Running 20A 240V To Garage For Table Saw


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Old 05-15-15, 03:34 PM
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Running 20A 240V To Garage For Table Saw

I've been planning this for a bit and have discovered I may be able to do this without the need to run additional wire, but I thought I'd check the wisdom of the interwebz first. I have a 2HP table saw that is currently running off my 20A 120V circuit that supplies all outlets and lights in my garage, so naturally my lights flicker when I start it up but otherwise it works fine. I've been looking at switching it to its own dedicated 240V circuit and have discovered a completely separate 120V line running to my attached garage. It appears to only power a single outlet on the wall, and two on the ceiling for some fluros that were added later. I can pull on the end near the panel and see movement in the garage (plus I've checked every other outlet in the house) so it seems to be a dedicated line (it's the one sticking out in the photo). I have just enough room in my main panel for a single two pole breaker (as seen below), so I believe I can use the existing 12/2 line for a 20A 240V outlet near my table saw. My plan is to mark the neutral black or red at each end, open up each outlet (3 total) along the daisy chain to remove the outlet plug and splice the line together, putting a blank faceplate back on, and run into a box where I end with a 240V female hookup. The research I've done indicates that 12 gauge is good for 20A, so does my setup sound alright? I'm wondering about the bare ground, can that be used in a 240V application?

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Last edited by Temp08; 05-15-15 at 03:54 PM.
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Old 05-15-15, 03:39 PM
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I don't understand why you would need 240V, for a 1HP table saw. Am I missing something?
 
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Old 05-15-15, 03:42 PM
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Yeah, because the motor is more efficient and will generally last longer using 240V. It would also be nice to have a 240V plug out there for when I get my jointer or planer.
 
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Old 05-15-15, 03:47 PM
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Ok but what kind of plug is on the table saw? If you want 240V for another reason, that's another story.
 
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Old 05-15-15, 03:53 PM
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Forgive me, it's a 2HP saw (had 1HP on the mind as I was just looking at my drill press). The saw is wired for 120 now, but I'll rewire for 240 and get a new plug.
 
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Old 05-15-15, 04:06 PM
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Is it a detached garage? How long is the 12/2 line that goes to the garage & is it the only line that goes there? I take it that there is no sub panel in the garage.
 
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Old 05-15-15, 04:14 PM
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No it's attached (the 200A sub panel upgrade to my detached shop is some time down the road). The run is probably 40-50ft after I take it to the other side of my garage where the saw is. It looks like this 12/2 line was put in during some remodeling when they had the sheet rock down, there is another 20A line that powers the rest of the garage and the lights.
 
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Old 05-15-15, 04:23 PM
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I'm not sure if it will handle the load or not. Wait for Ray, on that one. He'll answer you question.
 
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Old 05-15-15, 04:45 PM
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It would work but what about the lights and receptacles already on it? Can't you just run a new cable?
I'm wondering about the bare ground, can that be used in a 240V application?
It can be used for the required ground. Why were you wondering about it?
 
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Old 05-15-15, 05:55 PM
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The only light on it is plugged into a receptacle that's on a switch, the other garage lights are also on plugs so I'll just move it to one of those (I'd rather have it turn on with the rest anyway). Then all I'll have to do is close up that switch and the other 3 receptacles and the only thing on it will be the 240V plug at the end. As for the ground I was just wondering if it needed to be shielded as the photos I've seen have shown it that way.
 
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Old 05-15-15, 06:11 PM
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Sounds like you have this covered. Main thing is transferring existing fixtures/receptacle to the other circuit. Post back if you have problems.

As far as the 240, you will have a single receptacle as below:

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Black and white will go to double pole 20A breaker with white re-identified as hot with black tape. Bare ground will go to ground bar in panel.
 
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Old 05-15-15, 06:22 PM
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As for the ground I was just wondering if it needed to be shielded as the photos I've seen have shown it that way.
What do you mean by shielded? Weird things are posted on the internet by people who know less then they think they do. Just for giggles can you provide a link to what you are talking about. In this application a bare ground is okay and in fact normal.
 
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Old 05-15-15, 06:24 PM
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Awesome, exactly the way I was imagining it. Thanks for the sanity check.
 
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Old 05-15-15, 06:28 PM
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Er, maybe not shielded (I understand that can mean something different). Coated rather, in green, just the little wire pic in my table saw manual. I know logically it doesn't matter, but I just wanted to check and make sure since I'm relatively new to 240V. A bare ground will do apparently.
 
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Old 05-15-15, 06:34 PM
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The cord on your saw would have a green insulated wire for the ground. Cable and service cord are two different things. Hasn't been mentioned but just to add the obvious you will need to change the plug on your saw to a 6-20p
 
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Old 05-15-15, 06:39 PM
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Good point Ray, just making sure I didn't do anything dangerous (even though some grounds are through water pipes). Manual recommends 6-15 plug, which looks Handy's picture is compatible with.
 
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Old 05-15-15, 06:51 PM
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6-15 is not compatible with picture I posted. You need 6-20P.

6-15 has two horizontal prongs.
6-20 has one horizontal and one vertical prong.
 
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Old 05-15-15, 07:17 PM
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I have just enough room in my main panel for a single two pole breaker (as seen below), so I believe I can use the existing 12/2 line for a 20A 240V outlet near my table saw.
You have a split bus panel, the space you speak of is in the lighting section. Can the lighting main handle this? What is the amperage of the lighting section main breaker?

(the 200A sub panel upgrade to my detached shop is some time down the road).
Before I added a subpanel, I'd replace the split bus panel with a good main breaker panel.
 
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Old 05-15-15, 07:24 PM
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6-15 has two horizontal prongs.
6-20 has one horizontal and one vertical prong.
I thought that's what the horizontal+vertical feature was for? Anyway, the manual recommends 6-15, so I figure that's what I'll use.
 
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Old 05-15-15, 07:27 PM
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Anyway, the manual recommends 6-15, so I figure that's what I'll use.
That should work, but the circuit will have to be protected by a 15 amp breaker.
 
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Old 05-15-15, 07:27 PM
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You have a split bus panel, the space you speak of is in the lighting section. Can the lighting main handle this? What is the amperage of the lighting section main breaker?
Correct, it is a split bus, but the lower section isn't just lighting, it's the outlets and lighting for my entire house ranging from 15 to 30 amps. In the middle you'll see the wires that go to my "main" (somewhat of a misnomer), which is a 60A two pole. The other breakers up top are for dryer, heat pump, water heater, furnace, and stove.
 
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Old 05-15-15, 07:31 PM
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That should work, but the circuit will have to be protected by a 15 amp breaker.
Right, 6-15, makes sense (just realized that). Would there be any reason to not go 20A and 6-20 if I have the gauge?
 
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Old 05-15-15, 07:43 PM
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Would there be any reason to not go 20A and 6-20 if I have the gauge?
I'd go by the recommendation in the manual. You can still use 12-2 NM-B cable.
 
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Old 05-16-15, 09:25 PM
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Welp, install done and works like a charm. It should be noted I was mistaken about 240V being better for the motor, it's not. Single phase motors all run 120V internally on each coil, running 240V to them you have to re-wire the coils to run in series instead of parallel. The main benefit is that my saw now has it's own dedicated circuit, and seems to start near instantly. And now my lights don't flicker!

Edit: I went ahead with the 6-20 outlet because MOAR POWA!!


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