Electric Motor Fuse Sizing Chart

Read horizontally to the right until the distance is as great or greater than your installation.

Electric motor fuse sizing chart. The maximum safe current limit is 80 of the rated size of breaker except some motors. 8 branch circuit fuse size individual motor load with fuse overload protection no starter overload relays. A motors with 1 15 service factor or temperature rise not over 40 degrees c size fuses at not more than 125 of the motor nameplate current rating. B best protection is obtained by measuring motor running.

Yet for many cases this fuse amp rating selection is smaller than the maximums allowed per columns 5 or 6 430 52. This fuse sizing is normally large enough to allow the overload protective device to operate on overloads without opening the fuse. Keep in mind that the breaker size should not increase the max amperage rating of cable and wire. This fuse sizing is normally large enough to allow the.

Chart to determine fuse breaker and wire sizes for electric motors for single phase a c. Fuse ratings for motors with special characteristics may need to vary from given values. The wire breaker and fuse sizes are provided as a reference for the installer and are based on the 1996 national electrical code. Tection for motor branch circuits 430 52 but typically are not the maximum allowed.

430 250 covering standard speed ac motors with normal torque characteristics. The following table gives wire breaker and fuse sizes based on horsepower voltage and phase. Select fuse or breaker size from column 3 or 4. Single phase voltages are usually 115v or 120v while three phase voltages are typically 208v 230v or 480v.

Heater coils provide a delay and open the circuit if the average current over a period of time is greater than the circuit is designed for. Select motor size from horsepower column making certain you are in the correct voltage. Amperes enter the maximum current in amps that will flow through the circuit. In some cases this smaller amp rating.

Below is the given chart showing the of max current rating of breaker size for different types of load currents. Motors are usually protected by both fuses or circuit breakers and by heater coils in a magnetic starter. The largest size fuse shown in the chart is the 5ag or midget a name adopted from its use by the electrical industry and the national electrical code range which normally recognizes fuses of 9 16 x 2 as the smallest standard fuse in use. Motor full load amps are taken from motors currently used by champion.

Circuit breaker size and amps charts. Fuses open the circuit quickly in case of a massive overload or short circuit. For motors it is recommended to multiply the nameplate fla by 1 25 for wire sizing.