Learn everything about rooftop units (RTU’s). Discover how RTU’s work, their benefits, and why they are the preferred choice for commercial HVAC systems.
What is a Rooftop Units (RTU’s)?
A rooftop unit (RTU), also known as a packaged unit, is a self-contained HVAC system specifically designed for installation on the roofs of commercial and industrial buildings. RTUs are becoming increasingly popular because of their flexibility and efficiency in managing indoor environments, especially for large spaces.
RTU’s integrate key functions like cooling, heating, and ventilation, with some units also offering dehumidification. RTU’s are commonly used in commercial and industrial buildingsdue to their versatility and superior performance.
RTU Structure
There are various types of RTUs, but we’ll explore a basic version designed to use 100% fresh air, with no recirculation of exhaust air. The exhaust air is typically removed by an external fan to balance air pressure.
RTU Casing:
The outer casing must be robust to protect the mechanical and electrical components inside from weather conditions like heat, wind, rain, snow, and frost. It also includes access panels for maintenance.
Air Intake Port:
At one end, there’s an air intake port where outdoor air is drawn into the unit. These ports are designed to prevent the entry of water, snow, and debris. A mesh is often installed behind the intake port to block wildlife and foreign objects, which can cause clogging and damage the fan.
Dampers:
Dampers control the amount of air that enters the unit, either fully opening, closing, or partially adjusting based on the system’s needs.Filters:
Air filters clean incoming air by trapping dust and contaminants, preventing performance degradation and potential system failures.
Heat Exchanger Coils:
After the filters, you’ll find the heat exchanger coils, responsible for heating or cooling the air by adding or removing energy. Depending on the unit’s location and surrounding environment, some RTUs may have only cooling coils, others only heating coils, while some feature both.
- Cooling Only: The cooling coil is connected to a refrigeration system.
- Heating Only: Connected to a heat pump, gas burner, or electric heater.
- Heating and Cooling: Two separate coils—one for cooling connected to a refrigeration unit, and one for heating connected to a gas burner or electric heater.
Fans:
Following the heat exchangers, fans circulate the conditioned air. These are typically belt-driven centrifugal fans but may also include energy-efficient EC fans. Fans draw air through the dampers, filters, and heat exchangers, then distribute it throughout the building via ducts.
Types of RTU
1. RTU with Recirculated Air
Most RTUs recirculate indoor air through an exhaust system to save energy, especially during colder months when recirculating warm air reduces the heating load. These units include an additional exhaust damper, which works in sync with the main damper to regulate the ratio of fresh and return air.
2. RTU with Exhaust Discharge
Another common design features an exhaust discharge damper, allowing a portion or all of the exhaust air to be released outside. When outdoor temperatures are close to or lower than the desired indoor temperature, the unit may use 100% fresh air, a process known as free cooling or economizer mode.
3. RTU with Energy Recovery Wheel
In this type, an energy recovery wheel is integrated into the system to increase energy efficiency. The wheel transfers heat from the exhaust air to the fresh intake air, reducing energy costs. This system may include a secondary filter and a return air damper for recirculating a portion of the exhaust air back into the system.
Benefits of RTUs
- Space-Saving: RTUs are installed on the roof, freeing up valuable interior space.
- Easy Installation and Maintenance: All components are housed in a single unit.
- Flexible: RTUs can be easily added or replaced to accommodate changing needs.
- Energy Efficient: Modern RTUs are designed to be highly energy efficient.
- Improved Indoor Air Quality: Filters and ventilation systems help maintain a healthy indoor environment.
Applications of RTUs
RTUs are commonly used in:
- Commercial Buildings: Offices, retail stores, and shopping malls.
- Industrial Facilities: Warehouses, factories, and manufacturing plants.
Educational Institutions: Schools and universitiesHealthcare Facilities: Hospitals and clinics. 
Choosing the Right RTU
When selecting an RTU, consider factors such as:
- Building size and layout
- Local climate conditions
- Indoor air quality requirements
- Energy efficiency standards
Rooftop units offer a practical and efficient solution for commercial and industrial HVAC needs, providing reliable climate control with the added benefits of space-saving and ease of maintenance.
Trust AETHER for all your HVAC system needs. Contact us today at (713) 826-3979.
