Harold Brothers Blog | Harold Brothers Mechanical Contractors

Commercial HVAC and Plumbing Terms

Written by John Flaherty | Feb 18, 2025 4:29:18 PM

When dealing with commercial HVAC (Heating, Ventilation, and Air Conditioning) or plumbing systems, professionals often use technical terminology that can confuse business owners and facility managers. 

This guide breaks down the most common commercial HVAC and plumbing terms with clear definitions to help you better understand these essential systems.

AFUE (Annual Fuel Utilization Efficiency)

Measures how efficiently a furnace converts fuel into heat. A higher AFUE percentage indicates better efficiency.

Air Handler 

An air handler is a unit that circulates and regulates air within a commercial HVAC system, often connected to ductwork.

Auger (Plumber’s Snake)

A flexible tool used to clear clogs in pipes and drains.

Backflow

This is the reverse flow of contaminated water into a clean water supply. A backflow prevention device can prevent backflow.

BMS (Building Management System)

BMS is a centralized control system. It is used to monitor and manage HVAC, lighting, security, and other building systems.

BTU (British Thermal Unit)

A unit of measurement for heat energy. One BTU equals the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit.

CFM (Cubic Feet per Minute)

Measures the volume of air flowing through a space per minute, often used to determine proper ventilation and airflow in commercial HVAC systems.

Chiller

A cooling system that removes heat from a liquid. A chiller is commonly used for large commercial and industrial applications.

Compressor

The component in an air conditioner or heat pump that compresses and circulates refrigerant to facilitate heat exchange.

Condenser Coil

A coil in an air conditioning or refrigeration system that releases absorbed heat to the outside air.

Ductwork

A network of tubes or passages that distributes heated or cooled air throughout a commercial building.

Economizer

A system that uses outside air to reduce the need for mechanical cooling, improving energy efficiency in large buildings.

Evaporator Coil

A coil that absorbs heat from indoor air, allowing the refrigerant to cool the air before it is distributed throughout the building.

Expansion Tank

A small tank that is connected to a water heater to absorb excess pressure from thermal expansion.

Flapper Valve

A rubber or plastic valve inside a toilet tank. A flapper valve controls water flow from the tank to the bowl.

Four Pipe System

A four-pipe HVAC system uses separate piping for hot and chilled water, allowing simultaneous heating and cooling in different zones. This provides greater flexibility and comfort compared to a two-pipe system but at a higher cost.

GPM (Gallons Per Minute)

Measures the flow rate of water, commonly used for faucets, showers, and pumps.

Grease Trap

A plumbing device used in commercial kitchens to intercept fats, oils, and grease before they enter the sewer system.

Greywater

Greywater is wastewater from sinks, showers, and laundry. It can be reused for irrigation or flushing toilets.

Heat Exchanger

This is a component in a furnace that transfers heat from the combustion process to the air that is being circulated through the building.

HVAC Load Calculation

A process used to determine the proper size of an HVAC system based on factors such as square footage, insulation, occupancy, and climate conditions.

Hydronic Heating

A heating system that uses water or another liquid as a heat-transfer medium. Hydronic heating is commonly found in large commercial buildings.

MERV Rating (Minimum Efficiency Reporting Value)

A measurement of air filter efficiency. Higher MERV ratings indicate better filtration of dust, pollen, and other airborne particles.

PSI (Pounds per Square Inch): 

A unit of measurement for water pressure. Higher PSI indicates stronger water pressure in pipes and fixtures.

P-Trap

A curved pipe that is under sinks and drains. It prevents sewer gases from entering the building by trapping a small amount of water.

PVC (Polyvinyl Chloride)

PVC is a common type of plastic piping used in plumbing for drain and vent lines.

Refrigerant

Refrigerant is a chemical compound used in HVAC systems to absorb and release heat. Refrigerant enables the cooling and heating processes.

Return Air

Air that is drawn back into the HVAC system from indoor spaces to be reheated or re-cooled.

SEER (Seasonal Energy Efficiency Ratio)

Indicates the energy efficiency of an air conditioner or heat pump. A higher SEER rating means better efficiency and lower energy costs.

Shut-Off Valve

A shut-off valve is a valve that stops the flow of water to a particular fixture or section of plumbing.

Soldering

The process of joining metal pipes using a heated alloy. This method is commonly used in copper plumbing systems.

Sump Pump

A sump pump is a pump that is installed in basements or mechanical rooms to remove accumulated water and prevent flooding.

T&P Valve (Temperature and Pressure Relief Valve)

A safety valve on water heaters that releases excess pressure or temperature to prevent explosions.

Two Pipe System

A two-pipe HVAC system uses one set of pipes to supply either hot or cold water for heating or cooling, but not both at the same time. It’s a cost-effective solution but requires seasonal switching between heating and cooling modes.

Two-Stage Furnace

A furnace with two levels of heating output. This type of furnace allows for more efficient operation and improved comfort compared to single-stage models.

Vent Stack

A vertical pipe that releases sewer gases outside the building and maintains proper drainage pressure.

VRF (Variable Refrigerant Flow)

A highly efficient HVAC technology that uses refrigerant to provide simultaneous heating and cooling to different zones within a commercial building.

Water Hammer

A loud banging noise in pipes is caused by sudden changes in water flow, often due to fast-closing valves or high pressure.

Zoning System

A system that divides a building into different climate-controlled areas, allowing for customized heating and cooling settings in various spaces.

We Hope These Terms Will Help You Have a Greater Understanding of Your HVAC and Plumbing Equipment

 

Understanding commercial HVAC and plumbing terminology can help business owners and facility managers communicate effectively with professionals and make informed decisions about their systems.

If you are troubleshooting an issue or considering an upgrade, knowing these key terms will empower you to take control of the comfort and efficiency of your building.
If you have heard a term that isn't on this list that you need some help clarifying, please reach out to us.