Component Definitions:

Air handler: This is the indoor section of a heat pump or electric heat system. They are usually located in a mechanical closet, attic space or crawl space.

Blower assembly: Located in the indoor section, this is what moves the air inside the home or building.

Blower motor: The motor which drives the blower wheel.

Blower wheel: Attached to the blower motor and located inside the blower assembly. This is often called a squirrel cage. Consists of curved blades which scoop the air and then force it out of the unit.

Breaker: Breakers are installed to protect valuable components by stopping the flow of electricity to the component in the event of excessive amperage.

Capacitors: A capacitor in HVAC is used to assist motors with starting up and running. They provide a discharge of electricity into the circuit when the voltage drops within that circuit.

Central Air: This is a broad term used in the trade to describe a system that conditions an entire building or home.  There are many system types that fall into this category.

Condensing coil: This is where refrigerant gas is condensing into a liquid. When it does so, it releases heat.  On a heat pump system, the condensing of gas takes place on the outside during the cooling cycle and on the inside during the heating cycle.

Condensing unit: This is used to describe the outdoor section of an electric or gas heat system.

Contactor and relay: Contactors and relays are switches that allow the control circuit to turn on and off various components of the HVAC system. Just about everything in the HVAC system is powered through a contactor or relay and they are the most common item to fail. The control system is usually going to be a low voltage circuit (24 volts) and the contactor or relay will provide the high voltage (120 or 240 volts) to the actual component.

Defrost cycle: Heat pump systems will freeze up during the heating season and they go through a defrost cycle as needed to prevent the system from malfunctioning. When a heat pump goes into a defrost cycle it should cause the electric heating elements in the air handler to come on.

Drains: See Condensate drains.

Duct(s): Ducting can made of many types of materials while it’s purpose is to direct the conditioned air to the desired locations. Duct work should be insulated so that the maximum amount of heat transfer takes place in the home or building instead of the attic or crawl space.

Electric Heat system:  A system that does not use a gas furnace or heat pump to provide heat. Instead it uses electric heating elements for the heating.

Electronic air cleaner: There are several distinct types of electronic air cleaners and the simplest way to understand them is to think of them as a static electricity device. The air is charged as it passes through the cleaner and the particulate that we want to trap in the filter is attracted to the filter media. This results in a much higher filtration rate.

Energy recovery ventilator: This piece of equipment brings fresh outdoor air into the home and pushes air out at the same time. This helps to maintain healthy indoor air quality. What is unique about them is that the air is made to pass over a large media (think of it as a heat absorbing sponge) and the media rotates while the air runs through it. This conditions the outside air so that the air condition system does not need to run as often when trying to replace the stale air inside the home.  Larger versions are used commercially but they are called outdoor air units.

Envelope: This is a fancy way of defining the interior of a home or building. It is said that the envelope of a structure should be under a positive pressure to help maintain healthy indoor air quality.

Evaporator coil: This is where liquid refrigerant is caused to evaporate. When it does so, it absorbs heat. On a heat pump system, the evaporation of gas takes place on the inside during the cooling cycle and on the outside during the heating cycle.

Fan coil unit: Normally this is used to define an air-handler in a commercial application but sometimes we use this term for residential applications, just to keep things complicated.

Fuse: Fuses are installed to protect valuable components by stopping the flow of electricity to the component in the event of excessive amperage.

Gas furnace: This is the indoor section of an air conditioning system which uses gas for heating. They are usually located in a mechanical closet, attic space or crawl space.

Gas Valve: Used in gas furnaces and boilers, a gas valve is a component that controls the flow of gas through the heat exchanger. This valve is controlled by the system low voltage control circuit. The gas line which supplies gas to the unit is also equipped with a gas valve which is used to shut the gas off when needed for repair or replacement of the furnace.

Germicidal UV light:  UV light bulbs installed inside the duct work or the air handler next to the evaporator coil.  Sold as a method of sterilization but they are only effective on the surface area where the light strikes.  Often used to kill mold in an evaporator section.

Heat load: A heat load is the amount of energy needed to condition the air inside a home or building. A heat load calculation is performed to determine the proper size equipment to be installed.

Heat pump: The literal definition is a device that transfers heat from a colder area to a hotter area by means of mechanical energy.  In the trade we define a heat pump as a system that uses the compressor (located in the outdoor section) to both heat and cool a home. A heat pump system is an air conditioning system with a reversing valve. Heat pumps also have electric heating elements in the air handler.

Humidifier: Maintains a prescribed level of humidity by creating a mist or cool steam. Most people are more comfortable when the humidity levels are between 40 to 60%. If it is higher than that it will fell warm or muggy, if it is lower than that it will feel dry.

MERV Rating: Minimum Efficiency Reporting Value (MERV) is a standard that rates the overall effectiveness of air filters. Higher value MERV rating equates to finer filtration, meaning fewer dust particles and other airborne contaminants can pass through the filter.

Outdoor unit: Another trade term used to describe the condensing unit or heat pump unit located outside of the envelope.

Package unit: Not used on homes as often as it is on commercial buildings. A package unit contains both the condensing unit and air handling unit on one large enclosure. They are made with no heat, with electric heat, as a heat pump or with gas heat.

Photo-hydro-ionization: The most effective method of disinfection a building or home envelope. Produces oxidizing plasma which travels throughout the entire envelope. Often used in hospitals and subways as well as homes.

Refrigerant metering device: There are several types of metering devices and the most common in residential systems is the TXV (thermostatic expansion valve.) The metering device provides a pressure drop point and has two distinct purposes. It holds refrigerant back in a condensed state and feeds refrigerant into the evaporator at the correct flow rate.

Relay: See Contactor and relay.

Squirrel cage: An oddly shaped wheel that is driven by a motor. Curved blades pull air into and then force it out of the blower assembly.

Thermostat: This is what tells the equipment to turn on and off. There are several types with the most common being manual, programmable, and wireless.

TXV: See Refrigerant metering device