HVAC Basics is for HVAC students and working technicians who want clear, practical explanations of how systems work, and how to figure out what is wrong when they do not.
Here you will find theory and troubleshooting lessons: short, image-heavy lessons that explain one idea at a time, plus longer field guides that walk through a system or a diagnostic step by step. Use the search box or a topic below to find something specific, or start with the guides in the next section.
HVAC Basics is written by Jesse, a licensed gas technician working in commercial HVAC. The lessons explain theory the way it shows up on a service call, for students and working technicians. If a lesson is wrong or unclear, use the Contact form and say which post it is.
Start here
If you are new to the site, these guides are a good place to begin:
- The Basic Refrigeration Cycle: How Heat Actually Moves (And What Each Part Does)
- Heat Pump Reversing Valves: How They Work and How to Troubleshoot Them
- Superheat vs. Subcooling: What the Numbers Tell You
- Definitions, a reference for terms used across the lessons.
For hands-on practice, try the Field Simulator, a first-person troubleshooting simulator.
Browse by topic
- Electricity
- Combustion
- Refrigeration
- Airflow
- HVAC Components
- Sequence of Operation
- Wiring Diagrams
- Helpful Tools