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How Does a Rooftop Unit Work?

Rooftop AC Unit

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Packaged rooftop units are among the most common HVAC systems for commercial buildings in Chicago. They are cost-effective, pre-engineered, and adaptable for many applications. Learn more about how a rooftop unit works to keep your building cool in the summer and warm in the winter.

What Is a Rooftop Unit?

A rooftop unit, like the name implies, is a packaged unit installed on the roof. These packaged units contain all air conditioning components, including:

  • Evaporator coil
  • Fan
  • Compressor
  • Condenser

They also can be slab-mounted on the ground and have heating capabilities, depending on the particular model. Unlike split systems commonly used in residential properties, packaged units don’t separate the evaporator coil and fan from the compressor and condenser.

To install or service your building’s rooftop AC unit, contact Murphy & Miller online today!

How Does a Rooftop Unit Work?

Getting the Heat Out

Once a rooftop AC unit is installed, cool, low-pressure refrigerant arrives at the compressor as a gas and then compresses into a hot, high-pressure gas as it flows into the condenser coil. There, the metal fins on the coil absorb and disperse the heat, and the condenser fan blows the exhaust away from the building.

As warm return air travels through the ductwork into the rooftop unit, fresh air enters as well for ventilation. Positioned over the return air duct are air filters to prevent contaminants from landing on the sensitive cooling equipment.

The Refrigerant Cycle

Now that you understand how a packaged unit gets the heat out, below we’ve listed the steps in the refrigerant cycle:

  1. The now-cooled liquid refrigerant passes through the evaporator coil.
  2. As the pressure drops, the liquid converts back to a gas.
  3. As warm air from the building passes over the evaporator coil, the refrigerant extracts heat from the air.
  4. The evaporator fan returns the ice-cold air back into the building.
  5. The warmed refrigerant (having absorbed the heat) circulates back to the compressor to release its heat through the exhaust system.
  6. And the cycle repeats again and again until your building’s temperature reaches the thermostat setting.

Rooftop Units That Can Heat

Rooftop units that also provide heating often contain a gas heat exchanger downstream from the evaporator fan. In heating mode, return air is discharged into the heater and blows over gas-fired coils. A fan then sends newly heated supply air back into the building.

To learn more about heating and cooling rooftop units for your building, contact us online or call 1-312-427-8900 today!

What Are the Advantages of Installing a Rooftop Unit?

Rooftop units have a few advantages over split systems that you might want to consider when choosing your new AC system. Rooftop units:

  • Are quieter inside your building
  • Save space
  • Can undergo maintenance in one place
  • Are easier to install

Murphy & Miller’s Rooftop Unit Services in Chicago

Interested in installing a new HVAC system or having your existing rooftop packaged unit serviced? Murphy & Miller is the right company to ensure maximum comfort and efficient performance. We even provide custom ductwork and sheet metal fabrication services to help you make the most of your rooftop unit. If your goal is to save money, stay comfortable, and enjoy a high return on investment, contact Murphy & Miller online or give us a call at 1-312-427-8900 today!