Multiple 220V outlets?

[David Romano]

Does anyone know what the electrical code says about the number of outlets allowed on a 220V circuit. I'd like to operate my jointer and bandsaw with the same line, not running at the same time of course. It's a 12-3 line with a 220V 20 amp breaker. I'm thinking that only one 1 outlet is allowed, but I'm hoping I'm wrong.

David

[Rob Russell]

You can put as many outlets on the circuit as you want. You'll just trip the breaker if you try to run too many machines at once.

[Chris Padilla]

The AHJ (authority having jurisdiction) here likes to see single receptacles on all 240 V/30 A circuits however 240 V/20 A is fine with mulitples. It is the inspector's interpretation of how you plan to use the circuits that will sway him one way or the other.

So my point is that your local AHJ is the ultimate ruler and the NEC is just a guide for them to use.

[David G Baker]

Don't know what the code is in the USA but when I was in Germany many years ago every home I lived in had 220volts at every outlet in the house. I would run as many as I wanted up to a max of 6 per circuit as long as the current draw was no more than allowed for the wire.
In my shop I have a 220v #12 4 wire extension cord that has a 4 receptacle end on it that I use for a couple of my machines. This is a temporary set up until I run wire in the wall. The machine plugs and cord receptacles are all the correct connectors for what I am doing.

[JayStPeter]

I agree with Chris. I ran 3 20A recepticles on each of 2 circuits and had no problems. I wired them with 10-gauge in case I ever need them to be 30A. Call and ask the inspector, I couldn't find anybody else to answer that question.

[David Romano]

OK, I think I will go ahead and add a second one then. It is not too painful anyway if he tells me to remove it, I'll just end up with a junction box there

thanks
David

[Gary Curtis]

When my new shop was constructed, I wanted a 30-amp 220v circuit. The electrician told me that the building codes (at least for California) state only one machine at a time can be run off each circuit.

But it is OK, nevertheless, to have multiple outlets spotted around the shop. I had all the outlets installed at 50 inches off the floor, to allow for 4x8 sheets of plywood leaning against the wall without interfering with power cords.

To double check on this I called my machine dealer who sold me the 5hp cabinet saw. He confirmed the 1 machine only - 1 circuit rule. I'm not sure what the rule is for 20-amp circuits.

Gary Curtis:)

[Steven Wilson]

You should be fine David as you are wiring 220v branch circuits. The one tool, one circuit rule (rule of thumb) applies to motor circuits (as explained to me by my local inspector, YMMV) which is a different animal than a branch circuit. Anyhow, you will need to follow the NEC rules for conduit fill and box fill calculations. It's very easy to max out a box fill calculation if you have 30A circuits and have wires running through boxes. Use the largest size boxes and covers that you can.

[Tom Veatch]

OK, I think I will go ahead and add a second one then. ...

Steven is right. Add the outlets that you need. Just make sure the receptacles are rated for no less amperage than the breaker on that circuit. 30 amp breaker - not less than 30 amp outlets.

Plugging a motorized tool into an electric circuit in your workshop doesn't make that circuit a "motor circuit" under NEC 430 any more than plugging a vacuum cleaner into a wall socket in your living room makes that circuit a "motor circuit".

[Jim Becker]

Steven is right. Add the outlets that you need. Just make sure the receptacles are rated for no less amperage than the breaker on that circuit. 30 amp breaker - not less than 30 amp outlets..

I believe you mean "no more" than 30 amp outlets on a 30 amp circuit. You certainly do not want a 40 or 50 amp outlet on a 30 amp circuit...

[Chris Padilla]

I believe you mean "no more" than 30 amp outlets on a 30 amp circuit. You certainly do not want a 40 or 50 amp outlet on a 30 amp circuit...

Well, as long as the proper breaker is there to protect the in-the-wall wiring, does it really matter?

If your beast of a machine draws more than 30 A, it'll pop the breaker, and then you'll wonder what doofus put a 50 A receptacle on a 30 A circuit!!

However, I agree...the receptacles *should* match the breaker or they could be less, I guess....

[Lewis Cobb]

I believe you mean "no more" than 30 amp outlets on a 30 amp circuit. You certainly do not want a 40 or 50 amp outlet on a 30 amp circuit...


ok - sorry for the tangent here but Jim I just noticed your new pic - what's with the tux? Are you going James Bond on us or something?
:D

[Tom Veatch]

... You certainly do not want a 40 or 50 amp outlet on a 30 amp circuit...

Why not? With a 30 amp breaker, a 40/50 amp outlet will certainly not be overloaded whereas a 20 amp outlet could be continuously overloaded without tripping the breaker. Remember the breaker is for the purpose of protecting the circuit, and a 40/50 amp receptacle is certainly well protected by a 30 amp breaker.

Now, I'll grant that putting a 40/50 amp outlet on a a 30 amp breaker could lead to an awful lot of breaker trips since UL listed items that draw more than 30 amps could be plugged into the circuit. For that reason, using nothing but NEMA X-YY devices on YY amperage circuits is the proper practice. Then the device is protected by the breaker and only UL listed devices that don't exceed the current rating of the circuit can be used on the circuit. I'm aware of only one exception to that rule. Code allows the use of 15 amp receptacles on 20 amp circuits but only when there is more than one outlet on the circuit. (Duplex receptacle counts as two outlets.)

[Tom Veatch]

...or they could be less, I guess....

Only in the case of multiple outlets on 20 amp circuits. Then they can be 15 amp outlets. Otherwise, the device rating has to be at least as large as the breaker.

[Jim Becker]

What if someone plugs in a device into that 40 or 50 amp plug that draws more than 30 amps and for some reason the breaker fails to do its job? I guess as a somewhat anal person, I prefer that both ends and everything between of the installed circuit match to minimize "misunderstandings".

[Tom Veatch]

... I prefer that both ends and everything between of the installed circuit match to minimize "misunderstandings".

Me, too. That's why I said "using nothing but NEMA X-YY devices on YY amperage circuits is the proper practice".

In fact, when I wired my shop, I didn't even take advantage of the 15/20 amp exception. All the 20 amp circuits have NEMA X-20 receptacles. Cost a few bucks more, but all the receptacles will accommodate anything I happen to get that comes equipped with a 20 amp plug. That's a rare animal, but I did it anyway.

[Steven DeMars]

What if someone plugs in a device into that 40 or 50 amp plug that draws more than 30 amps and for some reason the breaker fails to do its job? I guess as a somewhat anal person, I prefer that both ends and everything between of the installed circuit match to minimize "misunderstandings".

What happens when someone buys your home . . . . goes into your old shop, sees a "30 AMP" receptacle and simply runs down to Home Depot buys a "matching" plug and attaches it to his welding machine . . . . Happens everyday with DRYER receptacles . . . .

It is simple, you can not idiot proof anything, they are turning out higher quality idiots everyday . .

All that is really important is that the breaker protect the in-the wall wiring . . . . period . . . that is the only purpose for a breaker . . . at least that is what the code book says . . . :)

Like you, I like it all to match . . .

[Jim Becker]

I agree, Steven...there will always be that one person who thinks just matching the pins on the plug and the receptacle is the only important thing to do. We can only hope that the breaker does its thing!

Tom, I did the 20 amp receptacle thing, too, in my shop and kitchen. The only tool (so far) that came with the 20 amp plug is my CT-22, although it has a handy pigtail adapter to convert to the 15 amp style, too.

[Rick Christopherson]

Why not? With a 30 amp breaker, a 40/50 amp outlet will certainly not be overloaded whereas a 20 amp outlet could be continuously overloaded without tripping the breaker. Remember the breaker is for the purpose of protecting the circuit, and a 40/50 amp receptacle is certainly well protected by a 30 amp breaker.It is a code violation to install a 15, 20, 40, or 50 amp receptacle on a 30 amp circuit.

On a 15 amp circuit you must use 15 amp plugs.
On a 20 amp circuit you can use either 15 or 20 amp plugs. Note that a single duplex outlet constitutes 2 outlets, so the single-outlet rule applies only to a single plug circuit, not a duplex.
On a 30 amp circuit, you must use 30 amp plugs.
On a 40 amp circuit, you must use 40 amp plugs.
On a 50 amp circuit, you can use either 40 or 50 amp plugs.

[Tom Veatch]

...On a 40 amp circuit, you must use 40 amp plugs.
On a 50 amp circuit, you can use either 40 or 50 amp plugs.

Are the 40 amp devices non-NEMA? What do they look like?

All the NEMA configuration charts I've see jump from 30 amp to 50 amp. No 40 amp configurations shown.

[Rick Christopherson]

Are the 40 amp devices non-NEMA? What do they look like?

All the NEMA configuration charts I've see jump from 30 amp to 50 amp. No 40 amp configurations shown.NEMA is only a limited subset of electrical connectors. It is not required that all devices be NEMA configuration. As a matter of fact, I don't believe there is a NEMA configuration for a 50 amp twist lock, but the CS6369 is pretty common. I have a customer that uses exclusively IEC connectors to prevent their cables from growing legs and walking off project sites. As you get into higher amperages, pin and sleeve connectors become more common, and even these come in quite a few different configurations ranging from ISO, IEC, and proprietary.

The image below is one of my testers for a cable manufacturer. It includes most of the common connectors, but with the CS6369 and a proprietary 100 amp pin and sleeve (big blue ones). The other unit (right side) is the same, but this is the customer that uses IEC for all of their pin and sleeve. The bottom red ones are the IEC equivalent to the big blue ones. The cute little blue ones are single phase 16 amp. (Oh, to put these pictures into scale, the horizontal unit is about 4-5 feet wide, and the vertical one is 4 feet tall.

http://www.rts-engineering.com/tempgraphics/R5-sm-lo.jpghttp://www.rts-engineering.com/tempgraphics/R4-sm-lo.jpg

[Dave MacArthur]

Ok, I'm sorry but THAT is just going to HAVE to have it's own thread! I must know more about THAT sweet looking device ;) What do you do with it, why do you have it, is it really as fun to plug and unplug stuff as it looks? Please post next time you've got a moment.

[Rick Christopherson]

They are power distribution testers that I design and build. I used to make the enclosures myself because it is the same as woodworking, except I use a wire-feed heat welder to seam the joints. However, I discovered that it is more economical to have a plastic fabricator make the enclosures now.

Inside is a Programmable Logic Controller (PLC), which is a type of industrial computer and a 6 inch color touch screen user interface (which is also a computer in itself). When you plug a cable or distribution panel into the tester, it scans through all of the conductors and analyzes them for proper configuration. The horizontal model is the newest generation and includes load testing capabilities to find excessive voltage drop due to poor connections.

It takes about 2-3 days to fabricate one, with a $4000 margin, although the computer software code is pretty complex. There is not a huge market for these, but mine is the only tester of its type.

[Dennis Peacock]

I've ran two outlets for each 220V circuit. I never run more than one tool at once...so this has worked very well for me. Of course, I used to do electrical work for a living. :)

[David Romano]

I've ran two outlets for each 220V circuit. I never run more than one tool at once...so this has worked very well for me. Of course, I used to do electrical work for a living. :)

I just installed a second outlet on the run. The only difficulty is that the receptacle doesn't have a second set of terminals, so I had to pigtail each wire. With 12/3 wire, the box has to be packed carefully but I think I did a good job on it and it works.

Thanks for everyone's advice

David

[Dave MacArthur]

It's a good idea to pigtail the terminals anyways... when you use the 2nd terminals on the back of a plug, the current "downrange" all flows through the receptacle, as well as whatever you're using from that plug itself. Obviously it's been engineered for that if the screws are there, or they wouldn't have the 2nd set, but with high-current machines I've read that the it's perhaps not wisest to flow the whole circuit through that wee plate on the back of the receptacle.

I wired my garage, and even on my 120v runs the inspector asked that I pigtail the receptacles instead of daisy chaining them... I couldn't find a NEC reference forcing me to do it, but since that was his only "finding" I was happy to do it.