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Old 11-14-2009, 05:45 PM   #1
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240v plugs, tablesaws, etc.


Hi guys,

I'm trying to set up my new tablesaw (this one) and I have to install a new plug. The outlet looks like this:

and so i bought this plug
My question is: the instructions for wiring the plug, that come with the plug, ask me to plug the black wire in to one prong, the green wire into the ground prong, and the white wire into the last prong (the "neutral").

But my saw has a red wire, a black wire and a green wire. My guess is that the saw's red wire should connect to the prong the plug thinks should be black, the saws black wire to the white, and the green to green.

What do you think? I don't want to screw up my saw by doing this wrong.

P.S. I bought the saw used, and the old plug that was on it had an x, a y and a g. The red was wired to the x, the black to the y and green to g. If that helps any...

Thanks in advance for any help

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Old 11-14-2009, 05:55 PM   #2
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240v plugs, tablesaws, etc.


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Old 11-14-2009, 06:04 PM   #3
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240v plugs, tablesaws, etc.


It seems like this model calls for a 20A circuit. You have the wrong plug and receptacle. You should use a 6-20. Check page 11 of the manual. Black/Black and Red/White should be your L1/L2 and then green to green(grounding).
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Old 11-14-2009, 07:40 PM   #4
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240v plugs, tablesaws, etc.


While you can use this 50 Amp monstrosity, it is not required to oversize your cord and plug connections like this.

One thing: There is no "neutral" connection for a 240 Volt apparatus. The white conductor is used as a hot line, simply mark it red with a magic marker or other suitable means.
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Old 11-14-2009, 08:25 PM   #5
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240v plugs, tablesaws, etc.


On a 220 volt single phase circuit, the only wire that matters is the green one.

If the saw has black-red-green, the green one must be connected to the ground terminal. Black and red go to the other two. It doesn't matter which one goes where.

If the receptacle is fed with NM (Romex), the bare wire (ground) must go to the ground terminal. Black and white go on the other two. It doesn't matter which one goes where.

Is the receptacle existing? It'll work just fine, as stated earlier, it's a bit of overkill.

If this were mine, I'd use a 30 amp receptacle and plug. either twist-lock or straight-blade. If it's fed with NM, I'd use 10/2. I'd use a 30 amp two pole breaker.

I don't think a 20 amp circuit is enough for a 3 HP motor. It might trip occasionally when starting.

Rob

P.S. In my opinion, Grizzly makes pretty good machinery.
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Old 11-14-2009, 11:15 PM   #6
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240v plugs, tablesaws, etc.


Quote:
Originally Posted by micromind View Post
On a 220 volt single phase circuit, the only wire that matters is the green one.

If the saw has black-red-green, the green one must be connected to the ground terminal. Black and red go to the other two. It doesn't matter which one goes where.

If the receptacle is fed with NM (Romex), the bare wire (ground) must go to the ground terminal. Black and white go on the other two. It doesn't matter which one goes where.

Is the receptacle existing? It'll work just fine, as stated earlier, it's a bit of overkill.

If this were mine, I'd use a 30 amp receptacle and plug. either twist-lock or straight-blade. If it's fed with NM, I'd use 10/2. I'd use a 30 amp two pole breaker.

I don't think a 20 amp circuit is enough for a 3 HP motor. It might trip occasionally when starting.

Rob

P.S. In my opinion, Grizzly makes pretty good machinery.
I respectfully disagree with your statement that 20a. @ 240v. is not enough to run a 3-HP motor.; 20x240=4800; 3hp=2238w. or 2.238kw.
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Old 11-14-2009, 11:51 PM   #7
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240v plugs, tablesaws, etc.


The full-load current of a typical 3 HP motor will be around 15 amps at 230 volts. The starting current will be about 90 amps.

The magnetic trip unit of a typical 20 amp breaker is set at around 100 - 150 amps, depending on the manufacturer. Magnetic trip units are notoriously inaccurate. 20 amp breakers I've tested have tripped as low as 70 amps, and as high as 200 amps.

The breaker might start the saw reliably forever, or it might trip once in a while. Or it might trip every time.

In my opinion, the starting current of the motor is too close to the trip current of the breaker to be reliable.

Rob

P.S. a 3 HP motor will consume 2238 watts only if it is 100% efficient. The efficiency of a typical 3 HP single phase motor is more like 75 - 80%. It doesn't matter anyway, current will cause a breaker to trip, not watts.

Last edited by micromind; 11-14-2009 at 11:56 PM. Reason: added P.S.
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Old 11-14-2009, 11:54 PM   #8
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240v plugs, tablesaws, etc.


Quote:
Originally Posted by micromind View Post
The full-load current of a typical 3 HP motor will be around 15 amps at 230 volts. The starting current will be about 90 amps.

The magnetic trip unit of a typical 20 amp breaker is set at around 100 - 150 amps, depending on the manufacturer. Magnetic trip units are notoriously inaccurate. 20 amp breakers I've tested have tripped as low as 70 amps, and as high as 200 amps.

The breaker might start the saw reliably forever, or it might trip once in a while. Or it might trip every time.

In my opinion, the starting current of the motor is too close to the trip current of the breaker to be reliable.

Rob
You're probably right on that point. But it has a lot with the starting Capacitor, too!

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