Secure Live Screw Terminals Against Accidental Contact (very Simple Technique)




In this instructable, we will be sharing with you an incredibly simple way to secure live screw terminals, thus giving you the peace of mind you deserve while not sacrificing the serviceability of your wiring harness (something that cannot be claimed with either electric tape or heat shrink tubing).

Attached to this introduction is a video that summarizes the technique. If the idea appeals to you, then please feel free to follow our instructions and recommendations in the following steps. Note that wiring AC is a risky endeavor, and hence it is assumed that you are well-versed in electrical systems and that you know what you are doing.

That being said, let's show you how to secure those terminals!


Step 1: Get Hold of the Screw Terminals and the Button-shaped Nylon PCB Clips

The screw terminal I am using can accommodate up to a 10mm2 wire, even though we do not intend to use them for a wire that thick.

The Nylon PCB clips we're using are designed to ensure a predefined spacing between a PCB and an enclosure, by providing two levels of clipping, for two predefined diameters:

(a) a diameter of 3mm for the PCB hole

(b) a diameter of 4.25mm for the corresponding hole in the enclosure

The latter of which fits the screw cavity in the screw terminal snuggly.

Step 2: Strip, Crimp, and Screw Your Wires in a Sound Order

A word of common sense. As you join AC cables, they should not be live or otherwise you risk electrocuting yourself.

It is advisable to crimp the AC wiring as opposed to letting the screw terminal tighten against the strands of the wires themselves. This ensures consistency and strength since the copper strands tend to weaken and break over time, not only reducing the effective surface area of the conductor but also loosening what was once a secure electrical connection.

I use insulated terminals for AC wiring, and so should you (for obvious reasons). Strip, crimp using the right die and inspect the crimped wires after crimping to ensure strength, safety and reliability.

Last but not least, it is advisable to position the live wire (the brown) in the middle, for a number of reasons (please check the photos attached to this step).

Step 3: Cut and Plug Into the Terminal's Screw Cavities

Use a side cutter to cut the secondary level of clipping on the Nylon PCB clip. Position the side cutter as shown in the photo and push the head of the clip towards the side cutter as you cut to ensure a more flushed and thus a more effective cut.

Once cut, use the modified clip to plug the holes in the screw terminal. Note that you may, if you wish, plug the live wire holes alone, or plug those of the neutral and the Earth wires as well.

Once done, you may provide a further level of stress relief by zip tying the two AC cables joined by the terminal block. This will prevent mechanical tension from pulling the cables at the point of the screw terminal block.

However, that is only a recommendation but for most practical purposes, you are done with the trick explained in this instructable. Thank you!



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    5 Discussions


    2 years ago

    Here's proof that the main difference between knowledge & stupidity is that there's a limit to knowledge: (1) What does the abbreviation "PCB" stand for (so I'll know in which section of the store (and what kind of store: Radio Shack or Lowe's) to start looking); and (2) you write " is advisable to position the live wire (the brown) in the middle...", yet the photograph that immediately follows the words "Step 2" has the blue wires at the top; the green in the middle; and the brown wires at the bottom.

    The article was otherwise excellent and timely (as I'm about to start putting together a home sound system).