IMC v. RMC

Another good question popped up on the first year homework check in page, it is:

.										What is the difference with RMC and IMC?

Answer:  Bottom line is that IMC has a thinner wall but the steel is processed in a way that makes it stronger, so IMC is lighter yet just as strong. For example 1" IMC weighs 119 lbs/100' while RMC weighs 161 lbs/100'.  They have the same external dimensions so they thread and bend in the same tools and screw into the same fittings.  The thinner wall gives IMC a larger internal diameter which, coupled with an internal coating not always found in RMC, makes it easier to pull wire through.  The manufacturers say that bending IMC is just the same as rigid.  Your results may vary.

Here are a couple of questions posted to the homework form.

The easy one first:
Question: Question number 14 on Lesson 23, im not quite sure what to answer there.

"What does OSHA require the employer to do concerning a written description of an employment grounding conductor program?"

Answer:  read a little more slowly, it is an EQUIPMENT grounding conductor.  The answer to your inquiry is to be found on page 141 in the top third of the right hand column.

Two other great questions came in:
Question: what is the differance between ampere rating and Ampacity? And would a Fuse or any type of OCPD work exactly they same if it was DC going through or AC passing through it?

Answer: Check Article 100 of the code book for the definition of ampacity.  Ampere ratings are within the context of OCPD's at this point,  ampacity ratings have to do with conductors, taking in to account their 'conditions of use'.  More on that later.
 
RMS AC current has the same heating effect as DC.  So if the OCPD is responding to HEAT, it will start to trip at the same time for AC or DC.  Some OCPD's respond to instantaneous current values through magnetic or electronic means, and so the response is based on the peak of the ac waveform and therefore would trip with a lower value of current for RMS AC versus DC.  Another issue this brings up is that AC current drops to zero and changes direction twice a cycle and is therefore 'easier' to interrupt than a like value of DC.  Switches and OCPD's for DC need to be specially rated because of this phenomenon. 

GREAT QUESTIONS.

Fourth Year Motor Control

I have been getting questions related to the Motor Controls homework.  Lessons 7-9 are the issue.  There are holdover questions from the previous text and workbook.  4th year people are getting to those lessons and hitting the brakes.  These questions are answerable but take some inference.  I have responded with, "use google, discuss with journeymen and other apprs."  I have also told them to do the best they can.  The best they can seems to be shaking out to somewhere between 95 and 100% done with 4A.  Another thing for 4th year folks to know is that starting at lesson 10 through the end of the workbook, the questions go back to the normal verbatim in order method much like lessons 1-6.

Fraternally,
Greg Greiner

Fifth Year Fire Alarm

This should be an exciting week, I think you have a great opportunity to walk out of class with an incredible depth of knowledge about fire alarm.  It won't happen if you don't get into it and study, though.  Get green, orange and yellow highlighters and do the codeology method of highlighting.  Get some generic tabs or postit notes for temporary tabs.  You will have plenty of opportunity to highlight pertinent sections in NFPA 72 and tab the book. It will be a great tool if you take the time to do it.

Greg McMurphy
Instructor
LU112-NECA Electrical Training Center
Kennewick, WA 99336

Fifth Year- NOTE WELL-
If you are having problems finding the references to NFPA 72 sections given in the information sheets, look at Annex I of NFPA 72, it is a cross reference from the old numbering scheme to the new one.  You should be looking up and hiliting references in the NFPA 72 as you look through the information sheets.  I am using codeology colors, green, orange and yellow.  I suggest you do the same. You will have a great reference for test taking if you do so.

Greg McMurphy

Rigging Saturday for Fifth Year


You  are going to want work clothes, work shoes, prescription safety glasses if needed.

Electric vehicles....Who knew they have been around as long as gas guzzlers? The LEAF is all about going green, here is a site http://www.teslamotors.com/models that shows just how awesome these machines can be. Three phase power at its finest! Best thing about it, every purchase will require a qualified electrician to facilitate an EVSE install.

Safety Reports

If you have time look around at the AFL-CIO workers memorial day website.
Here is one sheet that shows we still have a way to go.
http://www.aflcio.org/issues/safety/memorial/upload/_07B.pdf

First Year Orientation Night

After Orientation Night be sure to check in weekly on the following form.

https://spreadsheets.google.com/spreadsheet/embeddedform?formkey=dEdWV2J5U0pxb3ByaVc4NTNRaDliM2c6MQ

Year 4 Building Automation

Lesson 14 Building Automation lesson reference is chapter 12, NOT chapter 14.  Nota Bene

4th year PLC lessons

Do the "Questions"
NOT the
"Web and Data Questions"
and NOT
"Problems"

Hands on slots

During your next week of school we will be assigning slots for hands on testing in the summer. Look at your calendars and be ready. The tentative schedule is available to view at http://jatc112.org.

Sent from my handheld call dropping device

Grounding sections went well for 3A. Bring your Test Instruments Text in by mid week, we will be doing a lab that goes with next week's info.

will try to post here the workbook errata for the grounding book.  if it doesn't work you might want to check with Greg M or Sasha for a copy.

NJATC Grounding and Bonding, 2008
Lesson 1, Learning Objectives, Page 1 Question #0
Close the space between the "s" and the "c" in learning objective 5. The word should be "scenario".
Lesson 1, Questions, Page 4 Question #18
The word "described" should be changed to "describe"
Lesson 4, Questions, Page 15-16 Question #3
There is no question #3 in the workbook.
Add a new question 3 as follows:
3. A premises wiring system supplied by an ungrounded service shall have all of the following except a
_____________ conductor at each service.
a. equipment grounding conductor
b. grounding electrode conductor
c. grounding electrode
d. grounded conductor Key 250.24(E)
Lesson 7, Questions, Page 30 Question #6
Change choice "c" to "250.66"
Lesson 7, Questions, Page 32 Question #22
In the instructors guide answer to this question the last line should be changed to the following: "Table 250.66-
266,200 cmil requires 2 AWG".
Lesson 7, Questions, Page 32 Question #22
In the answer given, from step 3 in the answer to step 4 there is a misprint, the answer changes from 266,200 cmil
in step 3 to 255,200 cmil in step 4. The correct answer is 266,200 from step 3.
Lesson 9, Questions, Page 41 Question #1
Change 250.18 to 250.118 in the text.
Lesson 9, Questions, Page 42 Question #9
Add the following text after the word "metallic" and before the ______.
"raceway that is included in the types provided in 250.118?"
Lesson 9, Questions, Page 43 Question #19
Change lighting pane to lighting panelboard.
Lesson 9, Questions, Page 44 Question #26
Revise choice "c" as follows, "Where used to connect equipment where flexibility is NOT necessary after
installation"
Lesson 10, Questions, Page 49 Question #12
Change the word "sparate" to "separate"
Lesson 11, Questions, Page 54 Question #23
Add an Instructor Note.
J210IG.H page 2
INSTRUCTOR NOTE: Calculate as follows:
66360 (cm 2 AWG from Table 8) ÷ 29.1 (multiplier for bare conductor withstand ratings based on ICEA information
Soares Book Chapter 11, also see Table 11-14 column 7)
66360 ÷ 29.1 = 2280.4
Lesson 13, Questions, Page 64 Question #2
Revise choice 5 as "Rod and pipe electrodes"
Lesson 13, Questions, Page 66 Question #18
In the last part of the question, the voltage given is 480Y/222 volt. It should be 480Y/277 volt.
Lesson 15, Questions, Page 78 Question #24
Change choice b. to 208Y/120-volts?
Lesson 21, Questions, Page 118 Question #46
The NEC reference given in the answer is 250.122(F)(1), this is wrong. That NEC section does not exist, it should
be 250.122(F).