On an electrical schedule, a circuit is listed as '20A/1P/120V'. What does this designation indicate?
Correct Answer
B) 20 amp, 1 pole, 120 volt circuit
This designation indicates a 20 ampere, single pole, 120 volt circuit. The 'P' refers to poles on the circuit breaker, not phases. A single pole breaker controls one hot conductor.
Why This Is the Correct Answer
The designation '20A/1P/120V' stands for 20 amperes, 1 pole, and 120 volts. In electrical panel schedules, 'P' always refers to the number of poles on the circuit breaker — a single-pole breaker controls one hot conductor at 120V. This is the standard notation used by electricians and contractors when reading panel schedules and electrical drawings. Understanding this distinction is critical for verifying circuit capacity and breaker configuration before rough-in or service work.
Why the Other Options Are Wrong
Option A: 20 amp, 1 pole, 120 watt circuit
Option A incorrectly interprets 'P' as poles but substitutes 'watt' for 'volt.' Voltage (V) and wattage (W) are fundamentally different electrical quantities. Voltage is the potential difference driving current, while wattage is power (V × A). Circuit designations specify voltage, not wattage.
Option C: 20 amp, 1 phase, 120 watt circuit
Option C misreads 'P' as 'phase' instead of 'pole' and also incorrectly substitutes watts for volts. Single-phase circuits are described differently in specifications. 'P' on a breaker schedule always denotes poles, not phase count.
Option D: 20 amp, 1 phase, 120 volt circuit
Option D correctly identifies 120V but misreads '1P' as '1 phase' rather than '1 pole.' While single-pole breakers do operate on single-phase power, the 'P' in panel schedule notation specifically refers to the number of poles on the breaker, not the phase configuration of the supply.
Memory Technique
Remember 'P is for Pole, not Phase' — the breaker has poles, the system has phases. On a schedule, P always counts the breaker poles.
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