CSLB C-46 Solar ContractorSolar Thermal System InstallationMedium
A solar thermal system installer is connecting the circulating pump to the electrical supply. The pump is rated for 120V AC and draws 1.5 Amperes. Assuming a power factor of 0.8, what is the apparent power consumed by the pump?
- A225 VA
- B180 VA
- C192 Watts
- D144 Watts
Show answer & explanationAnswer & explanation
Correct answer: B. 180 VA
Apparent power (VA) is calculated as Voltage (V) multiplied by Current (A). In this case, 120V * 1.5A = 180 VA. The power factor is used to calculate real power (Watts), not apparent power.
Why the other options are wrong
- A. This is incorrect; it might be 1.5A * 1.5A * 100V or another miscalculation.
- C. This is incorrect; it seems to be 1.5A * 120V * (1 + 0.8) or some other miscalculation.
- D. This is real power (W) if power factor was 1.0 (120*1.5=180, 180*0.8=144).
Apparent Power (VA)
The product of the RMS voltage and RMS current in an AC circuit, measured in Volt-Amperes (VA). It represents the total power flowing in the circuit.
- Includes both real (useful) power and reactive (non-useful) power.
- Calculated as V x A.
- Different from real power (Watts), which considers the power factor.
Memory trick: Apparent power is just V times A, real power needs power factor to play.