HVAC Tech Tip: ARC Made Easy

Advanced rooftop unit controls, or ARC, is a retrofit controls solution for packaged constant volume rooftop units. ARC’s primary purpose is to convert a unit’s supply fan from single speed to multispeed. It accomplishes this through the installation of a new unit controller and a variable frequency drive or multispeed motor.

Recent studies have shown that ARC can reduce total unit energy consumption by up to 50%*. Those energy savings, plus the fact that the majority of commercial buildings nationwide are conditioned by constant volume RTUs, makes ARC incredibly relevant. Adding ARC to your portfolio of offerings is an easy win for both you and your customers. Especially so for trade allies, considering the ease of installation and commissioning making it readily scalable and repeatable. Lastly, you can take advantage of incentives of up to $200/ton** available from your local utility.

ARC retrofits come in two flavors, full and lite. For the “lite” version, the fan is converted from constant speed to variable or multispeed and commanded to slow down during unoccupied hours. Simply slowing the speed of the fan for a few hours a day can result in significant savings over the course of a year. The “full” ARC version builds upon varying fan speeds by also adding digital economizer control and demand control ventilation to further save energy.

Some of the energy saving options and non-energy benefits a full ARC retrofit can provide when configured appropriately are:

• Demand control ventilation (requires CO2 sensor) which can contribute to improved indoor air quality and limit energy wasted in spaces with variable occupancy.
• Digital economizer control and fault detection (requires additional temperature sensors) to take advantage of free cooling when outside air conditions match indoor space conditioning requirements.
• Web-based interface (requires internet access and often a gateway) that enables remote control and scheduling of the unit, remote monitoring of operation, and alarming capabilities.
• Reduced equipment cycling and noise as a result of the reduced fan speed and improved economizer functionality.

Are you interested in ARC and would like to learn more? Join us at an upcoming 2020 Trade Ally Network NW workshop for an in-depth, hands-on session on the installation and commissioning requirements of ARC. You’ll be surprised to learn just how simple these retrofits can be. Visit our Training & Resources pages for a complete list of workshop locations.

For more HVAC tips and best practices, search the Trade Ally Network website or contact your regional field specialist.

* Scaled Deployment of Advanced Rooftop Unit (RTU) Controls in New York State (Interim Report), November 2018
**Utility incentives and participation may vary. Contact your field specialist or local utility for more information.