The Essential Parts of an HVAC System

HVAC Los Angeles control temperatures and ventilation in homes, offices, apartment buildings, hospitals and other large structures. They’re also found in vehicles and ships.

A central system has an outdoor unit and indoor air handler that circulates conditioned air through ductwork into rooms. Ducts contain dampers that open and close to direct conditioned air where needed.


HVAC systems are what keep homes and other buildings warm in winter and cool in summer. They also filter and purify air, keeping it free from allergens, pollutants, and other contaminants. They do all this while maintaining temperature, humidity, and air flow. There are many parts that make up the different heating and cooling products within an HVAC system, including air conditioners, furnaces, heat pumps, ductwork, and thermostats.

Split systems are the most popular type of residential HVAC system. Their components are housed in one indoor unit and one outdoor unit, which are connected by ducts. Depending on the climate, these units may use gas, oil, or electricity to generate heat. They are usually installed in basements or closets, but can also be found in attics or near the foundation of the home.

Another type of residential HVAC system is a packaged unit. These are less common, but are more suited to small buildings that do not have the space for a basement-based system. Packaged units can be either a heat pump that contains evaporator coils or a traditional furnace with a separate air conditioning unit.

Larger commercial and industrial buildings often use packaged units to cool their spaces. These are typically larger than the units that can be found in homes and include compressors, condensers, and refrigerant lines to produce cold air. These are normally installed in the roof or a large room inside the building.


There are three essential parts to any HVAC system: a source for warming or cooling air, a way to distribute that air and a control mechanism like a thermostat. The ventilation part of your HVAC system is made up of return and supply vents (also called registers) ductwork, filters and a circulating fan. Ductwork transports the air from units like your furnace, heat pump or AC unit to different rooms in your home.

Cooling systems remove the warm air from your home and blow it outdoors, lowering your indoor temperature. They work with a device called a condenser or a heat pump, which are both conventional air conditioners. They may also include evaporator coils, which are used to dehumidify the air. Some systems also use fans, air cleaners and humidifiers to improve your indoor air quality.

You may notice that your HVAC system is cycling on and off more frequently than usual, which is a sign of excessive wear and tear. Having an understanding of what’s going on behind the scenes can help you decide if it’s time to replace your system. You may be able to save money in energy costs and repairs by investing in a more efficient system. For instance, look for a system with a SEER rating of at least 15 and an HSPF of at least 9.


Ventilation is an essential function of HVAC. It delivers fresh air from outside into a building through ductwork or directly into rooms. The ventilation system is also designed to remove pollutants from the indoor air. This is accomplished by running the outdoor air through filters to reduce contaminants like atmospheric dust, pet dander and infectious bacteria and viruses.

The ventilation system also includes a piping network that transports refrigerant, hot water, cooled water and steam to and from the HVAC equipment. The piping network is typically insulated to improve energy efficiency and lower operating costs.

In residential homes, HVAC systems can consist of central heating and cooling with a network of air ducts, or a ductless system. Ductless systems are becoming more popular because they are more efficient than window or unitary air conditioning units. The evaporator coil is located inside the living space and the condenser unit is placed outdoors. This allows for more flexibility in placement and design of the living spaces.

A quality ventilation system can help to maintain healthy indoor air for school occupants. It can remove contaminants, improve indoor temperature and humidity control and provide thermal comfort. It can also provide filtration for gases and volatile organic compounds (VOCs). Specially designed filter systems include permanganate oxidizers and activated charcoal to reduce VOCs in ventilation air. Corrosion resistant dampers and links are also available to prevent damage during use.


A thermostat is the brain of a system that manages a space’s temperature by relaying information to the equipment. It takes your chosen temperature set point and works towards it, activating the equipment to heat or cool based on its reading of the air temperature in the space.

The simple bimetal thermostats that are still used in older homes have a strip of metal with an electrical circuit in it. When the strip gets warm it expands and makes contact with the electrical circuit, allowing current to flow through and activate the air conditioner. When the thermostat senses the room has cooled enough, it will allow the strip to contract and pull away from the electrical contacts, stopping the flow of electricity and shutting off the air conditioning.

In modern digital thermostats, a small mercury switch moves inside of the case to make contact with different traces on the circuit board. The switch is tipped up or down depending on the temperature setting, allowing the thermostat to control the fan mode or heating mode.

A thermostat can also regulate the amount of line voltage a fan-coil unit needs to run off of, which allows it to control the circulation of air in a space that has no heater or cooling running. This can be beneficial to help with odor removal and filtering in spaces that aren’t being heated or cooled.

Combustion Chamber

The combustion chamber is the interior of a furnace that contains the burner. Its walls are made of a refractory material that protects it from the heat produced by the burning of fuels such as natural gas. The refractory is designed to withstand temperatures up to 1,800°F, so it can handle most any fuel. It also has ports that allow for the sampling of combustion gases and an exhaust vent, which allows for the removal of noxious emissions such as carbon monoxide.

The size of the combustion chamber determines how much power it can produce. A larger combustion chamber requires more compression and results in higher temperatures, while a smaller combustion chamber allows for better fuel efficiency. A direct-injection combustion system, popularized by Harry Ricardo’s diesel engine, uses a separate pre-combustion chamber to burn the air/fuel mixture before it enters the main combustion chamber.

The combustion chamber is designed for maximum utilization of the air, which helps to decrease HC and soot emissions, but this design may cause high in-cylinder temperatures, increasing NOx emissions. This can be overcome by using a multiport injection system, which injects oxidizer into the cylinder head to stimulate mixing. This also increases the overall velocity of the combustor, reducing the average diffusion length between high and low oxygen/fuel ratio operation.


An HVAC system’s filters are responsible for removing impurities before the blowers push heated or cooled air back into the building. This ensures that dust, pet dander and other debris doesn’t get blown around the facility.

The type of filter you use depends on your specific needs. For instance, individuals with asthma or allergies benefit from having filters with higher MERV ratings to remove a high percentage of offending particles such as mold spores and pollen. However, a higher MERV rating can restrict airflow, which can strain the system.

There are several different types of filters, ranging from disposable fiberglass models to reusable ones made from polyester or cotton. Filters with a MERV rating between 5 and 16 are typically found in homes. These are the least expensive types, but they still require replacement on a regular basis since they don’t catch as many contaminants as larger ones.

Alternatively, you can opt for pleated filters that have more surface area and are therefore more effective at trapping small particles. However, these can be more expensive than fiberglass filters and are often used in commercial or medical office spaces. The highest rated filters are HEPA, which are commonly found in hospitals and clean rooms since they can capture the smallest particles such as bacteria and tobacco smoke. However, they may not fit properly into HVAC systems without modification and can be difficult to install.