8/3UF inside?

[timewarp]

I have about 40' of 8/3 UF (underground feed), my question is can I use this in the walls of the garage, or is it not allowed to be used in a building? I tried to search this but couldn't find what the Nec says about this.
Thanks in advance.

 

[mrb]

from southwire:
Multiple conductor UF-B cable may be used for interior branch circuit wiring in residential or agricultural buildings at conductor temperatures not to exceed 90°C (with ampacity limited to that for 60°C conductors) as specified by the National Electrical Code. UF-B can be used in applications permitted for NMC in Section 334.10(B) of the National Electrical Code. Voltage rating for UF-B cable is 600

 

[timewarp]

Thanks,
I didn't even think to check the manufacturers sites. You just saved me some money, Thanks again.

 

[mrb]

remember, #8 romex is only good for 40 amps

 

[timewarp]

It'll work perfect for some 30 Amp Outlets for my welder.

 

[Norcal]

It'll work perfect for some 30 Amp Outlets for my welder.

Nope it will not...

You run afoul of NEC art 250.122.B .


(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.


The ECG, equipment grounding conductor is 10 AWG in NM or UF cable, when you upsize the conductors, the ECG will need to be 8 AWG also.

 

[mrb]

Nope it will not...

You run afoul of NEC art 250.122.B .


(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.


The ECG, equipment grounding conductor is 10 AWG in NM or UF cable, when you upsize the conductors, the ECG will need to be 8 AWG also.

ha! good catch.

 

[ishiboo]

Nope it will not...

You run afoul of NEC art 250.122.B .


(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.


The ECG, equipment grounding conductor is 10 AWG in NM or UF cable, when you upsize the conductors, the ECG will need to be 8 AWG also.

First, he said it'll work perfectly - which it will Not pass code perfectly

But I'm confused though at your statement about "increased in size." He's running a new install, and by your own statement 8/3 NM and 8/3 UF have the same ground size... so what's wrong with him using UF instead of NM per mrb's initial statement?

 

[walrus]

First, he said it'll work perfectly - which it will Not pass code perfectly

But I'm confused though at your statement about "increased in size." He's running a new install, and by your own statement 8/3 NM and 8/3 UF have the same ground size... so what's wrong with him using UF instead of NM per mrb's initial statement?

He isn't talking about that statement, he is talking about using it on a 30 amp outlet. Use the UF all he wants on a 40 amp outlet but not on a 30. In Maine you could use it on either a 30 or a 40, unless the inspector is sharp( I can think of a couple of towns after that...) it'd pass either way

 

[mrb]

First, he said it'll work perfectly - which it will Not pass code perfectly

But I'm confused though at your statement about "increased in size." He's running a new install, and by your own statement 8/3 NM and 8/3 UF have the same ground size... so what's wrong with him using UF instead of NM per mrb's initial statement?

its not an issue of using uf...you couldnt use #8nm on a 30 amp circuit either. when you upsize the conductor size, you have to upsize the ground as well which precludes you from using #8 romex since it has a #10 ground

 

[ishiboo]

its not an issue of using uf...you couldnt use #8nm on a 30 amp circuit either. when you upsize the conductor size, you have to upsize the ground as well which precludes you from using #8 romex since it has a #10 ground

Ah gotcha. I was thinking about it in a different manner. Thanks

 

[keweenawbee]

I wish I hadn't read this now I have to know. Use the UF all he wants on a 40 amp outlet but not on a 30? I don't get it, this "upsize" phrase. Does this mean mean during design calculation? So the smaller ground wire is fine on a 40 amp with more current but not fine on the 30 amp with less current? I am sure this is simple but it escapes me.

 

[mrb]

I wish I hadn't read this now I have to know. Use the UF all he wants on a 40 amp outlet but not on a 30? I don't get it, this "upsize" phrase. Does this mean mean during design calculation? So the smaller ground wire is fine on a 40 amp with more current but not fine on the 30 amp with less current? I am sure this is simple but it escapes me.

the problem we have here is an unintended consequence of the requirement to proportionally increase the EGC size when increasing conductor size for voltage drop. there is no exception to cover shorter runs where the smaller EGC would be ok.

heres the reason for the rule, (this is an example only, my wire sizes may not be accurate) say you have a 500ft run of 4/0 for a 100a feeder, you cant use a #8 ground because the impedance is such that the #8 couldnt carry enough current to cause the breaker to trip and clear the fault.

 

[keweenawbee]

I think I may get it now. With a 30 amp load on that wire there would not be enough emf in some cases with some distances because of the reactance of the smaller wire, but with a 40 amp load that would not be a problem since it would overcome the voltage drop. Coils/inductance/load-of would probably be the same on the breakers in either case. ?? Thanks

P.S. Wouldn't it have to be a dedicated fixed load, since connecting a smaller 30 amp load to the same outlet would create the same problem? I think I may be still off base here.

 

[fefarms]

I think I may get it now. With a 30 amp load on that wire there would not be enough emf in some cases with some distances because of the reactance of the smaller wire, but with a 40 amp load that would not be a problem since it would overcome the voltage drop. Coils/inductance/load-of would probably be the same on the breakers in either case. ?? Thanks

P.S. Wouldn't it have to be a dedicated fixed load, since connecting a smaller 30 amp load to the same outlet would create the same problem? I think I may be still off base here.

Don't read so much into it. There's no safety related issue going on here.

This provision of the code is badly written, and if interpreted literally leads to absurd results, which you are now trying to explain with a physics driven rationale that is just not there.

The intent of the code, as others have noted, was to require that the equipment grounding conductor be upsized in circumstances where the current carrying conductors were increased in size due to voltage drop issues. (THAT's a legitimate safety issue, but not likely to be experienced with 8AWG Romex, since a #10 AWG equipment ground is normally adequate for up to and including a 60 amp overcurrent protective device, so it already "upsized" from a safety perspective.)

There are other reasons why conductors might be larger than "required", such as having excess material laying around, or leaving some margin in the branch circuit for possible future applications.

Consider the following scenario: farmer joe installs an air compressor drawing 31 amps. He installs 8AWG Romex with its 10AWG equipment ground, protected with a 40 amp breaker. The air compressor is only 20 feet from the panel, so there are no voltage drop issues. Everything is fine with the wire sizing, including the EGC.

The air compressor breaks down, and farmer joe has had a bad year. All he can afford now is a smaller compressor drawing 22 amps. He replaces the breaker with a 30 amp breaker, and uses the same branch circuit. The current carrying conductors are now "oversized" compared to what is required for his air compressor. Does he now need to increase the size of the EGC, even though he is drawing less current, and has a smaller amperage circuit breaker protecting the branch circuit? That would be an absurd result.

 

[timewarp]

Can I recolor the white to green and have 3 8 gauge conductors since I really only need 3 conductors for my welder? I thought I saw somewhere that you can't relable the ground color but thought it might be worth a try, if not I guess I'll just spend some money on some 10/2 nm.

 

[djmartins]

Can I recolor the white to green and have 3 8 gauge conductors since I really only need 3 conductors for my welder? I thought I saw somewhere that you can't relable the ground color but thought it might be worth a try, if not I guess I'll just spend some money on some 10/2 nm.

I think a welder only needs two conductors and a ground.....

 

[Norcal]

Can I recolor the white to green and have 3 8 gauge conductors since I really only need 3 conductors for my welder? I thought I saw somewhere that you can't relable the ground color but thought it might be worth a try, if not I guess I'll just spend some money on some 10/2 nm.

No, that will run afoul of a NEC rule too....

 

[fefarms]

Can I recolor the white to green and have 3 8 gauge conductors since I really only need 3 conductors for my welder? I thought I saw somewhere that you can't relable the ground color but thought it might be worth a try, if not I guess I'll just spend some money on some 10/2 nm.

If you are getting your installation inspected, ask the inspector if the 8/3 UF will be OK, using two hots and the 10AWG ground. It really should be considered code compliant, despite the inadequate language of 250.122(B). Most inspectors have "office hours" where you can call in questions like this.

If you aren't getting it inspected, just go ahead and use the bare ground. Don't try to recolor a wire

 

[ishiboo]

If you are getting your installation inspected, ask the inspector if the 8/3 UF will be OK, using two hots and the 10AWG ground. It really should be considered code compliant, despite the inadequate language of 250.122(B). Most inspectors have "office hours" where you can call in questions like this.

If you aren't getting it inspected, just go ahead and use the bare ground. Don't try to recolor a wire

Agreed. I'd even recolor if necessary, if you move out or rent out the shop disconnect the wire at both ends. It's one of those "next guy" provisions - it's only a "problem" if the next person (or YOU) does not realize the unusual change which has been made.

 

[John in OH]

No, that will run afoul of a NEC rule too....

Why can't he just use green electrical tape on both ends of the white conductor to "recolor" the conductor?

 

[John in OH]

Nope it will not...

You run afoul of NEC art 250.122.B .


(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.


The ECG, equipment grounding conductor is 10 AWG in NM or UF cable, when you upsize the conductors, the ECG will need to be 8 AWG also.

I don't understand why there is any "upsizing" being done here. He isn't "upsizing" anything ... only using #8 conductors with a #10 ground for a 30amp load. Also, I don't see where there should be any voltage drop concerns ... he has only 40' of the 8/3 UF cable and he appears to be making use of it for more than one welder outlet installation, so I infer from that his runs will be less than 40' each. It seems as if the discussion here is getting way too literal and not sticking to the intent of the NEC paragraph.

I think that fefarms has given a very reasonable analogy of the actual situation. Requiring an increase in ECG for a reduced load is absurd.

 

[mrb]

I don't understand why there is any "upsizing" being done here. He isn't "upsizing" anything ...

there is upsizing. #10 is whats required for a 30 a circuit. if you use #8 you have increased the size and the nec article norcal posted somes into play

 

[John in OH]

there is upsizing. #10 is whats required for a 30 a circuit. if you use #8 you have increased the size and the nec article norcal posted somes into play

I still don't buy it .... I believe the use of the "upsizing" paragraph is being mis-interpreted. I don’t believe it is intended to apply to “oversized” conductors.

(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.

I believe this paragraph is intended … as it states … to address a physical situation where the “conductors are increased in size”. It applies to, say, a situation where #8 cables are being replaced by #6 cables. The paragraph requires that the ECG also be increased in size in proportion to the size of the new conductors. It prohibits one from pulling out the #8 ungrounded conductors and replacing them with #6 ungrounded conductors, but leaving the original #10 wire in place as the grounding conductor.

The paragraph is more applicable to situations where individual conductors are routed in conduit rather than a situation where a NM or UF cable is being used. In this latter case, one would remove the entire NM or UF cable (including the ground) when replacing the cable with a larger NM or UF size cable (and its integral, larger, ground conductor).

 

[mrb]

I still don't buy it .... I believe the use of the "upsizing" paragraph is being mis-interpreted. I don’t believe it is intended to apply to “oversized” conductors.

(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.

I believe this paragraph is intended … as it states … to address a physical situation where the “conductors are increased in size”. It applies to, say, a situation where #8 cables are being replaced by #6 cables. The paragraph requires that the ECG also be increased in size in proportion to the size of the new conductors. It prohibits one from pulling out the #8 ungrounded conductors and replacing them with #6 ungrounded conductors, but leaving the original #10 wire in place as the grounding conductor.

The paragraph is more applicable to situations where individual conductors are routed in conduit rather than a situation where a NM or UF cable is being used. In this latter case, one would remove the entire NM or UF cable (including the ground) when replacing the cable with a larger NM or UF size cable (and its integral, larger, ground conductor).

you're interpreting it wrong. doesnt have anything to do with conduit vs cable, or replacing existing conductors. The article is poorly written and *should* have an exception for distance but it does not. Read my previous post about why this requirement exists -if the conductors are oversized, the ground has to be oversized too. Practically speaking here there is no physical problem since the larger wire is not being used in a long run for voltage drop, but there is no exception in the applicable code section.

 

[oleguy]

nothing was up-sized.nothing in the nec disalowes a smaller breaker on a wire than what it is listed.example..the #8 is good for 40 amp.nothing disalowes a 30 amp breaker.in table 250.122 says a #10 is good for 60 amps.so since you can't pull out ungrounded conductors and change them,#8uf with a #10 ground is ok...

 

[mrb]

nothing was up-sized.nothing in the nec disalowes a smaller breaker on a wire than what it is listed.example..the #8 is good for 40 amp.nothing disalowes a 30 amp breaker.in table 250.122 says a #10 is good for 60 amps.so since you can't pull out ungrounded conductors and change them,#8uf with a #10 ground is ok...

yes a #10 is a suitable EGC for 60 amps, however when the conductor size is increased, the size of the ground has to be proportionally increased as well. A #10 ground may not be used on a 30 amp circuit with #8 conductors.

why do people keep saying nothing was upsized? The conductors ARE upsized if he's using #8 on a 30a circuit........

 

[oleguy]

BS as i said no where in the code does it say you cant use a 30 amp breaker on a 40 amp wire.the cable is not up sized...the #8 did not change,just the breaker.

 

[mrb]

BS as i said no where in the code does it say you cant use a 30 amp breaker on a 40 amp wire.the cable is not up sized...the #8 did not change,just the breaker.

wtf? wow. flipping some words around doesnt change the situation. bigger wire than whats required for the circuit invokes 250.122(B) simple as that.

 

[ishiboo]

wtf? wow. flipping some words around doesnt change the situation. bigger wire than whats required for the circuit invokes 250.122(B) simple as that.

Also doesn't change the fact that the code's fundamentally wrong in this case, and just plain stupid... not that you're not aware of that

There are portions of the code which are controversial, things which are a stretch of the imagination to legislate to prevent the potential outcome, but this is just clearly incomplete. Silly!

 

[oleguy]

point well taken...mrb...

 

[John in OH]

Let’s all stay cool here ….

What we have here is an honest and simple disagreement on how to interpret the subject “increase in size” paragraph. MRB sees it as a wire size vs. load issue. I see it as a Change in wire size requiring a corresponding change in ground wire size issue ... irrespective of load.

I don’t think we will be able to reach a resolution here … this is just so typical of language often found in Codes. The language is often vague and subject to interpretation and the bottom line is there is no clear resolution of the question. I’ve seen this same problem with the ASME Codes … vague language creating confusion ... and often a lot of unnecessary expense. Usually, the only way to clear up such an issue is to get an “official” code interpretation … and that is usually a major task! There is no magic decoder ring that will allow us to see into the mind of the bureaucratic code writer.

On the practical side … the local building inspector is the jurisdictional authority and it’s his interpretation that you have to live with. Just like an umpire in a baseball game … the pitch is what the umpire calls it, not necessarily what the pitch actually was!

Bottom line is Timewarp can safely use his 8/3 UF for his 30 amp welder outlets as long as his inspector has no problem with it.

 

[ishiboo]

Bottom line is Timewarp can safely use his 8/3 UF for his 30 amp welder outlets as long as his inspector has no problem with it.

Wrong.

He can safely use his 30 amp welder outlet with 8/3 UF regardless of whether or not the inspector has a problem with it.

 

[mrb]

MRB sees it as a wire size vs. load issue. I see it as a Change in wire size requiring a corresponding change in ground wire size issue ... irrespective of load.

i dont see it as wire size vs load at all. The load is irrelevant here. This is very simple and not really open to much interpretation. If the wire is bigger, the ground has to be proportionally bigger too. Simple as that.

If you can get a waiver (or whatever its called) from the AHJ then by all means do it. It has to be in wiriting from the building official. An inspector saying its ok or agreeing to overlook it isnt legally sufficient.

unfortunately, this article in the code is poorly written -it should have an exception for length or something, but until then the book says what it says regardless of what we think of it.

 

[ishiboo]

Reading more into it, I think your interpretation of 250.122(B) is wrong, and John's interpretation is correct. It says "where installed." His description is exactly correct - if you replace #14 with #8, you have to have an appropriately sized EGC conductor as well.

Elaborated, this means that if you ran #8 in a conduit for a 30A breaker, your EGC would have to be sized appropriately for the #8's carrying capacity, not 30A. This makes better sense even though in 30A your EGC would be big enough, if you someday saw "hey, there's #8!" and upgraded the circuit to 40A, you would be lacking an appropriately sized EGC. I think this is the purpose of (B).

The handbooks also carry an annotated note to help interpret the code, reading "Where the ungrounded circuit conductors are increased in size to compensate for voltage drop or for any other reason related to proper circuit operation, the equipment grounding conductors must be increased proportionately." IE, increasing the length of the run to handle voltage drop means you DO need to increase the ground size as well, but this doesn't apply to the OP's case.

 

[timewarp]

I'll just put a 40 amp breaker on my #8Uf and a 30 amp outlet


Just Joking!
I didn't realize that this would turn into as much discussion as it has, I'll ask the inspector about it before I do it, if he has a problem I'll buy some other wire. Yes there was no voltage drop worries, am placing 1 outlet 10' southwest of my load center and 1 outlet 20' north of my load center on one side of the wall and 1 outlet 5' north of the load center on the other side of the wall.(Load center is on an interior wall)

 

[mrb]

Reading more into it, I think your interpretation of 250.122(B) is wrong, and John's interpretation is correct. It says "where installed." His description is exactly correct - if you replace #14 with #8, you have to have an appropriately sized EGC conductor as well.

Elaborated, this means that if you ran #8 in a conduit for a 30A breaker, your EGC would have to be sized appropriately for the #8's carrying capacity, not 30A. This makes better sense even though in 30A your EGC would be big enough, if you someday saw "hey, there's #8!" and upgraded the circuit to 40A, you would be lacking an appropriately sized EGC. I think this is the purpose of (B).

The handbooks also carry an annotated note to help interpret the code, reading "Where the ungrounded circuit conductors are increased in size to compensate for voltage drop or for any other reason related to proper circuit operation, the equipment grounding conductors must be increased proportionately." IE, increasing the length of the run to handle voltage drop means you DO need to increase the ground size as well, but this doesn't apply to the OP's case.

hmm time for me to do some research.

 

[Norcal]

A home inspection forum had the same subject & a poster did email NFPA (Publisher of the NEC) here is a reply in the post.

http://www.inspectionnews.net/home_inspection/113762-post80.html

 

[nate379]

OK, so since the wire is good for 40 amps, why not just breaker it for 40 amps and simply avoid this overrating baloney? Most welders use a 50 amp outlet anyhow, NEMA 6-50

The breaker should be sized for the rating of the wire and outlet, not the load.
If I wire an outlet for my bedroom that would be used for an alarm clock, let's say a 2 amp draw, would I put a 5 amp breaker for it? Of course not!


I have 2 welder outlets in my garage, both are wired with #6 wire, breaker is 50 amps and have 50 amp outlets. The welder I have only pulls 23 amps, but what is to say that I don't buy a plasma cutter or bigger welder?

There is plenty of stuff in the NEC that is completely retarded and makes zero sense. I dug into alot of it when I was wiring my shed, and in the end I decided to just use common sense because there isn't enough BC headache powder in this state for me to decipher the NEC. I don't know if you pros get secret decoder rings or what?!

 

[walrus]

If you have a cable assy like 8-3 UF, isn't the ground already sized correctly for a 40 amp fault? So what difference does it make if you run it on a 30 A breaker, the ungrounded and grounded conductors are sized at 40 and so is the ground as its part of a listed assy approved for 40 amps.