How do you size a circuit for multiple motors?
Multiple motors (feeder). Per 430.24, size multiple motor conductors as follows. Multiply the FLC rating of the highest-load motor by 1.25 and add that to the sum of the FLC ratings of all the other motors in the group. That’s your motor load for calculating ampacity.
How do you calculate feeder for multiple motors?
Motor feeder conductor calculations
- 125% of the highest-rated motor FLC [430.17], plus.
- The sum of the FLCs of the other motors (on the same phase), as determined by 430.6(A), plus.
- The ampacity required to supply the other loads on that feeder.
When sizing a conductor for a motor circuit according to NEC 430 what is the minimum size of conductor allowed?
You must size the conductors at 125% of the motor FLC [430.22(A)]. You must size the overloads no more than 115% to 125% of the motor nameplate current rating, depending on the conditions [430.32(A)(1)]. You must size the short-circuit ground-fault protection device from 150% to 300% of the motor FLC [Table 430.52].
What are the OCPD for motors?
OCPDs protect against current in excess of the rated current of the equipment or ampacity of a conductor, whether it’s a motor circuit or not. Normally, the OCPD also handles overloads. But with motor circuits, separate thermal overloads do that.
How many conductors should be installed from the disconnect means in the power panelboard to the motor controller?
You are installing two disconnecting means for motor operation: One for disconnecting the motor and motor controller from the circuit, and one for disconnecting a separate motor control circuit from the power supply.
How do you size a motor controller?
The size of a motor controller is usually related to the maximum current it can provide. Larger current also means having to use larger diameter wires (the smaller the gauge number, the larger the diameter).
What size the conductor is required for a 5hp 230V single-phase motor?
In accordance with Table 430.248, the FLC for a 5-hp, 230V, single-phase motor is 28A. Because there is only one motor, the conductor can be sized in accordance with 430.22. The next step is to multiply the FLC rating of the highest rated motor by 125 percent.
What is the feeder overcurrent protection size?
The feeder overcurrent device must be sized not less than 125% of 184A, 184A x 125% = 230A.
What size branch circuit conductors are required for a 2 horsepower 230 volt single-phase motor?
The minimum rating in amperes for conductors supplying a 2 hp, 230-volt, single-phase motor is 15 amperes (see Figure 2).
What section of code article 430 is used to size the short circuit and ground fault protection for A single motor?
Section 430.52(B) states the motor branch-circuit short-circuit and ground-fault protective device shall be capable of carrying the motor’s starting current. It is important to size fuses and circuit breakers in motor circuits so they open if there is overcurrent because of a short circuit or ground fault.
What section of code article 430 is used to size the ampere rating for the disconnecting means used with A single motor?
4. Section 430.24 refers to 430.6(A) to determine the full-load currents of the motors. Section 430.6(A) requires the ampere rating of a motor to be taken from Article 430 tables where sizing of conductors is concerned. Table 430.248 rates a 5-horsepower single-phase, 230-volt motor full-load current at 28 amperes.
What is the minimum size permitted for Cu conductors supplying A 208V single phase 3 HP motor?
A 10 AWG conductor only has an allowable ampacity of 35A as shown in the 75°C column. The minimum size THHN copper conductors supplying power to a 10-hp, 208V, three-phase motor is 8 AWG (see Figure 3). Many motors are used in a continuous duty application, but not all.