Part 1: Advanced Rooftop Unit Controls Explained

What are Advanced Rooftop Unit Controls?

Advanced Rooftop Unit Controls (ARCs) are a low cost, easy to install, digital system that gives you better control over your HVAC system.

Most existing rooftop units (RTUs) have constant speed fan systems and lack sensor-based ventilation controls. This can leave fans running at a constant speed, regardless of a building’s heating, cooling, and ventilation needs resulting in more energy use and costs. By implementing ARCs like demand control ventilation (DCV) and switching to variable speed systems, you can significantly improve a RTUs efficiency, giving it the ability to optimize performance and respond to different heating, cooling, and ventilation requirements.

ARCs are ideal to use in high-occupancy spaces, such as classrooms, multipurpose rooms, theaters, conference rooms, or lobbies that may have ventilation designed for maximum occupancy (which may rarely happen). They are also often used in small-to-medium sized buildings under 100,000 sq ft, and heated/cooled by packaged RTUs. Other buildings which have fluctuating occupancy levels (or hours of use) can benefit as well.

What are the main components of an Advanced Rooftop Unit Control System?

The two main cost-effective components of an ARC system are Variable Frequency Drives (VFDs) and Demand-Controlled Ventilation (DCV).

    1. Demand-Controlled Ventilation is a control strategy that responds to the actual need or “demand” for ventilation in a building space. This is done by changing the rate at which outdoor air is delivered to a space. DCV saves energy by avoiding the heating, cooling, and delivery of more ventilation than needed.

Carbon dioxide (CO2) sensors are a common technology used for implementing DCV. Using sensors allows the system to respond to the building’s demands for ventilation as needed, and automatically reduces outdoor air intake when the occupancy of spaces is low or unoccupied.

2. Variable Frequency Drive (VFD) is a device that controls the speed of a motor from a control signal. Many existing rooftop units utilize fan systems that run at constant speed under all heating and cooling conditions. By installing a VFD on the fan motor, it can change the speed of the fan based on the operational needs. Even small reductions in fan speed can result in significant energy savings.

Learn more about the benefits of advanced rooftop unit controls and how we can help you get started with expert advice and rebates to help cover the cost of upgrading.