rg1
Well-known member
This may help you.
NEC
- Thread starter rg1
- Start date
Help Support Professional Engineer & PE Exam Forum:
Stephen2awesome
Well-known member
FPar
Member
rg1
Well-known member
FPar
Member
Last minute clarification from the video regarding nameplate amps and table amps for motors. (If you get confused blame it on Mr rg1 for coming with great info at the last minute lol!)
If full load current for motor "x" is 200amps by the tables but 300amps by the nameplate (In case it's a multispeed motor, high torque motor, or low speed motor ( low speed means less than 1200 rpm per NEC) go with the higher name plate current. If the low speed/high torque/multispeed motor nameplate is 200 amps but according to table is 300 amps go with the higher table current.
Am I right?
If full load current for motor "x" is 200amps by the tables but 300amps by the nameplate (In case it's a multispeed motor, high torque motor, or low speed motor ( low speed means less than 1200 rpm per NEC) go with the higher name plate current. If the low speed/high torque/multispeed motor nameplate is 200 amps but according to table is 300 amps go with the higher table current.
Am I right?
rg1
Well-known member
@FPar This info I had collected long back while surfing when I even did not know what NEC is, so it went in some corner of some folder and I was just going through the stuff I downloaded during preparation and came across it again. In any case I had planned to have look at all dirt at last moment. So that is the explanation for delay.
Coming to the point, IMHO and the I think I am right, we have to always use nameplate value for these specific motors because NEC tables are meant for majority motors and these specialized motors are not covered by NEC in that sense. Comparison is not required. Actually the last sentence of para 430.6.A.1 is explanation to the first sentence of same para. How is that?
Coming to the point, IMHO and the I think I am right, we have to always use nameplate value for these specific motors because NEC tables are meant for majority motors and these specialized motors are not covered by NEC in that sense. Comparison is not required. Actually the last sentence of para 430.6.A.1 is explanation to the first sentence of same para. How is that?
Stephen2awesome
Well-known member
The important thing is to READ THE NEC CAREFULLY! In some situations it will tell you to use nameplate, but in many you should use the NEC values instead. PAY ATTENTION TO 430.6 when it comes to motors!
For example, 430.6.A.1 Exception 3 states that you should use nameplate current instead of horsepower rating to determine FLC for an appliance (remember that a motor might not be considered an appliance) if both nameplate current and horsepower are marked on the device, to prevent confusion between which to use. 430.6.A.2 explicitly states that you should use nameplate rating for computing separate overload protection (a fuse, circuit breaker, etc) for a motor.
In most other circumstances (like sizing conductors, switches, sc/gf protection), it says to use the table FLC instead of the amperage rating, even if the amperage rating is marked on the device. Of course, there is the exception at the end of 430.6.1 -- if your motor is slower than 1200 rpm, high torque, or multispeed, you should use the nameplate instead of the table.
It's very confusing, but you will save yourself a lot of worry if you get it down!
For example, 430.6.A.1 Exception 3 states that you should use nameplate current instead of horsepower rating to determine FLC for an appliance (remember that a motor might not be considered an appliance) if both nameplate current and horsepower are marked on the device, to prevent confusion between which to use. 430.6.A.2 explicitly states that you should use nameplate rating for computing separate overload protection (a fuse, circuit breaker, etc) for a motor.
In most other circumstances (like sizing conductors, switches, sc/gf protection), it says to use the table FLC instead of the amperage rating, even if the amperage rating is marked on the device. Of course, there is the exception at the end of 430.6.1 -- if your motor is slower than 1200 rpm, high torque, or multispeed, you should use the nameplate instead of the table.
It's very confusing, but you will save yourself a lot of worry if you get it down!
