Breaker sizing

[infinity]

That is what I thought but I got corrected on this forum. I don't know how to explain 430.52 which clearly states the FLC

So Mike's graphic is incorrect?

 

[Dennis Alwon]

So Mike's graphic is incorrect?

That's my guess.

 

[Dennis Alwon]

All his examples in his test show using the table but that may be because he doesn't give an flc in the question

 

[Dennis Alwon]

So Mike's graphic is incorrect?

What do you think based on what I posted... I am open to being incorrect.

 

[infinity]

Table 430.52 says "Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit and Ground-Fault Protective Devices" and that is based on the FLC. The FLC comes from the tables, the FLA comes from the nameplate. So in the OP he's (assumption) asking about the short circuit and ground fault protection provided by the circuit breaker. I believe that should be calculated just as in the graphic 250% of the FLC from T430.250.

 

[Dennis Alwon]

Isn't the nameplate used for overload devices not the CB feeding the motor as per post #17?

Definitely...but I am confused.

He does seem to make a distinction between FLC and FLA. If that is the case then the overcurrent protective device must be based on the table

 

[Dennis Alwon]

Looks like you posted at the same time... I think we agree.. I stand corrected.... Now to figure out who told me I was wrong....hahaha

 

[infinity]

Now to figure out who told me I was wrong....hahaha

 

[david luchini]

He does seem to make a distinction between FLC and FLA.

FLA isn't a Code term, I think the graphic is just trying to explain when to use the different values.

Section 430.32 for Overload Protection talks about motor Full Load Current.

430.6(A)(1) & (2) explain when to use Table Values vs. Nameplate Values.

 

[SSDriver]

I agree with Mike's graphic that the table in the code is for OCPD/wire size and the motor name plate is for OL's. My understanding was that the code wants the wire/OCPD to be sized off the table which is usually the worst case scenario on amperage for a given motor/HP combination incase someone changes out the motor to a different brand etc. The OL would be sized to protect the motor and can be changed out easily if a motor is swapped, where wire and OCPD would most likely stay the same.

 

[don_resqcapt19]

That is what I thought but I got corrected on this forum. I don't know how to explain 430.52 which clearly states the FLC

FLA and FLA are not NEC terms. The code very clearly says the table currents are used for the conductor sizing and for branch circuit short circuit and ground fault protection. The nameplate current is used only for the selection of the raring of the overload device.
I know FLA and FLC have been used in books and by instructors, but the code does not use the term FLA, only FLC.
That is why, when I teach, I use NEC or Table current for wire size and branch circuit OCPD, and nameplate current for overload protection.

 

[topgone]

The full load current as listed in the code book is what is agreed upon as the figure that will normally be appearing if one uses a certain equipment of that capacity. One is given choices where to get data from, while still in the planning stage. When the equipment is on hand, a detailed review of the figures chosen will always result into an agreement or thereabouts since the figures from the code books are the normal range of values. But we usually tweak settings to perfectly fit the installation requirements, i.e. overload settings to exactly protect what the actual equipment there.

 

[mbrooke]

FLC = Full Load Code

FLA= Full Load Actual

 

[kwired]

35 amp breaker is not a code violation, but you can have higher setting the 2.5 times motor current is a maximum setting for the device, with some ability to increase that if breaker fails to hold during starting.