No matter what the size of the conduit, you always have to derate the conductors accordingly when you have over 3. Correct? So, like most people think, "put a bigger size conduit in and you can pull more wires!" For instance, putting 1/2" EMT in limits the # of conductors that can be pulled because of it's size. But really, even if I put a 1" EMT conduit in I can fit more conductors in but I have to start derating at 4-7 conductors. So even if I put a 2" EMT conduit in and I could physically fit alot of #12 THHN conductors inside I would have to derate the #12 THHN to 80% of its ampacity when I reached 4-7 conductors. If this is not correct please advise. Thanks!

You are correct, it doesn't matter what size conduit you use, the derating requirements start with 4 current carrying conductors

Roger

Look in the code though, the normal use amperage and derateing amperage of some guages of wire are different. No code book here at home, but you derate from the higher amperage, still paying attenetion to the max amperage for that particular guage. If I remember correctly.

Code theory is so fun...

Are you talking small wires or large? For #12 THHN (90C), for instance, Table 310.16 allows 30A, but 240.4(D) restricts #12 to 20A maximum. For derating, though, you would use table 310.16, and would be able to put 7-9 #12 THHN conductors in a conduit before having to derate below 20A.

You do not have to count grounds for derating purposes, and may or may not have to count the neutral, depending what kind of circuit(s) you have. And I don't know if there is a code that explicely states it, but switched conductors (like in a 3-way switch) should only count as one conductor too, as only one will ever be considered a "conductor" at any given time.

Also note that you can put up to 20 CCC's in one pipe if you use #10 for 20A, and #12 for 15A. That approach is used a good deal in commercial work.

Especially if you're upsizing the wire for voltage drop anyway.

Are you still having misunderstandings with your same piece of 2" conduit and the same plant engineer?

That would apply only to the travellers. The switchleg conductor must be counted as a current carrying conductor.

[

[This message has been edited by electure (edited 02-05-2007).]

Electure, I explained to the plant engineer that the larger size conduit does not mean that I can fill it all the way up. He wants to use it for "future expansion" but I told him about the code making me derate the conductors after 4. Anyway, I did everything legally, they just ended up eating alot of wire cost because I had to upsize the #12's to #10's and the #10's to #8's. Thanks for the input!

SolarPowered, what do you mean by CCC's? Something...Circuit Conductors. I need to know more about this. Thanks!

CCC = current carrying conductor

ccc = Current Carrying Conductor
See an earlier post for the definition

I know that this can be figured out using cost and labor data, but does anyone have a "rule of thumb" or equiviliant that shows when it's less expensive to go wtih another conduit or to upsize wires/consuit. ie is it better to do your homeruns with #10's in (1) 1" pipe...or run 2 3/4" pipes, etc?

As others have already said, CCC = current carrying conductor. A ground is not a CCC. A shared neutral is normally not a CCC, unless you are in a high-harmonics situation. (A shared neutral only carries the imbalance between the hots, so the total current carried by all the hots and the neutral will never be more than a full load on all the hots.)


[This message has been edited by SolarPowered (edited 02-05-2007).]

Did we ever answer the question about the 10 lamp holders, each on a snap switch and all connected to a single 20a circuit. You will have 11 current carrying conductors in the pipe but it is clear they can never overheat since total current is limited to 20a.
If anything the raceway will run cooler since 10 of them are sharing the 20a on the "hot" side.

Ah, it's times like this I'm glad I'm a PE. If the inspector doesn't like it, I stamp it, problem solved!

Please explain.

As there is no NEC exception for this IMO you have 11 CCCs minimum.

The NEC is only part of a building code.

All current national building codes allow engineering.

Any engineer can approve placing more than the NEC allowed number of conductors in a conduit.

---

That is false if your talking about raceway fill limits.

The only place the NEC allows an engineer any leeway is with conductor ampacity determination.

George that doesn't work here, if it's a violation it's tagged whether it's the installers or designers fault.

There are very few situations that would fall under "engineering supervision".

Why do you think drawings are turned down in plan review even though they are in fact sealed before they get into plan review?

A seal or stamp does not overrule code.

Roger

If this is true,why are we even required to submit engineered blueprints to plan check?

How come they get kicked back out, sometimes again and again? Do the building departments just not treat the PEs with the proper reverence that they deserve?


Bob & Roger, you beat me to it




[This message has been edited by electure (edited 02-06-2007).]

Scott, we were on the same page though.

Roger

Ditto on the Plan Review & Approvals. Between the Architects and the EE/PE's sometimes it can really get funny!!!!

LMAO a few weeks back....." did you de-rate for # of conductors?"; "how about ambient temp?"...long pause then reply 'did I sign & seal the drawings?' My reply, "well that depends; want them back?"

Sometimes, not always.

Hence, we do Plan Review!

John

I guess this is why we have to rewrite the code every 3 years. If common sense doesn't count for anything I guess we deserve it.
It is clear that if 2 wires carrying 20a are OK in this pipe 11 wires sharing the SAME 20 amps between them will run cooler.

Perhaps they feel an exception for this fairly rare problem would just add further confusion to an area that already causes confusion.

The answer is fairly easy, run a second raceway.

How is determining the derating factor and ampacity of 11 cables on a 20A circuit NOT related to determining ampacity, the one singular section of code where engineers are explicitely allowed to deviate?

At any rate, NEC is not the code, NEC is just the code invoked by the locality. The locality always has the final say, and the AHJ will grant engineers a lot more slack than they will for if they have to accept the liability themself. In my area, certain inspections can we waived completely if an engineer stamps a letter attesting to proper design and installation. Plan reviews are still important; I know it's hard to believe and very rarely happens, but engineers can make mistakes too!

Edit: NEC 90.2(C) and 90.4 states explicitely that AHJs can allow deviations.

[This message has been edited by SteveFehr (edited 02-07-2007).]

Steve, just out of curiosity, do you carry any type of liability or E and O insurance?

Roger

BTW, VA addopted the 2002 NEC in November of 05 I believe, so if that is the case it is in fact the code.

Roger

[This message has been edited by Roger (edited 02-07-2007).]

"There are very few situations that would fall under 'engineering supervision'."

---

While the NEC contains the phrase "engineering supervision", the national building codes do not.

The national building codes including the NEC portion are simply a set of prescriptions.

You either follow the prescription or you have an engineer deviate from the prescription and stamp the plans.

Conduit fill is a prescription. An engineer can deviate from it.

---

I think the above shows the legal reasoning that allows an engineer to practice engineering.

Roger, VA adopted IBC which invokes NEC by reference. And my locality adopted the VA uniform building code. There's a good deal of verbage on top of it all that I've never really gone into, I've never had a reason to, I only work on Federal projects and I'm the AHJ.

I just got my PE license 2 weeks ago, so I haven't actually stamped anything yet I don't plan to any time soon, because of liability but I'm sure proud to have those stamps! If nothing else, it's quite a confidence boost. I don't plan on getting E&O insurance because all my work is federal, and I don't actually have to stamp anything. If I start doing work on the side, I'll have to get insurance, but MAN it's expensive, even the cheapest policies are several thousand dollars! If I had to get insurance to work side jobs, it just wouldn't be worth it- I'm looking for niches where I can work maybe a few evenings and weekends and the occasional day off my "real" job and insurance wouldn't be required, like consulting for insurance adjustors.

[This message has been edited by SteveFehr (edited 02-07-2007).]

I've always understood the term "engineering supervision" to mean that the site had ongoing engineering oversight of the operation of the electrical system, such as you might find in a major industrial or institutional facility. And thus, that there is never "engineering supervision" of a residence or small business.

In other words, the word "supervision" implies an ongoing activity, as opposed to, say, "review", which would imply that an engineer did his calcs, stamped the drawing, and was done with it.

Any other thoughts on this?

If 15A happens to be enough to supply the load, you could put it all on a 15A circuit, and you'll be good to go. You can have up to 20 #12's in one pipe, if they are derated to 15A.

[This message has been edited by SolarPowered (edited 02-07-2007).]

Engineering supervision applies to the design process. A PE does not need to personally perform any calculations or draft any drawings to be able to stamp them, provided it is all done under his/her supervision. In this way, you can have large engineering departments that only have one actual PE that stamps everything.

That again is false.

Sorry George your PE seal does not make you all powerful.

You still must follow the NEC, at least in any of the 5 states I work in.

Where is it that you work?

Here in my area the building code has nothing to do with the NEC.

Bob

Duh! CCC = current carrying conductors! I just have never referred to it as "CCC". See, I learn new lingo everyday. Sorry about the brain fart. Thanks!

In reply to George's comments:
"You either follow the prescription or you have an engineer deviate from the prescription and stamp the plans.

Conduit fill is a prescription. An engineer can deviate from it."

This does not apply in NJ. (period)

UCC 5:23 et al is our 'Code'; NEC is slightly ammended and adopted as part of the UCC>

John

I was taught to always count the neutral as current-carrying ... shared or not.

George, you also bring up an interesting point ... I was given to understand that current flowing through neighboring wires created an impedance in a conductor, hence the de-rating. Less resistance countering the higher impedance, as it were.

If this is so, does it matter what circuit the current is from? Does it matter to our conductor if the wire next to it is from the same circuit? The same phase? Is it an ideal situation when the two wires are of differing phases - or one a neutral, with the current flowing in the opposite direction?

I always imagined this issue - de-rating - applied to pipe carrying multiple circuits. This thread has me thinking ... what about switch legs? Imagine your typical office, with four lighting "zones," and three-ways to boot. You have one 'power leg' shared between the four switches, and 8 travelers. That's 9 wires in a single pipe. De-rate? I never thought about that situation.

What say you all?

John what you describe is what pretty much the same as what Greg brought up.

The NEC requires those switch legs to be derated.

I agree with Greg that it makes little sense to derate.

However how many AHJ / inspectors are actually forcing compliance in those situations?

Bob:
In the real world, I have not encountered a situation that derating switch loops/legs would be an issue.

John

"Here in my area the building code has nothing to do with the NEC."

Perhaps you should review your building code and review the process that adopted that code and the process that adopted the NEC.

You will find they are connected. You will find that my belief outlined above is a reasonable interpretation of that connection.

George
Please show us some substantiation. Something written by someone other than you.

George, along with Electure, I would like to see some substantiation to your claim.

Steve, congratulations on your PE license.

Roger

Roger ---

Perhaps you could substantiate your position.

Perhaps with a state supreme court decision.

---

Asking for "substantiation" is a bit over the top.

An adopted code is a law; the last I looked, the only folks who get to set aside laws are judges.

Sure, there is often room for judgment in the application of a law, and often that's where additional documentation can be handy.

The NEC has numerous places where a provision mentions "engineering supervision." In places other than where such is specifically allowed, I read the code to say "I don't care if you're Thomas Edison - this is the rule!"

As for being part of the "building code," we have to be careful of our language. While there is usually a general 'building code,' such as the IBC, all of the locally adopted codes, as a group, can be said to comprise the "building code."

Some have chided me in the past for having a poor attitude towards engineers. Any cynicism I may have has been influenced by encounters with engineers who felt they had carte blanche to ignore all convention, and do whatever they wished. This is America, however, where the same laws apply to all ... even those with PE tickets.

It is also why I am so strident in asserting that it is the electrician, not the engineer, who is the expert in code matters. An electrician has years of formal training in electrical matters; even an "electrical engineer" has absolutely none. (Check the curriculum at the engineering school of your choice- don't just take my word for it!) Engineers, even EE's, are valuable applied trades, but electrical work is not their trade.

I will concede that the NEC is conservatively written; you can very often 'get away' with pushing things. It also ... pay attention here ... is not a design manual, an instruction manual, or interested in efficiency.

As for de-rating, I admit that applying the tables does not constitute a complete 'engineering analysis' of every possible situation. The tables, for example, do not make any distinction between a lightly loaded convenience circuit, and a fully loaded dedicated circuit. As I said earlier, the NEC is a conservative document.

The irony is that these code rules, as well as many unwritten trade practices, are even today proving their worth in ways that could never have been anticipated when they were written. We are only beginning to understand power quality, harmonics, and transients. Sometimes, the 'little things' make all the difference!

Using 1998 1&2 Family Dwelling Code as an example:

108.1 Allows engineering. Also allows deviations from the prescriptive code. Subsequent

3901.1 & 3901.2 Includes the current NEC as a prescriptive option.

That is sufficient to prove me correct.

George, why do you feel it is over the top ?

I feel it is a reasonable request.

Sorry, but making statements without substantiation is just making statements.

Pointing out codes that allow engineering supervision is not substantiation to your claims.

The provisions that allow engineering are few and are not open signed checks that allow an engineer to write or overrule the particular code.

The reality is that the inspector or AHJ has the hammer unless there is some documented rule that is part of the adopted code that says a PE seal is the hammer.

Roger

Because in being switchlegs, there will never be one time where both conductors will be carrying the same load correct?

'getting my code book for exact reference'..not because I disagree, but for continuing ed's sake.

To further what I stated above:
In New Jersey:
The 'Building Code' consists of one (1) main document (NJ UCC, 5:23) which is LAW, and written as such.

Within the UCC, and adopted are various 'Codes', one of which is the current 2005 NEC, with minor amendments.

The AHJ is responsible to enforce said Code, be it Electrical, Plumbing, Building, Fire, ADA, Asbestos Remediation, etc.

I am not 'anti-engineer'; I respect those that persue that career, but, rules (laws) are rules.

John

George your claim that "The NEC is not the Code" is not true in Texas, and that point is specifically stated in this NEMA release from a couple of years ago.

Here is substantiation:
_____________________________________________

Code Alert: Texas, 01 June 2005
NEMA > Standards > Field Representative Program > Code Alerts > Code Alert: Texas, 01 June 2005

On Wednesday, June 1, 2005 the Texas Commission of Licensing and Regulation formally adopted the 2005 edition of the National Electrical Code® as the State of Texas’ basic electrical installation code. Enforcement will be effective on July 1, 2005 and this adoption replaces the 2002 edition of the National Electrical Code®, which was the first State of Texas mandated electrical installation code for all classes of occupancies that was first adopted by the Commission in January 2004 and that went into effect on September 1, 2004.

However, even with the 2005 edition of the National Electrical Code® being adopted by the State of Texas as the basic electrical installation code in the state, incorporated cities in the state may amend the edition of the National Electrical Code® adopted by the state. But, for unincorporated areas outside a municipal jurisdiction, the 2005 National Electrical Code® as written will be the electrical installation code. Texas also adopts the International Residential Code (IRC) for all 1&2 Family Dwellings but did not adopt Chapters 33-42 (the electrical provisions chapters) of the IRC and continues to utilize the National Electrical Code® for electrical installations in one and two family dwellings.
____________________________________________

Here's one for Oklahoma
http://www.nema.org/stds/fieldreps/codealerts/20050719ok.cfm


You may want to update your information.

[This message has been edited by electure (edited 02-09-2007).]

I disagree- Electricians and Power Engineers are both required to be experts in code, but the areas of the code both are expert in vary. For example, engineers seldom get involved with the details- we require a component be grounded, but are largely unconcerned with HOW it be grounded, and the details are left to the electrician. I might specify RGS or compression-couplings on EMT in areas where I'm concerned about parasitic EMI in an electronic facility, or put certain requirements on the size of a neutral, though. Or ensure that specific types of transformers are installed that block harmonics and minimize fault current levels. All these things must be installed by code, and current levels calculated so that ampacities and derating can likewise meet code. So, if it's routine, my drawings tell you what to install, tell you what conductors to install in what conduit/cable tray/etc, and generally leave it at that.

If a question ever comes up on ANY issues of code or design, though, it's the engineer who's called in to make the final determination.

It's only if there are special situations where more detail is required- in some situations, I will pore endlessly over specifications and requirements and technical data from all involved and specify, for example, not only what bolt, which which PRECISE bolt be used and will give you a procedure on how to turn it; if you disagree and want to do it differently, it had better be on the proper form and in triplicate, and you'd better wait for my response before doing anything. I work for the federal government, though- this isn't very likely to happen when wiring up a wal-mart or mini-mall.

[This message has been edited by SteveFehr (edited 02-09-2007).]

A very good response, Steve. I don't want to get into an "us vs. them" thing here, but I do note you were quick to counter my assertion.

What I'd really like to know is what the engineers out there think of George's assertion that the engineer can over-rule the code.

I suppose, if you dig hard enough, you can find decent folks in any field. It's the arrogant loose cannons that make it hard to see them.

Between you and me, I sometimes rely on the electrician as a crutch. Every once in a while, a question or situation comes up but I don't know the answer. Even if I feel it's something that probably should be on the drawing, in these cases, I'll just stay silent on it and trust that the electrician knows that part of the code better than I do and will get it right

You might find some arrogant engineers, and tempers might fly whenever there's a disagreement (why else would the engineer and electrician be talking unless there's a problem? lol) but the engineers almost always have a great deal of respect for the electrians that install our projects. I certainly do! I wouldn't be on this forum otherwise And I'd like to think the respect is mutual, even as much as we're cursed!

[This message has been edited by SteveFehr (edited 02-09-2007).]

Steve I am not trying to stir up 'stuff' but I do not understand this.


Its not the engineer in my experience it will be the inspector / AHJ / Plans examiner who makes the final call on what is code and what is not code.

And I do want to point out I am not anti engineer either. We each have a job to do and like most things the more I learn what an engineer does the more I realize how much I don't know.

That said I am often more knowledgeable in the code than the engineers and many times have been the one 'blue collar' in a meeting of white collars as a code consultant. Also more than once this has resulted in complementary calls to my bosses about my ability to work together to find solutions to the problem at hand.

Well, I've had plenty of trouble calls where I go down to the jobsite and find that the electrician decided he knew more than me and had a "better" way of doing it, and ran into the exact problem I had forseen and designed around... No, sorry, you can NOT notch the flange and I'm not authorizing an impingement of shock clearance on the waveguide- I didn't spend 3 weeks working on that drawing so you could toss it aside, rip it out and do it like I told you!

Sometimes the electrian does know the better way- he/she certainly spends a lot more time on-site working than the engineer- but very often, the engineer has a very good reason for the design decisions made. Maybe there's a planned upgrade, maybe the "easy" conduit run is reserved for some HVAC ducting to be installed down the road. My name is on all the drawings, I have a phone, I have an email address, and have always been very willing to work with the electricians doing the install. 9 times out of 10, I'm not going to care if you pull 2 big cables or 4 smaller ones, so long as the [derated] ampacity matches- normally, I'll make a call based on the price sheets and go with that. That 1 time out of 10 though, I really do want you to install it like I asked- maybe we intend to splice it with some other cables down the road, maybe it's to suit the lugs on some proprietary equipment that's not on the jobsite yet. I try to usually notate cases like that on the drawing explitely for this reason. Either way, if we all communicate a little better, I think there would be a lot less bad blood and jobs would go up a lot smoother

------------------------------------
As for overruling the code, my experience is all at the federal level where the engineer is the AHJ and is the law; the codes are guidance, but I can overrule them as I wish. I can't speak so much for the city, but NEC and IBC give a lot of authority to the AHJs to deviate, and AHJs seems a lot more willing to allow an engineer who's assuming all liability to deviate than sign off work on their own authority.

[This message has been edited by SteveFehr (edited 02-09-2007).]

Steve


I agree with you entirely, the reason a smart customer hires an engineer is IMO to think of whole picture and at times prevent the EC from looking at only their own interests.


Steve I don't doubt you in the least.

However that situation is very unusually, of the approx 60,000 ECs in the US very few work on the type of jobs that you are designing.


I have no knowledge of the IBC, it is not used here. As far as the NEC I disagree there is a lot of room for judgment by an AHJ. There are a few specific sections intentionally left up to the AHJ but the majority is not up to interpretation.

That is why many areas feel they have to amend the NEC. If an area adopts the NEC and did not amend it the AHJ can not just ignore the NEC when an engineer (or even the AHJ themselves) decides they want to do something outside the NEC.



I don't see that here and it does not sound like John or George Little see it happening either.

If an AHJ allows the deviation from the NEC based on the engineers request wouldn't that in fact open the municipality to more liability?

JMHO, Bob

[This message has been edited by iwire (edited 02-09-2007).]

If the city retains full liability for approving a design even if an engineer stamps a drawing, then why the hell are my insurance rates so high? Well, that was an example from my last position, before my latest promotion, when I was working more on the electronics side. I'm now a "chief engineer" of sorts, and work almost exclusively commercial-power type work on US bases (or US buildings on allied bases.) Same type work you all do, basically. And I'm still learning, I've only been doing this for a little over a year now, it will take me at least 3 or 4 more before I can start calling myself an "expert!" I have to point out that I *did* pass the Power PE exam though, which proves I'm at least capable of being competant

Look up your state/city code. VA never actually invokes NEC; NEC is merely referenced as the electrical portion of the IBC. I imagine most states are similar.

At any rate, NEC 90.2(C) and 90.4 states explicitely that AHJs can allow deviations anywhere in the code they see fit.

No, NEC actually allows exactly that. No ammendments necessary.

[This message has been edited by SteveFehr (edited 02-09-2007).]

I guess you guys simply cannot read.

---

While I am an engineer, I always use the phrase "engineering is allowed. I allow anyone to do engineering.

States limit who may.

No George, we can all read, you just want to evade our request that you provide substantiation to your claims.

Now, without trying to attack us with snide remarks just post some documentation from the code adoption level that will support your statements.

Roger

[This message has been edited by Roger (edited 02-09-2007).]

Steve Fehr:
Now that I read you work Federal Jobs, please check my comments regarding that field:
Federal properties are not within the jurisdiction of NJ UCC. As a State Lic., municipal Inspector, I have NO authority on Federal, nor NJ State properties. State properties are under the UCC, but inspected by DCA (State employeed) Inspectors.

As to "George", he has no location in his profile, so my comments still apply to his posts. Perhaps Mr. Bill should require 'locations' in the profile?

John

quotes from some of George's previous posts.
_____________________________________________
"I am not an electrictian. I get paid to do design, engineering, and all construction except where a license is required (usally electric, plumbing, and HVAC).
No one drills holes or puts in any fasteners (that includes those MN staples) except me."
_____________________________________________
"The constitution of the State of Oklahoma requires electrical work to be done in accordance with ANY nationally recognized electrical code.
It allows anyone to do the work. Most local authorities limit the work that unlicensed people may do to property they own or are tenants at.
The assumption that a license is required to do electrical work is wrong.
I am unlicensed. I apply for electrical permits as necessary. Regardless of how the local authorities act on the permit application, I do the work."
_____________________________________________

"I used to be licensed"
_____________________________________________

(George lives near Tulsa, Oklahoma)

George, I still can't figure out what discipline of engineering you claim to be a PE in. Some other old posts make it sound like structural



[This message has been edited by electure (edited 02-09-2007).]

"How come they get kicked back out, sometimes again and again? Do the building departments just not treat the PEs with the proper reverence that they deserve?"

The building departments, are most likely scratching their heads, try to figure out where some of these guys got their seal from,
It's funny but I get better electrical prints, from mechanical engineers then I do from electrical engineers.

On the switch leg issue, I have seen switch leg conduits get so hot, you could cook an egg on them, signed, and sealed by an engineer.


Quote: I try to usually notate cases like that on the drawing explitely for this reason. Either way, if we all communicate a little better, I think there would be a lot less bad blood and jobs would go up a lot smoother

Steve, that is the way to go, it's a win win situation, when we work together.

"As to "George", he has no location in his profile, so my comments still apply to his posts. Perhaps Mr. Bill should require 'locations' in the profile?"

I agree!



[This message has been edited by LK (edited 02-09-2007).]

Guys,
Lets not get too silly here.
Once we start getting into petty insults, things tend to go down-hill.
Please stay on-topic.

This is in our city code on discussion of the electrical AHJ. Not sure if it applies to what was asked previously. The chapter it is refferring to is the Electrical Regulations.

D. Interpretation Of Regulations: The electrical inspector shall have full power to exercise judgment in a reasonable and proper manner and rule accordingly on all special cases in regard to any matters in this chapter or not specifically covered thereby, subject to section 9-3B-4 of this chapter, pertaining to appeals.

On the subject of the AHJs employer incurring liability I suspect that is unlikely. When I took my four semesters of fire service law the inspectors acting for local government had the same immunity that the state itself had as long as they were acting in good faith. Has that changed completely in the intervening years. The case we had to study involved a fire inspector ordering the installation of guards over the drying lamps in a auto body paint booth. The result of which was several ruined paint jobs. When the shop owner tried to sue the municipality the case hinged on the inspector being cloaked with his sovereign's immunity as long as he had acted in good faith. The ruling survived that states supreme court and there being no federal question it was considered to be settled law unless some other state supreme court found differently on those same facts. That decision is still taught to new fire marshals in order to impress upon them the need to act as a scrupulously neutral party when responding to public complaints. Taking sides in disputes between citizens can lead a court to conclude you acted in bad faith and are therefor not immune from civil liability.

[This message has been edited by tdhorne (edited 02-09-2007).]

(Without reading any comments since my last post) copied from another thread on this site ---

---

I would expect that the moderators and those who claim to be inspectors would have read the local laws that adopt the building codes.

Usually the process is that a national building code is adopted and that building code includes reference to the NEC.

All national building codes allow engineering. That includes engineering of the electrials.

The national building codes and the NEC are prescriptions. That is, based on general assumptions general engineering solutions have been produced and reduced to the tables and text of the codes and the NEC.

The engineering allowed by the national building codes and by included reference by the NEC consists of project specific assumptions and produces project specific engineering solution.

In general, an engineered solution will not "meet" the NEC. It will not "meet" the NEC because the design assumptions more accurately reflect the needs.

---

I suggest that those of you who hold a differing opinion consult your attornies before you reject an engineer's work.

Well, George, you bring up an interesting set of circumstances.

Let us say, for the sake of discussion, that a man puts 10 wires in a pipe that NEC says is full with 9. And, let's say the AHJ catches it, and refuses to sign off on the C of O.

Lawsuits follow, and it winds up before twelve of your neighbors for decision.

The first issue is one of competence. That is, who is qualified to make the decision. It's pretty hard to convince twelve strangers that YOU know better than a generally accepted code, that was applied fairly. The jury is going to want to hear of your schooling, your licenses, your specific experience. The burden is going to be on you to justify your breaking away from the proven path.

The next hurdle will be to show why there was no code compliant manner in which the job could have been done. Make no mistake - the code, having been accepted, and with a wealth of history behind it, will be presumed correct.

If you take the position that a "Professional Engineer" license, by statute, gives you absolute authority to do as you please, the jury will be shown how neither engineering school curriculum, nor the PE exam, have the slightest aquaintance with the electrical trade. Indeed, you'll be lucky to find a college bookstore that sells the NEC.

This will have you, in effect, making the case that you have superior knowledge in a subject in which you have absolutely no training.

It would help your argument if you could point to other situations that followed your example ... either as to the actual solution, or that supported the assertion that anyone could "engineer" themselves a variance.

It would be a lot like a traffic engineer arguing that speed limits didn't apply to him. I'd like to see the jury that would agree with that.

"I suggest that those of you who hold a differing opinion consult your attornies before you reject an engineer's work."


No need for us to reject anything, thousands of them get rejected at plan reviews every day, were lucky that way the building departments keep most of the poor design work from reaching us.

George, we're still waiting.

It's apparent that you have gotten in over your head and simply can not back up your statements can you?

Telling us to contact an attorney is not substantiation to your claims.

Roger

Actually... the PE Power exam is HIGHLY specific about power, covering a lot of extremely difficult power engineering principals as well as knowledge of NEC. There are elective EE courses in power engineering, too, that many prospective EEs will take. Not all will, though, just those going into power, just like power EEs don't generally take semiconductor engineering or electromagnetic fields and waves. The principals behind power engineering are a lot simpler than some of the other fields, and are generally covered in basic 1st year circuitry- the math just gets SO much easier when theta is always 60Hz!

Code is not emphisised because it's not as important during education as the engineering principals that underly it when you get to the types of issues the PE will be involved in. Codes differ from locality to locality and can always be looked up- engineers are expected to go far beyond this- and it's not like EEs are thrown right to the jackals; there is mandatory 4+years engineering experience required before one is allowed to even TRY to sit for the PE, ensuring real-world experience is gained in addition to the book learning. If knowledge of code was all that was required to be an EE, you'd see every 20-year master electricians sitting for the PE exam so they could become an EE PE. It's not like that though, there is a completely different skillset involved.

The Inspector and Electrician looks at that conduit with 12 wires in where NEC says only 11 are allowed and says "NO!" The engineer looks at that conduit and says "Why does NEC say only 11 are allowed? Is it because of installation difficulty and risk of damage to the cables? Lets test the cables and see if any are damaged..." and so on.

[This message has been edited by SteveFehr (edited 02-11-2007).]

If it's OK, I would like to add my comments to this thread, regarding my personal experiences in the subject of Power Engineering + Electrical Construction (applied to Commercial and Industrial Projects, as the Residential stuff I have dealt with would not include the same criteria).

First off, I am merely an Electrical Systems Designer - part of a Design/Build approach, Employed by an Electrical Contractor.

In a nutshell, I am nothing more than a glorified Draftsperson - one who compiles a Project's Design Concept into a workable reality, by performing Electrical Engineering to the system(s) and designed loads, then Drafts the compiled Engineered ideas to a Plan Set, which gets Plotted (Printed) in Hard Copy form.

Through the Engineering of the Electrical systems, I compile a set value to each and every Load, Circuit, Panelboard, Transformer, etc., which is a balance of many factors:

* Safe Installations,

* Trade-Specific / Common to the Trade,

* Adequate Capacity,

* Abilities for future loads or expansion,

* Most efficient and lowest losses, with the minimal expense possible,

* Specifically applied to the Client's needs (per specific equipment demands),

* Designed to accommodate the Client's needs, not my feelings (Engineering Ethics),

* Oriented around + related to local codes and ordinances:
Compliance applies to many codes - not just the NEC, but the California version - the CEC, per "Title 24, Part 6 Energy Conservation" codes, per Title 24, part 2 - California Building Codes, per California Mechanical, Plumbing and Fire Codes, along with Local Power Utilities Electrical Service Requirements, sometimes the Local Building Department's Planning Division, and finally - but most specifically, the AHJ and that Local Building Department's requirements for a given Project.

As I said before, I am a glorified Draftsperson that applies Electrical Power Engineering techniques to a design concept, compiles the data to related documents, then produces a visible + workable version of this stuff on hard copy documents, for use in real world applications.

Re: P.E. Certification...

The California version of the "EIT" (Engineer In Training) for Electrical Engineering Discipline, did not contain any NEC references at all.

The "Morning Section" was 4 Hours of "Everything" - all related Engineering principles, some Nuclear Physics, Ethics, etc.
The "Afternoon Section" was Discipline Specific, which was 4 Hours of Electrical Engineering calculations and figures for Power, Signal and anything else related to the field of Electrical Engineering.
The only thing related to the NEC was Ampacity Tables, Voltage Drop, and SCA.

I have not applied for the PE Exam (and I am wondering if I will do in the next 10 years!, but this is another story!),
but have heard that there is little - if any - NEC related stuff involved.
From what I know (and have witnessed many times over the past 25 years), an EIT holding "Green-EE" learns Code related stuff during their Internship with an EE Firm.

Back to my Work Experience:

My Designing experience + applications, is a very unique blend of "In-Field" Work Experience, coupled to Electrical Project Design and Engineering work.
I know of a few, and am sure there are many more Electrical Designers and EEs, whom also have come from the field into the Office, for which the same may be said of them, as well.

Being in the Field at Journeyman and Foreman level for many years, has given me the basis of code compliance, plus trade common design ideals, of which I use during every design task.
In addition to these experiences, having been involved in Management, Estimation and Consultant positions, along with working in conjunction to Communications, Data, Security, CCTV, Mechanical, Plumbing, Structural, Framing Contractors + Vendors, and Architects, has contributed to my designs.

The most basic consept is to design for ease of use and installation, for _ALL INVOLVED_

Re: Engineering Supervision:

The only time Article 310.15 (A)(1) and (C) have ever been applied (or considered) in my designs, were to address something which was _FACTORY ASSEMBLED_, and an Inspector had issues with something in that Equipment.

These issues were between the AHJ (Building Department and/or the Utility Department's Service Engineer), and the Manufacturer - I was only the one granted the lovely task of passing documents back and forth, along with hunting down the responsible personnel of design, following up on things, and all that baloney!.

For example, the most common occurrence was related to Switchgear (Service Equipment) and Factory Installed Conductors which were smaller than expected to see per Table 310.16 or 310.17.

Documentation supplied by the Manufacturer assumed liability per the design (and other disclaimers, which assured Engineered Supervision compliance per the AHJ involved), so the Equipment was finally accepted.

If I had known of the possibility for those issues prior to specifying / ordering the questionable equipment, it would have never been done! (one of those "Learn By Sample" things!).

One other issue involved an UPS Inverter, which had a HUGE label across the front stating:
"Not To Be Used On Systems Having Greater Than 5KAIC RMS SYM. Available", on a system with a listed Fault Value of 35KA at the Service, and 20KA at the UPS - and to make things even more exciting, on a Series Rated System!

The Foreman on the Project accepted the delivery of a non-spec'ed UPS Inverter (the one delivered was not the one specified in the contract documents - not even the specified manufacturer), which was the first mistake.
The Project was a Public Works job, with extreme specifications and little -if any allowed substitutions.

I was given the Project to both Manage (Project Manager) and to work as a Foreman, in order to "Put out the many, many fires lit by the previous Foreman".

The way we got the UPS to be compliant, was by installing a 60KAIR rated Circuit Breaker inside the unit, and terminate the Line Input through it.

Documentation from the Manufacturer, along with an on-site acceptance + certification by an NRTL (CSA to be exact) was required, and was sufficient for the AHJs (Building Department and the Q.C. Inspector for the Client).

These particular scenarios are some great examples of "How to work with everyone" discussions, I commonly discuss with personnel wanting to become either Forepersons, Project Managers, or Designers.

Nevertheless, I would only plan to apply Engineering Supervisions per Conductor Ampacities on something extremely specific - and believe me, just because I compiled documentation supporting it, I would _NEVER_ assume it to be anything definite - UNTIL ACCEPTED BY PLANCHECK + ACCEPTED BY THE INSPECTOR!!!
That just goes without saying!

Sorry, but I just do not have a high enough level of Testosterone, which would be required to tell a Building Department and/or Inspector to simply accept my design data, and forget everything else!
I have heard a few EEs attempting to do this, and the results were heated debates, followed by endless documentation, and eventually complying to the AHJ's NEC based requirements!

But then again, I am only speaking from the viewpoint of a glorified Draftsperson, with around 25 Years trade + Design experience, relating to Commercial and Industrial based Design/Build Projects.
One who not only creates the Plans (drafting and plotting), but submits them to Plan Check, obtains Permits, Meets with Inspectors, deals with Clients + Vendors, Subcontractors, Architects, other Engineers, General Contractors, Equipment Suppliers, Field Personnel, and related documents (faxes, "nasty-grams", E-mail status & discussions, cutsheet searching, yadda-yadda-yadda).

I can't think of anything else to add, as this message is wayyyyyy overblown right now!

Responses would be greatly appreciated!

Departing the proverbial Soapbox...

Scott35

edited after finding sum spelin airrorrs (corrected spelling)

[This message has been edited by Scott35 (edited 02-11-2007).]

Scott
Wow, more than 130 lines of text to say
"I do design/builds". (just teasing)
I do them too.

(BTW, for the others, a substantiation
CA Business and Professions Code 6737.3

..........."shall not prohibit a licensed contractor, while engaged in the business of contracting for the installation of electrical or mechanical systems or facilities, from designing those systems or facilities" ............. "to be performed and supervised by that contractor within the classification for which his or her license is issued,....."

We can't design/engineer for jobs others are to perform, otherwise anything other than civil/government projects are fair game for a contractor.

6737.1 Lets "any person" do the engineering for a single family or multi (up to 4) family dwelling up to 2 stories plus basement, so grandma or a 5 yr old can do it.

The plans go through the same review and approval process as those from a PE/EE.



[This message has been edited by electure (edited 02-11-2007).]

Quote "The Inspector and Electrician looks at that conduit with 12 wires in where NEC says only 11 are allowed and says "NO!" The engineer looks at that conduit and says "Why does NEC say only 11 are allowed? Is it because of installation difficulty and risk of damage to the cables? Lets test the cables and see if any are damaged..." and so on."


Good Luck in your endeavours! Pull that with an inpector who was in the trade for 25 plus years and is showing up to your job at 4:30 on his 5th inspection of the day.


That is the attitude problem that seems to get us to where we are now. Rather than learn the codes and standards and learn from the seasoned veteran electricians, the engineer assumes superiority and questions the standards and practices by which they work.

The NEC is not a new document, it is the result of years and years of compiled knowledge. By no means perfect, but unless we are talking about a completely new technology and installation method or environment - it is pretty damn thorough and comprehensive.

As is relates to issues like conduit fill etc. The answer to the question "why this many or only this many" (aside from the reasions documented by others earlier in the post) is...because it has to be something.

It is a standardized number that is part of a greater set of standards. It may be 11 conductors's because if the NEC did not prescribe a limit, certain EC's would install 25, 30 or more.

I think you misunderstand my point; I'm not saying I'd have submitted a job with 12 conductors where only 11 are legal. But the contractor had already installed it and somehow ended up in court and hired me as a consultant to analyze it, I wouldn't just take their money, smile and say "Sorry, rip it out!", I'd actually analyze it and give my "expert witness" testemony of whether I felt the installation sitting there on the jobsite was safe or not.

I meant this as a broader example of the thought process I take to the job. NEC is not there to **** me up and drive up the cost of jobs, it's a compilation of methods and guidance required for a safe installation. I don't go around looking for ways to cheat NEC, I keep a tabbed and annotated copy on my desk and normally comply 100%. But there are times when I have to go above and beyond what's in the book to get the job designed right.

The hardest decisions are when I get to the jobsite and find NEC violations and have to decide whether it's acceptable or not. As I stated before, I'm not just the engineer, I'm also the AHJ and the program manager responsible for funding the job. This example of 12 wires in an 11-wire conduit is typical of the type of violations I find and have to make a decision on whether the installation is safe and we can proceed with testing or whether to cost my program a ton of money and do it strictly IAW code. Sometimes I sign off on it, sometimes I make them fix it. Either way, I'm accepting full liability as the responsible engineer. That's why I'm paid the big bucks!

PE EE morning exam has a few NEC questions- enough to force the poor compsci and circuit EEs to buy a copy of NEC to drag to the test. PE EE Power Afternoon exam has more in depth NEC questions. (5% of the test, IIRC) It also has fault analysis, power factor and a boatload of other difficult power questions. I'll see if I can dig up a sample exam to share here, I think you guys might enjoy trying your luck at it

PE EE, Afternoon Power Module (40 multiple-choice problems, 4 hours) http://ppi2pass.com/ppi/PPIInfo_pg_myppi-faqs-ee.html

General Power Engineering: approx. 15% of problems
Measurement, instrumentation, and statistics: 5%
Power metering
Instrument transformers
Transducers
Frequency responses of measurement devices
Data evaluation
Reliability

Special applications: 2%
Illumination design
Lightning and surge protection

Codes and standards: 8%
ANSI standards
NEC (code)
IEEE standards
NEMA standards
NESC (code)

Circuit analysis: approx. 28% of problems
Analysis: 15%
Short-circuit analysis
Wye-Delta transformation
Three-phase circuit analysis
Symmetrical components
Balanced and unbalanced systems
Per-unit analysis

Devices and power electronic circuits: 8%
Solid-state power device characteristics and ratings
Battery characteristics and ratings
Power supplies
Relays and switches
Power electronics

Electric and magnetic fields and applications: 5%
Transmission line models
Mechanical forces between components
Electromagentic fields, coupling, and interference
Electrostatics
Ferroresonance

Rotating Machines and Electromagnetic Devices: approx. 27% of problems
Rotating machines: 18%
Synchronous machines
Induction machines
DC machines
Machine constants and nameplate data
Equivalent circuits
Response times
Speed-torque characteristics
Speed control
Motor starting
Variable speed drives
Testing

Electromagnetic devices: 9%
Transformers
Reactors
Magnetic circuit theory
Testing

Transmission and Distribution: approx. 30% of problems
System analysis: 15%
Voltage drop and voltage regulation
Power factor correction
Parallel three-phase systems
Surge protection
Power quality
Fault current analysis
Grounding
Resistance grounding
Transformer connections
Models

Power system performance: 6%
Load flow
Models
Power system stability
Voltage profile
Computer control and monitoring

Protection: 9%
Overcurrent protection
Protective relaying
Protective devices
Coordination


- Historic pass rates for engineers who have graduated with at least a bachelors of science degree in engineer, passed the EIT/FE exam, and had 4+ years relavent experience and sat for the PE Electrical exam have been between 28-68% for different exams over the past 6 years. 2000 was a very bad year to have taken the PE, I think, lol...

[This message has been edited by SteveFehr (edited 02-11-2007).]

This post is intended to inject a "smile break" into the discussion:

If the PE exam has 40 questions, and 8% are based upon codes, how many code related questions are there?

If there are five categories of codes, and 3.2 questions, how many questions relate to the NEC?

I suppose it is fitting to ask engineers to answer .64 of a question- and do it in 1.2 minutes.



[This message has been edited by renosteinke (edited 02-11-2007).]

Well, seeing as there are two widely used Standards listed - ANSI and IEEE, I would bet that 2 of the 3.2 "Codes + Standards Multiple Guess Questions" would be related to ANSI and IEEE.

That leaves 1.2 "Codes + Standards Multiple Guess Questions" remaining.

Toss those into a Random Number Generator, and odds of getting the NEC Question would be 1:3 at best!

Maybe the remaining 1.2 Question would be a "50/50" between NEC and NESC, as NEMA is a Standard, and might be placed in Random Selection Cache with ANSI and IEEE!

My luck, I would draw an NESC Question, since I never deal with stuff on the Utility side of the Service Disconnect (other than Service Entrance Ducts and Feeders, Transformer Vaults and Pads, and Primary Feeder Ducts).

If I have the desire + time, I will place these 5 Codes + Standards to numeric results of a "0-4" RNG, just to see what comes out!
(not very likely to happen!)

LOL- The test changes every 6 months; I think they must average the tests to come up with those numbers. The practice exam I took had 5 questions that specifically referenced the NEC and 3 others where you pretty much needed NEC tables to answer it- I thus studied it VERY heavily (and was pretty active on this forum as part of my studying!). The PE exam afternoon session I took (Oct 06) only had 2 questions that directly referenced the NEC (easy relative to the rest of the test!) and one NESC question that I was absolutely clueless on and just had to guess- it was far more heavily slanted towards poco type power engineering No IEEE or ANSI questions on that test, either. I did use the NEC voltage drop equation and tables for several other questions, though.

40 questions isn't going to cover every possible nuance of power engineering- the questions they choose are representative. I mean, if you can delve through some of the more arcane aspects of 430 and pull out the right answer, you're probably going to find the derating tables without much effort


[This message has been edited by SteveFehr (edited 02-11-2007).]

"Sometimes I sign off on it, sometimes I make them fix it. Either way, I'm accepting full liability as the responsible engineer. That's why I'm paid the big bucks!"

Good description of what is involved with working as a PE, I spent many years working with large engineering groups, and they are usually a mix of a few PE's a much larger number of Electrical Systems Designers, and a constant changing number of EIT's.

One thing i noticed over the years, was many in the Drafting group, would have all the building code books handy, and they did reference all the codes, not just the electrical, if there was a design problem, they had the PE's on staff ready to assist.

IMO what is all comes down to is, keeping the lines of communication open on any project, If a problem is found with the design bring it to the engineers attention and work together to resolve it, everyone wins.

I have a solution to your derating problem...just put a junction box every 24"...lol

I guess that would be a "no"

I believe that engineering supervision means that a PE has stamped the plans. It doesn't mean that he has made any calculations, but he is approving the work of someone who doesn't have the PE. As Steve pointed out, the liability issue of stamping plans that aren't in compliance is huge. As far as being able to override a pertinent provision of the NEC, the NEC allows for this in 310.15.

NEC 310.15(A)(1) states:

"Tables or Engineering Supervision.

Ampacities for conductors shall be permitted to be determined by tables as provided in 310.15(B) or under engineering supervision, as provided in 310.15(C). "

310.15(C) states:

"NEC 310.15(C) Engineering Supervision

Under engineering supervision, conductor ampacities shall be permitted to be calculated by means of the following general formula: [FORMULA]"

In Wisconsin, the derating factors do not apply to residential branch circuits.

“ARTICLE 310 – CONDUCTORS FOR GENERAL WIRING

Comm 16.30 Ampacities for conductors rated 0 – 2000 volts [NEC310.15]. (1) ADJUSTMENT FACTORS [NEC 310.15 (B)(2). This is a department exception in addition to the exceptions specified in NEC 310.15(B)(2)(a):

Exception No. 6: The derating factors shown in Table 310.15(B)(2)(a) do not apply to branch circuits supplying an individual dwelling unit.”

It appears to me that Steve is on firm ground for applying the 310.15(C) formula. If he is trying to approve something that exceeds the 310.15(C) formula, I don't think he can legally do that.

As far as overriding the NEC absent a specific provision, I don't think that's true. Of course, if the local AHJ is willing to go with it, perhaps it is acceptable.

Sounds like something a bunch of lawyers would argue over!

By the way, I am also a PE in Electrical Engineering. The biggest thing you learn being a PE is not to sign something unless you can back it up. Caution is the order of the day.

Frank