Even further problems with reading Table 310.16, etc

I just purchased the McGraw Hill National Electrical Code Handbook for the 2005 NEC at our very fine brand spanking new Barnes and Noble Bookstore in Fairbanks, Alaska.
I have been reading and using McPartland's writings for years so I consider this a reliable source. There is much information on derating and using the ampacity tables in this handbook including some history on the subject. It is necessary to study this material in detail and compare it to the NEC handbook and find a solution as to exactly how ampacity and derating shall be applied consistently in a computer program. Evidently, this subject is one of varying opinions and inexact decision making. The question is, of course, how do electricians read this material and apply it on the job? I do believe this whole subject should be studied by a NFPA task force and simplified for real world applications. In my humble opinion, the code rules on this subject are entirely too complicated for wireman to apply in the field.

On the other hand, I am selling electrician.com domain name only and have moved everything of value for the continuing education courses, articles, calculators. etc to electrician2.com and that will be my new homepage location.

Table 310.16 and Motor Circuit Calculators Update

I have removed the links to these calculators until I can fine tune them. I have found that the NEC Handbook is arbitrary for some calculations and for determining equipment grounding conductor sizing. At least, that is what it appears to me. Until I can get a determination on just what the NEC people are trying to say, I think I will hold off on finishing the calculators. It appears that some people write one part of the NEC and others write other parts and they are not always in harmony. Of course, how dare I make such a statement as to question the integrity or validity of the almighty NEC, but it is so! It may be that the NEC rules have never been programmed to such length as to require a concrete and thorough application of semantics, syntax, and logic.

Also, I am selling electrician.com and will be involved in some new endeavors for a while. I have already moved all the pages to electrican2.com from electrician.com and most of the test scoring, etc. has been done at the electrician2.com server for some time anyway. I still need to go through and make sure all the links that refer to electrician.com are removed. The site is quite large about 65 megabytes and I think there are somewhere around 58,000 files. So removing all the electrician.com from electrician2.com may take some time.

On the back burner is completing the calculators and publishing a book titled computer applications for electricians where I plan to publish the source code, flow charts, and detailed information and instructions with a CD containing about 25 or 30 computer programs that can be used by electricians and engineers in the field. Part of my reason for selling electrician.com is to fund this effort.

Equipment Grounding Conductor Sizing Problem

I tried to put the equipment grounding conductor size in two of the calculators and that has opened a whole bottle of worms. The problem is the Code requires that the grounding conductor be resized in proportion to the resizing of the ungrounded conductors. This is not such a great problem for voltage drop and I added that to the 310.16 read calculator. The problem is for derating of conductors. This requires that a baseline be established for determining the original size for the equipment grounding conductors. The only baseline I can find is to use 60 degree ampacity for a load of 100 amperes or less and 75 degree ampacity for over 100 amperes 110.14. So each problem has to first determine what the OCPD would be for these temperatures and ampacities then find the correct initial size for the equipment grounding conductor. Then a proportionate determination has to be made for any increase in size of the ungrounded conductor because of derating and voltage drop. The total sum of programming for this just about doubles the program size when adding equipment grounding conductors. Furthermore, for No. 12 and 10 AWG sizes the calculations make the equipment grounding conductor size the same as the ungrounded conductor size. This becomes almost amusing. For instance for a total derating factor of 0.14 there would be a 4/0 equipment grounding conductor for 4/0 ungrounded conductors on a 30 ampere circuit breaker. This just does not seem right. Anyway, I am working on this additional programming for the calculators. Motor circuits are even more interesting.

New Table 310.16 Read, OCPD, and VD Calculator

I finished the final version of this calculator this AM. It lets the user select the wire size, insulation, ambient temp, number of conductors in a raceway or cable, and other special parameters. It then finds the derated ampacity, maximum overcurrent protective device, and sends the output to the voltage drop calculator. It is for persons that don't know the load yet, which is the case many times. It seems to check out ok, but as usual, there are more combinations to check.

Today the sun shined for over 12 hours here for the first time this year, and breakup is about 3 weeks away. I can't wait for the snow to melt after 6 months of it. I am getting anxious to do some hiking in the wilds of Alaska. I want to go down by the Alaska Range and hike to the very top of one of those mountains by Isabel Pass then sit there and take a long rest. There is nothing like reaching the top of a mountain after about 5 hours of hiking. Alaska has many mountains to climb.

More work on the Motor Circuit Calculator

I spend the day adding new features and debugging. The results now provide the overload sizes and equipment grounding conductor size. A bug where the calculator rounded up instead of down for high value branch circuit and ground fault protective devices was fixed. I also, provided code so that when the nameplate full load current is entered that value is transferred to the voltage drop calculator instead of using the full load current from the tables. I placed the new version online and will continue trying to find bugs, and other anomalies. This calculator now reads six tables and follows the NEC as far as I know how. It appears to find all the correct values when doing text book and handbook examples. But it does a lot of combinations, more than I care to ever try, but I will try to keep testing it.

More work needed for Motor Circuit Calculator

After reviewing the issues I must criticize my calculator. It does not give enough information. It should also provide the disconnect, equipment grounding conductor, raceway, and controller sizes. Also a summary with a graphic is needed to show the various components and sizes for a motor circuit. If only one size conductor were used for each motor this would be a simple technique of making up a table and then extracting the information. However, since the calculator determines size of conductors based on several variables the calculation method must be used. This can become very involved since the raceway fill calculator alone is 85k in length. So I may leave out the raceway size and make that another operation altogether. I spent most of the day again adding features to the calculator. Today I added the maximum allowable branch circuit ground fault and short circuit device sizes.

Motor Circuit Conductor and voltage drop Calculator uploaded

The new calculator for motor circuits finds the size of conductor and size of short circuit and ground fault protective devices. It does this for AC motors under 600 volts single phase and three phases as given in Tables 430.148 and 430.150. The duty cycle Table 430.22(e) is also included. Derating for ambient temperature and more than three current carrying conductors is also included. I have checked out many combinations of problems and there seems to be no bugs. I did notice that for small wire sizes of No. 14 copper, No. 12 and No. 10 copper and aluminum the limitations placed by the note at the bottom of Table 310.16 (Section 240.4(D) do not apply. This allows a higher ampacity to be used for these wire sizes. I plan to expand the results to include size of disconnect, overload devices, and controller.

The next project is to design a calculator to do a reverse Table 310.16 lookup. This program will find the ampacity after the user selects conductor size, insulation temperature, and other conditions.

New motor circuit calculator

I have begun work on a motor circuit calculator for under 600 volts and for up to 500 horsepower for one and three phase. This calculator uses features from the Table 310.16, OCPD, and voltage drop calculator expanded to find the nontime delay fuse, dual element time delay fuse, instantaneous trip circuit breaker, and inverse time trip circuit breaker sizes. It uses data from Tables 40.248, 430.250 and 430.52. I may add duty cycle from table 430.22(E), disconnect size, and motor controller size. I just started today and was surprised how fast it is coming together. After this one, I think I will do a motor compressor calculator.

On electricians and computers

I am sure not everyone shares my views about electricians and computers. Many contractors consider electricians specialized laborers that need few if any intellectual skills or what we call cognizant learning. I recall a contractor telling me that all he wanted was electricians that could bend and install pipe. He didn't care if they knew ohms law or how to use a meter, as long as they could run pipe and do a days work. That is all he cared about. However, this same contractor's wife ran the office for him using a computer. She did the payroll, the taxes, the billing, money in, money out, and all of it. The contractor himself could hardly turn the computer on! By the way this contractor is now retired and collects old automobiles for a hobby. He lives in Nome, Alaska, the last I knew.

Now about my views. I recently purchased two current college Calculus textbooks. Both contain CD's and both incorporate the use of computers and software such as Mathematica and Maple into the text assignments. The modern process is to use computers as a tool to increase understanding, learning, and perceptual intuition. A computer can in seconds graph a complex function and repeat the same process over and over with new inputs so a student can learn faster and better. I believe computers can be used the same way for electricians. The Table 310.16 calculator, for instance, can be used to better understand how wire size, derating, and overcurrent protection are related by speeding up the process so one can immediately see accurate results with new inputs.

I think this makes better electricians. It also enlightens us and allows us the opportunity to integrate computers into some of our tasks. I believe the NFPA should set up a department that accepts and evaluates, and endorses software that makes using the Code easier and faster.

It is in this respect that I am creating my next online continuing education course on computer applications for electricians.

Final edits to the Table 310.16 Calculator

This AM I addressed some of the out of range problems and the stop program function. I also, did final edits on the AC and MC Cable special features. I haven't put it online yet, but it looks like I have reached the final version. I will again attempt to get the program to do something abnormal and test it thoroughly before uploading it. That should happen within the next few days.

Type AC and MC Cable exception added to Table 310.16 Calculator

I spent most of the day adding Section 310.15(B)(2)(a) Exception No. 5 to the calculator program. This is where the special 60 per cent derating applies to MC and AC cables. Ambient derating still applies but the over three current carrying conductor derating does not apply as long as there are less than 20 current carrying conductors and each cable has no more than 3 current carrying conductors. There is one problem, though. The Code does not specify 90 degree insulation for the Type MC cable conductors but does so for the Type AC conductors.

Here is the exception:
310.15(B)(2)(a)
Exception No. 5: Adjustment factors shall not apply to
Type AC cable or to Type MC cable without an overall
outer jacket under the following conditions:
(1) Each cable has not more than three current-carrying
conductors.
(2) The conductors are 12 AWG copper.
(3) Not more than 20 current-carrying conductors are
bundled, stacked, or supported on “bridle rings.”
A 60 percent adjustment factor shall be applied where the
current-carrying conductors in these cables that are
stacked or bundled longer than 600 mm (24 in.) without
maintaining spacing exceeds 20.

Another day at computers, pipe tobacco, grinding coffee, and Calculus

I started the day by adding some code to the Table 310.16 Calculator. It didn’t have any check entry code and sure as anything some one will raise holy cain if they enter negative amperes and come up with an answer. So I added some dumb and dumber code to make sure negative numbers and letters cannot be entered. There are also some code that checks to make sure the maximum ampacities given in Table 310.16 are not exceeded. But I am sure there are other places where some form of concoction of entry will produce some ridiculous output that I have not found. So be it.

So what about the pipe smoking? I quit smoking pipes over 20 years ago, but have always had an affinity for the smell of good pipe tobacco. I stopped by our one and only genuine pipe and tobacco shop in Fairbanks owned by Dave Shaw and bought a small pipe and some of his famous Black Bear tobacco mix and some Black Vanilla mix. I also ordered a couple of Kirsten pipes from the shop in Seattle. I bought my first Kirsten pipe in about 1970 while working at Singer Kearfott in Little Falls, New Jersey when I was working my way through college. I was going to teach math after college, but after finding out I was making more than my professors on my night job, I just kept on going for the electrical career. Electrical covers a wide range of work, too say the least, and the pay is usually very good. I suppose I was just not dedicated enough to be a teacher or mathematician. Of course, graduating college with a wife and two kids had a lot to do with it. It was always a balancing act, and the electrical with the money won. Also, in general, mathematicians have always been as poor as church mice.

Now, about the Calculus. I studied Calculus over 30 years ago, but have always wanted to study it more. So I ordered Thomas' Calculus over the Internet thinking I would get the same book we used 30 years ago. Well, things certainly have changed. This new book incorporates computers, graphing calculators, and Mathematica and Maple software. Just to add some more variety, I also purchased Stewart’s Calculus from the University of Alaska Bookstore. I think I would just love to go back to school at the University of Washington and study just one subject - Math. I really would, but probably won't. The Stewart book has a online calculus course that comes with it. The book cost $156.00 so I guess I was paying for the course, too. It will be interesting to see how they put together an online course.

Now, about the coffee. I bought an individual coffee bean grinder at Fred Meyers and a bag of Star Buck’s coffee beans. Talk about coffee, now that is what I call superb coffee. There is nothing like freshly ground coffee beans for making fresh coffee, and a pipe full of black vanilla!