The Transformer: Where 24 Volts Comes From
In this instructional video, HVAC instructor Mike Plezia explains to new technicians how the transformer in an HVAC system converts the incoming high line voltage (typically 120 V or 240 V) to the low‑voltage 24 V control circuit used by thermostats, relays, and control boards. He describes the two sides of the transformer—primary (high‑voltage) and secondary (low‑voltage)—and stresses safety when working with the primary side. The video then walks through a practical troubleshooting workflow: measure voltage on both sides, recognize that a healthy primary with no secondary voltage indicates a bad transformer or an open low‑voltage fuse, and consider over‑current conditions as the root cause before replacing the unit. The presenter closes by encouraging viewers to share the knowledge with others.
