I recently inherited my dad's Delta/Rockwell Unisaw with a 220V
motor. The saw is a dream to use compared to my old Craftsman.
Luckily my shop is wired for 220 but I have a wiring question...
The wall plug is a 4 blade and the saw has a 3 blade plug so I need a
new plug for the saw. I was going to just buy a new 4 blade male plug
and replace the existing 3 blade on the saw.
So do I wire the ground/common from the saw to the ground or to the
common on the plug? I can't seem to figure out which is appropriate.
Or should I just buy a length of 12/3 and use all 4 lugs? Does it
matter? I assume if I did that all I would need to do is screw the
ground to the saw frame somewhere... right?
If I understand your comment...the receptacle is a 220v only. There is
no way to plug in a 120v line and it has a 40 amp breaker.
So you are saying wire the "common/grround" from the saw to the ground
on the receptacle... right?
I believe you have him backwards, the saw needs no neutral, since it
does not use 110v for anything. The outlet has a neutral, so it has 110
available. You should be able to change the plug to one that will fit
the outlet, ignoring the neutral.
No he wrote and was right that the receptacle is both 120 and 240
supply. You saw only can use the 240 part of that. Some things like an
electric range will have 240 heating elements and maybe a 120 clock so they
You could replace the plug on the saw and you would not connect any wire
to one of the connectors on the plug (the one that feeds the white wire, you
would only connect the red black and copper-green or as he suggested and so
do I, leave the plug as it is on the saw and replace the receptacle on the
wall with one that will fit the existing plug designed for 220 only, you
would not connect the white wire to any part of that receptacle.
The common and the ground are NOT the same thing. The only place the
connect is in the breaker box any where else the white is a current carrying
wire and should be treated as such, the ground is the only ground wire.
Yes... I have a "socket" in the wall. I had a new shop built on and it
was wired for 220 by a professional. I'm just an amateur trying to
figure out how to plug in my saw...
Thanks all... I think you straightened me out and I know what to do
I appreciate the help!
Well, you left me _very_ cornpuzzled... :)
A 4-hole wall outlet isn't what you want for a shop--that's for
something like a range or a clothes dryer.
What you really should do to do it correctly (but you don't say what
you think it is you think you know :) ) is get the proper socket for
the wall to match the saw and that matches the breaker amperage of the
circuit you're going to use. That is, don't use a 220V/15A rated
outlet in a 20A-protected circuit. The other way 'round is fine, (20A
outlet on a 15A circuit).
While it would function to put a plug on the saw to match the existing
outlet, why butcher a tool to a non-standard configuration when it's
just as simple to put the correct outlet in the wall? Plus, if you're
making a shop, you should standardize on a particular outlet choice
simply for future convenience.
IMO, YMMV, $0.02, etc., ...
It's probably a trifle cheaper and somewhat easier (aside from
having to kill the breaker) to change around the receptacle on
the wall than the plug on the cord.
Retrofit 220V plugs are clunky things. I'd prefer to leave a
molded cordset alone (if that's what the saw has), and do my
changes with solid copper.
Presuming of course that the thing isn't over-breakered for the
receptacle that matches the saw plug.
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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