# why we need the code book's motor FLA tables for?



## mike883 (Mar 22, 2016)

for the motors I have done so far,
the motor's nameplate always have the motors FLA (see the pictures)

and my question is why we need the code book's motor FLA tables for if we can easily find the motor FLA in the motor's nameplate?


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## rudiseldb (May 12, 2016)

The FLA are used in your calculations. Not all motors have the same ampacity 


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## Meadow (Jan 14, 2011)

$$$$$$$


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## mike883 (Mar 22, 2016)

AcidTrip said:


> $$$$$$$


??????


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## papaotis (Jun 8, 2013)

quick, i need to know more! i have this class tomorrow!


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## rudiseldb (May 12, 2016)

papaotis said:


> quick, i need to know more! i have this class tomorrow!




What would you like to know?? What code do you use??


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## Anathera (Feb 16, 2016)

You have to use the tables to do your feeder and breaker calculations not the name plate right? Sorry it's been awhile since someone explained it

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## kg7879 (Feb 3, 2014)

It might be different in Canada but the table in the NEC is for short circuit and ground fault protection and the FLA on the name plate is for overload protection.


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## rudiseldb (May 12, 2016)

Anathera said:


> You have to use the tables to do your feeder and breaker calculations not the name plate right? Sorry it's been awhile since someone explained it
> 
> Sent from my SM-G900R4 using Tapatalk




You are correct


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## mike883 (Mar 22, 2016)

Anathera said:


> You have to use the tables to do your feeder and breaker calculations not the name plate right? Sorry it's been awhile since someone explained it
> 
> Sent from my SM-G900R4 using Tapatalk


the code book says, if the table's FLA not matching the motor's nameplate amps 

always using the motor's nameplate amps


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## mike883 (Mar 22, 2016)

kg7879 said:


> It might be different in Canada but the table in the NEC is for short circuit and ground fault protection and the FLA on the name plate is for overload protection.


 please see the picture above


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## emtnut (Mar 1, 2015)

If too many people are on an elevator, would the O/L's trip :blink:

Or does everyone just fall down :laughing:


I'm just messin'....

what do you think would take precedence ... CEC table, or mfr nameplate ?


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## emtnut (Mar 1, 2015)

mike883 said:


> the code book says, if the table's FLA not matching the motor's nameplate amps
> 
> always using the motor's nameplate amps


Yep ... or if the nameplate was hit by a forklift, and unreadable, you can always go to T44 :thumbsup:


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## kg7879 (Feb 3, 2014)

mike883 said:


> please see the picture above


Like I said it is probably different in Canada.


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## rudiseldb (May 12, 2016)

I look at the discussion and think it's great but....its 8:20 in Oregon let's enjoy life too....signing off


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## emtnut (Mar 1, 2015)

mike883 said:


> the code book says, if the table's FLA not matching the motor's nameplate amps
> 
> always using the motor's nameplate amps



Backup the bus here .....

So why exactly are you posting questions you know the answer to ?


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## Meadow (Jan 14, 2011)

mike883 said:


> ??????



90% of the code is to rake in cash, nothing else. IF you have a nameplate FLC lower then the NEC, its lost wire to the manufactures.


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## Meadow (Jan 14, 2011)

emtnut said:


> Backup the bus here .....
> 
> So why exactly are you posting questions you know the answer to ?


Thats an awesome emoji, I like it


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## Meadow (Jan 14, 2011)

Ok, this might clear (muddy) the waters lol:






















I know this is the NEC rather than the CEC, but it might help.


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## rudiseldb (May 12, 2016)

AcidTrip said:


> 90% of the code is to rake in cash, nothing else. IF you have a nameplate FLC lower then the NEC, its lost wire to the manufactures.




I so disagree....your opinion is your...not about cash...about safety


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## rudiseldb (May 12, 2016)

Honestly here...yes the NEC or other state or national documents are put out by insurance companies and fire departments....but yes safety is key 


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## Meadow (Jan 14, 2011)

rudiseldb said:


> I so disagree....your opinion is your...not about cash...about safety




Yup, safety for untrained personnel. And my opinion is based on physics, not random inferences based on feelings. BTW, why do you disagree?


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## Meadow (Jan 14, 2011)

rudiseldb said:


> Honestly here...yes the NEC or other state or national documents are put out by insurance companies and fire departments....but yes safety is key
> 
> 
> Sent from my iPhone using Tapatalk





If safety is so key, why do insurance companies not hold AFCIs as a holly grail?


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## AK_sparky (Aug 13, 2013)

Not sure what you guys do with the NEC, but here in Awesome-land I've never used the tables. I always base it on the nameplate; never had an issue.


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## Meadow (Jan 14, 2011)

AK_sparky said:


> Not sure what you guys do with the NEC, but here in Awesome-land I've never used the tables. I always base it on the nameplate; never had an issue.



Exactly my point, its still safe despite not being to the ultra conservative code.


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## jeremy17 (Oct 6, 2011)

Motor nameplate Amps are used to size overload protection. The nec tables are used to size over current protection and wire size 


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## swimmer (Mar 19, 2011)

Deleted


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## swimmer (Mar 19, 2011)

mike883 said:


> for the motors I have done so far,
> the motor's nameplate always have the motors FLA (see the pictures)
> 
> and my question is why we need the code book's motor FLA tables for if we can easily find the motor FLA in the motor's nameplate?


This is table 430.250 in the NEC.
Here is my take on this. This is by no means a definitive answer.

For both equipment tags shown , the current on the tag is less than the current shown in the table. 

Suppose you have an expensive and efficient 30 hp motor that only takes 30A but it breaks down and you replace with a cheap inefficient 30 hp motor that takes 40A. Since this table is used to determine wire size, you are guaranteed that your old wire will accommodate the new cheap inefficient motor.


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## mike883 (Mar 22, 2016)

jeremy17 said:


> Motor nameplate Amps are used to size overload protection. The nec tables are used to size over current protection and wire size
> 
> 
> Sent from my iPhone using Tapatalk


 first of all,
the amps show on the nameplate is the FLA of the motor
and the formula for wire size is FLA*125%
for overcurrent (time delay fuse) is FLA*175%

I can't see why not we just go by the nameplate current
somebody tells us the reason why we can't do that


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## mike883 (Mar 22, 2016)

swimmer said:


> This is table 430.250 in the NEC.
> Here is my take on this. This is by no means a definitive answer.
> 
> For both equipment tags shown , the current on the tag is less than the current shown in the table.
> ...


 that is why we should always go by the nameplate current
the code book already says that
"if table FLA different from the nameplate current, always go by the nameplate current"


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## jeremy17 (Oct 6, 2011)

mike883 said:


> first of all,
> the amps show on the nameplate is the FLA of the motor
> and the formula for wire size is FLA*125%
> for overcurrent (time delay fuse) is FLA*175%
> ...



But that's not how you size overcurrent motors go by hp and voltage like in tables. The motor get protection from overloads which are by the nameplate. the tables are for overcurrent protection


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## jeremy17 (Oct 6, 2011)

Unless your talking about air conditioning which then you go by nameplate because manufacturers did all the formulas for us. 


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## Anathera (Feb 16, 2016)

mike883 said:


> that is why we should always go by the nameplate current
> the code book already says that
> "if table FLA different from the nameplate current, always go by the nameplate current"


Where is that at though anyone have a reference?


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## jeremy17 (Oct 6, 2011)

Code book doesn't say that. I think it's a misinterpretation of overcurrent protection and overload protection of motors


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## telsa (May 22, 2015)

The modern stencilled nameplate figures are just that: MODERN.

Older motors did NOT have all of the detail that is now NEMA standard -- customary.

The tables are ancient.

They pre-date the detailed stencil era.

You'll see the same transition with HVAC condensers.

Modern units have the critical facts stencilled on them -- max C/B, max fuse, ...

That started up only twenty-five years ago - - or some such.

&&&&&

There are STILL motors that can be placed in service that DON'T conform to NEMA nameplate standards -- namely imports.

So the FLA tables are still needed.

And, they're relevant when you're fiddling with ancient electric motors -- even as a hobbyist.

Could anything be more obvious ?

The word you're hunting for is "Tradition."


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## Family guy (May 15, 2016)

Anathera said:


> Where is that at though anyone have a reference?




It says in 430.6(a)(1) that the tables are to be used for all motors except those that are built for low speeds or high torques, and for multispeed motors. 
The reason given that these motors may have a higher fla for low speed and high torque motors. Multispeed motors have a fla varying with speed. In these cases the nameplate is used.


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## papaotis (Jun 8, 2013)

in class yesterday i was told we MUST use the NEC tables for overcurrent protection no matter what the name plate says. this was from a hvac guy


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## mike883 (Mar 22, 2016)

jeremy17 said:


> Code book doesn't say that. I think it's a misinterpretation of overcurrent protection and overload protection of motors
> 
> 
> Sent from my iPhone using Tapatalk


check the picture


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## jeremy17 (Oct 6, 2011)

mike883 said:


> check the picture




But on all other "typical"(normal speed and torque)motors you go by tables for your overcurrent. Your motor will be protected by the nameplate overload protection


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## RePhase277 (Feb 5, 2008)

For the overload that protects the motor, you use the nameplate rating on the motor, that is what note 1 of table 44 means.

But for sizing the circuit conductors, you use the table. Note 2 is for special specific-use circumstances where a motor isn't simply on and off.


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## Signal1 (Feb 10, 2016)

Mike, you need to look at your own picture, it says right on it "(e.g.for motor protection) always use the values on the motor nameplate"

The tables are used for overcurrent protection (breaker and conductor size) as the tables are a worse case value because one 30HP motor may use less current than a replacement 30HP motor but the wires will be good because they were sized by the book. The 125% that you keep referring to is a "not less than" number not a formula.

The motor overload protection (motor protection, like in your picture) is more specific to the actual motor that is being connected and the nameplate value of that particular motor is what is used to size the overload protection, i.e. the heaters in the starter. A replacement motor of the same HP may need different overload protection.

This has been answered by Jeremy, Swimmer and others. I always encourage apprentices to ask questions, however it would be appreciated if you would pay attention to those that take the time to try and help you.


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