220v Neutral Wire

[thirdgoat]

I am installing 2 new circuits for a heater, 220/30 amp, and a 220/50 amp for my inverter TIG welder. I had on hand some 8/3 and 6/3 wire, and didn't even think of the neutral wire when I pulled it. I don't need a neutral in either applications. What should I do with it? Beginning at the breaker panel, should I connect it to the bus as normal, cut it out, or tape/cable tie it back from any possible contact with anything in the panel. Also, what to do with it at the individual outlets? Cut it out or coil it back in the box, or just cut it out at both ends and ignore it as if it was never there? I really don't want to purchase new cable since I already have enough to do the job.

Thanks!

 

[wyliesdiesels]

Just leave it alone. Never know if you might need it someday. You could tape the ends but it wont harm anything to just leave it sitting there.

Why did you use 8/3 for a 30a circuit? Only need 10/3 for 30a.

 

[thirdgoat]

I had access to it for free, so it was hard to turn down. Better overkill than underkill is the way I look at it!

 

[fachries]

Just leave it alone. Never know if you might need it someday. You could tape the ends but it wont harm anything to just leave it sitting there.

Why did you use 8/3 for a 30a circuit? Only need 10/3 for 30a.

+1

 

[wyliesdiesels]

I had access to it for free, so it was hard to turn down. Better overkill than underkill is the way I look at it!

Theres one problem with doing that when one uses NM-b wire. Code is violated when the grounding conductor is not increased in size proportionately to the increase of size of the ungrounded conductors.

A 30a circuit requires #10 conductors. So if you increase ungrounded conductors to #8 then the gounding conductor needs to be increased to #8 as well.

 

[brewchief]

Theres one problem with doing that when one uses NM-b wire. Code is violated when the grounding conductor is not increased in size proportionately to the increase of size of the ungrounded conductors.



A 30a circuit requires #10 conductors. So if you increase ungrounded conductors to #8 then the gounding conductor needs to be increased to #8 as well.

I thought that there was an exception when the wire used was a cable assembly, that or I remember it being talked about that an exception needed to be added on the next code cycle.

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[Norcal]

I thought that there was an exception when the wire used was a cable assembly, that or I remember it being talked about that an exception needed to be added on the next code cycle.

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No exception, & a exception in a future code edition has no relevance now.

 

[u3b3rg33k]

you could put in 14-** outlets instead of 6-** outlets. of course then you'd need adapters for your welders. I just put a 14-30P on my 5kW heater and called it a day. a 14-** outlet is less "limiting" for future applications (you get an RV, electric car, build a funky appliance, wire up a welding cart with a local breaker box with 6-50R and 5-15R for grinders, etc).

 

[Brandon_oma#692]

Theres one problem with doing that when one uses NM-b wire. Code is violated when the grounding conductor is not increased in size proportionately to the increase of size of the ungrounded conductors.

A 30a circuit requires #10 conductors. So if you increase ungrounded conductors to #8 then the gounding conductor needs to be increased to #8 as well.

So can you not use 8-3 for a 40 amp circuit then?

 

[wyliesdiesels]

So can you not use 8-3 for a 40 amp circuit then?

A 8/x NM-b is rated for 40a so thats the size of circuit its made for.

 

[Brandon_oma#692]

A 8/x NM-b is rated for 40a so thats the size of circuit its made for.

Please help me understand. So you are saying 8/2 or 8/3 is ok for 40 amps but not ok for 30 amps? I must be missing something......

 

[Terry D]

Please help me understand. So you are saying 8/2 or 8/3 is ok for 40 amps but not ok for 30 amps? I must be missing something......

I understand with what your saying, it is confusing. But a violation. If you look at 250.122(B), that's where it is explained. I argued this to, but I was wrong. I still really don't understand why. If you look at table 250.122 you will see that a # 10 copper is good for the EGC for a circuit up 60 amps. But that doesn't matter anymore once you increase the ungrounded conductors. The table is designed on a curve, the ratio between the ungrounded conductors and the EGC. Once you change the ratio, then the table doesn't apply anymore. Make sense know, Hell no. LOL but still a violation. I wasn't aware of this till about 2 weeks ago, and I agued my heart out on it, to finally realize I was wrong. I have seen this done in the past, probably done it my self, and didn't even realize it. There is a bunch of sites on the internet explaining this. Mike Holt shows how to size the new EGC right. What ever ratio you increase the ungrounded conductors, you have to increase the EGC by the same ratio. Amperage seems to have nothing to do with it, its the cir. mils of the ungrounded conductors. But in no case is the EGC ever required to be larger than the ungrounded conductors. So to me, using a 12 romex on a 15 amp circuit is ok, and a # 10 on a 15amp and 20 amp circuit is ok. Its once you get to a # 8 romex is where it changes. This goes for any cable with the EGC already in it. They only way to correct this is to run conduit or get a special cable made.

 

[sberry]

There was some argument on,, if you were doing it for voltage drop it applied, if it was simply free wire then not,,, ha,, but I am a believer , I use it anyway and not lose sleep,,, or, remark the white in this cable if it bothers you.

 

[wyliesdiesels]

Please help me understand. So you are saying 8/2 or 8/3 is ok for 40 amps but not ok for 30 amps? I must be missing something......

Correct because the EGC is #10 NOT #8...

The EGC needs to be #8 in order to not violate code.

There was some argument on,, if you were doing it for voltage drop it applied, if it was simply free wire then not,,, ha,, but I am a believer , I use it anyway and not lose sleep,,, or, remark the white in this cable if it bothers you.

CANNOT remark the white to green because code requires the entire insulation to be green not just the ends.

 

[sberry]

I thought we could remark in cable?

 

[Terry D]

I thought we could remark in cable?

#4 and larger

 

[theoldwizard1]

Just leave it alone. Never know if you might need it someday. You could tape the ends but it wont harm anything to just leave it sitting there.

Do NOT cut them short !

My sons house had 10/3 running to the garage, but they were only only using 1 leg. There was "just enough" of the other leg left in the bottom of the load center that I could splice onto when we wanted to go 240V.

 

[sberry]

4 and larger in pipe?

 

[alfredeneuman]

4 and larger in pipe?

Yes, #4 and larger in conduit.
An alternative to green marking is stripping the wire for its entire exposed length (in boxes and panels).

(220 doesn't exist in the US or Canada)
Even the members over at the DIY Chatroom have a better record than this place for describing the voltage.

 

[TexMedium]

Okay, i've re-read this thread about four times and i am still confused. I have a small sub-panel in my basement, apparently installed professionally, as it has an "Inspected-Approved" sticker. It is fed from the main with three 6ga. and one 10ga. thhn/thwn wire in conduit, connected to 60amp fuses(yes, FUSES). I am assuming legal because of the "Inspected-Approved" label. Now if i were to install a two-pole 40amp breaker(yes, breaker) and run 8ga wire to my, say Heathkit Blast-matic 3000 home blast furnace, i would need FOUR 8ga wires, the two hots, the neutral, AND the ground? Seems counter intuitive...

 

[sberry]

Not at 40, this only applies if it is used for voltage drop.

 

[sberry]

What comp is it going on?

 

[fitter30]

Are they wrapped clockwise or clockwise?

 

[yatg]

Okay, i've re-read this thread about four times and i am still confused. I have a small sub-panel in my basement, apparently installed professionally, as it has an "Inspected-Approved" sticker. It is fed from the main with three 6ga. and one 10ga. thhn/thwn wire in conduit, connected to 60amp fuses(yes, FUSES). I am assuming legal because of the "Inspected-Approved" label. Now if i were to install a two-pole 40amp breaker(yes, breaker) and run 8ga wire to my, say Heathkit Blast-matic 3000 home blast furnace, i would need FOUR 8ga wires, the two hots, the neutral, AND the ground? Seems counter intuitive...

You don't need to run a neutral if the Blaster only needs 240V (or 220V for that matter). But that's not relevant to the sizing.

Rule of thumb:
10/2 or 10/3 NM with a 10 gauge EGC is good on a 30A circuit.
8/2 or 8/3 NM with a 10 gauge EGC is good on a 40A circuit.
6/2 or 6/3 NM with a 10 gauge EGC is good on a 50A circuit.

When you upsize a 10 NM to an 8 or 6 NM on a 30A circuit, the code says you have to upsize the EGC proportionally. Since the 8 NM has a 10 EGC, its not allowed. Somebody posted the math in another thread.

NEC 250.122(B)
(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.

The reasoning behind the rule is that if you upsize the ungrounded (hot) conductors for voltage drop because of a long run, the EGC needs to be upsized as well so it has the same impedance (aka resistance) as the ungrounded conductors.

This seems to keep coming up because people are wiring for equipment needing 30A circuits with 6 or 8 NM just in case they upgrade later.

If you're gonna do that, just run 6/3 to a small subpanel, add a 30A breaker, and run 10/2 to the receptacle.

For your example with the Blaster 3000, assuming it needs a neutral and also assuming its not a continuous load appliance ...
If it was rated 28A at 240V, you'd only need 10/3 NM and a 30A breaker.
But, if you were planning on upgrading some day to the Blaster 5000, rated 47A at 240V, and wanted to run the 6/3 NM cable now but put it on a 30A breaker until you upgraded, its not allowed. You could (a) put 10-10-10-10 THWN in conduit (rated 35A at 75c) and replace it later, (b) put 8-8-8-8 THWN in conduit (rated 50A at 75c), (c) use 6/3 NM and a subpanel.

I think I got all the numbers right. I'll get bashed on something.

 

[sberry]

I have heard the argument that you were not doing it for v drop but simply that you had free wire.

 

[anythingyoucanimagine]

I have heard the argument that you were not doing it for v drop but simply that you had free wire.

When taking distance into consideration, if the load-to-ps is short enough such that VD is not a factor, why can't you upsize nm?

Is this just an issue when upsizing conductors on 30A circuits because 10ga nm is 1:1:1 ratio? Is the ratio the same going from 8ga to 6ga nm?

Are you allowed to combine cross sections of EMT and a grounded conductor? If you can fit it, can you pull bigger ungrounded conductors and a smaller grounded and combine the cross-sections between the ground conductor and the grounded EMT?

Asking for no reason other than curiosity.

 

[sberry]

There is a plan behind it from guys with minds way greater than my own. It doesn't have to be bigger than the ungrounded conductors. No you cant combine the emt with the smaller wire.

 

[dscheidt]

When taking distance into consideration, if the load-to-ps is short enough such that VD is not a factor, why can't you upsize nm?

Is this just an issue when upsizing conductors on 30A circuits because 10ga nm is 1:1:1 ratio? Is the ratio the same going from 8ga to 6ga nm?

Are you allowed to combine cross sections of EMT and a grounded conductor? If you can fit it, can you pull bigger ungrounded conductors and a smaller grounded and combine the cross-sections between the ground conductor and the grounded EMT?

Asking for no reason other than curiosity.

If you're using EMT, you don't need the grounding wire. EMT (and RMC and IMC) have much, much lower impedance than a wire when properly installed. If you have both a wire and the conduit, it n the event of ground short, the conduit is going to carry the fault current. If you do install a ground conductor in the conduit, it needs to be properly sized. (That's done by amateurs who don't understand what they're doing, and professionals where they're worried about the conduit being damaged or corroding away.)

If I remember right, both 8 and 6 gauge NM-B have 10 gauge ground conductor, so you can't use 6 where you should use 8, because the ground wire size is too small. I also doubt anyone gets called on that by any inspector, since it's an insane requirement for cables.

 

[u3b3rg33k]

If you're using EMT, you don't need the grounding wire. EMT (and RMC and IMC) have much, much lower impedance than a wire when properly installed. If you have both a wire and the conduit, it n the event of ground short, the conduit is going to carry the fault current. If you do install a ground conductor in the conduit, it needs to be properly sized. (That's done by amateurs who don't understand what they're doing, and professionals where they're worried about the conduit being damaged or corroding away.)

If I remember right, both 8 and 6 gauge NM-B have 10 gauge ground conductor, so you can't use 6 where you should use 8, because the ground wire size is too small. I also doubt anyone gets called on that by any inspector, since it's an insane requirement for cables.

that's the rub - if some homeowner "accidentally" disconnects conduit, you've lost your ground. if there's a ground wire inside the conduit, that isn't a problem.

 

[Norcal]

that's the rub - if some homeowner "accidentally" disconnects conduit, you've lost your ground. if there's a ground wire inside the conduit, that isn't a problem.

Life is full of “what if’s” one can only make something compliant when the job is done. Do you wear Depends in case you **** your pants? That is how crazy a path one can go asking what if somebody does something in the future.

 

[brewchief]

Life is full of “what if’s” one can only make something compliant when the job is done. Do you wear Depends in case you **** your pants? That is how crazy a path one can go asking what if somebody does something in the future.

Lol, I hope you don't mind if I steal that

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[sberry]

That is how crazy a path one can go asking what if somebody does something in the future.

While that is true the code seems to catch up or is forward thinking to some extent.
Some of this isn't new, its been that way for decades. The pipe is good as a ground, still is, looks like it will be. According to minds greater than my own is actually preferred.
They adapt equipment to wire to code and even existing installatipons, the dvi welder is one.

 

[u3b3rg33k]

it's not that uncommon. plenty of environments use conduit and pull a ground wire, even though the conduit is grounded.