What size wire and breaker is needed for a single phase 240 volt 5 hp well pump?

Answer 1

The following is for distances up to 50 feet, longer runs would have to take voltage drop into consideration. To give an accurate answer the nameplate amperage should be known. The code book states that a single phase 5 HP motor at 230 volts draws 28 amps. You would need a conductor capable of handling 35 amps (or 125% of the nameplate current). This would be a #8 copper conductor with an insulation factor of 90 degrees C which is good for 45 amps. The fusing for this circuit would be 90 amp non-time delay or 50 amp type D time delay fuse. A two pole breaker for 230 volts would be sized at 70 amps.

Answer 2

It depends on how long the electrical run is. (less than 50 feet, less than 150ft, or etc).

Convert horsepower into kilowatts

40*.746=29,000 watts

Convert watts to amperage:

29000/230v=126 amps

Since it is 3 phase, you divide amperage by approx 1/2 for each leg:

126/2=63 amps for each leg running draw.

You could use (3) 80 amp breakers and 4 ga wire for runs 50 feet or less. 2 ga for longer runs. You may have to use a 100 amp breaker for starting surges.

Check with a professional electrician to make sure this meets code and is adequate. 40hp motor wiring needs advice of an expert!!!!

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The formula you are looking for is I = HP x 745/1.73 x E x 5eff x pf. I = 40 x 746 = 29840. 29840/1.73 x 230 x .87 x .89 = 29840/308 = 97 amps.

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.

A feeder for a motor has to be rated at 125% of the motors full load amps 97 x 125% = 121 amps

A #2 copper conductor with an insulation rating of 90 degrees C is rated at 130 amps.

A breaker for a motor has to be rated at 250% of the motors full load amps 97 x 250% = 242. A three pole 250 amp breaker will be appropiate in this situation.

Answer 3

Answer for UK, Europe and countries running a 50 Hz supply service.

5 HP is equal to 3730 watts. Assuming that the motor is 90% efficient it uses 3730/0.9 or 4144 watts of power. If its power factor is 0.75 it uses 4144/0.75 or 5526 VA so the current is 5526/240 = 23 amps. The wire size would be 4 sq. mm. and the breaker should be set to at least 30 amps.

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Answer for USA, Canada and countries running a 60 Hz supply service.

Motor nameplate data should always be used in any calculations. Without these nameplate values, the code book values presides, where regulations state that a 5 HP motor operating on 230 volts is rated at 28 amps.

Motor feeder conductors have to be rated at 125% of the motors full load amperage. 28 x 125% = 35 amps. This relates to a #8 copper conductor with an insulation factor of 90 degrees C which is rated for 45 amps.

For over current protection, non time delay fuses will be 80 amps, time delay fuses will be 45 amps and the breaker which has to be rated at 250% for motor starting, which can drive the current up to 300% of the motor's full load amps, will be rated at 70 amps.

Answer 4

Wire sizing is based on the amperage needed by the load. The equation used to find amperage when the HP is shown is; A = HP x 746/1.73 x V x %eff x pf. Amps = 25 x 746 = 18650/1.73 x 240 x .87 x .87 = 18650/314 = 60 amps.

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.

Motor feeders have to be rated at 125% of the motors full load amperage. 60 x 125% = 75 amps.

A #4 copper conductor with an insulation rating of 75 or 90 degrees C are both rated at 85 amps.

The breaker has to be 250% of the motors full load amperage 60 x 250% = 150 amps

The breaker will be a three pole 150 amp breaker connected to three #4 copper conductors to operate a 25 HP 240 volt three phase motor.

Answer 5

Assuming 240 volt supply, use 7 amps per HP which gives a current of 35 amps. The wire must be rated at 125% of the current, which is 44 amps. That requires 4 AWG cable or 16 mm2. Use a 60 A breaker.

Answer 6

The rule of thumb for a single phase 240 volt motor is 7 amps per HP. The code book only includes up to 10 HP motors. So 7 x 15 = 105 amps. Motor conductors have to be rated at 125% of the full load amps. 105 x 125% = 131 amps. A #1 copper wire with an insulation factor of 90 degrees C is rated at 140 amps. The breaker for a motor load should be 250 % of the full load amperage. 105 x 250% = 263 amps. The next biggest size breaker up from 200 amps is 300 amps which will work and still be within the electrical code standards. It is for this exact reason that larger size motors are usually three phase and require higher working voltages to reduce the wire size and breaker sizes.

Answer 7

Use #8 copper wire THHN on a 70 amp breaker.

Answer 8

The current is reckoned as 7 amps on a 240 v single-phase motor, and that would need a 1 mm2 wire, or preferably 1.5 mm2 if run for mor than 6 hours per day.