multiple outlets on one 240-volt circuit?

[Bill Bryant]

A 240-volt line runs between the floor joists directly above my basement shop on the way to an outlet upstairs behind the stove. I have a gas stove, so I could re-route the line entirely and put the outlet down in the shop. But it got me curious. What about two or three outlets on the same 240-volt line? I'm fairly familiar with 120-volt wiring conventions (I recently finished 1300 sq. ft. of basement and ran multiple circuits without a hitch and passed inspection) but I don't know what's kosher with 240.

[Tom Veatch]

... What about two or three outlets on the same 240-volt line? ...

There seems to be some sentiment that there can only be one outlet on a 240 circuit. That is not the case. A 240 circuit can feed multiple outlets just as a 120 circuit can feed multiple outlets. The only differences are that there is a 240 volt potential between the two conductors instead of a 120 volts and that both conductors instead of just one have a 120 volt potential relative to ground.

My shop, wired by a licensed electrician and inspected by the local code enforcement inspectors, has 4 separate general purpose circuits, all of which are 240 volt and each of which feeds multiple outlets. The wiring is 3-wire plus ground and the outlets are dual-voltage duplex receptacles - one 120 and one 240 outlet in each receptacle. If I hadn't wanted the 120 available, it could have been wired with 2 + ground and with multiple 240 volt outlets.

[Rob Will]

A 240-volt line runs between the floor joists directly above my basement shop on the way to an outlet upstairs behind the stove. I have a gas stove, so I could re-route the line entirely and put the outlet down in the shop. But it got me curious. What about two or three outlets on the same 240-volt line? I'm fairly familiar with 120-volt wiring conventions (I recently finished 1300 sq. ft. of basement and ran multiple circuits without a hitch and passed inspection) but I don't know what's kosher with 240.

Bill, if the stove wire is 4-wire you could use it to feed a sub panel in the basement. That would be an easy way to terminate the existing wire and provide a good take off point for extra circuits.

If the stove wire happens to be 6/4 romex, I would install a sub panel with a 50 amp breaker as a main disconnect. The main problem with using your existing wire alone is that the breaker in the panel upstairs is also probably 50 amp. For anything short of a welder plug or a range plug, that is too big. You will want to step down to smaller wire for most of your tool outlets. These wires must be individually protected with the proper size breaker, hence the sub-panel.

Rob

[Mike Cutler]

Bill There is nothing in the NEC that precludes multiple outlets off a 220 branch circuit.
I believe that the reason that you read "there can only be one" is that typically 220 supplies motors in the shop. Placing multiple motors on a single 220 circuit requires that the branch, and breaker be sized accordingly to run multiple 220 loads simultaneously.
The motors section of the NEC has covers this. There is a little flowchart at the beginning of the motors sections that guides you through it.
In a small shop though, it may be easier, and more cost effective to run seperate circuits depending on the layout, machinery involved and the local inspectors interpertation and application of the code requirements.

In the scenario you described you may be better off running a complete seperate circuit from the breaker,and "spare" the existing circuit to the electric range for future reuse. If the breaker panel is not in your shop area, consider placing a subpanel off the main panel breaker to assist you in having more flexibility meeting the line of sight disconnect requirements should that become an issue.
If you passed one inspection already. You have a relationship established with the local inspector. Ask the inspector what the "best way" to do it would be, and what would they be looking for on the inspection.

[Ray Knight]

I just checked on this. You can absolutely run more than one 240 receptacle on one breaker. The issue is the wire might need to be big enough to accommodate both receptacles being used simulataneously, something we home hobbyists don't tend to do, and our argument we use when we push code. I just finished my rough in, 3 240 circuits, one dedicated to air conditioner/heat pump (code requires dedicated), and two 240 receptacle circuits, one with two receptacle and one with three. Used the bigger wire, so I could use them simulaneously, but keeping breakers at 20A for now, to discourage that (since my feed is only 50A)Ray Knight

[Brad Townsend]

I have two 240v circuits in my shop, each with multiple outlets. My logic being that I am only one person and can only run one machine at a time. Having said that, I had a friend over a couple of weeks ago and we were running my Griz 8" jointer and Unisaw at the same time off the same circuit and I didn't even think about it until later. No problem whatsoever.

[Gary Herrmann]

I'm running two outlets off each 220 off each 220 breaker in my shop.

[Rick Christopherson]

I think Rob addressed this situation the best. Because this circuit is probably a 50-amp circuit, you will need to step it down to more reasonable size. You cannot install any other size outlet on a 50-amp circuit besides 40-amp or 50-amp, and these can be very expensive.

Install the 50-amp subpanel and then you can run your circuits how ever you choose down in the shop.

[Bill Bryant]

I just looked the situation over.

The circuit going to my stove is on a 40-amp breaker and uses 8/3 with ground.

Does this change anybody's thinking?

[Keith Carscadden]

I have no idea what your local electrical code may require but where I live, a plug is required for an electric stove, even if you have a gas stove. This means that you should check local rules before reusing the wire for the stove plug.


Keith

[Mike Cutler]

I have no idea what your local electrical code may require but where I live, a plug is required for an electric stove, even if you have a gas stove. This means that you should check local rules before reusing the wire for the stove plug.


Keith

Not sure about that one Keith. 210.52 doesn't have anything addressing a "requirement" for the stove. Only the requirements for the dedicated appliances and service with reference to 410. Individual local reg's for a CO could require it. I don't know though.
I have a gas stove and no electric wired for an electric stove. My house was built to code in '81 though.

I would still leave it there though, as I recommended. It would only be more expensive to re-install it at a later date.

[Roy Hill]

I have two 220 volt circuits in my shop with 2 tools on each circuit. Each circuit has a junction box with two DPST open power relays and a 3 position switch (closed/open/closed). I have a band saw and planer on one circuit and a jointer and tablesaw on the other circuit. I can only run one machine at a time on each circuit due to the 3 position switch. The switch allows only one machine to receive power at a time, therefore no way to overload the circuit. At the end of the day I turn both switches to the center/off position and the machines have no power at the machine switches for unsupervised hands or unauthorized users to turn on.

Roy Hill

[Tom Veatch]

... The issue is the wire might need to be big enough to accommodate both receptacles being used simulataneously...

Any particular idea as to why this might be a requirement and, more to the point, how would it be implemented. Seems like there are some inherent contradictions in that requirement as stated.

Say you have 3 20 amp outlets on the circuit. Simultaneous use could draw current up to 60 amps. Therefore you would need wire with a 60 amp capacity. But without a 60 amp breaker, you couldn't use the 3 outlets simultaneously at their full capacity. So, adding a 60 amp breaker makes it a 60 amp circuit. But now you have 20 amp outlets on a 60 amp circuit....? So, increase the receptacles to 60 amp capacity. Now you're looking a a possible simultaneous draw of up to 180 amps ....?

There's got to be more to it than just what you stated because it seems to me that way lies madness.

[Mike Cutler]

Any particular idea as to why this might be a requirement and, more to the point, how would it be implemented. Seems like there are some inherent contradictions in that requirement as stated.

Say you have 3 20 amp outlets on the circuit. Simultaneous use could draw current up to 60 amps. Therefore you would need wire with a 60 amp capacity. But without a 60 amp breaker, you couldn't use the 3 outlets simultaneously at their full capacity. So, adding a 60 amp breaker makes it a 60 amp circuit. But now you have 20 amp outlets on a 60 amp circuit....? So, increase the receptacles to 60 amp capacity. Now you're looking a a possible simultaneous draw of up to 180 amps ....?

There's got to be more to it than just what you stated because it seems to me that way lies madness.

There are two things that need protection on a motor circuit. Whether there is a single motor, or multiple motors.
The motor(s) needs to be protected. This is accomplished by determining the correct size wiring to carry the current.
The wires, or conductors, or branch circuit need to be protected. These are protected by selecting the correct breaker size.
The particular section of the NEC that deals with motors is Article 430. At the beginning of article 430 there is a flow diagram that breaks down the article into the parts and the sections of the code that apply to each part, and the reference to the correct article, not contained in 430, that apply.

NEC 430.24 addresses multiple motors and branch circuit sizing requirements;
125% of the FLC of the largest motor plus the sum of FLC of the other motors . to determine branch circuit sizing and breaker protection.
My copy of the 2005 code is at work, so I'm kinda running off memory right now. Dangerous,I know.
If someone has an NEC copy, perhaps they can work through Article 430 to answer the question more completely.

[Rob Russell]

There are two things that need protection on a motor circuit. Whether there is a single motor, or multiple motors.
The motor(s) needs to be protected. This is accomplished by determining the correct size wiring to carry the current.
The wires, or conductors, or branch circuit need to be protected. These are protected by selecting the correct breaker size.
The particular section of the NEC that deals with motors is Article 430. At the beginning of article 430 there is a flow diagram that breaks down the article into the parts and the sections of the code that apply to each part, and the reference to the correct article, not contained in 430, that apply.

NEC 430.24 addresses multiple motors and branch circuit sizing requirements;
125% of the FLC of the largest motor plus the sum of FLC of the other motors . to determine branch circuit sizing and breaker protection.
My copy of the 2005 code is at work, so I'm kinda running off memory right now. Dangerous,I know.
If someone has an NEC copy, perhaps they can work through Article 430 to answer the question more completely.

Mike,

I generally agree with what you posted, but there is another factor with motors - overload protection for the motors. To run multiple motors on the same circuit, one would need to ensure that the individual motors have appropriate overload protection. The circuit breaker protecting the wiring could well be too large to protect the motor. In that case, a separate overload is required to protect individual motors.

Rob

[Tom Veatch]

Is there a presumption in the code that if the circuit is 240 volts, it is a "motor" circuit? If the circuit feeds wall outlets, then anything, not necessarily motors, can be plugged into those outlets. And, even if it is a motor, it's impossible to determine in advance what the FLA of those motors might be. How then can a 240v circuit that feeds wall receptacles be sized per Article 430.

If it is assumed that the FLA won't be in excess of the current rating of the outlet, and there are multiple outlets, does not the circumstances of my previous post then come into play. Or does the code allow, for example, 20 amp receptacles in circuits protected by 60 amp breakers?

[Rob Will]

I just looked the situation over.

The circuit going to my stove is on a 40-amp breaker and uses 8/3 with ground.

Does this change anybody's thinking?

Nope, I would install a small sub panel in the basement with a 40amp 2 pole breaker as a main disconnect. (Since this is a home shop and not a production shop, the chance of multiple machines running at the same time is small). I think you will be fine with about four 20amp 230v circuits. Just make sure you use 12 ga wire. Personally, I would avoid 30amp branch circuits in this setup and also avoid things that turn on automaticaly like a big air compressor.

BTW: It is normal for the total capacity of the branch circuits to exceed the capacity of the main. For example, the 200 amp panel in my house has branch circuits totaling 635 amps.

Rob

[Louis Rucci]

I'm presently wiring my shop and designed it with 4 240VAC circuits per example:

1. Single receptacle to the Cyclone
2. Single receptacle to my Woodmaster sander
3. Two receptacles to my Tablesaw and Bandsaw.
4. Two receptacles to my Jointer and Planer.

The cyclone and Woodmaster each require 30 amp circuit or 10Ga wire. So I'm wiring all with 10Ga.

I can't use both saws or jointer or planer at the same time, so only one tool will draw power at a time. But I will use the cyclone with everything, hence it's own circuit.

[Rick Christopherson]

I have no idea what your local electrical code may require but where I live, a plug is required for an electric stove, even if you have a gas stove. This means that you should check local rules before reusing the wire for the stove plug.

KeithIs this really what is stated in your local code, or simply what someone told you was required? I see a lot of postings like this that state that a local code has some sort of obscure requirement, but upon further scrutiny, they almost always turn out to be hearsay, the advice of an acquaintance, or a misinterpretation from what was stated by an inspector for a specific application.

[Mike Cutler]

Mike,

I generally agree with what you posted, but there is another factor with motors - overload protection for the motors. To run multiple motors on the same circuit, one would need to ensure that the individual motors have appropriate overload protection. The circuit breaker protecting the wiring could well be too large to protect the motor. In that case, a separate overload is required to protect individual motors.

Rob

Absolutely agree Rob. This is also covered in 430. I was just trying to Keep things a little simple(r).
Sorry for the omission.

[Mike Cutler]

Is there a presumption in the code that if the circuit is 240 volts, it is a "motor" circuit? If the circuit feeds wall outlets, then anything, not necessarily motors, can be plugged into those outlets. And, even if it is a motor, it's impossible to determine in advance what the FLA of those motors might be. How then can a 240v circuit that feeds wall receptacles be sized per Article 430.

If it is assumed that the FLA won't be in excess of the current rating of the outlet, and there are multiple outlets, does not the circumstances of my previous post then come into play. Or does the code allow, for example, 20 amp receptacles in circuits protected by 60 amp breakers?

1st question

Article 430 deals only with motors. Receptacles for dryers, ranges, hottubs, AC units, evaporators, are covered in other sections. The sizing requirements are in other articles. 210, 220,250, etc.There are a lot of them.
This would be a huge discussion to get into, so I'm going to stick with motors as the point of discussion.
The FLA is marked on the motor by the manufacturer. Most, if not all motors have a UL approval. In absence of manufacturers name plate data there are Tables 247-251 at the back of 430 based on HP ratings.
Most od the motors in a shop will run at a current draw significantally less than FLA. The biggest load, in terms of continuous current draw while in operatoin is most likely the dust collector.
You want the motor and the wiring protected

2nd question

In this example the answer would be no. The code would not allow this much downsizing. Additionally there are max breaker sizing requirements. Add to this that there are manufaturers specified breaker requirements also.
Remember we want to not challenge the wiring, or the motor. We want that breaker to trip on a high current condition. Supplying a 20 amp load with potentially 60 amps is asking for trouble.

While it is fun to discuss these subjects, and a good learning experience. I hope that folks are taking away from threads like these that this work is really best left up to a liscensed electricians.
There is a lot to the code.(NEC)

[Ted Jay]

A 240-volt line runs between the floor joists directly above my basement shop on the way to an outlet upstairs behind the stove. I have a gas stove, so I could re-route the line entirely and put the outlet down in the shop. But it got me curious. What about two or three outlets on the same 240-volt line? I'm fairly familiar with 120-volt wiring conventions (I recently finished 1300 sq. ft. of basement and ran multiple circuits without a hitch and passed inspection) but I don't know what's kosher with 240.

Bill,
Since you mentioned you have a gas stove then it is more likely you also have a gas dryer. That means you also have another 220 outlet you can use for the shop.. even mo betta'!!:D
Ted

[Tom Veatch]

...
Article 430 deals only with motors. ...

Thank you. That was my point. The discussion of requirements on dedicated motor circuits is independent of and not responsive to the original question in this thread, which was whether or not a 240v circuit can have multiple outlets. The requirements of Article 430 are no more applicable to a 240 volt circuit which feeds a series of receptacles than it is when the voltage is 120.

[Mike Cutler]

Thank you. That was my point. The discussion of requirements on dedicated motor circuits is independent of and not responsive to the original question in this thread, which was whether or not a 240v circuit can have multiple outlets. The requirements of Article 430 are no more applicable to a 240 volt circuit which feeds a series of receptacles than it is when the voltage is 120.


????? Confused here Tom.:confused:

I think we pretty much established early on that there could be more than one receptacle on a 240 circuit. Nothing prohibits it.
I guess I made a presumption that multiple outlets were intended to facilitate the ease of utilizing mobile machinery at differing locations throughout the shop depending on space requirements. Why else would someone do this? Article 430 is completely relevant to the application of multiple 240 outlets in a shop if the intended application is to power motors. The inspector is going to inspect to the criteria established on the application permit.
In that scenario a person would still have to be aware of, and plan for the use of such circuits and size them accordingly. In a home shop, ie. mine, There are two 220 circuits, each protected by a seperate 20 amp breaker. Each has 2 receptacles on it. I know that there will almost always be two 220 loads running at the same time. One is the DC at 1 1/2 hp. The max on the other would be the 3 hp planer or sander.

All branch circuits, whether 120, or 240 are sized according to the code. The 120's are a little more cut and dried. There are specific minimum required receptacles,and dedicated circuits to preclude the overloading of any single branch circuit based on the theoretical intended application and the anticipation of loads being utilized in a given room. Additionally these circuits have to account for lighting loads and the receptacle can be downsized because of this.
Inside the home(dwelling) I can't think of a single application in the US for multiple 240 receptacles on an individual branch circuit. Dryers, Stoves, Heat pumps, Hot tubs, Water pumps, all have their own breaker. Hardwired loads like electric baseboard heaters are sized according to the room size. The wattage of the heater(s) determines the wire size and breaker. requirement. there can be more than 1 heater on a breaker certainely, but the wire size and the breaker are still calculated based on the anticipated load.

I'm not really sure where you're coming from here, and I am most certainley not trying to be argumentetive. You're presenting a thought that deserves merit and discussion, so I'm trying to understand what it is you are driving at.

[Rick Christopherson]

Mike and Tom,
I really can't make heads or tails of who is supporting/contradicting what, but I will state that Article 430 is the most frequently misinterpreted, misapplied, and misquoted article of the NEC as it applies to woodworking equipment.

If either of you is planning to bring Article 430 into this discussion regarding general purpose outlets, please be careful about proper interpretation of the Article as it pertains to woodworking equipment. There are a lot of readers here that get needlessly confused by similar discussions all the time.

[Mike Cutler]

Rick

I agree completely. Article 430 is tough! Even on Mike Holt's forum there is always a lot of debate concerning 430, and those guys do this kind of work daily.

I'm only referring to 430 because of the intended use of the receptacles in the shop. Chiefly to power motors on woodworking equipment. I'm not factoring in a general purpose receptacle at all

[Tom Veatch]

...If either of you is planning to bring Article 430 into this discussion regarding general purpose outlets, please be careful about proper interpretation of the Article as it pertains to woodworking equipment. There are a lot of readers here that get needlessly confused by similar discussions all the time.

Honestly, I'm not intentionally trying to be a wise-acre. What I am trying to say is precisely what your last sentence above says. It is terribly confusing to mention Article 430 in this context.

Article 430 is excellent in its proper application - dedicated motor circuits. I have two such circuits in my shop and the equipment on each circuit is hardwired through disconnects. Trying to apply 430, or reference it, or enforce it, in relation to circuits in which equipment can be plugged and unplugged at will is an exercise in futility. I'd hoped that the somewhat retorical questions I posed in previous posts would have brought some of that futility to light. Apparently that was a forelorn hope.

I'll leave it with one last attempt. Consider this scenario. I'm building a shop. I plan on having several machines in that shop. I haven't purchased them yet, but I expect there will be 6 or 7 stationary machines along with several handheld tools and maybe a couple of shop-vac type units. They all contain motors - the subject of Article 430. I don't imagine there will be any larger than 3HP but there may be any mix of that size and smaller. All that can be run on 240 volts will be. In fact, the ability to run on 240 volts will be a prime consideration, but not a deal breaker, when I purchase the tool. Oh, yes, there may also be a couple of portable electric heaters as well as some portable task lighting. (Note, I did not say a "woodworking" shop.)

Now, according to Article 430, how large does the circuit (or circuits) have to be? And if I unplug my shop-vac from one circuit and plug it into another I don't need to worry about the first circuit since the load on it has been reduced. But, do I need a permit, electrician, and inspection to ensure that I haven't violated the requirements of Article 430 in the second circuit? How about if I move one of those electric heaters? How about moving one of those 3HP stationary machines?

It's futile to try to extend Article 430 to apply to a circuit that consists of several plug/receptacle outlets.

[Jerry Booher]

I have a 50 amp 240v receptacle in my shop with a 5hp single stage air compressor with a huge plug that matches the plug I have on my welders. I am awaiting shipment of an Oneida 2.5hp cyclone and I need an outlet next to the existing receptacle.

Should I just cut a hole in the cement block wall and feed a new box with a 6-20R receptacle? Or do I need a subpanel?

[Tom Veatch]

I have a 50 amp 240v receptacle in my shop with a 5hp single stage air compressor with a huge plug that matches the plug I have on my welders. I am awaiting shipment of an Oneida 2.5hp cyclone and I need an outlet next to the existing receptacle.

Should I just cut a hole in the cement block wall and feed a new box with a 6-20R receptacle? Or do I need a subpanel?

If it were me doing it, I'd run a dedicated 20 amp circuit and hardwire the cyclone through a disconnect switch. I assume the compressor circuit has a 50 amp breaker. If that's the case, adding a 6-20R to the existing line would not be advisable. That receptacle would not be properly protected by a 50 amp breaker. If you are intent on breaking into the existing circuit, use a 6-50R like the one already there. Depending on the FLA of the motors involved, the (assumed) 50 amp circuit should support both motors running simultaneously.

I don't know what size your cyclone motor might be. The separate, dedicated 20 amp circuit mentioned should be good for any motor up to about 3 - 4 HP. If the motor on your cyclone is larger than that, it would probably call for at least a 30 amp circuit and matching receptacle, or hardwiring through a 30 amp disconnect switch.

Best advice you're going to get here (or any online source) is, regardless of the above, talk to a licensed electrician on the scene and follow his/her advice.