AFUE:
Annual Fuel Utilization Efficiency. A measure of your heating equipment’s heating efficiency. The higher the AFUE%, the more efficient the product. The government’s established minimum AFUE rating for all gas fired heating equipment.

Air Handler:
In a cooling only or heat pump system, an air handler (also called a fan coil depending on installation application) takes the place of an evaporator coil and the variable speed fan from a gas powered furnace. Air handlers extract heat from the air with refrigerant supplied by the air conditioner (or heat pump) in the summer, and move heated air from the heat pump through the home’s ductwork during colder weather.

Balance Point:
An outdoor temperature, usually between 30° F and 45° F, at which a heat pump’s output exactly equals the heating needs of the home. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.

BTU:
British thermal unit. The amount of heat required to raise the temperature of one pound of water by one degree F.

Condensing Unit:
Normally referred to as an air conditioner or heat pump, a condensing unit functions as a heat transfer point. The heated refrigerant returned from the evaporator coil (or air handler/fan coil) located inside the home is sent outside to the air conditioner/heat pump where it is pressurized and sent through the condensing coil. Under high pressure the refrigerant gives up the heat which is dispelled into the outside air, thus cooling the refrigerant to then be sent back inside to the evaporator coil or air handler to repeat the process.

Evaporator Coil:
The portion of a central air conditioning system that is located in the building and connected to the air handler. It functions as the heat transfer point for cooling indoor air. An evaporator coil is comprised of a series of coils filled with refrigerant. As the warm/hot air from the building is returned to the HVAC system it blows through the evaporator coil where the refrigerant filled tubes extract both heat and extra moisture, thus cooling the air. When heating with a heat pump, this processed is reversed to provide heat.

Fan Coil:
(See Air Handler)

Heat Pump:
A heat pump is an all electric unit that cools like an air conditioner using refrigerant. The primary difference is that a heat pump can also provide heat by reversing the cooling process. Heat pumps extract heat from the air as even in cold weather, heat exists in the outside air. They then send the heated refrigerant inside to the coil to heat the indoor air.

Heat Source:
A body of air or liquid from which heat is collected. With heat pumps, the air outside the building is used as the heat source during the heating cycle. For geothermal heat pumps (also referred to as ground or water source) heat is removed from the earth or body of water.

HSPF:
Heating Seasonal Performance Factor. A measure of a heat pump’s heating efficiency. The higher the HSPF, the more efficient the product. There is no government established minimum HSPF rating for heat pumps.

MERV:
The Minimum Efficiency Reporting Value is the standard comparison of the efficiency of an air filter/air cleaner. The MERV scale ranges from 1 (least efficient) to 16 (most efficient), and measures a filter’s ability remove particles from 3 to 10 microns in size.

Packaged System:
A year-round heating and air conditioning system that has all of the components of a normal split system completely encased in one unit. These are located outside the building either on the roof or concrete slab in the yard. Packaged systems can come as cooling only, cooling and gas furnace, heat pump (all electric) or hybrid (electric cooling with dual fuel source heating).

Refrigerant:
A chemical that produces a refrigerating effect while expanding and vaporizing. Most Commercial air conditioning systems contain R-410A, 134A or R22 refrigerant. R-410A is the new government mandate for air conditioners and heat pumps since R-22 has been proven to be dangerous to the environment.

SEER:
Seasonal Energy Efficiency Ratio. A measure of the amount of energy an air conditioner or heat pump requires to cool a certain space. The higher the SEER, the more efficient the product. The government’s established minimum SEER rating for air conditioners manufactured after January 2006 is 13.

Split System:
An air conditioning and heating system with components located both inside and outside the building. This is the most common design for home use.

Supplementary Heat:
The auxiliary or emergency heat, usually electrical resistance heat, provided at temperatures below a heat pump’s balance point.

Ventilator (Air Exchanger):
Part of a complete indoor air quality solution, a ventilator exchanges stale indoor air with fresh air from outside with minimal energy loss regardless of the temperature/humidity level outside.

UV Lamp (UVC):
Part of a complete indoor air quality solution, UV lamps are often mounted in the evaporator coil to kill mold for the purpose of purifying the air and maintaining efficient operation of the coils.

Zoning:
A method of dividing a building into different comfort zones, so each zone can be independently controlled, depending on use and need.

How A Central Air Conditioning System Works
In the typical split system design, the air handler or furnace contains a fan that forces air through the system during both the winter and summer months. A variable speed fan in your air handlers improves heating and cooling efficiency, provides better comfort and indoor air quality control – always get air handler equipped with a variable speed fan!

1) Once indoor air is pulled to the HVAC system. The air is filtered. Quality filters and air cleaners have a high MERV rating (MERV-used to rate the effectiveness of air cleaners), with the ability to filter microscopic elements out of the air. These work much more effectively than normal filters, and some models can even capture and kill the common flu virus! (for more information see: indoor air quality)

2) The air is cooled. The building air is then pulled into the air handler by a variable speed fan, and forced through the evaporator coil. An evaporator coil is a series of piping containing chilled refrigerant from the air conditioner (at a low pressure). The cold piping absorbs heat and causes moisture to condense, thus cooling and dehumidifying the air. This conditioned air is pushed on by the fan while the heated refrigerant is sent back outside to the condensing unit. The refrigerant is pressurized in the condensing unit and a fan blows cooler outside air over the condenser which removes the heat. Then the cycle repeats.

3) Cooled air sent back into the building. After leaving the evaporator coil, the cool, dehumidified air is pushed through the distribution system and back into the building suites. In extremely humid climates, a separate dehumidifier can be installed to remove more humidity from the air than is removed by the evaporator coil.

4) Mold is killed & coil efficiency kept high. In the damp interior of an evaporator coil system, mold can grow which can affect not only the health of your tenants (mold spores in the air), but the health of your HVAC system by decreasing the efficiency of the evaporator coil. UV lamps can be mounted within the evaporator section to prevent this. UV lamps are able to kill and prevent mold from growing, thus keeping your home healthy and your cooling efficiency high.

5) Air is exchanged. HRV AND ERV Ventilators are quite amazing. They are part of complete indoor air quality solutions as they exchange fresh outdoor air for stale indoor air. They are able to do this with minimal loss of energy, and they retain the cooled and dehumidified air your HVAC system worked hard to produce!
How The Above Scenario Changes When Heating
A central air conditioning system is usually combined with a heating system because they share some of the same devices, and of course the same ductwork for distributing conditioned air:

1) The Air is filtered. As with air conditioning, the air is filtered before entering the air handler.

2) The air is heated. The gas (or oil fired) furnace heats the air by igniting (from the pilot) flames and heating a metal unit called the heat exchanger. This heat exchanger then heats the air as it is forced through the system (via the same fan used to bring air through the evaporator coil when cooling in the summer). Note: as mentioned earlier, a variable speed fan in n air handler produces higher efficiency for both heating and cooling. Is able to move at different speeds to efficiently keep air moving through your building even when heating is not required. This improves building comfort and humidity levels when indoor air quality products are in place like air cleaners, humidifiers, UV lamps and ventilators.

3) The air is humidified. Since air is normally dry in the winter, and heating will zap more moisture, a humidifier can be mounted with-in your system to properly humidify the indoor air. This helps the air feel warmer which means you can keep the temperature lower, resolves the health related irritations of dry air, and protects paintings, woodwork and instruments in your space.

4) Air is exchanged. As in the summer, an energy recovery ventilator can exchange outside air with stale indoor air without losing the energy used to heat and humidify the building.