I know that I'm supposed to use nominal voltages for load calcs (not the actual measured voltages of the service). But when calculating the specific loads of equipment, which are the correct values to use?
For example, I'm calculating loads for 208/120V service. But the equipment specs are as follows:
Then there's the question of motor loads. Example equipment specs:
It's my understanding that I ignore the current in the specs and use the NEC tables 430.247 - 430.250. Correct? So for a 1/2hp single-phase AC motor, the full-load current from Table 430.248 is 9.8A. But that column lists the voltage as 115V. So which voltage value do I use for the power calculation?
Do I calculate power as: 115V * 9.8A = 1,127VA
In this piece of equipment, I believe the motor is a universal type. Table 430.248 doesn't make a distinction between induction or universal. So every single-phase 1/2hp AC motor is calculated with the same values despite how the motor is designed? Then why do the amperages on the specs/nameplates vary so widely? And what about when the specs list the FLA for the motor?
I realize the difference in these examples are small and probably irrelevant in the overall load calcs, but I want to understand the correct way to do these calculations.
For example, I'm calculating loads for 208/120V service. But the equipment specs are as follows:
Voltage: 110V
Amps: 2A
Watts: 200W
Do I calculate power as: 110V * 2A = 220VAAmps: 2A
Watts: 200W
or as: 120V * 2A = 240VA
Then there's the question of motor loads. Example equipment specs:
Voltage: 120V
Amps: 8A
HP: 1/2
Amps: 8A
HP: 1/2
It's my understanding that I ignore the current in the specs and use the NEC tables 430.247 - 430.250. Correct? So for a 1/2hp single-phase AC motor, the full-load current from Table 430.248 is 9.8A. But that column lists the voltage as 115V. So which voltage value do I use for the power calculation?
Do I calculate power as: 115V * 9.8A = 1,127VA
or as: 120V * 9.8A = 1,176VA
In this piece of equipment, I believe the motor is a universal type. Table 430.248 doesn't make a distinction between induction or universal. So every single-phase 1/2hp AC motor is calculated with the same values despite how the motor is designed? Then why do the amperages on the specs/nameplates vary so widely? And what about when the specs list the FLA for the motor?
I realize the difference in these examples are small and probably irrelevant in the overall load calcs, but I want to understand the correct way to do these calculations.
