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	Subject - Exam questions David Hyatt 1) What size disconnecting means is required for a 3hp, 230volt, single phase motor? A)20amp B)25amp C)30amp D)40amp 2)What is the min. size EMT conduit permitted which contains the following conductors? 5- #14RHH with outer covering 6- #10THW 5- #12RHW without outer covering 2- #6XHHW 1- #8 Bare copper a)1" B)1 1/4 C)1 1/2 D)2" JimmyDee Looks like an 1 1/2" will do it if my math is correct. Chapter 9, table 1, looking at the EMT chart and 40% fill for conduits with 2 or more conductors we see that 40% of the total area for 1" is .346 sq in; 1 1/4" is .598 sq in; 1 1/2 is .814 sq in and 2" is 1.342 sq in. The following areas of conductors are found in Chapter 9 tables 5 and 8. #14 RHH is .0145 sq in X 5 = .0725 sq in #10 THW is .0333 sq in X 6 = .1998 sq in #12 RHW is .0260 sq in X 5 = .13 sq in #6 XHHW is .0590 sq in X 2 = .118 sq in #8 Bare is .017 sq in X 1 = .017 sq in Adding, the total is .7173 sq in an that is greater than the 1 1/4" area @ 40% but less than the .814 sq in of the 1 1/2" so it would be the 1 1/2" conduit. Now for the other one. (good thing I'm on Spring Break this week) Jim JimmyDee Looks like a 20 amp will do. Not sure I would use one this small but it seems like the code says it is OK. Artical 430.110 says The disconnect is to be at least 115% of the motor's full load amps and in artical 430.148 a 3HP single phase motor's FLA is 17 amps. 115% of 17 amps is 19.55 amps. A little close, but. Jim David Hyatt Jimmy, Some of your values in the tables for question 1 was wrong, I think I have the right answer which is B) 1 1/4, Tom Henry says 1 1/2 also, he has the same values as I do but the answer is different. You definatley knew where to go to find the answer.14RHH with outer covering is .0293 / 10THW is .0243, change these values and see if 1 1/4 will work. As for question 2)I came up with the same answer as you but can you buy a 20amp disconnect? I thought this was a trick question because 30 amp is the smallest you can buy? Thanks for your help, David JimmyDee You are correct about the mistake of the wire size. I just remembered a glitch one of my students found on the #10 THW wire. You are correct about the area of that wire, however, in the early code books of the 2002 printing, which I have, the #10 THW is listed in 2 places with 2 different areas and I am sure that has been changed. The one I used was listed as .0333 sq inches but a little common since would have told me that was not correct. I did screw up on the #14 wire. However, I still come up with .7368 sq in and that is 1 1/2" conduit. I hate this kind of stuff. Yes you are correct about the disconnect size being a 30 amp as the smallest. I got a mind set on a double pole, 20 amp switch, forgetting that they are not HP rated. Maybe I don't hate it too much as I actually had fun showing the world someone that has been around 40+ years in the electrical trade can still make mistakes. Jim David Hyatt Heres what I have in 2002 code: #14RHH with outer covering .0293 X 5= .1465 #10THW .0243 X 6 = .1458 #12RHW without covering .0260 X 5 = .13 #6XHHW .0590 X 2 = .118 #8Bare stranded = .017 _______ .5573 sq. in. table 4 EMT 1 1/4 =.598 would be OK right? JimmyDee You are 100% correct. Jim David Hyatt Tom Henry was wrong on several answers in his new book, about 5 I think. But there are probably 500 questions so I gues thats not bad. I just get so confused when he makes mistakes, I second guess myself until it drives me crazy. I just finished my master calculations practice exam and only missed one. Hope I can do as well on the 17th when I do it for real. Scott Vickrey Good luck on the test David. This is actually a good question. We should do more of these. Maybe one a week. I would recommend one question per topic. Sorry I've been out. I've been repairing storm damage. We had 20 minutes of golf ball hail at AM. A town near by had softball hail.