HVAC basics

HVAC, the acronym referring to heating, ventilation, and air conditioning pertains to all matters relative to heating and A/C. The A/C side of the system utilizes the evaporation of refrigerant in order to provide cooling. On the other side of things, the heating side relies on a heat pump or furnace to provide heating through the same system. The process is accomplished through warming heat exchanges that end up warming the air, passing though the HVAC system in a business or home. In recent years, heat pumps have been quite popular, though both variants are still used.

The basic idea behind the refrigeration aspects of the system is the removal of heat from air that is being pulled into the system. The compressor causes coolant to warm due to compression. This coolant then passes through the coils, where it effectively dissipates heat, causing it to condense into a liquid. Liquid coolant then passes through an expansion valve, at which point it evaporates into a cold gas. Refrigerant passes through the coils, absorbing the heat from the passing air. This all causes the air to cool itself and then dissipates throughout the area. When in heating mode, either a heat pump, furnace, or variant system is used to provide heat to heat exchanges, which warm the cool air passing through, thus providing hot air to heat the desired area.

Overall, there are four common systems currently in use today. Packaged, zoning, heat pump and fan coil, and furnace and condensing.

In the furnace and condensing system, outside air is pulled inward through the ERV/HRVs that act to replace inside air with fresh resources. The occurs while recovering energy from the inside area prior to disposing of the polluted air outside. The motor and blower wheel serve as the primary mover of air. The heat exchangers in the furnace are then heated, warming the air as it passes through. However, in cooling mode, the furnace remains powered off. As air passes through the coils, the temperature of the air is lowered while humidity is removed. In A/C mode, air condensers remove hot air from inside and exhaust it outside.

Heat pump and fan coil systems work by pulling air from outside though the ERV/HRVs as well. The overall process is quite similar to that of the furnace and condensing system, though the cooling and heating is performed via heat pump, which is generally powered electrically.

In zoning systems, the indoor area is segregated into various zones, each with their own thermostat control. If the system is set to be hotter or cooler than the overall zone tempurature, the system sends to corresponding heating or cooling to that zone.

Packaged systems combine elements of heat pump and fan coil systems into somewhat of a hybrid unit. These types of units can be located outside, in a place where the air condenser would typically be located for a home. Packaged systems may also use combinations of electricity to help with air conditioning and natural gas for heat.