If you’ve ever paid attention to commercial buildings, you may have noticed rooftop HVAC units dotted around. Many people wonder about rooftop HVAC equipment and whether it is only used exclusively for commercial applications. So, here we’ll delve into this topic to help you gain an understanding of this equipment and how it is used.

The Basics

Rooftop HVAC units or RTUs work in a similar way to most indoor HVAC systems. Air passes through the equipment to heat or cool it before it is then circulated in specific areas.

Specifically, the rooftop equipment is an air handler. So, it is responsible for conditioning and circulating the air. From there, the air moves through ductwork and vents to reach the desired area.

What is different about RTUs compared to indoor HVAC equipment is the location, and as a result, they are designed differently to account for being outdoors. RTUs are made to be weather proof and robust. They can handle snow, rain, and other debris. They are even designed to prevent animals from getting in. All of this while still allowing air to flow through. They are also self contained. There is a built in heating device and chiller. This allows the air to be treated without needing to pass further into the system.

The Parts of RTUs

When you look at an RTU, you’re likely to see a rectangular casing. All the parts are contained inside the unit. Here we’ll look at what parts are actually contained inside an RTU, so you can gain a better understanding of how they work.

  • The Air Hood: You may notice the air hood on the side of the unit. This allows air to enter the unit from outside, where it can get warmed or cooled. There is an awning that allows the air to enter from underneath, preventing rain and other debris from getting in. There is also netting to prevent birds or animals from getting in and setting up a nest.
  • Dampers, Coils and Filters: The air is then passed through rotating metal sheets or dampers. These can run at different speeds to control the amount of air that gets in and prevent air from escaping. There are then coils and filters. Like a standard indoor unit, the filters remove any debris while the coils transfer thermal energy. In cooling mode, heat is removed from the air while adding warmth in heating mode.
  • The Fan: Finally, there is a fan that pulls air into the unit and pushes the treated air out into the ducts. There are also condensers and compressors behind the fan that actually heat or cool the air.

How RTUs Actually Work

Now that we’ve looked at the components inside an RTU, we can get a better idea of how they actually work. It is important to note that while some RTUs can heat and cool, others can only heat or cool. But, the principle of how they work remains the same.

  • Heating: The RTU heats the air by connecting to either a gas burner, heat pump, or electrical heating element. It is rare that an RTU will heat using a gas heat exchanger or furnace, but this is sometimes possible.
  • Cooling: In the case that RTUs solely have a cooling function, there is only one coil and a refrigerator unit inside. This operates like a standard air conditioning unit. There is refrigerant inside that turns from a liquid to a gas state to transfer heat. In a liquid form, heat is absorbed and then released when the refrigerant reverts to a gas state.

The Advantages of an RTU Over an Indoor Unit

Since they operate in a similar way, you may wonder why building owners opt for an RTU. There are two main advantages that an RTU offers to aid building owners with space and noise. Generally, commercial spaces require larger HVAC units that would create a noise issue if they were placed inside. These units often need to work harder and cover more space. So, by placing the unit on the roof, there is less chance that you will hear them working.

The other advantage is space. Commercial premises often have space at a premium. With a larger building, you can enjoy better heating and cooling results by zoning the HVAC system. So, multiple units would take up a great deal of space. You can use multiple RTUs, so each one will handle a different area of the building without wasting valuable real estate.

While space and noise are crucial, there is another advantage of RTUs, which is security. Since the units are on the roof, there is no easy access. This can protect the equipment against accidents or vandalism. There is no danger of someone accidentally hitting the unit with their vehicle or potential thieves breaking open the unit to steal costly components.

How Long Do RTUs Last?

RTUs are designed to be durable, so you can expect a typical lifespan of 10 to 20 years. While they won’t last as long as a furnace or other types of indoor appliances, RTUs can handle exposure to rain, snow, ice, wind, or sun continually.

Of course, this lifespan will depend on maintenance. If the unit is allowed to run with no maintenance or servicing, you would be lucky to reach even the low end of the average lifespan. Regular servicing allows for preventative maintenance, so worn components can be replaced before they trigger a cascade failure and breakdown. This is particularly important for commercial units that may rely on the equipment all year to maintain the optimum temperature and circulate air.

Most RTUs should be cleaned and inspected twice a year. A professional technician will gain access to the roof and perform the necessary maintenance. This ensures the equipment is operating properly and efficiently.

If you’re considering the correct HVAC equipment for your home or business, you can rely on the expertise of a professional HVAC technician. An experienced pro can evaluate your property to help you determine the system that will provide the greatest efficiency and best comfort level.