The New Heating and Air-Conditioning (HVAC) Technician
By: JADE Learning | Aug 05, 2020
If you have a newfound interest in Heating and Air-Conditioning, whether as a hobbyist, a DIY homeowner, or as a career-minded technician, here is some information that can help you become more familiar with basic HVAC concepts and components.
Heating, Ventilation, & Air Conditioning
While it is possible to install heat only or air-conditioning only to serve a building or occupied space, the HVAC technician is typically called upon to install or service a system capable of performing both tasks. The complete system is a Heating, Ventilation, & Air Conditioning system, or HVAC for short.
An interesting fact about the HVAC system is that it not only changes the temperature of air in a designated space, but it also changes the humidity within that space.
In most cases it is counter-productive to install a system (rated in BTUs) that exceeds the air-conditioning needs of your building. An oversized cooling system can be so effective at reducing air temperature in a short amount of time that the system fails to stay on long enough to remove the humidity from that same space. That humidity can lead to odors in the space, as well as dampness on cloth furniture, clothing, and carpeting, and can even lead to mold growth inside the occupancy.
HVAC systems are typically constructed as either Package Units, where the main components are all housed inside one enclosure located on the outside of the building, or as a Split System, where the components are divided between two different enclosures – one located outside for housing cooling components such as the condenser and compressor – and another located inside for housing the heating components such as electric heating strips or a burner & heat exchanger. The inside unit, called the furnace, also contains an evaporator coil that works as part of the cooling system, and a blower motor that is responsible for circulating air in conditioned spaces regardless of whether the air is cooled or heated by the system.
When the system is a split system, the furnace is often installed in a crawl space, attic, or even a closet or mechanical room.
When the wall-mounted thermostat in a conditioned space is set to Cool, the blower motor inside the furnace draws room temperature air through the return so that it is pulled across the evaporator coil inside the furnace. The refrigerant in the system keeps the evaporator coil extremely cold so that when the warmer air passes over, the heat is transferred to this extremely cold refrigerant.
It helps to understand that air in an unaltered state is extremely cold. Heat is added to air by the sun warming our atmosphere, or by mechanical means. To cool the air, one must only remove the heat.
The same blower motor then forces that cooled air out of the vents and into the conditioned spaces.
To keep this process going the compressor located in the outside unit keeps pressure on the refrigerant and keeps it circulating so that cold refrigerant remains available at the evaporator coil in the furnace and the air being forced to pass over that coil can continue to displace its heat into that refrigerant. The warmed refrigerant is then pushed to the outside unit where its heat can be displaced outside the building. This cycle continues until the room temperature reaches the setting that is dialed into the wall-mounted thermostat.
When the wall-mounted thermostat is set to Heat, the cooling components (evaporator coil inside the furnace and compressor & condenser located inside the outdoor unit) are left out of the loop. The blower motor previously used during the cooling process is once again called upon for circulating air in the system, but this time the air that is being pulled through the return is passed through electric heating strips or a heat exchanger fueled by a gas burner. These heat sources transfer their heat to the air passing through, which is then forced out the supply vents. This circulation of air across the heat source within the furnace continues until the temperature of the room reaches the desired temperature that is dialed into the wall-mounted thermostat.
There are several variations to the components and system operations discussed in this article, including heat pumps as part of outdoor condensing units and ever-growing geothermal system technology. There are also components and functions at work that have not been discussed here but are mandatory for the system to maintain comfortable temperatures and humidity levels within a conditioned space. But we leave those advanced topics for another day.
Careers in HVAC
HVAC technicians are currently in high demand. To get started in the field, an HVAC technician typically attends a training program that includes 576 hours of related instruction and 8,000 hours of on-the-job-training. Some states require licensing and regular continuing education. Check with your state to learn more.