HVAC design is based on the concept of mechanical engineering and the principles of thermodynamics. The system operates by controlling the temperature of the air by removing moisture and replenishing oxygen. A good unit will also remove dust, smoke, heat, odors and some gasses. The ventilation in the system uses the air outside to keep the air inside of the home circulating. This prevents the air from stagnating. This greatly aids in the air quality experienced inside your home. The types of ventilation are mechanical, natural and forced.
The modern air conditioning systems integrate all the necessary components into one unit. The specific size of the unit depends on the total square feet of the residence. Often, different types of coolants are used to lower the temperature inside of your home. Ductwork then carries the cooled air throughout the home. This happens when fresh air is pulled into the system by a vent. The exchanger section uses this air to create positive pressure in the air. Typically, the fresh air being drawn in is around ten per cent. The air conditioning is provided by removing the heat. This can be done by convection, radiation or conduction. Elements such as air, water, chemicals and ice are used as refrigerants. These refrigerants are used by a heat pump system. A compressor using a thermodynamic refrigeration cycle circulates the refrigerant throughout the ductwork and cools the home.
A refrigerant cycle consists of an expansion valve, a condensing coil, a compressor and an evaporator coil. The combination of these components are what is required to cool your home. The refrigerant cycle begins in what is called a gaseous state. The compressor is then used until the refrigerant is at a high enough pressure and temperature. The condensing coil takes over when energy is lost and condenses this energy into a liquid phase. The expansion valve is responsible for regulating the refrigerant so it flows at the correct rate. The liquid refrigerant is then sent to a different heat exchanger to evaporate. As the liquid evaporates it goes back to the compressor and the cycle repeats. This causes the heat inside to be transferred outside and cools the home.
Certain climates require a reversing valve in the system. This enables the system to go from heating the home in the winter to keeping it cool in the summer. When the flow of the refrigerant has reversed the cycle for heat pump refrigeration is changed. This is what gives the system the ability to switch from cooling to heating and back again. This means your home can be both cooled and heated by the same piece of equipment with the exact same hardware.