NEC Changes For #14 Ampacity

[mbrooke]

Note that whatever the UL related justification for the 50' number may be, it occurs only in the section which allows the use of a receptacle or outlet type AFCI in conjunction with a breaker which is NOT a full branch circuit protection AFCI.

That is true because flexible cords (and splices) are left out of series arc protection. The theory is low magnetic trip will be able to catch parallel arc faults from a nail or over driven staple between the breaker and AFCI receptacle.

There is no such limitation on the run to a first outlet in a circuit which does not require AFCI or is protected by a full branch circuit AFCI breaker.

True, which imo proves my point (regarding none AFCI circuits) that the NEC is not (or was not) concerned about magnetic trip.

And I do not want to get into the arguments on the relative merits of low magnetic trip versus arc signature detection which is only enabled in the presence of a current that is already an overload.

I dont blame you, whether a short circuit clears in 3 cycles or 60 cycles has yet to be proven to be the cause of dwelling fires.

I mostly want to inject a measure of skepticism into the analysis of any Code language related to AFCIs. (The whole barrel of apples have been spoiled at this point IMHO.)

You are doing the right thing, I welcome it. Yes our systems dont always trip magnetically, but that has yet to be demonstrated as serious danger. As is the IEC's primary concern is voltage drop along the EGC, and as such 120 volts is less of a concern.

I am not defending AFCIs posting the UL documents, rather demonstrating that IMO I do not believe the intent of 240.4D or conservative ampacity tables is achieve magnetic tripping in a circuit.

This of course does not mean I am against magnetic trip. A 13x magnetic trip is a good idea where say 10,000 amps of fault current exists from the utility with a fault close to the panel. Subjecting a wiring system to extended magnetic forces has no benefit.

 

[mbrooke]

Of course but how did they arrive at those numbers in the first place?

Real world testing.

Of course, after a theoretical hypothesis is formed :thumbsup:

 

[GoldDigger]

Of course, after a theoretical hypothesis is formed :thumbsup:

There is a great parody book called Science Made Stupid.
One page discusses the Scientific Method and describes the Inductive and Deductive variants as follows (I may have the names reversed)

Inductive Method steps:
1. Formulate a hypotheses
2. Apply for a grant
3. Perform the experiment
4. Analyze the results
5. Change the data to fit the hypothesis.

Deductive Method steps:
1. Formulate a hypotheses
2. Apply for a grant
3. Perform the experiment
4. Analyze the results
5. Change and backdate the hypothesis to match the data.

 

[mbrooke]

There is a great parody book called Science Made Stupid.
One page discusses the Scientific Method and describes the Inductive and Deductive variants as follows (I may have the names reversed)

Inductive Method steps:
1. Formulate a hypotheses
2. Apply for a grant
3. Perform the experiment
4. Analyze the results
5. Change the data to fit the hypothesis.

Deductive Method steps:
1. Formulate a hypotheses
2. Apply for a grant
3. Perform the experiment
4. Analyze the results
5. Change and backdate the hypothesis to match the data.

^^^^^^^ :lol::lol::lol::lol: I am laughing because its so true in the real world. Its like drug studies where outcome data is rigged to support that original claim. AFCIs are an even better example with manufactures and NEMA doing everything to get their claimed "arcing". That is not to say UL data is wrong, rather cherry picked by NEMA to fit made claims.

 

[romex jockey]

I'll take #2 for $5000 Alex....

I'll take #2 for $5000 Alex....

Give this rural spark some grant $$$, and i'll write you studies promoting my dog as a chessmaster instead of a cheesemaster

~RJ~

 

[romex jockey]

What would you like to know?

.

Everything Mr MBooke........know that this is something the ave spark here isn't normally schooled in ....


Why are smaller resi (miniature) breakers manufactured with fixed values, and larger 250A and up breakers adjustable?

Does any viable reason exist, other than system coordination, or equipment AIC ratings....?

Circuit Breaker Characteristic Trip Curves and Coordination



If so, why have most major OCPD manufacturers spent significant R&D on Adj Mag Trip patents?

patent

patent

(my google runneth over)

~RJ~

 

[mbrooke]

Everything Mr MBooke........know that this is something the ave spark here isn't normally schooled in ....


Why are smaller resi (miniature) breakers manufactured with fixed values, and larger 250A and up breakers adjustable?

Does any viable reason exist, other than system coordination, or equipment AIC ratings....?

Circuit Breaker Characteristic Trip Curves and Coordination



If so, why have most major OCPD manufacturers spent significant R&D on Adj Mag Trip patents?

patent

patent

(my google runneth over)

~RJ~

Well where do I begin... any question you have that is specific?

I do know for some odd reason in the 90s they started lowering the mag trip values on single pole 15 and 20amp breakers. No solid reason is stated, however values started going down from 20x, 32x, 35x and no mag trip down to about 12x. Interestingly well before that Square D had breakers with a low 8-10x value, which I would guess is the brand "D" noted in the UL reports.

 

[mivey]

Anyone with who has wired a home or has blueprints can figure out short circuit with with a basic computation.

I know I can since I've been there and done that. And you?

So you admit it is possible

Not only possible but factual. Been there, done that.

I will let you answer this:

1. What are circuit lengths in most homes? Min from max

2. Knowing the length, what is the total AC impedance of the fault loop?

3. What the typical fault current from a none network service or what is the impedance of the transformer and service drop?

4. What is the typical mag trip threshold of new single pole 15 and 20 single pole amp breakers?

5. What is the typical mag trip threshold in old 15 and 20 amp single pole breakers?

Using 1-5 what is the fault current of the mins? The maxes? which ones will trip the old breakers? The new ones?

How about you do your own homework since it is your thesis? I'll tell you flat out that I do not have the necessary statistics, nor do I feel like researching them, if they can even be found.

 

[mbrooke]

I know I can since I've been there and done that. And you?

:roll: I fail to understand why you and Iwire think Im speaking Chinese despite nearly everything Im saying is both quantifiable and readily available.

Not only possible but factual. Been there, done that.

So then why are you so skeptical about what Im saying?

How about you do your own homework since it is your thesis? I'll tell you flat out that I do not have the necessary statistics, nor do I feel like researching them, if they can even be found.

You asked and I explained where I came from.

 

[mivey]

Both us know in a typical 2,000 sqft dwelling the average home run length is about 125 feet from the panel to the furthest point.

Those of us that have wired homes for a living know you don't know what you are talking about here.

Anyone doing resi knows most home runs exceed 50 feet.

You are also swinging blind here.

Anyone with who has wired a home or has blueprints can figure out short circuit with a basic computation.

Roughly. But many folks wiring homes, at least many that I have run across in the last 4 decades would not have a clue about how to do that. I did not either until later in my career. Many who have been roping for much longer and much more than I have will never know nor care to know.

There are circuits less then 50 feet, and anyone wiring a home knows circuits can also exceed 50 feet.

They certainly can. Finally you slung enough out there to hit a target.

Both us know in a typical 2,000 sqft dwelling...

Anyone doing resi knows...

Anyone with who has wired a home...

anyone wiring a home knows...

How about leaving these for those who really do know and then you can just expound on what you know? It will make your points much more believable.

 

[mbrooke]

Those of us that have wired homes for a living know you don't know what you are talking about here.

Then please tell me where I am wrong. What have I said that is incorrect pertaining to resi?

You are also swinging blind here.

For stating a fact? Iwire looked skeptical when I brought up 50 feet, at least thats what I read.

Lie? No numbers don't lie. But incorrect assumptions and application of numbers can produce meaningless results.

Thus, my application of numbers to runs exceeding 50 feet is correct. :thumbsup:

Roughly. But many folks wiring homes, at least many that I have run across in the last 4 decades would not have a clue about how to do that. I did not either until later in my career. Many who have been roping for much longer and much more than I have will never know nor care to know.

Not when they are taught ohms law, basic fault current equation and are aware of typical circuit design. I keep reading it as though you think I don't know what typical lengths are involved in home runs, but I know that not to be the case on my part.

They certainly can. Finally you slung enough out there to hit a target.

I think you are nit picking. Nothing about assuming 50, 75 even 250 feet is wrong about a dwelling.

How about leaving these for those who really do know and then you can just expound on what you know? It will make your points much more believable.

Again, where am I wrong?

 

[mivey]

I fail to understand why you and Iwire think Im speaking Chinese despite nearly everything Im saying is both quantifiable and readily available.

You asked so I'll tell you as nicely as I can at the moment and apologize if I don't take the time to word-smith enough sugar-coat.

You fail to understand because you lack the expertise in some areas that you pretend to have. Speak about what you know. Some of what you say is true. Some of what you say is nonsense because you don't know what you are talking about even though you would like to pretend you do.

The mixture of the two taints the true part.

So then why are you so skeptical about what Im saying?

I know for a fact that some circuits will not magnetically trip a breaker. What I don't know is the validity of the claim you made about the extent of these circuits in North America. At this point I would wonder if you are over-cooking it a bit.

You asked and I explained where I came from.

You might have outlined where you would like to have come from but did very little else to support your position. Feel free to present your numbers if you expect a buy-in. Right now it is just one big wild assumption.

 

[mbrooke]

You asked so I'll tell you as nicely as I can at the moment and apologize if I don't take the time to word-smith enough sugar-coat.

You fail to understand because you lack the expertise in some areas that you pretend to have. Speak about what you know. Some of what you say is true.

So I dont know that home run lengths can exceed 50 feet or that 14 gauge wire is frequently used here?

Now if I said the typical home run length was 6,000 feet then I would raise an eyebrow.

Some of what you say is nonsense because you don't know what you are talking about even though you would like to pretend you do. The mixture of the two taints the true part.

Example.

I know for a fact that some circuits will not magnetically trip a breaker. What I don't know is the validity of the claim you made about the extent of these circuits in North America. At this point I would wonder if you are over-cooking it a bit.

Sit down with a pencil and paper can calculate the fault current for each circuit in a 2,000 square foot dwelling. You will find my claim is not all that far off. In fact the UL reports have a handy chart.

You might have outlined where you would like to have come from but did very little else to support your position. Feel free to present your numbers if you expect a buy-in. Right now it is just one big wild assumption.

I already stated simple easy to understand numbers and they are still being met with opposition.

Ok, lets say I dont know anything about resi wiring. I can just as easily say you and Iwire know nothing about electrical theory. I dont assume so I normally bight my tongue.

 

[mivey]

Then please tell me where I am wrong. What have I said that is incorrect pertaining to resi?

Already have.

For stating a fact? Iwire looked skeptical when I brought up 50 feet, at least thats what I read.

I believe he was talking about your 125 ft. number that changed. Ask him to be sure.

Thus, my application of numbers to runs exceeding 50 feet is correct. :thumbsup:

For those runs, :thumbsup:

Not when they are taught ohms law, basic fault current equation and are aware of typical circuit design.

I don't know how much time you spend around other electricians but kudos to your lat-long if they all know that.

I keep reading it as though you think I don't know what typical lengths are involved in home runs, but I know that not to be the case on my part.

Then what information do you have to support your statement: "Both of us know in a typical 2,000 sqft dwelling the average home run length is about 125 feet from the panel to the furthest point."?

I think you are nit picking. Nothing about assuming 50, 75 even 250 feet is wrong about a dwelling.

One thing that is wrong is to assume some unusual length is typical, or applies to 2/3 of the circuits in North America.

Again, where am I wrong?

Again, I already have.

 

[mivey]

So I dont know that home run lengths can exceed 50 feet or that 14 gauge wire is frequently used here?

Nice straw-man.:roll:

Now if I said the typical home run length was 6,000 feet then I would raise an eyebrow.

Probably both.

Sit down with a pencil and paper can calculate the fault current for each circuit in a 2,000 square foot dwelling.

No thanks, I would just use the software I wrote. What would be difficult is finding those 125 ft home runs YOU said that you and Iwire know are typical.

Ok, lets say I dont know anything about resi wiring.

I would not say you don't know anything, just that you lack the experience you need to make some of the claims you make on this site.

I can just as easily say you and Iwire know nothing about electrical theory.

You could, but I can let my posts speak for themselves. I'm sure I know at least most of Ohm's Law. From what I can tell, Iwire knows a good bit for an electrician.

 

[mbrooke]

Already have.

I believe he was talking about your 125 ft. number that changed. Ask him to be sure.

Calc the lengths and my number will not change...

For those runs, :thumbsup:

which usually trip the breaker magnetically, not all runs above that. If home runs never exceeded 50 feet then I would see why Iwire would say my 2/3 guess is incorrect, but real world we know that not to be so.

I don't know how much time you spend around other electricians but kudos to your lat-long if they all know that.

And I would say you are correct not all know that, but Iwire would call it disparaging.

Then what information do you have to support your statement: "Both of us know in a typical 2,000 sqft dwelling the average home run length is about 125 feet from the panel to the furthest point."?

Any home blueprints? How much do you pull off a real for your 3va per foot circuits? You kitchen home runs? The others?

Write is down and tell me. Then average them together.

One thing that is wrong is to assume some unusual length is typical, or applies to 2/3 of the circuits in North America.

And this is where you missed my point. And take things at concrete value. I never stated at 2/3 of all circuits are 125 feet in length. Everyone doing real world knows that.

My point is when all circuit lengths are evaluated for available fault current at the furthest point in a typical home, then compared against a breaker's magnetic trip, and then plotted on a graph as mag trip vs none mag trip its about 1/3 to 2/3 on average.

Yes its not exact as scientists can no put the earth or sun on a scale, but they can surely guesstimate the weight of the earth based on what they already know. Please forgive those men for not having a larger scale. Please forgive me that I can not obtain expansive test equipment and short circuit every single branch circuit in North America.

 

[jim dungar]

When the sniping starts into sentence by sentence 'quote-reply', it is time to consider a thread as probably being irreconcilable.

Consider this as a last warning.

 

[mbrooke]

When the sniping starts into sentence by sentence 'quote-reply', it is time to consider a thread as probably being irreconcilable.

Consider this as a last warning.

I am not snipping (at least not my intention), just defending my points.

Anyway, going back to FionaZappa. What are R values would be sufficient for #14, 12 and 10 to meet the 15 amp requirement plus 134% for overloads?

 

[iwire]

Any home blueprints? How much do you pull off a real for your 3va per foot circuits? You kitchen home runs? The others?

Write is down and tell me. Then average them together.

2,000 sq ft home, two story, with basement, panel in front right corner of basement.

Need to run a homerun to a window AC second floor rear left corner and being the neat freak I am I will not run the wire diagonally.

• 6' from breaker to ceiling of basement
• 8' from ceiling of basement to ceiling of first floor.
• 31' from from to front to rear.
• 31' from one side to the other
• 4' up from first floor ceiling to receptacle in bedroom

80' total homerun length.


Now that is would be the longest homerun in the home, all other homeruns would be shorter cutting into your average.

 

[mbrooke]

2,000 sq ft home, two story, with basement, panel in front right corner of basement.

Need to run a homerun to a window AC second floor rear left corner and being the neat freak I am I will not run the wire diagonally.

• 6' from breaker to ceiling of basement
• 8' from ceiling of basement to ceiling of first floor.
• 31' from from to front to rear.
• 31' from one side to the other
• 4' up from first floor ceiling to receptacle in bedroom

80' total homerun length.


Now that is would be the longest homerun in the home, all other homeruns would be shorter cutting into your average.

Ok, that is a good start. :thumbsup: But what about a 3va per foot lighting/outlet circuit?