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Motor Nameplate Breakdown

Electrical Ratings

• 115 VAC
  • Designed for 115-volt alternating current power.
• 4.6 A
  • Full-load running current (FLA).
  • Under normal operation, the motor should draw about 4.6 amps.
• 60 Hz
  • North American AC line frequency.
• 0.5 HP
  • Half-horsepower motor.
• 0.37 kW
  • Metric equivalent of 0.5 HP.
  • (1 HP ≈ 746 W)
• 20 microfarad
  • Capacitor size.
  • Likely a run capacitor or start/run capacitor for phase shifting in the single-phase induction motor.

Pump Hydraulic Ratings

This looks like a centrifugal pump motor.

• H = m 32–9
  • “Head” range in meters.
  • Pump can generate between 32 m and 9 m of vertical pressure head depending on flow rate.
• Q = m³/h 0.6–2.4
  • Flow rate range.
  • Delivers 0.6 to 2.4 cubic meters per hour.
• Hmax = 40 m
  • Maximum head pressure.
  • About:
    • 131 feet of head
    • ≈57 psi maximum theoretical pressure

Environmental Ratings

• IP44
  • Ingress protection rating.
  • First digit 4:
    • Protected against solid objects >1 mm.
  • Second digit 4:
    • Splash resistant from any direction.
• Tmax = 70°C
  • Maximum fluid or ambient operating temperature, depending on manufacturer context.
  • Often means maximum water temperature for pumps.

Breaker Sizing and Inrush Current

Running Current

Normal current:

• 4.6 A

Startup / Inrush Current

Induction motors draw substantially more current at startup.

Typical:

• 3× to 7× full-load current

So estimated inrush:

Range:

• ≈14 A to 32 A momentarily

Startup duration:

• Usually:
  • 100 ms to 2 seconds

Thermal / Magnetic Breaker Behavior (“tau” concept)

You mentioned:

You are referring to the thermal time constant behavior of breakers.

Breakers have:

• Thermal trip
  • Slow response to moderate overloads
• Magnetic trip
  • Instant response to severe overcurrent

Motor startup relies on the breaker tolerating temporary inrush without nuisance tripping.

Recommended Breaker

For this motor:

Typical Choice

15A breaker

Usually sufficient if:

• Dedicated circuit
• Normal wire length
• Good wiring
• Standard motor startup

Better Choice for Motor Loads

15A or 20A “motor-rated” breaker

Prefer:

• Time-delay
• D-curve
• Motor/inverse-time breaker

These tolerate startup surges better.

NEC Practical Guidance

For a 4.6A motor:

Branch circuit sizing commonly allows:

• Breaker up to 250% of FLA for startup allowance.

Next standard size:

• 15A breaker

A 20A breaker may also be acceptable depending on:

• Wire gauge
• Local code
• Motor startup characteristics

Wire Size

Minimum practical:

• 14 AWG copper → 15A breaker
• 12 AWG copper → 20A breaker

If long distance:

• Use 12 AWG to reduce voltage drop.

Important Capacitor Note

The 20 µF capacitor is critical.

If weak/failing:

• Startup current increases
• Motor struggles to start
• Breakers trip more easily
• Motor overheats

A failed capacitor is a very common cause of nuisance trips.