Okay forget everything you know about table 310.15(B)(16) and learn this. If you have a piece of THHN sitting on the table in front you it is rated 90°C.

If you are planning on connecting that conductor to a device or piece of equipment rated for less than 100 amps, that piece of THHN is now sized from the 60° column.

If you are planning on connecting that conductor to a device or piece of equipment rated for 100 amps or more, that piece of THHN is now sized from the 75°C column.

Equipment and devices manufactured for less than 100 amps have terminations rated 60°C. Equipment manufactured for 100 amps have terminations rated for 75°C. You must size your conductor for the weakest link in the system.

Now say you have determined that a receptacle is going to need 20 amp wire. You size the wire from the 60°C column of table 310.15(B)(16) and find #12AWG but now those current carrying conductors are going through a conduit with 20 other current carrying conductors. You will have to derate that wire by 50% but you’re not derating the termination (you have already figured for that) now you’re just derating the conductor which (#12 THHN) is rated for 30 Amps 90°C. Well that brings it down to 15 amps so find the conductor size that 50% at 90°C will be 20 amps.

AuthorJim Smith

Just this week in my study class I had a guy who passed his journeyman electrician exam.

 When I asked him the difference between the day he passed and the day he failed I got a great story out of him.

About 12 days ago a man is cramming the night before a major exam. He is stressing a little and not going to get a very good night sleep. He wakes up in the morning rushing to get out of the house with all his testing material. Locating exactly where the testing facility proves to be difficult. You see in this area the Pearson Vue is on the third floor of an office building right in the middle of downtown. Even when you get inside the building you have to read the signs to find out what floor.

Okay so after circling the block a few times he finds a parking garage and goes in to park. The problem is that this is a metered parking lot so you must go to the kiosk to get your ticket. By this time he is starting to run a bit later than he expected. He goes to the kiosk and slides his credit card in and it does not read it. He doesn't have any change on him so he goes to another kiosk, again no luck so basically he left his car parked in the garage expecting to get a ticket when he returns.

He finally gets into the building and find Pearson Vue. The man is stressed out and since he is running late he goes right in and starts the computer and the questions are coming, and they are hard, and he is gripping, his mind is already mush and he's only an hour into what turns out to be a grueling 4 hours with 15 questions marked for review that he is struggling to get answered, guessing, down to the last second.

Well guess what? He failed. but not to bad he got a 64 and needed a 70.

Now, fast forward 6 days he comes to his first class. I ask him when he plans to test again and he says asap. Ok great. That will prove to be 6 days from now. We start by answering the questions he got wrong on the exam. They don't give you the questions you got wrong but what I mean is we went over questions and I made sure he was doing things the right way.

It turns out my man was having trouble with some series circuit General knowledge questions, how to properly use table 310.15(B)(16), transposing the voltage drop formula, and where to find the motor calculations.

Honestly, everyone has these same issues but none the less his electrician exam was in NH and this is like 75% of that test. 

So here is what we did. I emailed him a copy of the Electrical Exam Academy Study Guide and just told him to go through the table of contents and click and read the chapters he had trouble with. Then in class we ironed out all the formulas and calculations which are not bad if some tells you exactly how to do um. He took the quizzes from the study guide and learned how to use the code book's index. This was all done in three 3 hour classes.

He was able to get a seat at the testing facility that Thursday morning because someone cancelled. Honestly I thought he could have used one more class but Pearson Vue is very busy and hard to get seats. They said they were booked out a month. The last thing we talked about was easy questions.

We talked about missing easy questions because even when he was preparing for the exam he was rushing and missing gimme exam prep questions. I told him that you can't rush the study or the quizzes this is what your trying to learn. On this exam the easy questions are to important. 

It is okay to hurry on the exam but you cant rush past the questions. You have time to read each question 3-4 times if you have to. If you rush past the easy questions and get them wrong you are going fail.

So now the night before the exam. He is confident about the exam location, he is prepared with the meter change, and laid out everything he needs for the morning commute. He is still stressed out but more prepared to answer questions plus he has seen the exam so he knows what to expect. 

Exam day.

He is much less stressed. He arrives at the facility early enough to use the bathroom. When he sat down to the computer he takes a deep breath. His agenda was to answer each question straight through. He muscled through the calculations, had the general knowledge locked, crushed the special occupancy that he was working on from the study guide, used the index like a pro and found tough questions and word for word answers from articles.

No shit 2 1/2 hours later he was done 105 questions with 10 very hard to find questions marked for review. He spent another hour finding those answers and had his license with 30 min to spare.



AuthorJim Smith

Take the time to make extensive hand written notes and highlights on common Tables (electrode conductors, bonding jumpers, Grounding conductors, ovens, fill volumes, ampacities, flexible cord, working spaces, motor full-load, Annex C), Load calculations, swimming pools, bonding and grounding, wiring methods, controls, special occupancies (Hazardous locations), derating ampacities, types of conductors and uses permitted, types of wire ways and uses permitted, devices, equipment, luminaries, definitions, services, motors, generators, transformers, AC and refrigeration, fixed space heating equipment, Annex D and whatever else you can learn in this time right now. You may never get this involved with your code book again in your career. Make the best of it!

AuthorJim Smith


I want to give you an example of good highlighting. I was talking with Luis last night and we were discussing a question about GFCI protection in the bathroom of a health care facility (we were not in the bathroom together hahaha). A question he had recently seen on his exam. He said the answers were

a) Shall be GFCI protected

b) Shall be arc fault protected

c) surge protected

d) he couldn't remember

I asked him if the answer was "none required" because I remember reading this article several weeks ago. Maybe I was studying with someone else I can't remember. I said let's go to the index and look up Health Care Facilities and GFCI.

I only had my 2011 book with me at the time. This book I use for some things but it's not the one I have recently highlighted but whatever let's just find the answer. We both immediately went to 517.20(A) and read the section. Well it was about 11pm and I was fatigued and ended up not even seeing the answer. I told him I would find it and get back to him I knew I had seen it somewhere.

Now fast forward to 5 am i quickly check my 2014 code book before leaving to work. I just went to section 517.20(A) again and what do know the highlighted answer caught my eye right in the next section 517.21

It just goes to show you that a little fatigue and pressure will make an easy answer you know you've read seem really hard to find.

My properly highlighted 2014 code book and knowing the phrase or subject I highlighted weeks ago made all the difference.

Jim Smith


AuthorJim Smith

Well my study guide is first on the list obviously but here is the breakdown.

Electrical Exam Academy Study Guide learn quickly how to answer electrician exam questions. Get comfortable with your NEC book and study recent exam questions from around the country. Highlight relevant keywords for quick associations. How do I know? I talk to guys taking exams from around the country.

If you want question, question, questions my students tell me the DeWalt Electrical Exam Study guide is the best. If you know from taking my electrician practice test what areas are giving you trouble then use this book for repetition in those areas.

If you want detailed information on every possible question then go with Mike Holt. Mike Holt is the man. Mike Holt videos on YouTube are very informative and could give you that Ah Ha moment that make you wrap your head around a problem. Just go to YouTube and search your question.


AuthorJim Smith