HVAC/R & Electrical
This section brings together the HVAC/R and electrical training material on cmolnar.com. The emphasis is on practical understanding: how circuits work, how HVAC controls, motors, capacitors, and pressure switches operate, how to use electrical test equipment, and how to troubleshoot systems safely and logically.
Begin with the complete electrical course, study individual HVAC/R electrical components, develop practical meter skills, or use the troubleshooting material to build a systematic approach to electrical diagnosis.
Build Electrical Knowledge One Section at a Time
The material is arranged so that electrical principles lead naturally into circuit construction, measurements, HVAC controls, motors, capacitors, pressure switches, schematics, and systematic troubleshooting.
Learn the Fundamentals
Understand voltage, current, resistance, circuits, and Ohm’s Law.
Study Components
Learn how relays, transformers, thermostats, motors, capacitors, and pressure switches operate.
Test and Troubleshoot
Use schematics, sequence of operation, and electrical measurements to isolate faults logically.
Choose a Training Path
Use these entry points to begin the complete electrical course, study electric motors, develop troubleshooting skills, review meter use, or browse the broader HVAC/R archive.
Electrical Training
Follow a complete electrical course written for HVAC technicians, from electrical fundamentals through controls, schematics, shop projects, and troubleshooting.
Circuits
Controls
Troubleshooting
Electric Motors in HVAC/R
Study motor construction, single-phase and three-phase motors, compressor windings, ECMs, VFDs, controls, protection, and electrical diagnosis.
Three-Phase
ECMs
VFDs
HVAC Electrical Troubleshooting
Learn a systematic process for finding electrical problems by using circuit operation and measurements instead of guessing which component is defective.
Measurements
Fault Isolation
Diagnosis
How to Use a Meter
Learn how voltage, current, and resistance measurements can be used to determine what an electrical circuit is actually doing.
Current
Resistance
Circuit Tracing
HVAC/R Articles
Browse HVAC/R technical articles, training material, field observations, and other resources related to heating, ventilation, air conditioning, and refrigeration.
Field Notes
Training
HVAC/R
Basic Electrical for the Heating, Ventilation, and Air Conditioning Technician
This course was developed specifically to teach electrical theory and troubleshooting in the context of HVAC/R work. It begins with basic electrical concepts and progresses through real circuits, meter use, relays, transformers, thermostats, schematics, and troubleshooting.
The lessons connect theory to the kinds of circuits and components technicians encounter in the field rather than treating electricity as an isolated academic subject.
New to Electrical Work?
Begin with the course introduction and complete the lessons and shop projects in sequence.
Reviewing a Specific Topic?
Experienced technicians can use the training cards below to move directly to a lesson or component section.
Electrical Training Sections
The material progresses from basic electrical principles through circuits, controls, motors, capacitors, pressure switches, electrical testing, schematics, and systematic troubleshooting.
Electrical Fundamentals
Begin with the nature of electricity and the relationships among voltage, current, and resistance.
Voltage
Current
Ohm’s Law
Understanding Circuits
Build and examine basic, series, and parallel circuits while learning to recognize the source, switch, path, and load.
Series
Parallel
Source to Load
Electrical Test Equipment
Measure voltage, current, and resistance and use those measurements to understand what a circuit is doing.
Current
Resistance
Circuit Tracing
Relays & Controls
Learn how relay coils and contacts control electrical loads and how sequence of operation applies to control circuits.
Contacts
Loads
Sequence
Transformers
Understand how transformers create control voltage and how the primary and secondary sides fit into HVAC control circuits.
Secondary
Control Voltage
Circuits
Thermostats
Study heating and cooling thermostats, sensing elements, control operation, and thermostat wiring.
Cooling
Sensing
Wiring
Electric Motors in HVAC/R
Follow the complete motor section from construction and single-phase operation through compressor windings, ECMs, three-phase motors, VFDs, controls, and diagnosis.
Three-Phase
ECMs
Troubleshooting
- Motor construction and electromagnetic operation
- Motor nameplates and replacement
- Single-phase and capacitor-start motors
- Hermetic compressor motor windings
- ECMs, three-phase motors, and VFDs
- Motor controls, protection, and diagnosis
Capacitors in HVAC/R
Study capacitor construction and operation, run and start applications, dual-run terminals, start-assist components, replacement requirements, safe testing, troubleshooting, and inverter DC bus capacitors.
Start Capacitors
Testing
DC Bus
- Capacitor operation and construction
- Run and dual-run capacitors
- Start capacitors and start-assist components
- Ratings, selection, and replacement
- Testing and troubleshooting
- Inverter DC bus capacitors
Pressure Switches in HVAC/R
Study low- and high-pressure switches, automatic and manual reset, fixed and adjustable controls, cut-in, cut-out, differential, offset settings, electrical testing, and systematic diagnosis.
High Pressure
Cut-In & Cut-Out
Troubleshooting
- Pressure-switch purpose and operation
- Low- and high-pressure controls
- Automatic and manual reset
- Fixed and adjustable switches
- Cut-in, cut-out, differential, and offset
- Electrical testing and systematic diagnosis
Electrical Troubleshooting
Apply electrical principles to practical field diagnosis using the complaint, sequence of operation, measurements, expected operation, and fault isolation.
Measurements
Fault Isolation
Diagnosis
Schematics & Symbols
Use schematic diagrams and electrical symbols to understand circuit operation before troubleshooting equipment in the field.
Symbols
Circuits
Field Use
Learn by Building, Measuring, and Troubleshooting
Electrical theory becomes easier to understand when it is connected to an actual circuit, a useful measurement, or a logical diagnostic process.
Build Circuits
The training course includes shop exercises for basic, series, parallel, relay, and transformer circuits so electrical theory can be connected directly to circuit behavior.
Measure Circuit Operation
Understanding voltage, current, and resistance measurements is fundamental to diagnosing electrical problems rather than simply replacing parts.
Understand HVAC Controls
Relays, transformers, and thermostats form much of the control system found in traditional HVAC equipment. Understanding how each operates makes control troubleshooting considerably easier.
Troubleshoot Logically
Understand the complaint, know the sequence of operation, make measurements, compare them with expected operation, and isolate the fault.
How to Work Through This Material
Begin With Electrical Fundamentals
Learn the relationships among voltage, current, resistance, and power before applying those ideas to complete circuits.
Build and Examine Basic Circuits
Identify the source, switch, path, and load, and compare the operation of basic, series, and parallel circuits.
Develop Meter Skills
Learn to measure voltage, current, and resistance and use those measurements to determine what is happening inside a circuit.
Study HVAC Controls and Components
Learn how relays, transformers, thermostats, motors, capacitors, and pressure switches operate individually and as parts of complete HVAC systems.
Read Schematics and Follow the Sequence of Operation
Use the equipment schematic to determine which components should operate, when they should operate, and what conditions must be present.
Apply a Systematic Troubleshooting Process
Verify the complaint, follow the sequence of operation, make meaningful measurements, compare actual conditions with expected conditions, and isolate the fault.
This Training Collection Will Continue to Grow
The HVAC/R & Electrical material is organized into focused course sections so new lessons can be added without making the main training page difficult to navigate.
Additional electrical components, controls, diagnostic procedures, and shop projects can be incorporated while the existing training remains organized in a consistent sequence.
More HVAC/R and Electrical Resources
Continue into the full electrical course, the motor, capacitor, and pressure-switch lesson series, the troubleshooting guide, or the broader collection of HVAC/R articles and training material.
Complete Electrical Course
Study the full electrical training manual for HVAC/R technicians.
Electric Motors in HVAC/R
Work through the complete 18-lesson motor training section.
Capacitors in HVAC/R
Study run, start, dual-run, start-assist, and inverter DC bus capacitors.
Pressure Switches in HVAC/R
Study pressure-switch operation, adjustment, testing, and diagnosis.
Electrical Troubleshooting
Develop a systematic approach to practical electrical diagnosis.
Articles & Training
Browse technical articles, training material, and field observations.
Explore Air Conditioning and Refrigeration
Continue with the refrigeration cycle, refrigeration theory, major system components, refrigerant piping, and complete air-conditioning systems.