Plug Wiring

Fitting a single phase plug top the right way:

The importance of a properly wired mains plug can not be over stated. Servicing electronic equipment has shown me some badly wired plugs, and many times that is part of the unreliabilty problems some equipment have.

Here is a typical example:

Note that the insulation of the brown (live) and blue (neutral) is cut back more than necessary, leaving dangerous open copper. Also see that the yellow/green (earth) wire shows signs of melting.

First stage:

Disassemble the whole plug

Look for the correct insertion point in the brass hole. The smooth machined bevelled hole is the correct side to insert the wire.

Cut off the mangled end of the three wire cable, and start by cutting back enough insulation  to allow connection to the earth terminal (top thick terminal). Be careful to not cut into the conductor sheathing (the brow/blue/yellow leads)

Next cut back the conductor sheathing to allow insertion through the whole diameter of the brass shaft.

Bend the copper back over the insulation and insert the conductor into the brass shaft hole with the naked copper below the screw. Tighten the screw till you feel the screw stops going in. This is when the insulation has been compressed, but the copper is still firm. Driving the screw too far can damage the copper, or even cut it through.

Do all three conductors the same way.

Insert the copper terminals back into the plug base at the correct positions. As you can see 




All done. Put the plug top back in position, and replace the screws. Tighten only to compact the plastic. Over tightening the screws can break the plug housing… which is dangerous, especially for the person inserting, or removing the plug from a live mains socket.

Now go and check all your single phase plug tops, and fix any bad workmanship.

I hope this instruction was of value to you. Leave comments if you feel inclined. 

Keep safe and enjoy the music.



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