Also known as a heating, ventilation, and cooling system, an HVAC system offers complete control over your indoor environment. The goal of the system is to provide ample heating, a good indoor air quality, and a reliable air conditioning system into one machine. HVAC is very important in the design of everything from small homes to large industrial buildings. Everything from skyscrapers to aquariums require HVAC systems to regulate the building’s internal systems, so a safe and comfortable temperature and humidity can be maintained at all times.
The majority of HVAC systems are what would be referred to as an individual system, which means that the building is its own enclosed environment. In modern buildings, the design, installation, and control systems are all integrated into one or more HVAC systems. Sometimes the heating, ventilation, and air conditioning all come from separate appliances and need to be combined in the same ductwork. When building a house, the contractor would normally estimate the system’s capacity and select the individual systems. Then he would engineer the system and run ducts to every room. In larger buildings, building service designers, mechanical engineers, and building service engineers work together to analyze and design a specific HVAC system for the building. Specialty mechanical contractors then fabricate the commissioned systems, and then the custom system is installed in the building.
For the most part, residential HVAC systems are not that complex; the system can be broken down into two parts: heating and cooling. The ventilation usually comes when the ducts are installed, but in some cases a separate ventilation system is installed.
The Types HVAC Heating Systems
There are several different types of heating devices that can be used in an HVAC system, but there are two main options: furnaces or heat pumps.
One of the most common heating systems, furnaces (wiki) can be found in homes all over the world. The furnace heats air and uses a motor to propel the air through a series of ducts that go into every part of the house, which then heats the home. Furnaces can use natural gas, propane, heating oil, or electricity to generate heat and send the heat through the system. Depending on the fuel you’re using and the system’s age, a furnace can be anywhere from 59 percent to 98.5 percent fuel-efficient. If you’re using an electric furnace, that number gets even closer to 100 percent. Quite a few furnace systems have an Energy Star certificate. A furnace is a powerful, affordable, and user friendly heating system that can easily be incorporated into an HVAC system. The blower can be loud at times, but the furnace is usually located in the basement, far away from where anyone can hear it operate.
In order for a furnace to become part of an HVAC system, it needs to be hooked up to a forced air system, which distributes the air around the house using a series of ducts. This is one of the most common types of heat distribution systems found in any house, and it is the basis of almost every HVAC system.
A popular modern heating appliance, a heat pump pulls heat from the outside air to warm the inside of the house. Heat pumps can also reverse the process and act as an air conditioner. The versatility and efficiency of heat pumps has made them very popular among users everywhere. Heat pumps can run using electricity or geothermal energy (national geographic link), which means that they both cost very little to run and require little maintenance. One of the perks of using a heat pump is that you never have to refuel it. The device has a life expectancy of over 15 years, so it doesn’t have to be replaced for a long time. Unfortunately, heat pumps can sometimes be expensive to install.
Heat pumps can hook up to forced air systems as well as a radiant heat system. Also called an under-floor heating, radiant heat connects to the central heating system and helps maintain a steady indoor climate. If the under-floor heating system is connected to a heat pump it can also be used for cooling, but it’s primarily used for heating.
HVAC Cooling System
One of the main types of systems that can be incorporated into an HVAC system is a central air conditioner. Reasonably priced and easy to maintain, a central ac unit circulates cool air throughout the home using a system of ducts and registers that are combined with an existing forced air system. The average central ac unit has a lifespan of fifteen to twenty years, so it’s very likely that you won’t have to do any major work on the device for quite a while.
A central air conditioning system will provide the most even cooling throughout the home, and if you already have the ducts installed it can be a cost-effective option. A central air conditioning unit is quiet and convenient to operate. They’re also much more efficient than having a singe window unit in each room. In the long run they cost less, too. A central cooling system operates similarly to a refrigerator and has seven key parts including:
- An Evaporator – A series of cooling coils that removes heat and humidity from the air by using refrigerant. The evaporator is the first thing that incoming air passes through other than a few filters.
- A Blower – Also called a fan, a blower circulates air over an evaporator, dispersing the chilled air and removing some of the captured humidity.
- The Condenser – The condenser is a hot coil that releases the collected heat back into the outside air. The condenser collects the excess heat from the evaporator coils an removes any excess heat from the system.
- The Compressor – A pump that moves refrigerant between the evaporator and the condenser to help chill the indoor air. The compressor keeps the refrigerant cool by moving the heated refrigerant to the condenser where it can be released, thus returning the refrigerant back to it’s chilled state
- The Fan – A fan that blows air over the condenser to dissipate the heat and remove it from the system. The fan is one of the most important parts of the heating system because it is what keeps the entire system cool, so it can efficiently lower the air temperature. If the heat was allowed to remain in the system, the device would just continue to build up heat and not function properly
- The Filter – located in front of the air duct, the filtering unit removes unwanted particles from the air that enters the machine. This helps to reduce the amount of dust, dirt, and allergens in the air, and improve the overall air quality. The filter has to be cleaned every so often, but maintenance is practically non-existent
- The Thermostat – A control system that allows the user to regulate the amount of cool air that is distributed around the house. The thermostat can be located anywhere in the house, and many houses have specific zones set up to control the air temperature in each section of the house.
Along with being a conventional heating system, a heat pump can double as an efficient cooling system. A heat pump can connect to a forced air system and blow hat and cold air to each zone of the house, or it can be used with a radiant heating system built into the walls, floors, and ceilings. The majority of heat pumps that are used for heating and air conditioning are used with a forced air system. Once a forced air distribution system has been installed into the house, almost any type of heater or air conditioner can easily tap into the system. The vents become sort of like the house’s central nervous system, transferring both hot and cool air around the house.
Just as important as heating and air conditioning is ventilation. Ventilation is the process of changing or replacing air in any space to control the temperature, remove moisture, and improve the overall air quality. Ventilation systems are very important because they remove smoke, heat, dust, airborne bacteria, and carbon monoxide from your house and replace it with clean, breathable air. A proper ventilation system is very important in any sized HVAC system, because it directly affects the content of the indoor air quality. Ventilation methods vary between two types: forced and natural.
Also referred to as mechanical ventilation, forced ventilation uses a device like a blower to draw air into the system, distribute it throughout the building, and remove it from the system after a certain amount of time. The ducts in the house that are also used for heating and cooling are used for ventilation. An example of forced circulation outside of an HVAC system is the household ceiling fan (see here), which circulates air within a room.
Natural ventilation is the ventilation of a building with outside air without using ceiling fans or any other mechanical mechanisms. This can be achieved by using an operable window or trickle vent. In extreme climates, opening a window to help achieve thermal comfort may not be possible, so many people prefer to use mechanical ventilation systems. Achieving a constant indoor temperature with an open window can be difficult, unless you want the inside of you house to be the same temperature as the outside. Opening a window while your heater or AC is running is not recommended (more tips).
How does a HVAC work?
Watch this youtube movie to understand everything of HVAC systems and how they work.