What is the difference between alternating current (AC) and direct current (DC)?

The key distinction between alternating current (AC) and direct current (DC) lies in the direction of the current flow. AC periodically reverses direction, meaning that the flow of electric charge changes from positive to negative and back again at regular intervals. This characteristic allows AC to be transmitted over long distances with greater efficiency, which is why it is the primary form of electrical power used in homes and buildings, including HVAC systems.

In contrast, DC flows steadily in one direction only. This unidirectional flow is typical of power supplied by batteries, where the electrons move consistently from the negative side to the positive side. This fundamental difference in the way these currents behave is crucial for their applications; AC is generally used for high voltage and long-distance transmission, while DC is often employed for low voltage applications and in devices that require a steady voltage supply.

This understanding is essential in the field of HVAC, as many modern systems and components rely on AC power for their operation, while DC is more common in certain control devices and digital electronics. Recognizing these characteristics aids in selecting the appropriate type of current for various tasks and components within HVAC systems.