Last week I had to re-wire my table saw because the shop I am now in
has different 220V/20A outlets. The table saw is a Powermatic 66 220V
single-phase 3HP. About an hour after I did this, I was checking the
run-out, pressed my knee against the power switch box, and got a sharp
shock! Fortunately, only my right side was leaning against the saw at
the time; my left hand and leg were not touching it, so the shock did
not pass through my heart. It did wake me up a bit.
Today I pulled the wiring out and found a couple of places where the
wires had gotten nicked, so I re-wired it. I protected the power cable
where it goes into the power switch box with electrical tape as it
appeared that was where it had shorted out.
My question is this. How do I verify/check my connections without
getting shocked again? How does an electrician do this?
The proper way is to use an isolation measurement device, which puts
the wires on a rather high tension (500 od 1000V) and then with a
special probe all the surfaces are checked.
Another point to check is the conductivity of the wires, where the
right way is to measure with short high current pulses, again with a
Anyway it seems that the protective earth of your saw was not
connected properly, otherwise the fuse would have blown, saving you
from shock. Maybe also the wall receptacle has no proper protective
Interesting... Did you make certain that the ground wire (it is either the
bare one or the green one) is connected to the box which is then bolted to
the saw? Your experience indicates not. There should be no need for tape
inside a box; in fact, if the tape helps, you have not connected everything
By the way, does your switch disconnect both hot wires? That 220v motor
won't appreciate getting 110v from one leg of the wiring.
That 240V motor won't care any more about one side of the circuit
being disconnected than a light bulb does in a lamp with a non
polarized plug that has the neutral side of the plug in the hot socket
(normal and legal for many, many years).
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