Journeyman Plumber ExamFixtures, Faucets, and Other AppliancesHard
A plumber is installing a new kitchen sink and plans to connect a garbage disposal to it. The local code requires a dedicated circuit for the garbage disposal. If the garbage disposal is rated at 1/2 horsepower, what is the minimum amperage rating for the dedicated branch circuit overcurrent protection, assuming a standard 120-volt supply?
- A10 Amperes
- B30 Amperes
- C20 Amperes
- D15 Amperes
Show answer & explanationAnswer & explanation
Correct answer: C. 20 Amperes
While a 1/2 HP motor might draw around 9-10 amps at full load, plumbing and electrical codes typically require dedicated circuits for garbage disposals to be protected by a 20-amp, 120-volt circuit breaker. This provides a safety margin for starting current and potential overloads.
Why the other options are wrong
- A. 10 Amperes is generally insufficient for a dedicated garbage disposal circuit due to starting current and safety margins.
- B. 30 Amperes is typically for larger appliances like electric water heaters or ranges, and would be excessive and potentially unsafe for a 1/2 HP disposal.
- D. 15 Amperes might be sufficient for very small disposals, but 20 amps is the standard for most residential units to prevent nuisance tripping.
Garbage Disposal Circuit Amperage
The minimum electrical amperage rating required for the dedicated branch circuit providing power to a garbage disposal unit.
- Dedicated circuit required to prevent overloading other circuits.
- Amperage must safely handle starting current and running load.
- Typically 20 Amps for most residential disposals.
Memory trick: Each appliance has its own 'power lane' on the electrical highway.