IEC Version of NEC Table 9 2

[VTer]

Hi All,

I was wondering if there is an IEC version of NEC Chapter 9 Table 9 that has all the various cable sizes in mm2 and 50Hz resistances and reactances?

If there is not, do you know of nay such table in other standards that is used in the IEC world?

Thanks!

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". û Nikola Tesla

 

[cuky2000]

Here is a partial quick comparison between the cable sizing between the IEC and the NEC as follow:

1) The IEC 60364 Part 5-52: "Selection and erection of electrical equipment - Wiring systems" is the closest equivalent to the NEC ampacity associated with cable sizing.

2)The NEC ampacity tables and the IEEE Std 835 are based in the Neher-McGrath equation published in 195o's.Link although good for many applications such as concrete encased duct banks but doesn't consider the soil dry-out. The cable ampacity per IEC considers soil dry-out(Ex. Link). This is appropriate for direct burying cable applications due to the heat generated by the cables in direct contact with the soil.

3)The ampacities under the rules of both codes appear to be relatively equivalent. There is some difference that impacting the cable ampacity since the max. conductor temperature is 70°C per IEC and 75°C NEC resulting that the IEC been less conservative than the NEC, in the range of 5% to 7.5%

4) The NEC establishes a uniform level of safety that evolved more than 100 years ago in the USA. The IEC 60364 stablished in 1969 to harmonize electrical installation rules among European countries.

5) Here is a sample of the IEC ampacity table as per the following Link and also a cable sizing calculator for both standards Link for your use.

I hope this helps.

 

[VTer]

Hi cuky200, thank you for your replay. However, I was asking with respect to conductor resistance and reactance values (ohms/km or ohms/1000ft) that are listed in NEC Chapter 9 Table 9. Is there an equivalent IEC version of this with standard mm2 codncutor sizes?

"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". û Nikola Tesla

 

[Mbrooke]

I'm working on a similar project. BS7671 has tables- I can post them. What are you specifically looking for in terms of wire type?



Here is an appetizer

Conversion Chart:

4) The NEC establishes a uniform level of safety that evolved more than 100 years ago in the USA. The IEC 60364 stablished in 1969 to harmonize electrical installation rules among European countries.

Uniform? I can legally run 2000 feet of #14 (2.08mm2) to a light post. Ground fault develops, wire is to long to pull enough current to trip a breaker. Poll sits at 138 volts to ground and kills someone. When it goes to court absolutely no one can be found at fault- other than the NEC itself. In this case, would the NFPA be accountable?

 

[cuky2000]

There are few options to obtain the cable resistance and reactance in compliance with the IEC standard.
1)RESISTANCE: The dc and ac resistance of cable conductors can be calculated based on IEC 60287-1 Example of (DC resistance ) & AC Resistance

2) REACTANCE:
. 2.1 Can be calculated per IEC using the reactance formula shown in this Link.
. 2.2 Values can be obtained from cable manufacturers.
(Example of reactance table)

 

[cuky2000]

[highlight #FCE94F]No, you can not comply with NEC running 2000 feet of #14 AWG.[/highlight]

 

[Mbrooke]

Show me the code article which makes it none compliant. Any silence from here on in I'll take as a sign of agreement with my original post.

And 138 volts to ground during a fault would mean a 277 volt circuit, not 120 volts. Load doesn't have to be 10amps- 1/4 of an amp for a LED light is ok.

 

[waross]

Well I want to run a 1 Amp LED fixture on a pole 2000 feet away from the panel.
That is 4000 Ft of #14 wire for a total resistance of 10.1Ohms and a voltage drop of 10.1 Volts.
That is an 8% voltage drop and is not acceptable.
Try #12 AWG.
4000 of #12 wire for a resistance of 6.35 Ohms and a voltage drop of 6.35 Volts
That is a 5.3% voltage drop and is not acceptable.
Try #10 AWG
4000 of #10 wire for a resistance of 4 Ohms and a voltage drop of 4 Volts.
That is a 3.3% voltage drop and is not acceptable.
If we shorten the run to 1800 feet we get:
Resistance of 3600 feet of #10 AWG = 3.6 Ohms
Voltage drop = 3.6 Volts = 3% of 120 Volts.
Ground fault circuit = 1800 feet of #10 AWG at 1.8 Ohms, plus 1800 feet of #12 AWG equipment grounding conductor at 2.58 Ohms.
Total resistance = 4.38 Ohms.
Fault current at 120 Volts = 27 amps.
The #10 AWG may be protected by a 30 Amp breaker that will never trip.
The voltage appearing on the light standard in the even t of a fault to the standard = 70 Volts.
Not good.
Despite a poor example, your point is well taken.
At one time, local grounding was required at lamp standards but the latest edition of the CEC has removed this requirement.
Not Good.
Note also that this is based on a 120 Volt circuit.
If we consider a 277/480 Volt circuit we can demonstrate a situation with a much higher voltage on the surface of the lamp standard.
We can get a lot of illumination with LEDs at 277 Volts with less than 1 Amp. 28 Watts is only about 0.1 Amps at 277 Volts.
But where would this ever happen, right?
Well if I wished to put a marker light beside the highway at the north east corner of my place, the point to point distance from the property corner to the corner of my garage is 1919 feet. Realistically it would take close to 2000 feet of conductors to put a light out there.
Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Mbrooke]

Remember- code does not enforce voltage drop. 8% drop may not even effect an 85-300 volt LED driver.

Despite a poor example, your point is well taken.

Not poor IMO, these installations in existence all over some parking lots and many rural properties.

But where would this ever happen, right?

Few anecdotes

https://forums.mikeholt.com/forum/active-forums/general-electrical-forum/2548368-oven/page4

https://forums.mikeholt.com/forum/a...-120-volts-vs-150-volts?p=2545925#post2545925

https://forums.mikeholt.com/forum/a...-120-volts-vs-150-volts?p=2545930#post2545930

Truth is there are plenty of real world installations from pools, to carnival rides to light posts to athletic fields to detached buildings where a fault will never trip a breaker.

The CMPs over the years have begun to realize this through electrocutions and fires but sadly instead of addressing it directly they are slowly yet quietly mandating GFCIs and special GFCIs which aren't as reliable is a low impedance EGC. Nor should the code mandate only one fix without other options. That in of itself is bias...

 

[ScottyUK]

mbrooke,

Under the BS7671 regulations I would think you'd either fall foul of one or both of the disconnection time requirements under fault conditions or the prevention of damage to the cable due to thermal effects - usually referred to as the adiabatic limit. Is there nothing broadly equivalent to these requirements in the NEC?

 

[waross]

Remember- code does not enforce voltage drop. 8% drop may not even effect an 85-300 volt LED driver.

The Canadian Electrical Code has a 3% voltage drop rule.
My post was in support of you even under the 3% rule.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cuky2000]

Mbrooke:

It is our understanding that the NEC provides the minimum requirements for installations and should not be used as a design guide. The engineers should have the ultima responsibility to perform a safe and suitable electrical design using good engineering practice while meeting all codes, regulations, and laws applicable to a particular project.

The example of 2000 ft with #14 wires does not appear a convincing argument to belive that the NEC is a bad document. This is not new since in several posts you expressed an unfavorable opinion of the NEC.

Perhaps the following questionary will help to understand your frequent position regarding NEC matters.
1) What proportion of the NEC is considered good or bad in your opinion?
2) Should the NEC drop or replaced?
3) For what guide or code are you recommend to replace the NEC?
4) How the NEC is compared with other similar codes such as the Canadian Electrical(CSA C22.1), European Code(IEC 60364) or other international documents?

Here are some suggested options in case of disagreement with the NEC:
5)Are you free to request interpretations of a particular article to the NEC committee?
6) Are you wheeling to propose changes in the NEC for the next editions?

The NEC is not an enforced document by itself.
7) Are you aware that the electrical utilities are exempt to comply with NEC?
8) Notice that many States adopt the different editions of the NEC as part of the building code and after that became enforced by the IHJ?

From a liability perspective:
9) How insurance companies,(Ex FM Global) engineers or electricians operate in the US without a reference document such as the NEC?

I hope this helps us to understand better how we should reconsider the use and applications of the NEC

 

[Mbrooke]

@Scotty UK: Under BS7671 it would violate the disconnection time requirements- hence the circuit would need to be up-sized. Nothing similar exists in the NEC.


@Waross: I know- and you proved my point better than I did



@Cuky2000: Cite a code article and prove me wrong. Your opinion of the code as well as my opinion of the code is irrelevant to this discussion.

 

[Mbrooke]

Ok- I'll answer your questions in hopes of setting forth a thought provoking discussion.

Mbrooke:

It is our understanding that the NEC provides the minimum requirements for installations and should not be used as a design guide.

Correct. No disagreement here. And it is even in the mission statement of the NEC which is key to understanding where I'm going next.

-But- the NEC is in many ways evolving into a design guide.

The engineers should have the ultima responsibility to perform a safe and suitable electrical design using good engineering practice while meeting all codes, regulations, and laws applicable to a particular project.

Sure. But what if code legally lets you get away with bad designs that are sure to get someone injured or killed? Keep in mind its not only engineers who use the NEC but also electricians. How many US electricians know at which point any given circuit run will no longer trip the breaker (or fast enough) for any given source impedance? How does an inspector fail an electrician who ran ran power to a pool house 600 feet away?

The example of 2000 ft with #14 wires does not appear a convincing argument to belive that the NEC is a bad document.

Its a convincing argument that there is basic, fundamental, yet significant hazard the NEC does not address.

This is not new since in several posts you expressed an unfavorable opinion of the NEC.

What is wrong with holding such views? Why scold the messenger so to speak? My opinions are not without inference. The code is neither a protected individual nor a human victim, it is a piece of work open to discussion and criticism. To the contrary, being used as a rule of law and a doctrine of law grants individuals the right to seek redress- the right to question, challenge and scrutinize it and any authority using it.

Perhaps the following questionary will help to understand your frequent position regarding NEC matters.
1) What proportion of the NEC is considered good or bad in your opinion?

Its difficult to put a number on it. Roughly 50% as a whole. Less so 30 years ago.

In particular Article 250 which is out-and-out trash. It is not written on the basis of sound electrical theory. Evidence of that is rampant and one well known example are CMP members who in the majority 40 years ago believed ground rods facilitated the operation of OCPDs and brought exposed metal work to zero potential.

2) Should the NEC drop or replaced?

It needs to be overhauled, more so the NFPA itself which is no longer a neutral entity.

3) For what guide or code are you recommend to replace the NEC?

Physics and Electrical theory driven reasoning, evidence as gained through INDEPENDENT testing (UL is a marionette) and enhanced safety were seen in other electrical codes used through out the globe.

A code similar to this one in size and scope would be ideal:

https://files.engineering.com/getfi...-7fbb53d8a3b4&file=Indian_Electrical_Code.pdf

However a carbon copy would not be ideal first requiring fine tuning (ie, American wire gauges should not be automatically discarded)- and the fact we can do even better. For one, joule heating is responsible for at least 90% of all electrical fires on earth yet there is not a single electrical in the globe which addresses this issue.

4) How the NEC is compared with other similar codes such as the Canadian Electrical(CSA C22.1), European Code(IEC 60364) or other international documents?

Honestly, it is dead last. It may not seem that way as compared to other countries especially 3rd world countries but while they lack competent installers, electricians and engineers the US lacks a competent code making body.

Here are some suggested options in case of disagreement with the NEC:
5)Are you free to request interpretations of a particular article to the NEC committee?

Sure- this one good thing.

6) Are you wheeling to propose changes in the NEC for the next editions?

Which does nothing meaningful. The CMPs are no longer a serious public process. Eaton and other various manufacturers own the NFPA and their code making bodies.

The NEC is not an enforced document by itself.
7) Are you aware that the electrical utilities are exempt to comply with NEC?

Have you seen my posts here? Of course I know that, and why we pay 11 cents per kw hour on average. Unfortunately NERC and FERC are encroaching into solemn affairs... but that is a conversation for another thread.

8) Notice that many States adopt the different editions of the NEC as part of the building code and after that became enforced by the IHJ?

And how much of the NEC is amended? Not much and little is questioned.

From a liability perspective:
9) How insurance companies,(Ex FM Global) engineers or electricians operate in the US without a reference document such as the NEC?

The would go by a better document. I don't want to rid us of any code, but rather code that fulfills its desired mission statement.

 

[Mbrooke]

Gold Star given to Cuky's post- sigh. To bad no one gets it or cares to get it. So sad. People are taken back at my indifference, but this why I frequently have so little sympathy for people as a whole. Defending dogma simply because one can not realize the next person's knowledge goes well beyond any frame of reference they have access to.

I'll said it here and I'll say it again: The NFPA is no longer a neutral organization. It is now entirely owned and driven by the manufacturers, and any changes forward are predominantly with the intent to drive business revenue. This is not my opinion, but an educated conclusion acquired through research and first had accounts by people involved in the process. Does anyone here seriously believe that the electrical industry is immune to corruption much less a code making body?


What I can't figure out is why some professionals take great offense or see me as less(er) when I bring this up. If you want to that is fine by me- I'd rather know where folks stand.

Give it a decade- revolution is not only unavoidable it is inevitable.

Lastly anyone who is defending the code's lack of disconnection times and loop impedance has no concern with life safety reasoning solely on exceptionalism.

 

[Parchie]

It doesn't need a scientist to know that #14 wire doesn't always make a good sized wiring. Just keep it stupidly simple: compute for the voltage at the delivery point and see if the load end is served properly! That simple!

 

[Mbrooke]

#14 isn't the only wire size that has impedance. #2 doesn't always make good sized wire either. Keeping voltage drop to 3-5% for any given load does not guarantee an OCPD will trip for a fault.