Commercial HVAC Glossary

Plain-English explainers for the technical terms, rebates, regulations, and acronyms that show up when you shop for Commercial HVAC systems and services. Each entry links the underlying source, lists the numbers that matter, and points to related concepts.

Air-Side Economizer
The "free cooling" damper that pulls in cool outside air — required by code on most larger commercial units.
ASHRAE Standard 90.1
The national commercial-building energy standard — the rulebook behind the economizer, controls, and efficiency requirements on your job.
BAS / BMS (Building Automation System) & Tridium Niagara
The digital brain that runs commercial HVAC centrally — and the vendor-neutral platform that ties mixed equipment together.
COI (Certificate of Insurance)
The one-page proof of liability coverage every commercial property manager demands before a contractor sets foot on-site.
Commercial Chiller (Air-Cooled vs Water-Cooled)
The central machine that makes chilled water for large buildings — and the air-cooled vs water-cooled choice that drives efficiency.
Commercial Contractor License — Class A vs Class B (the 25-Ton Line)
The state-license tier that legally separates commercial-scale HVAC work from residential — drawn at 25 tons of cooling.
EPA Section 608 Type III Certification
The federal refrigerant credential for low-pressure centrifugal chillers — the line between chiller-capable and residential techs.
IEER (Integrated Energy Efficiency Ratio)
The commercial part-load efficiency rating — the equipment number that matters because rooftop units rarely run at full load.
RTU (Rooftop Unit / Packaged Unit)
The self-contained packaged air conditioner on a commercial roof — the workhorse most light-commercial HVAC work revolves around.
TAB (Test & Balance) and AABC
Independent measurement that proves every zone gets its design airflow — and the certifying body that bans contractor affiliation.
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