FLA VS FLC for motor overload protection

[Jpflex]

This is getting confusing

I thought overload heaters within a motor starter were to be specifically sized according the the motor FULL LOAD CURRENT listed on its label x either 125%, 115% or max 140% whether motor has a temp rise of 40 degrees c or service factor rating BUT NOT

125% of motor full load current looked up on NEC chart for single or polyphase motors?

I will attempt to paste a YouTube video of a vocational instructor using NEC BOOK FLC full load current to calculate overload protection. Is he not wrong?

 

[Jpflex]

Correction to top; I thought overload was to be sized to motor nameplate FULL LOAD AMPS

not full load current from NEC FLC CHART

 

[don_resqcapt19]

The code does not use the term FLA. It only uses full load current

In general 430.22 requires that the conductors be sized at 125% of the full-load current rating, as determined by 430.6(A)(1). 430.6(A)(1) tells you to use the table value for this purpose.
430.6(A)(1) also says we use the table values for the application of 430.52.
430.32(A)(1) says to use the motor nameplate full-load current rating for the overload protection.

As far as I know the FLA and FLC terms were used by some instructors to teach motor circuits, with FLA = nameplate full load current and FLC = code table full load current.

I prefer to use the terms "code or table current" and "nameplate current".

 

[Jpflex]

The code does not use the term FLA. It only uses full load current

In general 430.22 requires that the conductors be sized at 125% of the full-load current rating, as determined by 430.6(A)(1). 430.6(A)(1) tells you to use the table value for this purpose.
430.6(A)(1) also says we use the table values for the application of 430.52.
430.32(A)(1) says to use the motor nameplate full-load current rating for the overload protection.

As far as I know the FLA and FLC terms were used by some instructors to teach motor circuits, with FLA = nameplate full load current and FLC = code table full load current.

I prefer to use the terms "code or table current" and "nameplate current".

Yes but Mike holt did a great job at distinguishing full load current from full load amperes

The ambiguity may be as you have stated, that the NEC book may not be using the term FLC but only full load current

So just to be clear use nameplate full load current x 1.25 percent for overload?

 

[Jpflex]

The video I posted of the professor did not use the nameplate current but the NEC chart and FLC to determine overload current

 

[jim dungar]

The video I posted of the professor did not use the nameplate current but the NEC chart and FLC to determine overload current

Then they fid not follow the directions from any of the manufacturers instructions which is against the NEC.

 

[augie47]

Different manufacturers have different instructions for selection of overload elements and even different methods depending the particular starter involved and the environment of the starter and the motor.
There is no "one size fits all rule"
Here is an example from Schnieder:

https://www.productinfo.schneider-electric.com/nadigest/5c51d645347bdf0001f1f280/Master/17716_MAIN%20(bookmap)_0000062583.xml/$/_17716116_Heading2_2

and one from A-B:

https://literature.rockwellautomation.com/idc/groups/literature/documents/td/592-td010_-en-p.pdf

 

[jim dungar]

Different manufacturers have different instructions for selection of overload elements and even different methods depending the particular starter involved and the environment of the starter and the motor.
There is no "one size fits all rule"
Here is an example from Schnieder:

https://www.productinfo.schneider-electric.com/nadigest/5c51d645347bdf0001f1f280/Master/17716_MAIN%20(bookmap)_0000062583.xml/$/_17716116_Heading2_2

and one from A-B:

https://literature.rockwellautomation.com/idc/groups/literature/documents/td/592-td010_-en-p.pdf

Both of those documents say to get the full load current from the motor.
They say to use the table values for an estimated amount.

 

[don_resqcapt19]

Yes but Mike holt did a great job at distinguishing full load current from full load amperes

The ambiguity may be as you have stated, that the NEC book may not be using the term FLC but only full load current

So just to be clear use nameplate full load current x 1.25 percent for overload?

He is one of the instructors that did that, but I find it misleading and when I teach I use full load code and full load nameplate as there is no confusion that way.
The section I referenced in my earlier post tells you that the overload is based on the current as found on the motor nameplate.

 

[David Castor]

Use the motor nameplate current to size the overload heaters or settings. Use the NEC motor tables to size the conductors and breaker size. I've always treated "Amperes" and "Current" as basically the same thing.