A homeowner is replacing an old garbage disposal. The new disposal has a 1/2 horsepower motor. According to common plumbing practices and electrical codes, what is the minimum typical branch circuit amperage required for a permanently wired garbage disposal operating at 120V?
- A10 Amperes
- B20 Amperes
- C30 Amperes
- D15 Amperes
Show answer & explanationAnswer & explanation
Correct answer: D. 15 Amperes
While many disposals could operate on a 15A circuit, a 1/2 HP disposal often draws around 7-8 amps when running, but starting current can be higher. It's common practice and often code to place disposals on a dedicated 15-amp circuit, or a shared 20-amp circuit with other small appliances. For a minimum *typical* branch circuit, 15A is the standard for a dedicated circuit for a disposal. (Power (W) = Voltage (V) * Amperage (A). For a 1/2 HP motor, 1 HP ≈ 746W, so 0.5 HP ≈ 373W. At 120V, A = W/V = 373/120 ≈ 3.1A running. However, motors have high starting currents and are often rated for higher breakers due to this and safety factors, making 15A a common minimum dedicated circuit.)
Why the other options are wrong
- A. 10 Amperes is generally insufficient for a dedicated garbage disposal circuit due to starting current demands.
- B. 20 Amperes is often used for kitchen small appliance circuits, or for disposals combined with other appliances, but 15A is often sufficient for a dedicated unit.
- C. 30 Amperes is typically reserved for larger appliances like electric clothes dryers or ranges, far exceeding a standard garbage disposal's needs.
Garbage Disposal Circuit
The dedicated electrical branch circuit providing power to a garbage disposal unit, sized to handle its running and starting current demands.
- Typically a 15-amp or 20-amp circuit.
- Often dedicated or shared with other small kitchen appliances.
- Proper sizing prevents tripping breakers and ensures safe operation.
Memory trick: Match the appliance's power to the circuit's might, for a safe and steady light.