220V wiring question

[Michael Liechty]

Got the shop wiring underway. using 6-20 outlet.
I need to make up an extension cord for my 3 Hp 220v TS.
What color wire goes to what terminal on the plug and outlet?






ML

[Jason Whelehon]

you'll want the top wire run from the box, NOT the bottom wire.


Red and Black are "hot" each carrying 120V to ground (white/green). Combined, they offer 220V total potential since it's AC (the difference between hots at full phase is 220V).

You'll need a special breaker as well that will pull 110V from each side of your box.

That said, this is not your "I've never messed with electricity" project.

[Jason Whelehon]

Just re-read your post. You need to make sure you use the appropriate sized wire for that current. The longer the wire, the more resistance it has. So, you'll need a thicker gauge wire if you want a longer cord.

[Rob Russell]

Michael,

Since you're asking about making up an 'extension cord', I'm going to take it that you need a flexible cord with a male plug on one end and a female connector body on the other. This cord will run from your wall outlet to the table saw.

The cable that you would use is one of the SJ types that you can get at the big box stores. You need a 3-conductor cable, #12 if the run isn't too long - #10 if the run is longer or you want to prevent voltage drop. It will have a black, white and green conductor. The green conductor goes to the round equipment grounding conductor pin. The screw on the terminal in the plug and connector body should be green. For the other 2 conductors, as long as you have the equipment grounding conductor wired correctly - it doesn't matter which of the flat blade/slot terminals you land the black and white conductors on.

For the folks who will say that the white conductor needs to be reidentified with black tape or similar means, remember that this is an extension cord and not permanent house wiring. The NEC doesn't apply here. Anyone looking at the extension cord will know that it's a 240v cord because of the plug/connector body pin configuration. If they don't recognize that, it's moulded right into the end of the plug and connector body - 250V/20A.

Rob

[Michael Liechty]

Just re-read your post. You need to make sure you use the appropriate sized wire for that current. The longer the wire, the more resistance it has. So, you'll need a thicker gauge wire if you want a longer cord.

Correct. I'm planning on making up a 20' cord using 10 ga. wire.

My electrician wired the shop using 10/3 and set the outlets, I just need to make up the longer cord since the outlets are on the front wall and the TS will be placed closer to the middle of the space.

ML

[Rollie Meyers]

Correct. I'm planning on making up a 20' cord using 10 ga. wire.

My electrician wired the shop using 10/3 and set the outlets, I just need to make up the longer cord since the outlets are on the front wall and the TS will be placed closer to the middle of the space.

ML

10/3??? Why? It's a extreme waste of money to use a 3 conductor W/ground for a 240 volt circuit since a neutral is not required for a motor run at that voltage,and for a 20' extension cord 12 AWG will do quite well 10AWG in the device you show will be like trying to stuff 10 lbs. of manure in a 5 lb. bag.

[Wayne Cannon]

Red and black (or black and black) go to the two flat blades -- it doesn't matter which goes to which blade as they are both hot. Green (ground) goes to the U-shaped blade.

There is no neutral/white for a three-prong 240 V plug, such as the one pictured. There is a neutral/white for a four-prong plug, like some electric ranges/ovens that use 120 V for clock/timer and indicator/oven lights.

[Rollie Meyers]

A flexable cord w/ 3 conductors will have black,white,green colored conductors, a 4 wire will be the same + a red . As long as the equipment grounding conductor is landed on the correct terminal, the other 2 do not matter which ones are used, BUT on a 120 V cord it does matter which end of the cord the cap and connector is placed, if you have to cross the black & white to maintain correct polarity they are on the wrong end just reverse the cord cap & connector and they land in their proper locations.(Just to veer off topic for a sec. ).

[Wayne Cannon]

Agreed. If you are using a three-wire flexible cord designed for 120 V in a 240 V application (i.e., rewired with 240 V plug and receptacle), you are using the white wire as a replacement for a red (or a second black) wire.

It may not be required, but I still color the white wire black or red on both ends with electrical tape or a magic marker just to make it clear what's going on. I figure it never hurts to make things extra clear. I'll probably be the person to screw it up some time in the future if I don't!

[Bill Brady]

I would replace the wire from the switch on the saw and make it long enough to reach, if you are buying wire any way it will make a better job. You will only need 12-3 cord, I have found it is cheaper and the cord is better to buy an extension cord the needed lenght and cut the ends off.

[Tom Veatch]

Ground (Green or bare) goes to the blade marked "G" in the picture. It doesn't matter which color goes to which of the other blades, they are both "hot". That's different from the 120 volt plug/receptacle hookup. There it does matter which gets the white and which gets the black wires.

[Jim Becker]

10/3??? Why? It's a extreme waste of money to use a 3 conductor W/ground for a 240 volt circuit since a neutral is not required for a motor run at that voltage,and for a 20' extension cord 12 AWG will do quite well 10AWG in the device you show will be like trying to stuff 10 lbs. of manure in a 5 lb. bag.

While it's true that the neutral conductor is not needed for a pure 240v circuit and is a 'waste of money', there are some localities that will force you to install it when you are working under a permit...this for the in-the-wall wiring. Sucks, but it happens.
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On the extension, I typically use the 12 gage or 10 gage rubber cord available from the 'borg with two conductors plus a ground to make them up, depending on the machine. I also like twist locks for this application. Not "necessary", but I like the locking action despite the higher cost of the termination gear.

[Paul Gatti]

I also like twist locks for this application. Not "necessary", but I like the locking action despite the higher cost of the termination gear.

I would also recommend using twist lock plugs. I find it keeps the plugs from coming apart. There's nothing more frustrating than being in the middle of a cut only to have to power cut out because the plug has come loose. I've used these in the 20 and 30 amp flavor.