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Hey Jim,

I am a 9 year apprentice in Oklahoma. I have two questions that i need explained to me!! Question #1 My whole career i have been taught to memorize the 90 degree wire column and according to your study guide i use 60 for under 100amps and so on. It makes perfect sense to me but when would i ever use the 90 degree column again?

 Question #2  I dont understand the reason behind why we bond the neutrals and grounds in the main service in a house? It makes more sense to keep them separate but they are terminated at the same place in the meter base. I have been told by other electricians that all other sub panels after that need to be seperated?  



I am so glad you asked and thank you for studying with Electrical Exam Academy.

I just recently demoed an old cooling tower and wired a new cooling tower in it's place atop a 17 story condo in Manchester NH.

Here is what we found 

The old cooling tower had two, 3phase, 480 volt, 10 HP motors

The new had two, 3phase, 480 volt, 25 HP motors.

The conductors for both motors came up through the roof in a single 1 1/2" conduit. This means I have 6 current carrying conductors in the conduit. 

They originally wired one motor with number 8 THHN and one motor with number 6 THHN. 

I want to reuse the conductors if possible.

Table 430.250

25 HP = 34 amps

430.22 single motor continuous use = 125%

34 amps x 1.25 = 42.5 amps

Table 310.15(B)16

Here it is! The motor and equipment are less than 100 amps so I will use the 60° column to find a conductor that will carry 42.5 amps.


But wait there is more. Remember I had 6 current carrying conductors in the conduit coming up. I have to adjust my conductor ampacity for more than 3 current carrying conductors.

Table 310.15(B)3(a)

6 conductors = 80% 

Now here is the good part. I don't have to adjust from the 60° column of the table, the code allows us to adjust from the 90° column.

So #6 = 75 amp in the 90° column

75 amps x .8 = 60 amps

This is great news to me because I only have to replace the # 8 feeds coming from below.

The moral of the story is you only use the 90° column for ampacity adjustments or temperature corrections. Other then that you shall use the 60° and 75° column for 100 amps and less and above 100 amps respectively.


The reason that the grounding electrode conductor is tied to the neutral at the first point of disconnect and floated everywhere else is this.

When a ground fault happens as in the ungrounded conductor touching something that is grounded. That massive current as a result is not trying to get to the actual earth ground it is trying to get back to the source (the utility neutral)!

So we give the fault current a direct path (with the equipment grounding conductor) to get back to the first point of disconnect where it is bonded to the neutral. You can imagine if all the panels were bonded ground and neutral how much longer it would take.

I hope this explains a little.


Jim Smith

Josh: ok let me get this straight! everytime i use 4 or more conductors in a raceway and derate my wire i use the 90degree column? 


This means typically you will only have 4 circuits in one conduit no matter what size conduit. If you have more you shall increase the wire size.

Say you have 4 circuits or 8 current carrying conductors in a conduit. Table 310.15(B)(3)(a) says you shall adjust the ampacity of the conductors 70%

#12 THHN is rated for 30 amps. Notice we use the 90° column.

30 amps x .7 = 21 amps

That's how we do it. If you need more 20 amp circuits in a conduit run then we use #10's and possibly bigger conduit.


Josh: thank you

Hi Jim,


I am looking for anything to help prepare my fiancé for the NEC. He is a fiber technician now and has been working with licensed electricians here in California. He wants to be certified and for our anniversary, I wanted to get him all the things he would need to get him prepared for the test. I don’t want to keep asking him what it all means, considering I’m in Medical billing software and know nothing about this area of work. Would he start as a journeyman? Any suggestions on where I would begin to help him get to where he should be and be supportive.


Any advice or suggestions would be helpful.

Thank you,


Thank you for reaching out. 

The first thing needed in the license process is to fill out the application. Once the application is on file you will receive an approval letter letting you know you are eligible for the Journeyman or master exam. 

I find this step very difficult for many students so anything you can do would be very helpful. You can find the application on the electrical board website for your area.

Once you have been approved you have one year to take the exam.

That's when the study begins.


Jim Smith

Thank you so very much for your reply. I will start the process with him and study with him. I was looking over your website and even electricians on reddit were saying your course was extremely helpful. I can't wait to get started.


Yes! When you get into studying let me know. I usually chat with guys after they have gotten into my book a little and done a few practice exam questions.




if i want to derate 500kcmil do i start in the 75degree column or the 90degree column? 



Hey Josh,

The code allows us to make adjustments for conductor bundling and corrections for ambient temperature from the full allowable ampacity rating of conductors from the 90° table. No matter the size of the conductor as long as the jacket is in fact rates for 90°  i.e... THWN-2



thanks again! i'm testing tomorrow in OKLAHOMA. 


Message: Jim, I work at an open pit copper mine, we work on anything from 100KV substations, to 7200V electric shovels with 4-20 mA signals, not to mention regular shop maintenance with 3 phase 480v to single phase 120/208/240. I am currently trying to move up in my position from diagnostic electrician to certified diagnostic electrician (nothing to do with an actual journeymans test). I am currently not a journeyman but I have over 10 years of experience, due to the wide scope of work here we do some install related jobs (lighting circuits, motor controls, services, panel upgrades), but mining is regulated by MSHA and not OSHA, and most of their inspectors are not too electrical savvy. We do use the NEC and try to follow it as closely as possible, but it is hardly inspected. I am hoping that if I take your study guide it will help me pass the companies test and I also would like to take the journeymens test. Is your information based off of the current NEC? and is it NEC only? not a guide to passing a journeymens test?

Thanks in advance,
Richard Hernandez

I understand the technique, I guess my question is that I saw your website was dated at 2013, and with the current NEC being 2014, I am wondering if you have compensated for any code changes such as the wire sizing table that has changed from previous versions?

Sent from my iPhone

Yes, Electrical Exam Academy Study Guide 2.1 is up to date with relevant articles from the 2014 NEC.

Message: Will this help me with the New Jersey test




Message: I am the owner of ... and need to take the NEC exam. I have not tested in over 20 years and 53 yrs old so the brain does not respond to reading as quick as it used to. Is your material helpful for me I been electrician for 30 years.


Hello, David 

My goal is to get you deep into your code book with relevant code articles that are on the most recent exams around the country. It's a 100 page book that is easy to read. Honestly the book alone is worth a 60% on your exam. The other 10% (to pass) is up to you but I'm working on it. The thing is 20 questions from your exam may not be in the NEC 2014 and 10 questions may be local laws from the AHJ (authority having jurisdiction). The other 10% you may just not find.




Email Address: 

Message: Trying to find out if I can highlight in my own code book for the CA exam. Also would like clarification on exam registration - I need to submit the SSA form 7050 then include that along with my application and fee. Once all of that is submitted they will send me my test schedule and allow me to register for a date to take the exam? Thanks for the help


I am not sure. Let me look into it and get back to you.

On Dec 22, 2016, at 10:22 PM, Squarespace <> wrote:


Message: Can I ask questions prior to purchase? I flunked the test yesterday and now I have 3 months before I can reapply for another test. I would like to pass the next one with a lot better score. Do you give out practice tests and how many times can they be taken.


Yes the practice quizzes go along with the study guide. 

I recommend DEWALT study guide if you want questions questions questions. 

The book should be studied 3 hours a night for 5-10 days so plan according 

You can take the practice quizzes as much as you like. 



Thank you 


Jim Smith

Message: Hello, seems that i lost the email for the study guide i ordered back on Nov.07-16 (#00190). Is there anything i can do? thank you Robert Hernandez-(


No problem I will just send the PDF to your email. Enjoy!

Let me know if you have any questions.

-Jim Smith

Name: Luan T

State: G

Email Address: lu

Message: I Just Purchased your book on line today. But I would like to receive the hard copy of the book ASAP sending to my home at Luan 14 Mountain View Rd ....., , GA 30012. I will pay any additional cost for the shipping.! Thanks !


Here is the Amazon Link click the blue when you hover over it.