Oversize wire

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infinity said:
I don't know. What I said was that if you wanted to use 20 amp duplex receptacles you can not use 15 amp circuits. Is that what you meant?
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I'm sitting here thinking....we put a number of 15A devices on a 20A OCPD....and I know that is fine codewise.

I look in the NEC and what I "see" isn't what we do ???


I seem to be experiencing "technical difficulties" LOL.
 
Dave58er said:
A violation of what? :)
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Voltage drop limitations.

Voltage drop is based on wire gauge and length. At 16A (80% of 20A), each percent VD at 120v is caused by 0.075 ohms resistance (R = E / I, R = 1.2 / 16, R = 0.075).

Using some common wire gauges, 1% drop is 23' of 12/2 (assuming 1.618 ohms / kilofoot) (L = 0.0750 / 1.618, L = 0.0463 kilofeet, or L = 23' out and back), 36' of 10/2 (assuming 1.018 ohms / kilofoot) and 58' of 8/2 (assuming 0.6405 ohms / kilofoot).

So, if you had a 20A BC with a 150' length and 3% VD limit, you'd have to run 8/2. 150' of 10/2 would have a total there-and-back resistance of .3054 (1.018 ohms per kilofoot times 300' total = .3054 ohms) and a VD at 16A of 4.9v (E = I * R, E = 16 * .3054, E = 4.9), or 4%. 150' of 8/2 would have a VD of 3.1v, or 2.6%.
 
tallgirl said:
Voltage drop limitations.

Voltage drop is based on wire gauge and length. At 16A (80% of 20A), each percent VD at 120v is caused by 0.075 ohms resistance (R = E / I, R = 1.2 / 16, R = 0.075).

Using some common wire gauges, 1% drop is 23' of 12/2 (assuming 1.618 ohms / kilofoot) (L = 0.0750 / 1.618, L = 0.0463 kilofeet, or L = 23' out and back), 36' of 10/2 (assuming 1.018 ohms / kilofoot) and 58' of 8/2 (assuming 0.6405 ohms / kilofoot).

So, if you had a 20A BC with a 150' length and 3% VD limit, you'd have to run 8/2. 150' of 10/2 would have a total there-and-back resistance of .3054 (1.018 ohms per kilofoot times 300' total = .3054 ohms) and a VD at 16A of 4.9v (E = I * R, E = 16 * .3054, E = 4.9), or 4%. 150' of 8/2 would have a VD of 3.1v, or 2.6%.
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His point was that voltage drop is a design consideration not a code violation.
 
infinity said:
His point was that voltage drop is a design consideration not a code violation.
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210.19 (A) (1) FPN 4?

The "FPN" things aren't part of the code, they are just nice little notes?
 
The "FPN" things aren't part of the code, they are just nice little notes?
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Correct....
90.5(C) Explanatory Material Explanatory material, such as references to other standards, references to related sections of this Code, or information related to a Code rule, is included in this Code in the form of fine print notes (FPNs). Fine print notes are informational only and are not enforceable as requirements of this Code.
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Thanks for the heads-up.

I think I'll stick to following the FPN's. I've only had the voltage drop issue come up once because most of the time the runs aren't long enough to be an issue. In that instance the decision was to add another circuit and shorten up the run that was causing the concern.
 
tallgirl said:
I've only had the voltage drop issue come up once because most of the time the runs aren't long enough to be an issue. In that instance the decision was to add another circuit and shorten up the run that was causing the concern.
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What was the issue?

What was the concern?

What utilization equipment in a home will 'care' if you have some voltage drop?
 
iwire said:
What was the issue?

What was the concern?

What utilization equipment in a home will 'care' if you have some voltage drop?
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First, it wasn't a home.

It was a circuit that originally was about 70' long or so that serviced outlets down a hallway and then out into a meeting hall for things like vacuum cleaners and floor polishers. The building had been expanded at some point in the past and whatever electrician did the electrical work made it about 60 or 80' longer, so it was a total of something like 130 to 150' in length. We felt that was (a) too long and (b) the voltage drop would be too high.

The EC (licensed master electrician) agreed that while we were fixing things, we might as well fix that. A new 20A BC was added and the original 70' long circuit was put back the way it was before the earlier work and the new 20A BC was run out into the (earlier) remodelled area about 70' or so.

I don't know if commercial floor polishers and vacuums much care about that much voltage drop. It's not my decision to make. I just say "Hey, this looks weird, what do you think?" and they give me answers. If they say "Nope, looks fine", I file that under "Useful information". If they say "Yup, looks like a problem", I tell them what I think, they tell me if I'm right, I grab some wire and I get to work.
 
infinity said:
No problem Dave. You should thank Don for posting 90.5(C).:)
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I wanted to, but I still don't know how to quote twice in one post.

Sooner or later I'll have to get my kids to show me how these new computer things work. ;)
 
Dave58er said:
I wanted to, but I still don't know how to quote twice in one post.

Sooner or later I'll have to get my kids to show me how these new computer things work. ;)
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You just add your own [quote][/quote] tags.

If you want to add a specific person, use [quote=username][/quote].

Entering [quote=Elsie the Cow]To err is human, to moo bovine.[/quote] becomes

Elsie the Cow said:
To err is human, to moo bovine.
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tallgirl said:
210.19 (A) (1) FPN 4?
The "FPN" things aren't part of the code, they are just nice little notes?
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And then there was the AHJ that got somewhat upset with me for pointing out that VD was an FPN. Also had to point out 90.5.

Later he was overheard, by a reliable source, saying, "I can enforce an FPN if I want to."

Left me with my mouth hanging open. I have no clues on how to deal with this one.

carl
 
coulter said:
And then there was the AHJ that got somewhat upset with me for pointing out that VD was an FPN. Also had to point out 90.5.

Later he was overheard, by a reliable source, saying, "I can enforce an FPN if I want to."

Left me with my mouth hanging open. I have no clues on how to deal with this one.
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I must confess I find what y'all have to put up with beyond the pale. I've never had to put up with an inspector in person because I usually bug out of New Orleans on Sunday afternoons. One of these days I'll have to stick around when the building inspectors come by and watch things first-hand, instead of hearing about it weeks later. On the other paw, at the rate IT jobs are being sent to India and China, I could wind up having to deal with them in person sooner rather than later :-(
 
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Tallgirl, I just learned something here. Thank you.

Typing [noparse][/noparse] around the tags keeps them from actually doing what they're designed to do, so it can be demonstrated. That's awesome. :)
 
georgestolz said:
Tallgirl, I just learned something here. Thank you.

Typing [noparse][/noparse] around the tags keeps them from actually doing what they're designed to do, so it can be demonstrated. That's awesome. :)
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Hey, glad to be of service. You can get the entire list of tags here.
 
georgestolz said:
Tallgirl, I just learned something here. Thank you.
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I also say thanks, that was one I did not know, in the past I have usually added a space to make them show up and than have to explain not to leave a space...did that make sense.;) :D
 
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