NEC Motor Load Calculations Example

[@Sincoola27]

I took this guys full prep class a few years ago. Passed my masters exam on the first try thanks to it! great teacher

[@soundman2604]

Very well laid ou,t with Code articles as references. Nice job!

[@electrical1019]

Thank you!

[@jeremyjpegan]

agreed! Thank you for the schooling. Do you do anything on motor controls?

[@electrical1019]

Thank you, it's what our goal is! We're hoping to have some material on controls as well as basic branch wiring up once the fall semester of school is out!

[@stevenwarren206]

The overloads are calculated at nameplate FLA, right? Everything else is calculated from the FLC from from 430 tables , am I right about this?

[@electrical1019]

For field calculations that is correct. These lectures are intended for students taking a licensing exam in Kentucky, in which on the exam typically the FLC is used to calculate overload protection.

[@santiagocid5908]

You are right 👍

[@reynaldomartinez4918]

I find that pretty odd since the motor nameplate FLA is tipically different than the FLC. If the FLC is much higher than the FLA by many amps, then the overload will be set much higher than the FLA.. interesting

[@wesleythorpe7855]

@@electrical1019wouldn’t you use the FLA from the name plate for overload for exam purposes as well? It calls out name plate in the code reference.

[@TheMadhatter0710]

Information is thrown out very thoroughly. Thumbs up!

[@JesusCruz-wt2zp]

Your videos are great. Please do more ..

[@electrical1019]

Thank you! We are always looking to upload new content!

[@daltondelaney9534]

Why do you always use 75C degrees column for motor feeder wire size? (8:30 in video)

[@JV503]

110.14 NEC

[@EbagOmocaigid]

wouldn't the feeder size in step 5 be calculated as THWN-2 like the motor wires? And thus be a number 6 wire rated for 75 AMPS? Great video though, thanks

[@controlsgirl]

Great example!! Way to walk through it!

[@electrical1019]

Thank you!

[@kylecropanese8744]

Thank you so much about to go for my exam shitting bricks this helps so much

[@marmars1081]

Did you pass?

[@Luminous116]

I've noticed you use 75° column for the branch ckt conductor size. However I was told to use 60°C column for circuits rated 100 amperes or less (per NEC 110.14-C) regardless of conductor insulation rating. Was there an exception that I missed?

[@Makitafan]

I'm not sitting in front of my code book but he said all motors are size it 75 degree column. Finger your way through 430 and see if you can find something backing up his statement.

[@mywifesboyfriendisfire]

He used 90°C for the branch circuits since we're told we're running THWN-2 wire to the motors. The *feeders* to the panel main breaker are calculated using the 75°C column for motors.

[@BobbaFett312]

i have same question as others on using 75C when ampacity column. 75C can be used only when terminations are also 75C. why is 75C used here?

[@rigobertoruiz6136]

Amazing video thanks!

[@MensLifestyle1985]

For Step #6, why wouldn't you add 150A to 20A for the remaining motor? Why did you only add the FLC and not the Branch Circuit protection from step #4 like you did for the larger motor?

[@juliorojas7276]

Service factor is 1.4 and the code is 1.5 or grater to be × 125%. If is not 1.5 por greater it should be × 1.15.

[@MrTomObama]

On step #3 if its THWN-2 at 9.5 amps wouldn't the answer be 18 for copper? Or is it 14 because of the temp rating? Confused. I understand how you got the answer for the 65 amps just not the 9.5 amps.

[@narendergodara1992]

EXCELLENT VEDIO👌👌🙏🙏

[@mcarroll598]

When you size breakers for motors, wouldn’t you round down to the next standard circuit breaker size?

[@electrical1019]

430.52 exception number 1 allows us to go up to the next standard size for overprotective devices serving branch circuits for motors; 430.62 does not have this exception, so we have to go down to the next standard size for overcurrent devices serving feeder circuits for motors.

[@mcarroll598]

@@electrical1019 thank you so much

[@mr.write1433]

what nec edition is this ?

[@oscar27ization]

I think you made a small mistake by multiplying your overload protection device with your FULL LOAD CURRENT instead of your FULL LOAD AMP??

[@sekwanmerritt6235]

Yes for step 3 Sizing the Branch Circuit conductor he multiplied a %125 by the value of Overload Protection instead of the instead of the Full Load Current.

[@paulpbe1]

Overload size should be sized by the amperage on the motor name plate not the the FLC table

[@wadetaney8642]

Well put!! Great teacher.

[@mcarroll598]

Wouldn’t you size your OVERLOADS to your FLA on the motor? Not your FLC from the code book?

[@electrical1019]

In the field/"real-world", yes, you would. This video assumes you do not have that information, and is more for those taking a licensing exam rather than practical application.

[@mcarroll598]

@@electrical1019 thanks. One other question. I understand how to size for fuses and breakers but what’s confusing is when you round up or round down. Any explanation would be great. Thank you.

[@electrical1019]

@@mcarroll598 I believe we just responded to that in another comment you left!

[@mcarroll598]

@@electrical1019 thank you

[@hebrewlessons2348]

great great great instruction!

[@thanmaysudev]

Could you please tell me why the 40hp motor doesn't have any starter

[@Tito-nw6te]

How can i get these work sheets ??

[@Mike-ec4zp]

Where does table 430.22(E) fall in these steps? If asked for any of these rating percentages? Answer be helpful

[@electrical1019]

You would only use table 430.22(E) if you are sizing conductors for a motor that is not continuous duty (step 4). The NEC tells us that anytime we use a motor we have to consider it to be for continuous duty unless we meet certain conditions, so we generally speaking don't bring this table up. If you are using this information for real work application, and you consistently work with intermittent use motors like on an elevator, it is very good to know though!

[@Primez8902]

You dont need the FLA to do these calculations?

[@Primez8902]

Im using the 2014 code book

[@electrical1019]

Actually, FLA comes from the motor nameplate. FLC comes from tables 430.248 and 430.250. 430.6(A)(1) requires us to use the FLC from the tables for all calculation other than overload protection rather than the FLA (in this videos we assume that the FLA is not provided and just use the FLC for over overload protection). Hope that helps!

[@kythuatcongnghiep8559]

thank you, very helpfully for me

[@scottdonahue6417]

There is a standard 70 amp breaker by the way

[@aaronwidder9624]

I thought if you rated your ocp at 250% it would be the next "lowest" size breaker or if it's sized at 125% it would be the next "highest" size breaker? Great Info sir! 👍

[@aaronwidder9624]

@@mitcheljames7053 ooo ok, I read over that and understand now. Thanks for the clarification sir! 🫡

[@theonetrueanthonylong1843]

@@mitcheljames7053 Yes, thank you!

[@electrical1019]

It looks like we got beat to the explanation, but yes, Mitchel provided a perfect breakdown of why we are able to go up to the next size breaker!

[@CallmeDr773]

Super helpful! Thank you

[@purpleraptor1183]

I am doing 50 HP [FLC= 65A, 65A*125% = 81.25A got Conductor size AWG 4] and 250 HP [FLC= 302A, 302A*125% = 377.5A got Conductor size AWG 500MCM table 310.16(75 ,Copper)]. For 50 HP - I am doing 65 A * 250% = 162.5 Amp breaker. But from ugly book, for 50 HP size breaker-150A. Same for 250 HP - 302 * 250% = 755 A. Should I not go up and standard size of breaker?

[@johnnyroloff8118]

I think it is because the 250% from Table 430.52(C)(1) is a maximum rating, so the ugly book selects the closest standard size under 250% of the FLC.

[@cevtongooden1836]

Thanks so much send more

[@paasdfasd]

what happens if the motor is 400V AC?

[@danielgriffin2674]

Some guys are just cut out to be teachers, nice job.

[@Kowloonhongkong]

why dont protect the wire?

[@stuffthings9618]

Arent you supposed to calculate the Overload from nameplate amps????

[@Resistculturaldecline]

If the nameplate info is provided, you are to use nameplate for separate overload devices. If nameplate is not given, you're to use table FLC. At least, that how I think I understand it.

[@TheKaracay]

he messed up on overload for big motor other than that I like the way he teaches

[@natename797]

Why is the first wire size not # 18?

[@TheMoody2006]

I'm looking for the same answer. I THINK he made a mistake with the chart (read the AMPS as the wire size) but was technically correct because 14 AWG is the smallest size permissible for a branch circuit.

[@mr.write1433]

FLA not equal to flc? Why put FLC?

[@kentbinaoro9164]

I am now very confused, but anyways I only know things for residential wiring only, I thought 14awg must use 15a breaker to protect the wire

[@Makitafan]

The "test" gave a wire insulation choice that was in the 90 degree C column. So that's why it was chosen.

[@alexramos9459]

So I just did this by calculator and field knowledge on wires and experience wiring things actual amperage it’s 7.7 not 6 learning ohms law helps a lot and makes easy to calculate by using the calculator

[@pingpongpaddlehead]

fascinating

[@jass1989]

Last i checked. 1.4 was less than 1.5 Mis heard him

[@jacobhess3n327]

Yeah I’m confused too. There are inaccuracies throughout the entire video

[@jass1989]

​@jacobhess3n327 I re-watched it. Sf of the motor is 1.4. Code says 1.15 or greater. 1.4 is .35 great then 1.15.

[@orangaharris640]

Beginer here.. dont understand most of it 😅

[@mywifesboyfriendisfire]

Watch it over and over