Demystifying HVAC/R: 20 More Common Terms Every Building Owner Should Know (Part 2)
We’re back with Part 2 of our HVAC/R glossary—breaking down another set of essential terms that help building owners, facility managers, and general contractors make smarter decisions and speak confidently with their service partners.
If you missed Part 1, check it out here for terms like BTU, heat pump, VRF, and superheat. This week, we go even deeper.
1. SEER (Seasonal Energy Efficiency Ratio)
A measure of an air conditioner or heat pump’s efficiency over a typical cooling season. The higher the SEER rating, the more efficient the system.
2. EER (Energy Efficiency Ratio)
Similar to SEER, but calculated using a constant outdoor temperature. It gives a more immediate look at system performance under specific conditions.
3. COP (Coefficient of Performance)
A ratio of useful heating or cooling provided to the energy used. COP is a key efficiency metric—higher numbers indicate better performance.
4. BAS (Building Automation System)
A centralized system that automates the control of HVAC, lighting, security, and other building systems to optimize comfort, efficiency, and performance.
5. Demand Control Ventilation (DCV)
An energy-saving strategy where ventilation is adjusted based on building occupancy using COâ‚‚ or occupancy sensors.
6. Reheat Coil
A device used to warm air that has been cooled and dehumidified. Common in systems that need to tightly control humidity and temperature.
7. Economizer Cycle
Uses outdoor air to cool a building when conditions allow, reducing the need for mechanical cooling and improving efficiency.
8. Thermostatic Expansion Valve (TXV)
A valve that regulates the flow of refrigerant into the evaporator based on system demand. It helps maintain efficiency and protects the compressor.
9. Head Pressure Control
A system or strategy used to manage refrigerant pressure, especially in low ambient temperatures, to ensure proper operation of condensers.
10. Variable Frequency Drive (VFD)
Controls motor speed in pumps and fans, reducing energy use and improving part-load efficiency in HVAC systems.
11. Air Handling Unit (AHU)
A device that conditions and circulates air. Usually includes a blower, heating/cooling elements, filters, and dampers.
12. Direct Expansion (DX) System
A type of cooling system where refrigerant absorbs heat directly from the air (as opposed to chilled water systems).
13. Hydronic System
A heating or cooling system that uses water or a water-glycol mix as the heat transfer medium. Common in radiant heating and chilled water systems.
14. Make-Up Air Unit (MAU)
Introduces fresh, tempered outdoor air into a building to replace exhaust air—often used in commercial kitchens, labs, and process facilities.
15. Plenum
An air compartment (usually above ceilings) where air is distributed before being delivered to or returned from occupied spaces.
16. Zone Control
Allows different areas (zones) of a building to be heated or cooled independently, often using dampers and multiple thermostats.
17. CAV (Constant Air Volume)
A system that delivers a constant airflow at varying temperatures. Less efficient than its counterpart, VAV.
18. VAV (Variable Air Volume)
Delivers varying airflow at constant temperature based on demand—used to improve comfort and energy efficiency.
19. Air Balancing
The process of adjusting HVAC system dampers and controls to ensure consistent airflow and temperature across all zones.
20. Commissioning
A quality assurance process for verifying and documenting that HVAC systems are designed, installed, and operating as intended.
Knowledge Is Power
At Northstar Refrigeration, we believe that informed clients are empowered clients. The more you understand your system and its terminology, the better positioned you are to make sound operational and capital decisions.
Stay tuned for Part 3, where we’ll decode regulatory acronyms, green building certifications, and emerging HVAC/R technologies.
Have questions about a system upgrade or service need? Call us today at (508) 888-3692
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