FLC of motor when HP is not listed

[Luke McCulley]

I am sizing the conductors, overcurrent, and overload protection for a motor. The HP of the motor (3.5), is not listed in the table 430.250 to determine the FLC. I have contacted the manufacturer and was told to calculate everything based of the FLA. Not sure how to determine the FLC that is not listed or if I should calculate using the FLA. Attached is the nameplate of the motor.

 

[charlie b]

Your attachment is not visible, at least not to my computer.

 

[Luke McCulley]

INS class : F
Phase : 3
Rated Voltage : 230/460V
Rated Freq : 60Hz
Rated Effy : 86.5%
Time : cont
Frame : FF165
Ip55 AMB 40c
HP(KW) : 3.5 / (2.55)
Rated current : 7 / 4 A
Rated speed : 3450
Service factor : 1.10
Rated power factor : 92%
Bearings : 6205z/6203z

 

[Besoeker]

Can't think of any reason why you wouldn't use the nameplate data.

 

[Luke McCulley]

From what i've read in the nec, the FLA shouldn't be used to size the conductors, short circuit, ground fault protection.

 

[drktmplr12]

From what i've read in the nec, the FLA shouldn't be used to size the conductors, short circuit, ground fault protection.

overload protection MUST be based on the nameplate FLA.

conductors and short circuit protection wont change from 3.5 to 5 HP, at 460V 3 phase. Run #12's and install a listed motor controller, unless its a long distance where voltage drop must be considered.

OP didn't state the voltage.

 

[Jraef]

overload protection MUST be based on the nameplate FLA.

conductors and short circuit protection wont change from 3.5 to 5 HP, at 460V 3 phase. Run #12's and install a listed motor controller, unless its a long distance where voltage drop must be considered.

OP didn't state the voltage.

Bingo.

This is a somewhat common issue now as EU suppliers send equipment over here. The motors are rated in kW sizes that are common for them, but don't translate to the right HP values as motors over here would have. In this case I suspect that this is a standard 2.2kW 230/400V 50Hz design, so 2.2kW translates to about 3HP mechanically. But when used at 60Hz over here, the speed increases by 20%, so the HP increases by the same amount and since 2.2kW is actually 2.95 HP, a 20% increase actually becomes 3.54HP and they are just rounding down, or because of some tested value or decrease in efficiency.

But to satisfy the NEC requirements for using the charts in Article 430 based on the HP values, not the FLA, you must round up to the nearest HP, so 5HP in this case.

 

[Besoeker]

Bingo.

This is a somewhat common issue now as EU suppliers send equipment over here. The motors are rated in kW sizes that are common for them, but don't translate to the right HP values as motors over here would have. In this case I suspect that this is a standard 2.2kW 230/400V 50Hz design, so 2.2kW translates to about 3HP mechanically. But when used at 60Hz over here, the speed increases by 20%, so the HP increases by the same amount and since 2.2kW is actually 2.95 HP, a 20% increase actually becomes 3.54HP and they are just rounding down, or because of some tested value or decrease in efficiency.

But to satisfy the NEC requirements for using the charts in Article 430 based on the HP values, not the FLA, you must round up to the nearest HP, so 5HP in this case.

Yet more reasons to adopt SI.......

 

[kingpb]

Yet more reasons to adopt SI.......

I agree. A lot easier to relate to kW. I for one am older but not old enough to relate to a horse to work.

 

[don_resqcapt19]

...
But to satisfy the NEC requirements for using the charts in Article 430 based on the HP values, not the FLA, you must round up to the nearest HP, so 5HP in this case.

What section says I have to do it that way? Why can't I interpolate between the values given in the table?

 

[Jraef]

What section says I have to do it that way?

430.6 (A) 1

can't I interpolate between the values given in the table?

Well technically you can under the exceptions in 430.6, but what the OP described didn't fit any off those exceptions.