Energy Assessment and Instrumentation
What the exam expects
Energy assessments range from a walkthrough to an investment-grade audit. ASHRAE 211 defines commercial audit levels; Level 1 is a screening walkthrough, Level 2 adds detailed surveys and analysis, and Level 3 adds rigorous engineering and financial analysis. Know instruments: power meters, data loggers, ultrasonic flow meters, infrared cameras, combustion analyzers, balometers, anemometers, and light meters. Measurement accuracy, calibration, sampling, and safe access matter. Spot readings may miss duty cycles, so logging over representative periods is preferred.
Traps
Treating a single spot measurement as an annual average is a common mistake. Another is ignoring power factor when calculating kW from amps and volts, or using nameplate data instead of measured load. Watch instrument range and accuracy, especially at low load.
Worked example
A three-phase 480 V motor draws 40 A at 0.85 power factor. Input kW = 1.732 x 480 x 40 x 0.85 / 1,000 = 28.3 kW. If it runs 4,000 hours per year, energy is 113,200 kWh. Multiplying 480 x 40 x 1.732 without power factor would overstate the load.