 2 to 3 minutes (a similar guideline is given on the double-line diagram explanation site).
If you decide, ``If it takes more than 5 minutes, I'll cut it off and start construction.'' This will reduce your impatience.
Step 2: Cut all cables (approximately 10 minutes)
- Cut out all the cables at once while looking at the "specified dimensions" on the question paper.
- Approximate extra length
- Instrument side: +150mm
- Inside the joint box: +100mm
- Around the terminal block: Since there are screws, it is easier to work if there is +150 to 200 mm.
The allowable current for VVF/VVR 1.6mm is approximately 18A, and the load current of the test circuit is several A or less (as a guide from the standard values such as JIS C 3342). In other words, there is plenty of room in the thickness, so there is no problem in determining the length by prioritizing the bending radius and ease of handling during construction.
Take a breather here. When you have finished cutting all the cables, take a deep breath and quickly check that the number and length match the double-track diagram.
Step 3: Exterior stripping and core processing (approximately 10 minutes)
- Exterior stripping length
- Appliance connection part: Approximately 100mm (please be careful as it varies depending on the appliance. Thread type is 50mm, if there is a gauge follow that, otherwise it is basically 1000mm)
- Exposed length of core wire
- Terminal block/switch: about 10 to 12 mm
- Ring sleeve connection part: about 15 to 20 mm once aligned
If you use the stripper groove of a HOZAN-approved multi-tool, you will be able to strip the strip at approximately the same length each time, resulting in a stable finish (HOZAN).
Step 4: Temporary connection → Check with double track diagram (approximately 10 minutes)
- First, temporarily connect the parts that do not require screwing.
- White line inside the joint box
- some black lines
- Just twist the core wires slightly and gather them together, but don't crimp them yet.
At this point, compare the double-track diagram with the actual object and point to the number, color, and destination of the lines.
The most time-efficient method is to find the mistake here and fix it. If you try again after crimping, you will have to do the extra work of cutting the ring sleeve.
Step 5: Main wiring of terminal blocks, switches, and equipment (approximately 5 to 8 minutes)
- terminal block
- Arrange so that only black lines are included (be careful not to get the white lines mixed in)
- Check whether the number of pieces inserted into one hole is within the specified limit (usually up to 2 pieces)
- switch
- Do not confuse the common terminal with the load side terminal.
- Align the orientation and fix it to the mounting frame.
- lighting equipment
- Lamp receptacle: White line on the W side, black line on the other side
- Hanging ceiling: White line on the W display side
Again, take a deep breath. If you forcefully pull the screws after tightening them, the core wires will loosen and lead to defects, so be aware of ``arranging the wire routing before tightening.''
Step 6: Crimping and insulation treatment (approximately 5 minutes)
- Check the size and crimp mark of the ring sleeve according to the double line diagram.
- 1.6mm x 2: Small / "◯"
- 1.6mm x 3-4: Small, "Small", etc. (Memorize 6 typical patterns)
- Push the core wire deep with a HOZAN-approved multi-tool
- If the core wire is visible from the bottom of the ring sleeve for more than 1cm, it is a defect, so "push it in until it is invisible" (HOZAN)
- After crimping, be sure to pull each wire lightly to make sure they don't come off.
Finally, wrap the ring sleeve part with insulating tape and visually check for twisting or exposed core wire.
Items to check for defects and oversights
Here is a list of the most common flaws in published question 8 and how to check them.
- White wires are mixed on the terminal block
- Remember that the terminal block is for "phase (black) only"
- Before completing the test, be sure to check if there is any white on the terminal block.
- Insufficient tightening of the terminal block
- VVR has a hard coating and tends to return easily, so check by pulling lightly after tightening.
- If it remains loose, it will be treated as a "poor contact" and become a defect.
- More than 1cm of the core wire is visible from the bottom of the ring sleeve.
- Get into the habit of pressing and crimping with a HOZAN-approved multi-tool (HOZAN)
- Mismatch between switches and lights
- Simulate in your head whether ``if you turn on the switch in A, the light in A'' will turn on.
- Check the switch return line (black) against the double track diagram to see if it is connected to the wrong light.
- Mistaking the grounded side and non-grounded side
- Are the white lines on the W side of the lamp receptacle and the W side of the outlet?
- Are you connecting white and black together in the joint box?
- Forgetting to wrap insulation tape
- The ring sleeve connection basically requires wrapping with tape.
- Also check that the core wire does not protrude from the screw part of the terminal block.
- VVR too bent
- The approximate allowable bending radius for VVR cables is approximately 6 times the outer diameter (as a guide from the JIS standard value for general low voltage cables)kaneshindenki.co.jp）
- If you bend it too tightly, it may be considered a ``defective construction'', so be aware of bending it with a gentle radius.
Reference materials/videos
The content of this article has been reconstructed based on the following materials and video manuscripts. It will be easier to visualize the actual hand movements and tempo if you watch the video as well.
- HOZAN "Class 2 Electrician Skills Test Published Question 8" explanation page/video manuscript (used to confirm the structure of the remote control relay question and cable type)Hozan Co., Ltd.
- Eleking “Class 2 Electrician Candidate Question No. 8 How to draw a double-track diagram”
- Electrical Qualification Lab “Class 2 Electrician Published Question 8 Double Line Diagram Creation Procedures and Points”
- Qualified shop｜Second class electrician double line diagram explanation series (list of ring sleeve crimping patterns)
- HOZAN Electrician Examination Tiger video manuscript (instruction on ring sleeve insertion and how to use the passing multi-tool) (Hozan)
- Gamidenki Channel Published Problem Series Video Manuscript (Fixing the mounting frame, lock nut processing, usage example of the passing multi-tool)
- Electrician Peko's skill test explanation video (confirmation of wiring image and actual procedure for problems using terminal blocks)
If you treat published problem 8 as a problem of ``organizing the flow of black around the terminal block'' like this, it will become much easier.
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