# Can I run two 220 volt devices off of one outlet



## Just Bill (Dec 21, 2008)

Yes, you can chain 200 outlets just like you do 120, but I am not sure you can run the saw and the A/C at the same time. Sorry, extension cords not recommended, especially not a 25' cord.


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## Speedy Petey (Feb 1, 2004)

Also, you say this is a 30A circuit. You CANNOT have 20A receptacles on a 30A circuit. 
A 16kBTU window A/C will NOT require a 30A receptacle. More like 15A.


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## Yoyizit (Jul 11, 2008)

stringpickin said:


> I have a 3hp 220 tablesaw
> 
> a 16,000 btu window air conditioning unit on that same line.


3hp @ 220v = ~10A
A/C @ 220v = ~7A

Depending on the trip curve of the breaker you might never have a problem but the NEC may have some things to say about this.


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## Speedy Petey (Feb 1, 2004)

Yoyizit said:


> 3hp @ 220v = ~10A


HUH??? 

Try 17A.
NEC Table 430.248

This is of course if it is a REAL 3HP and not a BS "developed" HP number that Sears might try to sell.


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## Yoyizit (Jul 11, 2008)

Speedy Petey said:


> HUH???
> 
> Try 17A.
> NEC Table 430.248
> ...


I did 3 hp x 746w/hp divided by 220v. How'd they do it?


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## Bigplanz (Apr 10, 2009)

I think a dryer or baseboard heater has to be on a separate 240V circuit. I guess you can string them for general purpose outlets though. Can't find anywhere that says you can't.


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## Speedy Petey (Feb 1, 2004)

Bigplanz said:


> I think a dryer or baseboard heater has to be on a separate 240V circuit. I guess you can string them for general purpose outlets though. Can't find anywhere that says you can't.


???
"You think..."
"You guess..."
"Can't find anywhere that says you can't."

How 'bout the NEC?


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## unclduey (Mar 2, 2009)

Did anybody notice if he said what voltage his AC unit was? Does his 220v 30 A circuit have a neutral?


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## unclduey (Mar 2, 2009)

unclduey said:


> Did anybody notice if he said what voltage his AC unit was? Does his 220v 30 A circuit have a neutral?


my mistake, didnt see the voltage in the header


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## Bigplanz (Apr 10, 2009)

Speedy Petey said:


> ???
> "You think..."
> "You guess..."
> "Can't find anywhere that says you can't."
> ...


 I was busy chasing the kids as they were running all over the backyard. Didn't feel like looking it up. Google is your friend though. I was just going off what I remembered off the top of my head. Is there going to be a test later?

Edit to add: "Can't find anywhere that says you can't." I should have said I can't 'remember' rather than find. Sorry about your confusion.


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## J. V. (Jun 1, 2007)

Bigplanz said:


> I was busy chasing the kids as they were running all over the backyard. Didn't feel like looking it up. Google is your friend though. I was just going off what I remembered off the top of my head. Is there going to be a test later?
> 
> Edit to add: "Can't find anywhere that says you can't." I should have said I can't 'remember' rather than find. Sorry about your confusion.


Google is not any help in any NEC discussions. You either have the NEC code or you don't.
Do not take offense. Speedy is knowledgeable and his answers are reliable. We have to be very careful in this format. This is a DIY forum and we do not want bad information to be taken literally. I have made this mistake before, and was corrected immediately. If you do not know the answer for sure, do not give advice on the question. As you see, it will get corrected in a hurrry and not all here are as easy as Speedy was on you. John :thumbsup:


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## Speedy Petey (Feb 1, 2004)

I'll admit, my internet persona is not one of being warm and fuzzy, and I tell it like it is, and I can be quite sarcastic, but I do try to post facts and correct information. If I post an opinion I will make that very clear also.



Bigplanz said:


> Edit to add: "Can't find anywhere that says you can't." I should have said I can't 'remember' rather than find. Sorry about your confusion.


You post incorrect information; and post "You think" and "You guess"; and you say you can't remember; and *I* am the one that's confused? 
Nice try. :laughing:


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## nap (Dec 4, 2007)

Ya, petey is just a big softy. 


as petey suspects, and I, the recep needed for the AC will be of lesser ampacity rating than the saw circuit is fused for. As such, you cannot install such a lesser rated receptacle on that circuit without proper fusing.


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## Bigplanz (Apr 10, 2009)

If you can't find the NEC in a PDF format on-line you aren't looking very hard. You can even download the 2005 or 2008 legally, since if a code is adopted by a jurisdiction it becomes part of the public record and has to be made available to the public. If you want I could post a link. Just let me know. 

I did a key word search on "dedicated circuit" and the only one I found was for a hot tub/ hydrospa.

I suppose my memory is from an internal document we have at the office concerning wiring requirement for single family permits. We give it to homeowners when they pull a homeowners permit.


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## Bigplanz (Apr 10, 2009)

Speedy Petey said:


> You post incorrect information; and post "You think" and "You guess"; and you say you can't remember; and *I* am the one that's confused?
> Nice try. :laughing:


Which part was incorrect? Please quote the NEC if you wish to be taken seriously.


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## nap (Dec 4, 2007)

> =Bigplanz;265353]If you can't find the NEC in a PDF format on-line you aren't looking very hard. You can even download the 2005 or 2008 legally, since if a code is adopted by a jurisdiction it becomes part of the public record and has to be made available to the public. If you want I could post a link. Just let me know.


 that is only if the code is accepted into the law by reproduction. The NFPA specifically does not allow this. They will only allow acceptance by reference which allows the NFPA to control the copywritten product and as such, can dissallow any reproduction.


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## Speedy Petey (Feb 1, 2004)

Bigplanz said:


> Which part was incorrect? Please quote the NEC if you wish to be taken seriously.


Like I would even give a crap if you took me seriously. 


For your education:



Bigplanz said:


> I think a dryer or baseboard heater has to be on a separate 240V circuit.


A 120v fixed in place heater can be shared with receptacles if it is 50% or less of the circuit.
NEC 210.23(A)(2)

Just being a baseboard heater does not require a "separate 240v circuit". You can have as much heat as you want up to 80% of the circuit. NEC 424.3(B)
Or you can share a 240v circuit provided you calculate the load properly.
If you share it with 240v receptacles then NEC 210.23(A)(2) again applies.
For a 30A circuit 210.23(B) applies and can only be shared with 30A receptacles. 30A receptacles are typically not considered "general purpose".
See also T210.24




Bigplanz said:


> I guess you can string them for general purpose outlets though.


Again, not the dryer circuit as it is 30A: Table 210.21(B)(2) & Table 210.21(B)(3) and T210.24

A 120v fixed in place heater can be shared with receptacles if it is 50% or less of the circuit.
NEC 210.23(A)(2)

Just being a baseboard heater does not require a "separate 240v circuit". You can have as much heat as you want up to 80% of the circuit. NEC 424.3(B)
Or you can share a 240v circuit provided you calculate the load properly.
If you share it with 240v receptacles then NEC 210.23(A)(2) again applies.
For a 30A circuit 210.23(B) applies and can only be shared with 30A receptacles. See also T210.24


Now please put me on ignore so you don't have to deal with me. You'll be better off. :whistling2:


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## Speedy Petey (Feb 1, 2004)

Now that we have gotten way off topic, let's get back to the OP. 

You can only do this if the A/C uses a 30A plug, which we are saying it should not.

What is the circuit wiring and receptacle for the 30A saw circuit? #10 and 30A I hope.


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## Bigplanz (Apr 10, 2009)

nap said:


> that is only if the code is accepted into the law by reproduction. The NFPA specifically does not allow this. They will only allow acceptance by reference which allows the NFPA to control the copywritten product and as such, can dissallow any reproduction.


All the PDF versions on line are state laws with a xeroxed copy of the NEC as an attachment. You are downloading the 'law' and a xeroxed (the PDF) copy of the NEC. It's still searchable, which is very helpful.


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## Yoyizit (Jul 11, 2008)

Bigplanz said:


> NEC in a PDF format on-line
> the 2005 or 2008
> adopted by a jurisdiction it becomes part of the public record
> has to be made available to the public.
> If you want I could post a link. Just let me know.


I had a lot of trouble searching those NEC links in a useful way, much more so than a paper copy. Please post your link. 
I can always use these kind of links.
Thanks.


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## Bigplanz (Apr 10, 2009)

Speedy Petey said:


> A 120v fixed in place heater can be shared with receptacles if it is 50% or less of the circuit. NEC 210.23(A)(2)
> 
> Just being a baseboard heater does not require a "separate 240v circuit". You can have as much heat as you want up to 80% of the circuit. NEC 424.3(B)
> Or you can share a 240v circuit provided you calculate the load properly.
> ...


Thanks, so the only dedicated circuit is for a spa or hot tub, correct? The others are all load based? I suppose my confusion has to do with the typical single family residential installation where a 20 amp baseboard heater is installed, and they run a 20 amps circuit to it with 12-2 wire. It doesn't necessarily 'have to be dedicated,' though it usually is.

Why would I want to ignore you? I appreciate factual information that improves my understanding of this subject.


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## nap (Dec 4, 2007)

Bigplanz said:


> All the PDF versions on line are state laws with a xeroxed copy of the NEC as an attachment. You are downloading the 'law' and a xeroxed (the PDF) copy of the NEC. It's still searchable, which is very helpful.


please provide a link. I read directly from the NFPA that they do not allow this and as such, there may be a few places that are breaking the law in an attempt to enforce the law.

here is an excerpt from a site that states is concisely:



> n the 1987 edition of the NEC the NFPA deletes a licensing provision the allows governing bodies to republish the the code. Beginning in 1987 governing bodies who adopt the NEC into law can do so only by "Adoption by Reference." The NFPA defines "Adoption by Reference" as the citing of the title and publishing information only


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## Bigplanz (Apr 10, 2009)

nap said:


> please provide a link. I read directly from the NFPA that they do not allow this and as such, there may be a few places that are breaking the law in an attempt to enforce the law.
> 
> here is an excerpt from a site that states is concisely:


Link, as requested. I have no idea as to the legality of this, but here they are:

http://bulk.resource.org/codes.gov/


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## Speedy Petey (Feb 1, 2004)

Bigplanz said:


> Thanks, so the only dedicated circuit is for a spa or hot tub, correct? The others are all load based?


No, there are other loads that are required to be "dedicated, such as a plug-in range hood, 15A refer circuit or central heat (with exceptions).


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## Bigplanz (Apr 10, 2009)

Speedy Petey said:


> No, there are other loads that are required to be "dedicated, such as a plug-in range hood, 15A refer circuit or central heat (with exceptions).


Thanks again.

For those who are interested, here is a link to the 2008 NEC 'draft' on the NFPA web site. It is the draft, not the final adopted version, but it is free and very easy to search. Although this is virtually identical to what was finally adopted, it isn't the final version so take it with a grain of salt.

http://www.nfpa.org/assets/files/_PDF_/necdigest/_NEC2008ROPDraft_._pdf _


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## 220/221 (Oct 9, 2007)

> You can only do this if the A/C uses a 30A plug, which we are saying it should not.


Can he install a sub at the saw and split it?


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## Bigplanz (Apr 10, 2009)

Here is a hypothetical question: suppose you wanted a dryer and baseboard heater in the basement. The dryer is 30A and the heater is 20A. Both are, of course, 240V. Could you install a 50A breaker and run both off of it? (Wire sized appropriately, of course.) Could you run the heavy line (8 gauge? 6?) to a junction box, then run 12 gauge to the heater and 10 gauge to the dryer?

I 'think' the answer is yes, but, well, I'll ask rather than 'guess' or 'suppose.:laughing:'


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## 220/221 (Oct 9, 2007)

There is a tap down rule that applies in some cases. They used to install an oven and a cooktop on a 50 amp circuit and split them off with 10's.

It is still legal but with some restrictions. I know that the tapped dwn wire must be #10. It doesn't come up often enough for me to remember it.:jester:


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## Speedy Petey (Feb 1, 2004)

Bigplanz said:


> Here is a hypothetical question: suppose you wanted a dryer and baseboard heater in the basement. The dryer is 30A and the heater is 20A. Both are, of course, 240V. Could you install a 50A breaker and run both off of it? (Wire sized appropriately, of course.) Could you run the heavy line (8 gauge? 6?) to a junction box, then run 12 gauge to the heater and 10 gauge to the dryer?
> 
> I 'think' the answer is yes, but, well, I'll ask rather than 'guess' or 'suppose.:laughing:'


Nope, wouldn't work.

For household cooking appliances the tap codes are more lenient. 

For a dryer and heater 210.19(A)(4) would apply and the taps could be #14 or #12 but would be restricted to 18" in length.


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## kbsparky (Sep 11, 2008)

Yoyizit said:


> I did 3 hp x 746w/hp divided by 220v. How'd they do it?


You are ignoring power factor and efficiency in your calculation there. No motor operates at 100% power factor or efficiency.:whistling2:


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## Bigplanz (Apr 10, 2009)

Speedy Petey said:


> Nope, wouldn't work.
> 
> For household cooking appliances the tap codes are more lenient.
> 
> For a dryer and heater 210.19(A)(4) would apply and the taps could be #14 or #12 but would be restricted to 18" in length.


Ok, well what if you sized the wire to handle the maximum amperage of the total circuit? Could you, theoretically, have a 20A and 30A device, both operating at 240V on a single line rated with 50A overcurrent protection if the wire was sized appropriately?


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## Yoyizit (Jul 11, 2008)

kbsparky said:


> You are ignoring power factor and efficiency in your calculation there. No motor operates at 100% power factor or efficiency.:whistling2:


Well, k x 3 x 746/220 then, and k = 5/4 or 4/3 or some generic factor.
17A/10A implies an effic. , PF, etc of 0.6. I guess it's possible, worst case.

Since the cost of change is probably high in this case, the OP could make some educated guesses about his particular setup and check if it will work on paper.
I guess that's why the NEC is conservative; it keeps people from having to make all these tedious calculations each time.

In this case, (10+7)A/30A means the saw and A/C could both be 20% "lossy" or whatever and still meet the [115% of] rated breaker value. Then it comes down to the trip curve and the unlikely event that the A/C compressor and the saw start at the same time.

If I were the OP I'd gamble a $20 or so on parts that it would work. The parts won't go to waste in any case, not with e-bay.


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## InPhase277 (Feb 9, 2008)

Bigplanz said:


> Ok, well what if you sized the wire to handle the maximum amperage of the total circuit? Could you, theoretically, have a 20A and 30A device, both operating at 240V on a single line rated with 50A overcurrent protection if the wire was sized appropriately?


If the 20 A and 30 A devices you wanted to power fell under the auspices of the various tap rules then yes, it would be permissible. Otherwise, each sub-branch from the 50 A circuit would need overcurrent protection where they received their supply.


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## InPhase277 (Feb 9, 2008)

I'm too lazy today to A) go get my code book from the trailer, and B) look through said code book. I'm sure someone will respond if it is not permissible for whatever reason. Why not put a fused disconnect at the A/C and wire a 6-20R into it?


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## hayewe farm (Mar 15, 2009)

Speedy Petey said:


> HUH???
> 
> Try 17A.
> NEC Table 430.248
> ...





Yoyizit said:


> I did 3 hp x 746w/hp divided by 220v. How'd they do it?


Actually both are correct and wrong. Table 430.248 (3 HP 17a @ 240 VAC) is used to determine the ampacity of conductors or the amperage ratings of switches,branch circuit short circuit and ground fault protection, instead of the actual current rating marked on the motor name plate. Where the motor is marked in amperes but not horse power, the horse power rating shall be assumed to that correspond to the value given in table 430.247. (3 Hp 12.2amps @240 VAC) See section 430.6(A)(1)

Table 430.248 takes into account the start surge to size circuit componets, Yoyizit's formula while a standard gives a result slightly less than the NEC table 430.247.


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## Speedy Petey (Feb 1, 2004)

hayewe farm said:


> Actually both are correct. Table 430.248 (3 HP 17a @ 240 VAC) is used to determine the ampacity of conductors or the amperage ratings of switches,branch circuit short circuit and ground fault protection, instead of the actual current rating marked on the motor name plate. Where the motor is marked in amperes but not horse power, the horse power rating shall be assumed to that correspond to the value given in table 430.247. (3 Hp @240 12.2amps) See section 430.6(A)(1)
> 
> Table 430.248 takes into account the start surge.


This is when the motor is marked only in amps, but not HP. This is to give an interpreted HP rating to the given amp number.
The OP says 3HP and has not returned to clarify anything. Since it is a 240v motor I/we can only assume it is a "real" 3HP.

The 12.2 you quote from 430.247 is for *DC* motors. Go to T430.248


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## Speedy Petey (Feb 1, 2004)

Also, the values in 430.248 are not considering start-up current. They are running current values.
Here is the direct text from that table:



> The following values of full-load currents are for motors running at usual speeds and motors with normal torque characteristics.


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## hayewe farm (Mar 15, 2009)

Sorry mistook a comma for a period. However my point is the T430.248 is an allowable rating for a given HP not an actual amperage usage table much the same as the allowable rating for 14 ga. wire is 15 amps which does not match the actual ampacity of 14 ga. wire. Yoyizit's formula is a standard HP to watt estimating formula but doesn't guarantee the correct amperage for a particular motors.


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## Yoyizit (Jul 11, 2008)

Something else occurs to me. The NEC can't use the typical [50th percentile] value for current because then half the time the installation would be overloaded. 
They need the 95th percentile or the 99th, so then their values must be higher than typical values. The NEC is a design for High Reliability and "High reliability is informally reported in "nines". With 20k fires due to elec. each year and 90M houses, it looks like we're at 99.98% reliability due to the NEC and common sense.

This table does seem to address the lesser efficiency and worse PF of smaller motors.

For DIY, though, for a quick and/or temporary fix the homeowner can probably use measured values or generic calc'd values but it won't be within code for the next homeowner.

For background context, what percent of homes don't meet code and we're still getting 99.98%?


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