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I’m planning to use my basement as a shop. Is it within code to have three 240 volt wall outlets served by the same 20 amp circuit, or does each outlet have to be on a separate circuit? I’ll only be using one tool at a time, but want to stay within code. Also, would like to know advantages of using 12/3 wire versus 12/2 wire. Thanks in advance for your time.
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What would the outlets be rated at? Sounds legal so far, as long as the outlets are rated no more than 20 amps apiece.
-Rob
*Joe:I take it your purpose is to have several (3) outlets around your shop to have a table saw, radial arm saw, lathe, whatever all plugged in at the same time, but only plan to use one tool at a time. Just like the 120 volt outlets in the rest of the house have multiple items plugged in at various times, but not everything on at once.NEC 210-21 also says you may mix 15 and 20 amp receptacles on a 20 amp circuit.12/2 vs 12/3 wire both with ground, depends on what you are plugging in. 12/2 with gnd will give you 3 wire 240 volt power and a ground, the typical 3 prong plug. 12/3 with ground will give you 4 wire 240 volt and 120 volt power to the tool through a 4 prong plug. This 4 wire is not typical for tools, but is very common now on dryers and stoves.Frank
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Rob,
The circuit(s) would have a 20-amp breaker and would be used with tools drawing less than 20 amps. I've been hearing from some seemingly knowledgeable people that it is against code to have more than one outlet per 240 volt circuit. I need to nail this one down - guess I could just call up the inspector's office. Thanks for your response.
*Frank, my idea for the shop was what you had in mind (that is, multiple tools plugged in to one 240 volt circuit, but only one in use at a time). I thought this would be okay, but have heard from several people I'm inclined to respect that code requires each 240 volt outlet to be on its own separate circuit. I also heard that it was wise to use 12/3 wire for 240 volt circuits serving machines that had an accessory outlet or appliance. Anyway, thanks for your response.
*Joe...You can do it!!!! Now as for the 12/2 or 12/3 it depends on what your ratings are on the saws and lathe, and other assorted machines. If the rating is 120/240 run 12/3 because it is telling you that this machine needs both voltages, if it says 240 then just run 12/2 to that particular machine. The only thing is the pigtail and the recpt must match and if it is 120/240 then a 4 wire device and pigtail are required. With a 240 only just a 3 wire device and pigtail are required. I would run a 12/3 then branch from it according to your needs. I find it a little hard to believe that you will ALWAYS use one 240 outlet at a time, even you cannot really say that. It may be wise (code or otherwise) to run two or three 120/240v circuits..good luck....tom
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Industrial electricians do not like to do 240 outlets, they want to wire the machine to the circuit and want each machine on its own circuit. If your machine is down and you turn off the breaker and more than one machine is on the circuit the possibility exists for someone to switch on the breaker while the other is being worked on. It's the lock-out rule.
*single circuits to each plug....That's the only way to do it.Saving you and any that come after you....J
*Article 210-23a-d covers requirements for branch circuit conductors with more than one receptacle and makes no distinction between 120 and 240 volt outlets.Article 430 covers dedicated motor circuits and specifically illustrates multi motor connections on a branch circuit in figure 430-3. I don't have a problem with this, and it's done all the time in industry. However, we always install individual overcurrent protection at each motor. Typically, a pushbutton motor starter with heaters is all you need.I don't believe 430 applies to this however, because you are talking about plug and cord connected devices, equipment that is not "installed", and multiple receptacles per branch. This seems to fall squarely into article 210. I have the 1996 NEC and the handbook for code interpretation and the distinction is for 277 volt lighting loads, below 30 volts DC, and over 600 volts. My opinion is that 120 an 240 is no difference.None of this makes a damn difference if the local inspector says "NO." I share Gene's frustration with codes and local interpretations and local "accepted practice."Use plugs and receptacles from the NEMA 14 series (3 pole, 4 wire grounding) and run 3-wire plus ground. This way you can mount convenience oulets and lights affixed to the machines that are 120 volt, and unplug then with the same cord and no transformer.-Rob
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Thanks for all the responses - they're much appreciated.
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I just saw a GFCI breaker, 60 amp for $100. Is this a good idea for a shop? Would 220v machinery run on that without any problem?
*While one circuit per receptacle is never wrong and is probably the best way to go, it is to code to have multiple 240V, 20A receptacles, under certain conditions. NEC ('96) section 210-23 spells it out. From 210-23(a): ..."The rating of any one cord and plug connected utilization equipment shall not exceed 80% of the the branch circuit ampere rating."... That means 16A. From the requirments of section 430, a motor circuit must be rated at 125% of full load current, which translates to about 2hp at 240V. So for small machines, you can get away with it, but if you have a dust collector (and if you don't I'll bet you soon will), you won't just be running one machine at a time. If you're short on breakers, consider a sub-panel to feed the shop.I don't see any reason to run 12/3 for machines; dryers and ranges, yes, but not for the machines one would ordinarily find in a home shop.
*RJT:Cord and plug connected appliances/tools follow the lock out rule really easily, just unplug them. And mark the plug with a tag. Hardwired appliances/tools are where it is inconvienient to have more than one item on a circuit.But, it is common in industry to have one circuit feeding many motors, with a motor starter at each motor for overcurrent protection. You just will be locking the whole circuit out when working on one motor.Frank
*Frank, what you described is "tag out." Locking out would involve one of those things that you lock over the plug that makes it physically impossible to plug it in. It also could be locked out with mechanisms on the starter. Not a big deal in a one person shop. I try to do onbe more thing - tie wrap the end of the cord near the reason the machine is out in the first place. I typically start something one month and finish it two or three later, after I've had time to forget why I had it off in the first place.-Rob
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I'm planning to use my basement as a shop. Is it within code to have three 240 volt wall outlets served by the same 20 amp circuit, or does each outlet have to be on a separate circuit? I'll only be using one tool at a time, but want to stay within code. Also, would like to know advantages of using 12/3 wire versus 12/2 wire. Thanks in advance for your time.