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Electrical question

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Stephen Newell
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PostPosted: Sun Nov 18, 2012 1:49 am    Post subject: Electrical question Reply to specific post Reply with quote

I have a table saw that runs on 220v and the cord is only three prong with two hot and a neutral. Is there any benefit of putting a wire with a four prong plug on it and attaching a ground wire to the body of the machine.
 
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Mike (WA)
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PostPosted: Sun Nov 18, 2012 2:28 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

Its always a good idea to ground the frame of any device, IMHO. Assuming the socket you're plugging into is 4 prong and is grounded back to the panel, of course.

Got fired from a carpentry job one time because I complained about being shocked by the boss's ancient ungrounded circular saw while using it in the rain.
 
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Bob Bancroft
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PostPosted: Sun Nov 18, 2012 3:06 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

I would guess that if you placed ohmmeter leads between the motor/saw frame and third prong you would find that is your ground.
 
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evilboweivel
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PostPosted: Sun Nov 18, 2012 4:25 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

if it is wired properly then it has two hot leads and a grounding conductor not a nuetral conductor
 
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oliver power
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PostPosted: Sun Nov 18, 2012 4:38 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

If you are not getting shocked by touching the table saw, then don't worry about it. If you are getting shocked, do as you say. Run a wire from frame of table saw to ground (cement floor, dirt, etc.). I use to do it all the time when working outside in elements. Also, if you're getting shocked, check for wrong polarity in electrical wiring.
 
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oliver power
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PostPosted: Sun Nov 18, 2012 4:42 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

You did say 220V. I was thinking 110V when I mentioned polarity.
 
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TomH in PA
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PostPosted: Sun Nov 18, 2012 4:48 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

The 220v you have now is the voltage difference between the two hots (+110 to -110 as they alternate out of phase with each other).

You only need a fourth conductor if you want 110v at the saw and use either of the hot leads to get it. In that case you would need to add a neutral; you already have a ground.
 
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paul
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PostPosted: Sun Nov 18, 2012 5:39 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

A ground is of course a good thing!
However, people so often get a neutral and a ground wire confused, it is hard to advise you without seeing what you really have.

If the saw has no 110v features (electronic controls, clock, etc) then there is no need for a neutral on a pure 220v machine, and you likely already would have the two hots plus a ground, with no neutral?

--->Paul
 
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JimB2
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PostPosted: Sun Nov 18, 2012 6:13 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

Mike, better to be fired than end dead like a friend of mine's brother using an electric drill that the ground pin cutoff. Company got a big fine but someone died. That was 30 years ago.
Now, my neighbor works in construction and he says the Inspectors are always doing work site spot checks of electrical equipment, checking for damaged and ungrounded power cords and equipment. Cordless and air tools have eliminated some of the problems.

JimB
 
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John T
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PostPosted: Sun Nov 18, 2012 6:43 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

Without being there I have to take an "educated guess" at what you have which may or may NOT be what your post indicated. I just cant say settin here from your post alone, sorry.

If you really have a straight 220 volt (i.e. NO 120) device/saw and it has a factory installed 3 wire cord and/or plug Id GUESS THAT THIRD WIRE (especially if its bare or green instead of white) is the safety equipment GroundING Conductor NOT a Neutral !!!!!!!!!!!!

Put an ohm meter or continuity tester on that third wire and see if it's electrically attached to the saws outer conductive metal case/frame??? IF SO, ITS THE SAFETY EQUIPMENT GROUND ING CONDUCTOR NOT A NEUTRAL.

The ONLY reason you would need 4 (2 Hots, Neutral, Equipment GroundING Conductor) wires is iffffffffffffffff the device requires BOTH 120 and 240 volts. THEN AND IF SO YESSSSSSS USE 4 WIRES

HOWEVER if its straight 240 (NO 120) all you need is 2 Hots and the Equipment GroundING Conductor which is attached to the outer conductive metallic case/frame. Similar, if it were 120 volt ONLY, again all you need is 3 wires, Hot, Neutral, Equipment Ground

THE SAFETY EQUIPMENT GROUND ING CONDUCTOR ATTACHED TO A DEVICES OUTER CONDUCTIVE METALLIC CASE/FRAME SHOULD ALWAYSSSSSSSSSSSSS BE USED REGARDLESS IF 120 OR 240 VOLT.......... IT CAN SAVE YOUR LIFE

NEVERRRRRRRRRRR MIX N MATCH OR USE GROUND FOR NEUTRAL OR NEUTRAL FOR GROUND IT CAN GET YOU KILLED THEY ARE NOTTTTTTTTTT REPEAT NOTTTTTTTTTTTTT THE SAME. The Neutral is a live return current carrying GrounDED Conductor, the Equipment Ground is a GroundING Conductor dedicated to provide a direct low resistance current carrying path FOR FAULT CURRENT ONLYYYYYYY so the breaker can trip and de energize the circuit and save your life.

The live current carrying Neutral is insulated for a reason, you wouldnt peel off the Neutral insulated jacket and touch the wire would you ??????????? BUTTTTTTTT if you start mixin n matching and using Ground for Neutral or Neutral for Ground THAT COULD BE WHAT YOURE EFFECTIVELY DOING

If I missed anything hopefully other professional electricians, electrical techs, and engineers (NOT Billy Bob and Bubba who wired their own houses over a case of beer lol) can add to this

John T Longgggggggg retired Electrical Engineer and yes rusty on latest NEC so no warranty, but believe all the above is still true and potentially life saving advice
 
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John T
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PostPosted: Sun Nov 18, 2012 7:52 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

Good Morning Oliver, I have a friendly and hopefully helpful comment on your statement: "Run a wire from frame of table saw to ground (cement floor, dirt, etc.). I use to do it all the time when working outside in elements."

While its true, that may indeed prevent you from feeling any shock THAT DOES NOT CURE THE HAZARDOUS PROBLEM if a hot wire is shorted the the metal case/frame. It stops the shock because theres a very low resistance and low voltage across the wire you ran to ground thats in paralell with your body.

WHAT REALLY NEEDS TO BE DONE TO STOP THE SHOCK AND MAYBE SAVE YOUR LIFE is run a third wire Equipment GroundING Conductor (usually bare or Green) from the device back to the Equipment Ground Buss in the Panel. That way the FAULT CURRENT caused buy a hot wire against the case/frame has a low resistance path back to the panel so the breaker can trip, de energize the circuit and save your life. The earth or concrete ect alone (i.e. no copper ground wire)is usually too high of a resistance to allow enough current to flow that trips say a 20 amp breaker so the case/frame remains HOT and you could still be killed since that only takes maybe 30 to 50 milliamps of current thru your old ticker ouchhhhhhhhhh.......

Fun chattin with ya, hope this helps

John T
 
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Walt Davies
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PostPosted: Sun Nov 18, 2012 8:50 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

Take a good look in your main box remove the inside cover and on one or both sides you will see an aluminum bar that it is bolted directly to the box. Now look to see where your white neutral wire and the bare copper wire are secured. This will answer a lot of questions as to what they both do. GO TO THE GROUND WIRE WHICH IS CONNECTED TO THE GROUNDING ROD.
So what does the bare copper wire do. Hey your guess is as good as mine but I bet Ol John T can tell you if he has enough time and space available.
Walt
 
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John T
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PostPosted: Sun Nov 18, 2012 10:11 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

Hey there Walt you rascal, I just came in to take a break from RV preventive maintenance before my Sunday afternoon nappy (I dont like to hit er quite so hard on the Sabbath dont ya know)lol so I have a few minutes.

Yeppers, youre on track, in the Main Service Panel the Ground Buss and the Neutral Buss are bonded together but thats NOTTTTTTT true if you feed a sub panel off of the Main. Also at EITHER the weatherhead riser orrrrrrrrrr the meter base orrrrrrrrrr the Main Service Panel, a Grounding Electrode Conductor (bare No 4 Copper Wire) is tied to the NEUTRAL and its leads outside to a GROUNDING ELECTRODE such as driven into earth copper rods (called made electrodes) or metal water pipes etc etc.

The Neutral, since its BOTH a live current carrying conductor for normal return current and its tied to mother earth with that Grounding Electrode Conductor, IS CALLED A GROUN DED CONDUCTOR.

The equipment Ground (green/bare 3rd wire) is called a GroundING Conductor and its ONLY purpose and the ONLY time it conducts is TO CARRY FAULT CURRENT back to the panel so the breaker trips and saves your life as opposed to you touching that hot frame/case and fault current flowing through your old ticker n you wakin up dead

Nap time

Ol John T and all
 
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buickanddeere
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PostPosted: Sun Nov 18, 2012 10:42 am    Post subject: Re: Electrical question Reply to specific post Reply with quote

What neutral wire on your saw?
 
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buickanddeere
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PostPosted: Sun Nov 18, 2012 10:48 am    Post subject: Union shop would have protected you Reply to specific post Reply with quote

Mike (WA) wrote:
(quoted from post at 06:28:45 11/18/12) Its always a good idea to ground the frame of any device, IMHO. Assuming the socket you're plugging into is 4 prong and is grounded back to the panel, of course.

Got fired from a carpentry job one time because I complained about being shocked by the boss's ancient ungrounded circular saw while using it in the rain.


A union would have mandated that the equipment be safe and that you not be fired for not wanting to use faulty equipment.
 
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