HVAC Technician Interview Prep Guide

Walk through the four stages clearly: the compressor increases refrigerant pressure and temperature, the condenser rejects heat as the refrigerant condenses from gas to liquid, the metering device reduces pressure and temperature creating a low-pressure liquid-vapor mix, and the evaporator absorbs heat as the refrigerant evaporates from liquid to gas. Discuss superheat and subcooling measurements, what they indicate about system charge, and how you use them for diagnostics.

Describe a systematic diagnostic approach: verify the thermostat is calling for cooling, check airflow at supply registers, inspect the air filter, measure supply and return air temperatures for proper temperature split of 15-20 degrees Fahrenheit, check refrigerant pressures and compare to manufacturer specifications, inspect the condenser coil for blockage, verify compressor operation with amp draw measurement, and check for duct leakage. Emphasize that you follow a logical sequence rather than guessing.

Share a specific example where the problem was not immediately obvious. Maybe an intermittent fault, a system interaction issue, or a problem caused by building conditions rather than equipment failure. Explain your diagnostic methodology, the tools and measurements you used, how you identified the root cause, and the solution you implemented. Show that you think critically rather than just replacing parts.

Demonstrate heat pump expertise as this is the fastest-growing segment. Explain that heat pumps reverse the refrigeration cycle using a reversing valve to provide both heating and cooling. Describe the defrost cycle: sensors detect frost accumulation on the outdoor coil, the system switches to cooling mode temporarily while the outdoor fan stops to melt frost, supplemental electric heat maintains indoor comfort during defrost. Discuss cold climate heat pump technology with enhanced vapor injection that operates efficiently below zero degrees Fahrenheit.

Discuss EPA Section 608 requirements: never venting refrigerants, using certified recovery equipment, maintaining accurate recovery and disposal records, understanding the phase-out schedule for R-22 and the transition to lower-GWP refrigerants like R-32 and R-454B, and proper recovery cylinder management. Mention your EPA certification type, whether Universal, Type I, II, or III, and your familiarity with the AIM Act requirements affecting refrigerant transitions in 2026.

Cover the key inputs: room-by-room measurement of square footage, window sizes and types, insulation values, construction type, orientation, number of occupants, and local design temperatures. Discuss the importance of proper load calculations for equipment sizing as oversized systems short-cycle, waste energy, and provide poor humidity control. Mention software tools you use like Wrightsoft or CoolCalc and how you verify results against the existing system performance.

Show ethical customer communication. Discuss presenting the repair cost versus replacement cost with honest lifecycle analysis: remaining expected life of the equipment, efficiency gains from a new system with estimated energy savings, availability of parts for the aging unit, and potential rebate and incentive programs. Provide clear options without pressuring. Mention the 50 percent rule as a guideline: if the repair cost exceeds 50 percent of replacement cost and the unit is past its expected life, replacement is usually advisable.

Discuss your familiarity with BAS platforms like Tridium Niagara, Johnson Controls Metasys, or Honeywell platforms, as well as residential smart thermostats like Ecobee and Google Nest. Cover communicating HVAC systems with variable speed technology, zone control strategies, and integration with building management systems. In 2026, understanding IoT-connected HVAC equipment and remote diagnostic capabilities is increasingly expected for commercial technicians.