Starting to look ahead to wiring the shop and need to know a couple of things.
1. How many 110 duplex outlets can you place on the same circuit 20 amp? I am thinking it is 4 since they are duplex. I am running 12/2 wire to all outlets.

2. How about 220, I have several tools that are mobile ie. Table saw and Radial arm saw and I am planning to rewire them to 220. I want to place several 220 outlets around the shop also appropiately marked or either 220 specific plugs, so I avoid someone pluging a 110 drill into the 220 and smoking it.

Any other I deas or tips for the wiring would be greatly appreciated.

 

How about making a long extension cord for 110/120v that runs off of one leg of the 220v circuit? You will have the higher amps that that 220v circuit allows for the long extension cord and the four gang box for hooking up high amp requirements for those projects that extend into the driveway or to the backyard. I did just that for a garage band in the neighborhood by running two four gang boxes for their amps and guitars, etc., off of the dryer 220v circuit. It has worked very well for them and they've never popped a cicuit breaker. This trick is popular with contractors and subs who are all battling to use 110/120v circuits when building houses and all trying to run their saws, compressors, paint guns etc. They tie into nad split the 220 cicuit and the amperage budget goes a longer way.

 

I I start trying to mix stuff Like that I will sure as heck have someone plug in my Milwaukee sawsall to 220 some how. I am thinking seperate runs with different plugs on all the 220 stuff.

 

Please don't do this. Just because it works, doesn't make it right. Over-current protection exists for a reason.

Any contractor who creates such a system on the jobs I work on would get thrown off the site immediately.

 

There is nothing wrong with placing 220V receptacles through-out the shop in places where you might plan to put a portable tool. The tricky part is not all tools have the same power requirements. Some need 20 amps, some 30 amps, and so on. A 20A plug will not fit into a 30A receptacle.

See this: http://www.hubbellnet.com/max_htm/te...EMA/front.html

 

grizz, go to the do it yourself.com (think that's it) and look it up or get the book by Stanley on wiring and read about it there. You have a couple of issues going on that just won't happen.

1. in order to place the maximum number of 110 outlets on one circuit, you have to know how many items are running at one time and the total amps they will draw. In order to max out a 20 amp circuit, the total amperage will have to be 20 amps. How many electrical devices can you plug in and actually operate at one time?

2. Rewiring a device to run from 110 on a 220 can't be done without using a stepdown transformer, or a bunch of resistors.

3. You would have to try pretty hard to plug a device wired for 110 into a 220 outlet.

4. Standard household outlets are 15 amp, though 20 amp outlets look similar, one of the spade slots looks like a sideways "T." A device that can be used in a 15 amp outlet, can also be used in a 20 amp outlet with out damaging it.

5. Code requires 12/2 wire for 15 or 20 amp outlets, lights require 14/2 wire

 

There is essentially no limit imposed by the code on the number of convenience receptacles you can put on a single 15 amp or 20 amp circuit in a residential situation.

Commercial installations use an assumption of 180 VA per receptacle. If you then de-rate the circuit to 80% of capacity, a 15 amp circuit is limited to 8 receptacles and a 20 amp circuit to 10 or 11.

(The above assumes that these receptacles are not serving equipment that is fixed in place, for which a load can then be calculated.)

Except for kitchens, bathrooms, and laundries, the NEC does NOT require 20 amp circuits nor does it require 12 AWG wire for receptacles. You can use 14 AWG wire on 15 amp circuits in your shop (or living room) if you want to. Personally, I wouldn't want to for work done on my own property. Electrical contractors working to a fixed price bid will be pushed towards 14 AWG wherever they can use it by the current price of copper. It is possible there are local codes requiring 12 AWG wire, but the NEC does not.

You can run a 240 volt circuit around your shop and put as many receptacles as you like on it. Just make sure they are proper NEMA receptacles for 240 volts (there are several choices) and that it is not possible to plug a 120 volt appliance into them. The wire needs to be sized for the overcurrent protection you provide. It is a good idea to size the wiring for the kind of receptacle you provide -- 20 amp receptacles get 12 AWG, 30 amp receptacles get 10 AWG, etc.

For a situation with modest sized table saws and radial arm saws, I would suggest a 20 amp 240 volt circuit and NEMA 6-20 cords and plugs. These are inexpensive, fit in ordinary device boxes, and the overcurrent protection is appropriate for the demand of the saw and the size of its attachment cord.

If you have heavier use equipment, the next step up is NEMA 14-30 plugs/receptacles, a 30 amp circuit, and 10 AWG wire.

 

When you design an electrical system things to remember.

The more outlets on a single circuit the more likely you will trip the circuit.
Always leave room for later expansion of the electrical system.

A couple hundred dollars spent in a larger system than is needed at the time can save a thousand or so when you buy a new tool later.
And also an overbuilt electrical system is cheaper than replacing the building because an overloaded circuit caught fire.

We are building a shop right now. Each outlet circuit has two duplex outlets per circuit.
Why? Look at a circular saw amp requirements, it will be in the 15 amp range.
Now look at a 1/2" drill which will be in the 6 amp range.
If you plug both of them in the same circuit and try to run both of them at the same time you will trip the 20 amp breaker since the load would be 21 amps. This could be done in one duplex outlet.

 

It is also illegal if you have an "occupational" work area. 220 must be GFIC protected (outdoors/garage) unless for a dedicated tool such as table saw or air compressor.

 

Thanks for the input guys. I broke the 110v duplexs out to 4 per circuit on saturday and plan on setting them to 20 amp in the panel. I am going to hardwire the compressor for 220 and add a couple of 220's for the saws after I double check the amperage on them and I will most likely put in a dedicated run for the the stick-welder in a couple of locations after I verify the amps for it. It is going to get a roller stand built for it so it will be mobile also and I should be good.

Thanks