How many 30A outlets on a circuit?
- Thread starter Sneeze357
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Charles (in GA)
Well-known member
There is, that I know of, no NEC restriction on multiple outlets on the circuit you describe. Others may differ with this, it has been discussed in the past 6 mo or so. No, you cannot upsize the breaker because the receptacle is not rated for the higher amperage.
NEC 210.21(B)(3) calls for only a 30 amp receptacle on a 30 amp circuit, and on a 40 amp circuit, 40 or 50 amp rated receptacles
Charles
NEC 210.21(B)(3) calls for only a 30 amp receptacle on a 30 amp circuit, and on a 40 amp circuit, 40 or 50 amp rated receptacles
Charles
98ssuck
Well-known member
Generally a outlet of that size is installed for a specific purpose and only feeds that circuit. Now being from Canuckistan what the NEC says I have no idea. What are you planning on using the circuits for?
You will need to upsize the grounding conductor if you use 8 AWG on a 30A circuit, I am assuming your using NM "Romex®" which has a 10 AWG grounding conductor, NEC art 250.122(B) does require a larger grounding conductor when ungrounded conductors are increased in size. The other issue is will the 30A receptacle accept 8 AWG wire? A straight blade will but a locking type may or may not. And as said above a 30A receptacle may not be used on a 40A circuit.
I would advise that 10 AWG is a better choice for a 30A circuit.
Mostly I'm going to split it up even further into 20A 120V circuits with a spider box. Also will occasionally plug in an air compressor. I already had the wire so....
I'm confused. Why would a 10ga ground not be enough for a 30A circuit? What application is 8/3 NM with a 10ga ground for then? Can I run a separate ground wire with the romex?
The outlets I'm using are like you would use on a dryer...almost exactly the same as a 50A, but with a slightly different blade. Pretty sure the wire terminals are the same.
Thanks for the info.
Mustang51js
Well-known member
According to that article posted, #10 ground is good up to 60 amps so why wouldn't it be good enough for 30. The biggest issue you are going to have is messing around with the wires inside of the box when you have multiple wires and a plu in there,it's hard enough with 10 wire and pigtails in a deep 1900 box.
2ManyProjects
Well-known member
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The question which immediately comes to mind is, why would you want to? 30A/240V circuits tend to be dedicated to particular devices.
Not with those outlets, you can't. The breaker MUST be sized for the "weakest link in the chain", so to speak.
Let's be clear here. Are you referring literally to a PORTABLE Spider box, such as:
http://www.grainger.com/product/HUBBELL-WIRING-DEVICE-KELLEMS-Box-4D572
Or are you talking about tapping off multiple permanently installed 20A/120V circuits from that single "feeder", in some sort of home-brew work box?
In the former case, the spider box would be considered ONE load; and what you run off it is purely a matter of the box's capabilities. That said, the circuit feeding the spider box must be capable of the full load that box could possibly impose. In the case of the example cited above, that would be 50A @ 120V.
In the latter case, you would need to install a proper sub-panel to support the branch circuits.
That further complicate things; but it doesn't fundamentally change them. The main thing is, if you're using the circuit for the air compressor, you cannot simultaneously use it for the spider box (and vice versa).
Besides, if you have an air compressor which needs 30A @ 240V, it's likely to be permanently installed anyway. So then, it's power feed should also be permanently installed, and dedicated to it (and probably hard-wired, for reasons we have not yet gotten into).
So I can move things around if I want to. I don't need 30 amps for the compressor but it shouldn't hurt either.
Yes, I have a 30A box. (The original twist lock cord has been replaced with a 30A dryer cord)
alfredeneuman
Well-known member
You're wrong as usual. You should get a Code book, and read it before you post.
250.122(B) Increased in Size.
Where ungrounded conductors are increased in size, equipment grounding conductors, where installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors
pattenp
Well-known member
I really believe that this section gets misapplied when it comes to the use of multiconductor cable such as NM-b. NEC 2011 250.122(A) says the equipment grounding conductor shall be permitted to be sectioned within the cable as long as it complies with table 250.122. To me it does not seem reasonable because of using 8/3 NM-b with a 30A breaker and 30A receptacles that the #10 ground within the cable would need to be increased.
sberry
Banned
This is where Norcal and Ace might be able to splain better but because the upsize often is for motor loads and specialty circuits such as welders this 8 wire could be breakered at 100A.
Mustang51js
Well-known member
Did you even read what I wrote in the post or just start opening your mouth before you finished. I will repeat it again, if you look up the specific article that was posted it clearly shows a #10 ground good up to 60 amps. I'm not talking about exceptions or anything else but that particular article. So maybe you should read the whole post before opening your yap.
Mustang51js
Well-known member
NEC 2008: Table 250.122
Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment
Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment, Conduit, etc., Not Exceeding
Size (AWG or kcmil)
Copper
(Amperes)
15 14 12 20 12 10 30 10 8 40 10 8 60 10 8
100 8 6 200 6 4 300 4 2 400 3 1 500 2 1/0 600 1 2/0 800 1/0 3/0
1000 2/0 4/0 1200 3/0 250 1600 4/0 350 2000 250 400 2500 350 600 3000 400 600 4000 500 800 5000 700 1200 6000 800 1200
Aluminum or Copper‐Clad Aluminum*
It didn't come in line but what code book you going by, 2008 or 2011 since I might have looked up wrong article.
Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment
Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment, Conduit, etc., Not Exceeding
Size (AWG or kcmil)
Copper
(Amperes)
15 14 12 20 12 10 30 10 8 40 10 8 60 10 8
100 8 6 200 6 4 300 4 2 400 3 1 500 2 1/0 600 1 2/0 800 1/0 3/0
1000 2/0 4/0 1200 3/0 250 1600 4/0 350 2000 250 400 2500 350 600 3000 400 600 4000 500 800 5000 700 1200 6000 800 1200
Aluminum or Copper‐Clad Aluminum*
It didn't come in line but what code book you going by, 2008 or 2011 since I might have looked up wrong article.
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alfredeneuman
Well-known member
It's the same in either the 2008 or 2011.
Simply using the table is a good way to get in trouble.
Read the actual text of Article 250.122 (B) hint: (B) and see for yourself.
It's not an exception, and is mandatory.
Simply using the table is a good way to get in trouble.
Read the actual text of Article 250.122 (B) hint: (B) and see for yourself.
It's not an exception, and is mandatory.
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pattenp
Well-known member
My understanding is that the 250.122(B) code section was originally intended to cover the increase in size of the ungrounded conductors to compensate for voltage drop saying the EGC also has to be increased in size. The code section reads for what ever reason that the ungrounded conductors are increased the EGC also needs to be increased. To me that blanket requirement makes no sense. I see in the 2014 NEC the 250.122(B) has had some clarification added.
Mustang51js
Well-known member
I just looked it up online and that table is what came up, I looked in code book later on and saw the other parts, and it was more of a question than a statement. I should've put a question mark at the end. I'm used to using romex 99% of the time so for what I do I don't have to go in code book much, and they were talking about 8/3 rx in the posts for a while.
Still not making any sense to me. What application is NM 8/3 with 10ga ground for if it is not suitable for a 30A circuit? But 10/3 would be just fine? Nonsense! Makes just as much sense as saying I have to wear red shoes when I'm installing it...
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It is what it is, that code section was only if the ungrounded conductors were upsized for voltage drop, so that if someone tossed in some larger wire because thats what they had on the truck it was fine, but the code committees chose to make it apply for any reason, so like it or not it supersedes the other code articles & tables, if we wish to do electrical work correctly we do not get to pick and choose the NEC articles we want to comply with. I have little use for AFCI requirements but they are code requirements & have to comply w/ it, even if I think it's snake oil.
Edit: Might be one reason to like EMT, if one uses EMT as the grounding conductor, you can upsize the conductors w/ no issues.
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So why then do they bother to sell 8/3 NM cable with a 10 gauge ground if you aren't allowed to use it?
Quite frankly I'm not going to get a permit so it doesn't really matter. I'll do it up to code in the name of safety but not in the name of ridiculousness. I'm not going to pay an inspector $100 to nit pick about things like this...
Quite frankly I'm not going to get a permit so it doesn't really matter. I'll do it up to code in the name of safety but not in the name of ridiculousness. I'm not going to pay an inspector $100 to nit pick about things like this...
cello
Member
Depending on the length of the run. I would also add a grounding rod if it was mine!
And what is that going to accomplish?
ambenz
Well-known member
I suppose you also have to consider the fact that after your dead and gone, the circuit will still be there. Consider the next owner will not know to not use both all the multiple outlet, you put in, at the same time.
pattenp
Well-known member
Sneeze, I don't know where you're located. But if you happen to be in Virginia and your shop is residential not commercial, the Virginia residential building code does not allow multiple outlets greater than 20 amps to be on a single circuit.
sberry
Banned
I got 1, its a convenience for a small welder, used it once. But I am with the others here that if possible to use a circuit per machine. I would assume if this was a multiple motor circuit would want the equipment hard wired to a disconnect? With no available for use recept?
It requires a more highly supervised installation. With a single outlet device circuit its way harder to hurt yourself short of adding a 12 romex to run a pottery kiln.
It requires a more highly supervised installation. With a single outlet device circuit its way harder to hurt yourself short of adding a 12 romex to run a pottery kiln.
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Dragster Racer
Well-known member
If the breaker is properly sized, then there would be no risk of overload.
What do we do in our houses? Each outlet on a circuit is rated for 15 amps, and we may have 8 outlets on a run. Do I need to run wire rated for 120 amps?
And again, this is why I am willing to follow the codes for safety, not for nonsense made up rules that have no clear reason. 
I will use a 30A breaker, so it shouldn't matter if I have a hundred outlets, and 47 different air compressors plugged in at one time.
Yes, it will still be there after I am dead and gone, this building is a hundred years old and it's full of 100 years of modifications. How much of it is up to code? Probably not a lot. I don't think they had a code when they started...
It's funny, I did have an electrician in to move a circuit to a different subpanel a few weeks ago. Part of this circuit he moved is incorrectly wired with 14ga wire on a 20A circuit. Also the Romex is run on the surface where it isn't really allowed. (part of somebody else's installation) Inspector passed this no questions asked.
I will use a 30A breaker, so it shouldn't matter if I have a hundred outlets, and 47 different air compressors plugged in at one time.Yes, it will still be there after I am dead and gone, this building is a hundred years old and it's full of 100 years of modifications. How much of it is up to code? Probably not a lot. I don't think they had a code when they started...
It's funny, I did have an electrician in to move a circuit to a different subpanel a few weeks ago. Part of this circuit he moved is incorrectly wired with 14ga wire on a 20A circuit. Also the Romex is run on the surface where it isn't really allowed. (part of somebody else's installation) Inspector passed this no questions asked.
sberry
Banned
Yup. A lot of shoddy stuff by those sposed to know better.
I did some stuff early on should have been inspected out. A few places in the local community have went back where I errored if I have a chance.
I did some stuff early on should have been inspected out. A few places in the local community have went back where I errored if I have a chance.
sberry
Banned
In fact look for those same issues that were not crystal clear in others work,,, I found a main in a place not too long ago with a missing bond. I happened on an old job I did out of high school to a garage and had a service call to the place for a furnace. While I was there I went to the garage, I suspect a later electrician in the family came along and fixed a couple glaring faults.
What I thought was funny is all the work my electrician did was all closed up inside EMT when the inspector got there. The inspector looked at some pipes and said ok. What could he possibly have seen? Obviously it's all about money, but I'm in a rural unincorporated area so they aren't too picky...
Obviously it's all about money, but I'm in a rural unincorporated area so they aren't too picky...Charles (in GA)
Well-known member
Because code allows #10 ground on a #8 wire, but the circuit has to be properly sized. Put the proper breaker and receptacles on a circuit wired with #8 and a #10 ground, and you have a legit circuit. Use that #8 with a #10 ground to upsize a smaller circuit, and you don't have a legit circuit.
Charles
So in other words with a 40A breaker and a 40A outlet I can use the 8/3, but if I go down to a 30A breaker and a 30A outlet I have to replace the 8/3 with smaller gauge?
I almost want to break that code out of principle alone.
Mustang51js
Well-known member
From the way I see it if you drop the 40 amp circuit to 30 amps you need to make the ground the same size as the other wires. Doesn't really make sense when you think about it.
alfredeneuman
Well-known member
In the 2014 NEC they have clarified the Article
(B) Increased in Size.
Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire type equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.
Like previously stated by Norcal, it's a good argument for just using EMT, which is acceptable as a grounding conductor on its own.
(B) Increased in Size.
Where ungrounded conductors are increased in size from the minimum size that has sufficient ampacity for the intended installation, wire type equipment grounding conductors, where installed, shall be increased in size proportionately according to the circular mil area of the ungrounded conductors.
Like previously stated by Norcal, it's a good argument for just using EMT, which is acceptable as a grounding conductor on its own.
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Mustang51js
Well-known member
Yeah I understand that but it's one of those things that don't make sense,I just found out today that arc fault will be required on kitchen circuits with gfci outlets also if my state adopts the code.
Yep, the more I think about it the more it pisses me off. The NEC is there for safety and no other reason. It should not ever cost anywhere near $100 to get a permit and an inspector, and the code itself should make perfect sense, and be easy to understand.
Just like traffic tickets it has turned into an overgrown bloated cash cow and they're milking it for everything it's worth...
Think how many different wiring projects would be permitted and inspected without all this BS. Instead they give us an incentive to do it behind their back - and they will never find out.
ishiboo
Well-known member
That is your local/state government at work, and unrelated to the NEC.
I do disagree with the ground upsizing though and definitely think there should be exceptions.
Is permitting/inspection free elsewhere? The NEC is what the locals follow. (I understand some areas have even stricter codes)
sberry
Banned
Contrary to popular belief the codes make sense and they don't just sit around and dream them up. I have made my point on the motor sizing thread and as Norcal said about this one they "call it something else",,, hence I didn't upsize for V drop, I just used it because its what I had.
I heard a couple technical explanations on how they came to this but its been a while and I forget the details.
I heard a couple technical explanations on how they came to this but its been a while and I forget the details.
Cannonball
Well-known member
So if think inspections are a joke here's a real cash grab.
So lets say you finished your basement but thought screw it I don't need a permit for development, plumbing or electrical!! A few years later you go to sell your house but it's identified that none of the inspections were completed. Well don't worry, if you pay double the fees they send an inspector out who inspects who knows what and signs off the finished basement.
Now the new owners don't have to worry because it was inspected.
Or should they worry???
I do believe the codes are here to protect us, but **** like this on the enforcement side make me wonder how much it does in the real world.
So lets say you finished your basement but thought screw it I don't need a permit for development, plumbing or electrical!! A few years later you go to sell your house but it's identified that none of the inspections were completed. Well don't worry, if you pay double the fees they send an inspector out who inspects who knows what and signs off the finished basement.
Now the new owners don't have to worry because it was inspected.
Or should they worry???
I do believe the codes are here to protect us, but **** like this on the enforcement side make me wonder how much it does in the real world.