AC vs. DC: Two Kinds of Power
In this brief instructional video, the presenter addresses new tradespeople and explains the fundamental differences between alternating current (AC) and direct current (DC) as they apply to HVAC systems. AC, which reverses direction periodically, powers most HVAC components such as compressors, blower motors, condenser fan motors, and electric heat strips. DC flows in a single direction and is found in control board modules, sensors, and often originates from a 24 V AC thermostat circuit that is converted to DC for electronic circuitry. The speaker emphasizes why recognizing the type of power matters: the multimeter must be set to the correct AC or DC voltage mode, otherwise readings can be misleading and cause misdiagnosis. He advises technicians to pause before testing, identify the component, consult wiring diagrams, and select the appropriate meter setting, thereby improving diagnostic accuracy and safety.
