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Help with wiring a 240 Volt receptacle

Am wiring a 240v dedicated receptacle. Line coming into receptacle is (black, white, ground). Plug coming from the dedicated table saw is (black, white, red, green/ground). The saw is 240v 5hp. So my question is what do I do with the red wire coming from the saw, since at the wall there is no red wire. It was suggested to tie the red and ground wires together. Wasn't sure about that Idea, so I thought I would toss it out for some help.

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Posted 2013-12-14T20:33:02+0000  by schapy schapy
 

THANK YOU JOESEPH VERY MUCH!!!!

Best Answer

Posted 2013-12-14T23:12:50+0000  by schapy

Hey schapy,

 

Thanks for your question and welcome to the community!

 

You basically have a properly grounded plug for your table saw (4 wires); however your receptacle that would feed it does not (3 wires).

 

Before we continue, 240V can mean anything in terms of a dedicated circuit. You'll need to make sure that the receptacle's amperage matches your table saw. Amperage, not voltage, is what more accurately determines how much or what can be placed on a circuit.

 

Hooking up less amps from the circuit than your saw can mean it won't work at all, and a higher amperage feeding the saw can mean it won't trip in time due to any overloads. Therefore, making sure the amp circuit breaker, wire, and receptacle is crucial to making sure this works.

 

The red and black wires coming from the saw are your hot, or load wires. These carry the 240 volts needed to power up the saw. The white is the neutral wire and the green would be the ground. DO NOT tie the red and green ground wires together!

 

You have several options to get a solution for safely wiring up your saw. One thing you can do is to change out the receptacle in the wall to a 4 prong plug. Only do this after making sure the saw, wire, and circuit breaker feeding it are all the same amps.

 

The 4th wire would the ground on the receptacle, which you can make it grounded in the box by running a bare copper wire to a ground screw in the junction box, IF it is a metal box. You can also run the bare copper and ground it to a metal pipe. This is done for safety, so leaving the 4th ground alone will not give you protection unless it is grounded.

 

I say run the ground wire versus running another new grounded line to the receptacle. It would be more time-consuming and may involve taking out pieces of sheetrock in order for it work.

 

The other option is to change out the plug on the saw to match your receptacle, provided it is the same amperage and size. It won't be grounded, but it can work.

Commercial Grade Angle 30 Amp 125-250-Volt 10-30-NEMA Rating Universal Power Plug

As always, check with a licensed electrician in your area if you aren't sure how or where to change out or wire your plug.

 

Those are the 2 options you can do to solve your problem. Please let me know if you have any further questions or concerns.

 

Regards,

Joseph

Posted 2013-12-14T21:12:00+0000  by Joseph_HD_ATL

Either I am dense or I am just not understanding your answer very well!!!! If I put a 4 prong receptacle in does that mean I would take the white hot wire in the box to the red terminal on the receptacle then, of course black-to-black, ground-to-ground and leave one receptacle vacant??? And yes the Amps are good to go. This 240v line is on a 40amp breaker and the saw only ask for 19 of those amps. The other option you addressed in your reply, went right over my head as to understanding what you meant anyway. THANK YOU VERY MUCH SO FAR!!!

Posted 2013-12-14T22:39:34+0000  by schapy
forgot to say, when I was speaking of 40amp breaker, I most likely should have said twin 20s not a straight 40 amp breaker.
Posted 2013-12-14T22:48:29+0000  by schapy

Sorry if my response confused you.

 

To keep the 4 prong cord you have now to go with your receptacle, you'll need to make sure all 4 wires will be there. Since you do not have a ground in the receptacle now (2 hots from the black and white and a neutral wire from the bare copper), you'll have to make a ground yourself. You would do this option of a 4 wire receptacle to match up your cord from your saw.

 

That can mean either in the junction box of the receptacle if its metal, or use a piece of bare copper wire and attach it to a metal pipe or something metal along the length of the circuit.

 

Your red and black terminals should always be hot wires, and only be connected to them. Your current white wire in the breaker/receptacle is most likely a hot used as one, and you can keep it as such.

 

All I was saying was to add a proper extra wire for grounding purposes. At the end of the day, you should have a black wire and white wire from the receptacle connecting to your hot wires, and the copper or third wire from the receptacle connecting to the neutral line wire from the saw. The 4th ground wire would be connected to a new ground wire you'd make that I mentioned earlier.

 

It's either that or change the plug on your saw to a 3 prong. It won't be properly grounded, but it still would work.

 

Always check your work by a voltage tester or meter to ensure that each hot wire is getting the proper voltage.

600 Amp AC Digital Clamp Meter with Temp

 

Again, sorry for the confusion. But your existing wiring in your receptacle should be 2 hots in the form of a black and white wire and a bare copper that would be the neutral wire.

 

Double check the breaker feeding the circuit to ensure thats what is happening.

 

Keep me posted on your progress, and always wire safely.

 

Joseph

Posted 2013-12-14T22:51:10+0000  by Joseph_HD_ATL

Yes I have checked the leads at the junction box. And they are as you mentioned. I think I have it now but let me double check.

 

Black at junction box to Black for saw.

White at junction box to Red for saw.

Bare neutral at junction box to white neutral for saw.

New Ground at junction box to green ground for saw.

 

Does that sound about right????????? (I hope).

By the way I easy to confuse!!

Posted 2013-12-14T23:08:02+0000  by schapy

Yes that would work, now just grab the right receptacle for your saw in 4 prong and you'll be good to go!

 

You got it, and hopefully your saw will be working in no time!

 

Joseph

Posted 2013-12-14T23:10:29+0000  by Joseph_HD_ATL

Most large table saws are straight 240 volts.  That's to say they use two (2) hot wires and 1 ground wire.  No neutral.  The fact that the plug has four wires concerns me.  Can you get me the exact make and model number of this saw.  Also is there a tag on it that describes the voltage requirements?  Did you buy it new or used?

Posted 2013-12-14T23:13:41+0000  by Adam444
Thanks for the thought, but this saw came right from the factory this way. Jet 10in 5hp LTAS. I
Posted 2013-12-14T23:24:28+0000  by schapy

I know you're excited about your new saw but lets slow down here for a second.  I'd hate you see you damage your new saw.

 

In your original post you said that you had three wires in your existing receptacle.  Now is this a 240v receptacle or 120v receptacles?  If your new saw does require 4 wires, you CAN NOT using the existing wiring.  If it requires a 4 wire circuit then you MUST rewire so that you have 4 wires.

 

You're model number seems incomplete.  Is there a product number?  It looks like should be six digits starting with a 7.

 

Does this saw have a downdraft table?

Posted 2013-12-14T23:55:39+0000  by Adam444
 
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