As of January 1, 2025, new HVAC equipment manufactured for the U.S. market can no longer use R-410A. The primary replacements—R-454B and R-32—are classified as A2L refrigerants: mildly flammable under ASHRAE Standard 34. For Texas HVAC contractors installing new equipment, that classification has practical implications for relay and switching device selection.
What A2L Means for Electrical Switching Devices
R-410A was classified A1, or non-flammable, so no special electrical precautions were required for switching devices near the refrigerant circuit. A2L refrigerants introduce a low but real flammability risk: under specific conditions (high concentration, sufficient ignition source), these refrigerants can ignite. Equipment manufacturers and standards bodies have responded by tightening requirements around arc-producing electrical components—including relays—used in A2L equipment design.
Therefore, arc-producing devices near A2L refrigerant systems should be properly enclosed so any switching arc cannot ignite refrigerant vapors in the event of a leak. This is less about everyday operation and more about worst-case leak scenarios where refrigerant concentration could reach flammable levels in an enclosed space.
Enclosed Relays for A2L HVAC Installations
For most Texas commercial HVAC applications, the guidance is straightforward: use enclosed relays, not open-frame relays, near A2L equipment. A properly enclosed relay, where the contact mechanism is housed and isolated, significantly reduces arc-ignition risk.
RIB® (Relay-In-a-Box®) relays from Functional Devices, Inc. are enclosed by design. The contact assembly, coil, and wiring are all housed within the relay’s enclosure—the same construction that has made them a standard in commercial HVAC and BAS applications for decades.
Commonly Specified Enclosed RIB® Models
The following models are among those commonly used in Texas commercial HVAC applications where an enclosed relay is appropriate. All are enclosed by design and UL Listed as complete assemblies; confirm suitability for your specific application against the equipment manufacturer's installation requirements and your AHJ.
RIBU1C: 10A SPDT, universal coil voltage (10–30 VAC/DC or 120 VAC). A widely specified light-duty relay for damper actuators, fan coil units, and pilot duty applications.
RIB2401B: 20A SPDT, 24 VAC/DC or 120 VAC coil. The standard workhorse for commercial HVAC switching applications where higher contact ratings are required.
RIB24P30: 30A DPDT, 24 VAC/DC coil. For higher-current loads or applications requiring two independently switched circuits from a single control output.
Browse the full RIB® relay lineup for additional enclosed models.
What Hasn’t Changed
The fundamental relay application in HVAC is unchanged. BAS controllers still drive binary outputs to relay coils; relay contacts still switch equipment loads. The control sequence, wiring topology, and relay selection criteria—coil voltage, contact rating, pilot duty for motor loads—are all the same. The A2L transition affects enclosure considerations near the refrigerant circuit. Enclosed RIB® relays have always met that standard.
For Texas HVAC contractors sourcing enclosed RIB® relays for A2L-compatible installations, find an authorized Functional Devices distributor in Texas.
Note: A2L installation requirements are evolving and vary by jurisdiction, equipment type, and AHJ interpretation. Always refer to the equipment manufacturer's installation instructions and current adopted codes in your Texas jurisdiction before specifying switching devices for A2L applications.