AFUE, SEER2, tonnage, short-cycling — every term that shows up on an HVAC quote, defined in plain English.
Decode the words that show up on HVAC quotes, permits, and inspections
This glossary explains the ratings, parts, design terms, and code language homeowners encounter when comparing repairs, replacements, rebates, and permit requirements. Use it as a quick reference, then confirm project-specific code requirements with the local jurisdiction before major work starts.
Terms to know before replacing equipment
Start here if a quote mentions Manual J, duct design, mechanical permits, or code compliance. These terms help you understand whether an installation is just legal — or actually designed to perform.
Manual J
The standard calculation that sizes HVAC equipment to a home.
Manual S
The method for selecting equipment that matches the Manual J load.
Manual D
The method for designing ducts to deliver the airflow the system needs.
Mechanical Permit
Local approval for qualifying HVAC installation or replacement work.
Code Compliance
Meeting local mechanical, fuel gas, electrical, and safety requirements.
Static Pressure
The resistance to airflow inside the duct system.
A
C
- Capacitor
- A part that stores and delivers the jolt to start motors.
- Code Compliance
- Meeting local mechanical, fuel gas, electrical, and safety requirements.
- Compressor
- The heart of the system that pumps refrigerant; the costliest part.
- Condensate Drain
- The line that carries away water the system removes from the air.
- Condenser (Outdoor Unit)
- The outdoor unit that releases or absorbs heat via refrigerant.
E
H
M
- Manual D (Duct Design)
- The method for designing ducts to deliver the airflow the system needs.
- Manual J (Load Calculation)
- The standard calculation that sizes HVAC equipment to a home.
- Manual S (Equipment Selection)
- The method for selecting equipment that matches the Manual J load.
- Mechanical Permit
- Local approval for qualifying HVAC installation or replacement work.
- MERV (Minimum Efficiency Reporting Value)
- A filter rating; higher MERV captures smaller particles.