Shop wiring

[Roy Smith]

You don't run a 220V outlet off "two different breakers". You run it off one double-pole breaker. The difference is that if one side trips, it opens the other side as well.

[Christopher]

I'm about to run some conduit and wiring in my garage for additional AC outlets. I'm fine with the basics but I want to allow for a 220V outlet for that new tablesaw I hope to have one of these days. I want to run hot wires from two different breakers and alternate 110 outlets between the two circuits but is it OK to end the run with the two hot wires going to the 220 volt outlet? It seems like it should be just fine but I thought I would ask before going out to buy the stuff. Is there any problem with using one of the 110 outlets at the same time I use the tablesaw connected across both of them? Assuming I don't draw more amps than the individual circuit can handle, of course.

Another question I have is whether there is any type of gadget available that will turn power on to my dust collector (shopvac) when I use the table saw and is there any special wiring I should consider in advance for something like that.

I know this isn't an electrical forum but I also know many here have done this before.

Thanks!

-Chris

[Morgans]

Not a good idea to have portions of two circuits in one box. Keep those two different 110's separate. My gut tells me there are other reasons, too, but I can't think of them all now.

Another reason is that you will want to wire the table saw for at least 25 amps, and that would be too large for 110 volt devices, and the wires would be too heavy to deal with.

Wire for the table saw with the two hot legs, and a neutral and a ground. You could then hook up a 110 outlet on the side of the saw hooked into the magnetic starter for your dust collector.

-- Jim in NC

[Christopher]

I should have thought of that. I think I would have caught it before it was too late but thanks.

-Chris

[Christopher]

I thought it was common practice to run two hot wires plus the neutral and ground and alternate the circuits as you go down the outlets. I can't remember if you have to have two neutral wires as well though. It's seems like you would need two or one wire would have to handle current flow for two different circuits. I understand DC circuits pretty well but AC behavior is not something I know very well.

I don't understand what you mean by 25 amp circuits being "too large" for

110volts. That's just the amperage the circuit will provide before the breaker trips. A 110V device will not draw more current than it needs no matter how many amps the circuit is capable of providing.

-Chris

[Doug Winterburn]

One word: subpanel

DAGS (Do A Google Search - tmLJ)

-Doug

[Phisherman]

Run a separate wire for the 220 circuit. Install at least two 220 receptacles. There should not be any 110 receptacles connected the the 220 circuit.

The "Long Ranger" comes in 110v or 220v models. It plugs into a receptacle then you plug in your DC. A remote turns it on/off.

A shopvac doesn't have the necessary cfm nor capacity for proper dust collection of most woodworking machines.

[Morgans]

"Christopher" wrote >

No, with 110, you go with one hot (black, or color) and one neutral, and one ground. To get 220, you use two hots and a ground. They are installed in breaker slots above and right next to each other in the breaker box. As has been posted, they will have a common handle. The only reason to run a neutral with your 220 circuit, is if you are going to use a 110 circuit as well as the 220. A welder, or table saw with only 220, would have three prong plugs. A stove will have 4 prongs, because it uses 220, and 110, for the timer and light bulb.

Do some research. It looks like you have a bit to learn.

Some will argue this, but in my view, the device (recepticle) is only rated at 15 or 20 amps. It is not guaranteed not to fry at higher amps. Also, the # 10 wire for a 25 amp circuit is so stiff, it is very difficult to work with, getting it all bent up and stuffing two cables in a box.

-- Jim in NC

[Wm Gardner]

Christopher,

It depends on how you are wiring. When I wired the receps in my garage I ran two complete circuits through the conduit runs. Meaning that I also had two "neutral" or "return" conductors. There are two reasons to do this with 110v circuits. #1- I had to as I am using GFCI breakers. They would trip instantly if I ran only one common as there would be a difference in current between the supply and the return. #2- The answer to this is hinted at above. Lets explain with an example..... #12 conductors are rated at 20 amps. Were you to put 20 amp loads on each of these circuits, but have only one return, you would actually be handling 40 amps through the return line. Definite code violation and unless you are running GFCI breaker it would work until the fire started......

While I agree with your statement that a device will only pull the amount of current it actually needs, I believe Jim was referring to the fact that you would need to use fairly heavy (#10 or better) conductors to handle this load. Were you to connect lighter wire (#12 or #14) to a 25 amp breaker you have committed a NEC violation. #12 is rated for 20 amps, #14 is rated for

15 amps. That you do not intend to draw 25 amps down that line does not matter. The potential is there, it could happen. An additional thing to consider is how difficult it will be to find 110v receps rated for above 20 amps. Again, draw more than the rated amperage from a recep and..........

I hope this helps. Absolutely no offense is intended but if these explanations do not make sense then it may be time to consult a professional. Electricity is not something to mess around with. If you have other questions you could try the Taunton book "Wiring a House" by Rex Cauldwell. It is a really good resource. Your local library probably has it but it is worth the $15 to buy your own copy that reflects the 2002 NEC changes.

Good luck, Bill

[Wade Lippman]

In residential electrical, you never run more than one device off a 240v circuit. I don't know if there is a specific code against it, or if it is just a matter of what is practical; all the wiring on the circuit (including the outlets) has to be capable of handling the current the breaker is rated at, so it might not even be possible.

You can run a 240v circuit to put the each 120v outlet on a box on a separate circuit. It is called a multiwire circuit, and it commonly done in kitchens; though I personally think it is a poor practice. I have never heard of mixing 240 outlets with 120v outlets on the same circuit; you probably run into the same problems mentioned above. You can check with your local building department, but it seems like a mistake even if not forbidden.

[Robert Bonomi]

Got a cite? I just completed an installation using a common neutral w/ independant single-pole breakers (on opposite phases -- wiring color-coded), which the city inspector _has_ signed off on.

[Al Reid]

I will get you the section of the NEC when I get home (I don't have it with me). This was obviously an oversight by the inspector. What is to stop you from now moving the second leg to a breaker on the same leg (inadvertently or purposely). As a degreed electrical engineer with over 20 years of experience, I would never condone such an installation and I would certainly not install a circuit like that for myself.

Another concern I have is that if one circuit is turned off w/o the other, the neutral may still be carrying current and can present a shock hazard.

I will follow up later.

Al

[Doug Miller]

This is prohibited, at least in homes, by Article 210-4(b): "In dwelling units, a multiwire branch circuit supplying more than one device or equipment on the same yoke shall be provided with a means to disconnect simultaneously all ungrounded conductors at the panelboard where the branch circuit originated." [1993 NEC]

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

[Gfretwell]

The catch here is "on the same yoke". If you hook this up "Canadian Kitchen" style with a duplex outlet having one phase on top and the other on the bottom (single yoke) you need the 2 pole breaker or single breakers with handle tie. If these feed separate devices you can use separate breakers. Personally I dissagree with this practice but it IS legal.

[Robert Bonomi]

AHA! That's why the inspector allowed it. I've got quad boxes, with one circuit feeding each duplex outlet.

[Gfretwell]

It's worth the 50 cents a handle tie costs to make this a little safer. Just remember to trip both breakers if you go into that box

[Robert Bonomi]

Oh yeah, I _do_ know what I'm doing. And, for the benefit of the _next_ person who has to work on the wiring, inside the box there's a _label_ on each outlet, identifying which breaker it's on. As well as a _pictoral_ map at the breaker panel.

[Wm Gardner]

Thank-you for clarifying this for everyone. I think there was some confusion caused by my original response to Christopher. My reference was to 120v circuits only (no mention of 240v in my post).

Thanks again, Bill