What size of wire and breaker do you need for a 10 KW electric furnace?

Answer 1

To answer this question, wire size is rated in the amount of amperage that it can legally carry. The formula to find amperage when the HP is known is I = HP x 746/1.73 x E x %eff x pf.

A standard motor's efficiency between 5 to 100 HP is .84 to .91.

A standard motor's power factor between 10 to 100 HP is .86 to .92.

Amps = 10 x 746 = 7460 = 7460/1.73 x 220 x .84 x .86 = 7460/275 = 27.1 amps.

The electrical code states that a motor conductor has to be rated at 125% of the motors full load amperage. 27.1 x 125% = 33.8

A #8 copper conductor with an insulation factor of 60, 75 or 90 degrees C is rated at 40, 50 and 55 amps respectively.

Answer 2

NEC motor table list this motor as drawing 16 amps, that would require wire size of # 12 copper.(16 amps X1.25=20) The breaker for this motor should be a 40 amp.(16 amps X 2.50=40) This allows for the high starting currents.

Answer 3

The current load of a 10 HP motor should be taken from the motors nameplate. It is this amperage that the wire size is calculated from. The code book states that a 10HP motor draws 50 amps at 230 volts. Motor overload protection of the code states that for 50 amps you need a conductor capacity of 62.5 amps. Fusing at 150 amps, time delay fusing at 90 amps or a breaker of 125 amps. The wire size you would need to wire this motor to code would be #4 copper with a wire insulation factor of 75 or 90 degrees C. This #4 wire capacity is 65 amps.

Answer 4

The breaker sizing will be governed by the size of the motor's full load amps. The wire used to feed the motor is based on the voltage of the motors full load amperage. Either the motor's full load amps or the motor's voltage have to be stated to calculate an answer this question.

Answer 5

i need to know the voltage and if its single phase or three phase

Answer 6

It's 100ft away and its 120 voltage

Answer 7

Three phase motor