HVACR lessons on your schedule. $15 a lesson.
Short, focused HVACR video lessons from Don Gillis. Watch from the truck, the shop or home. Each lesson includes a quick reference PDF, a quiz and a certificate of completion. Pay once, keep access.
Fundamentals
Start here. How the refrigeration cycle works and how refrigerant behaves.
HVAC Fundamentals: The 4 Main Components
Compressor, condenser, TXV and evaporator: what each one does and how they work together.
Understanding Saturation
See how pressure and temperature lock together at saturation, read a P/T chart, and build the foundation for superheat and subcooling.
The Three Conditions of Refrigerant
Subcooled liquid, saturated mixture, and superheated vapor: where each one lives in the system and how to read it on the job.
Compressors
Know the heart of the system: how it works, how to measure it and how to test it.
Compressor Fundamentals
How compressors work and what they need to survive in the field.
Scroll Compressor Anatomy
Inside a scroll: the parts, how they move, and what fails.
Calculating Compression Ratio
Work the math and use it to judge compressor and system health.
Testing a Single-Phase Compressor with a Multimeter
Read the windings, check every terminal to ground, and spot a tripped overload before you condemn a compressor.
Why Compressors Fail — And How to Prevent It
The six main reasons compressors fail, the 225°F discharge line limit, and how to find the root cause before the new compressor goes in.
Refrigerant Handling & Installation
Do the job right the first time, from recovery to line sets.
Refrigerant Recovery
Recovery basics: equipment, setup and doing it right.
Best Practices: ACR Pipe Sizing
ACR copper, volume vs. velocity, equivalent length, line-set protection, and when and how to use P-traps to get the oil back.
Charging a Suspected Low R-454B System
How to confirm an A/C system is really low on charge, then trim charge R-454B to the data plate target without slugging the compressor.
Airflow
Find the airflow problems that cause comfort complaints and failed equipment.
Static Pressure: What the Blower Is Fighting
Measure return and supply static, add them to get total external static pressure, and find which side is choking the airflow.
Training a whole crew? Ask about team pricing →