240 with table saw


  #1  
Old 07-20-02, 12:34 PM
jeff180548
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240 with table saw

I am in the process of installing a 240v outlet for my new table saw. A friend who is helping says that I can ground to the outlet box and run the two hot wires to the circuit panel and hook up to a pre-existing 240 volt running two 20 amp poles? Does this sound right?
 
  #2  
Old 07-20-02, 03:38 PM
MTgets
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What is the amp rating on your table saw?
Does it say what the max breaker rating can be?
When you say ground to the outlet box, why not ground to the ground screw on your outlet.
Have you bought the outlet yet and looked at the configuration?

Pre-existing 2 pole 20 amp breaker. meaning there is a unused one in the panel or you want to double up with something else that is hooked up to it? that is a no no. It must be on its own dedicated circuit, whether 20 amp or not we will see, (I bet 20 is the one to go with) but lets go step by step, thats how you learn!
Post back soon, lets get this saw spinning, I got wood ya can cut for me!!!!
 
  #3  
Old 07-20-02, 04:19 PM
jeff180548
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The amp rating on the table saw is 18.

Does it say what the max breaker rating can be? No, but shouldn't we have 30 amp breaker?

Regarding your suggestion: "When you say ground to the outlet box, why not ground to the ground screw on your outlet." that's what he said, but I thought it unusual to use a ground screw on the outlet box rather that run a ground wire to the house's main ground.

The outlet has two hot wires (black and red) and a green ground.

Regarding your comment: "Pre-existing 2 pole 20 amp breaker. meaning there is a unused one in the panel or you want to double up with something else that is hooked up to it? that is a no no. It must be on its own dedicated circuit, whether 20 amp or not we will see, (I bet 20 is the one to go with) but lets go step by step, thats how you learn! "
I have a pole with a 20 amp breaker 120 v line to a pool filter and another 20 amp 120 v to the pool heater. The suggestion from my friend was to put in one hot line into each establishing the prescribed juice. The filter runs at night, the table saw in the day. I'm leary.

Finally, if I can safely get this thing going I'll cut that wood for you. Thanks!
 
  #4  
Old 07-21-02, 12:52 AM
MTgets
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OK Jeff, here we go:

When I said hook up to the ground screw I meant on the actual outlet itself and the box, these both need to be grounded to the houses main ground, if you are running conduit, yes pull a #10 AWG green wire for this purpose.

For the power, pull #10 AWG THHN/THWN wire to the outlet and hook it up like you said, black and red, you seem to be on the ball up to here, great.

The only problem I see is you are not sure on how to terminate properly in the panel. You should have a dedicated 2 pole circuit for this piece of equiptment, meaning nothing else on the circuit. Leave the pool equiptment alone, this has nothing to do with that. You need to buy the correct 2 pole breaker with the common trip handle and install in a open slot in the panel, and hook up you black and red wire to each breaker screw, doesnt matter which color on what screw.
 
  #5  
Old 07-21-02, 01:05 AM
MTgets
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Do not hook the wires into the individual 1pole breakers running the pool equiptment!!!

Even so it is possible to procure 240 from 2 individual breakers if they are on opposite phases, one breaker doesnt know what the other one is doing.
If one phase/line/leg (which ever term you are familiar with) were to short and trip ITS OWN INDIVIDUAL breaker the other one does not know that and will continue to supply 120 volts to the table saw and trash it, this is called "single phaseing" when a piece of equiptment needs 2 phase and is only being supplied by 1.
This is also dangerous to someone troubleshooting the equiptment because 1 breaker is off they think the whole outlet is dead, while that other individual breaker is still on...ZAP!
This is why it is CRITICAL to power 240 volt anything with a DOUBLE POLE breaker designed just for this.
If you do not have room in your panel for the double pole 30 amp breaker post back and we will help you figure out what you can do!!
 
 

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