Arzel Zoning
There’s been a big change in HVAC with the introduction of A2L refrigerants like R-32 or R-454B. When you’re working with A2L refrigerants and Arzel Zoning systems, it’s important to understand the refrigerant detection system (RDS) and A2L mitigation controls that are built into the equipment. Here’s what you need to know.
Indoor coils that are designed for A2L refrigerants have a refrigerant detection system (RDS) because A2L refrigerants are mildly flammable. If there is a leak, the system needs to respond by dispersing the refrigerant.
The RDS includes a sensor that detects refrigerant and a mitigation control board that responds. Manufacturers might refer to these as mitigation boards, mitigation controls, or just the RDS.
According to UL, when an A2L refrigerant leak is detected, all zoning dampers need to be opened. When you’re installing A2L equipment with an Arzel Zoning system, you’ll need to add a relay to accomplish this functionality.
To add the necessary functionality to an Arzel Zoning system, follow the wiring diagram below. You will wire a double-pole double-throw relay to the mitigation board and the Arzel Zoning panel. This will shut off the panel and open all dampers in the event of a refrigerant leak.
Okay, so you added the relay for A2L mitigation. Now what? Here’s what will happen if the A2L control detects a leak:
If your A2L mitigation board has a set of contacts for directing 24VAC to an alarm, those can be used to energize the relay directly. Below is a wiring diagram that shows this scenario.
Sometimes RDS boards have a set of alarm contacts, but they operate in the inverse as the alarm contacts described above. Instead of energizing when a leak occurs, the alarm contacts on these boards provide a constant 24VAC that drops to 0VAC when a leak occurs. In that case, the relay would be wired in as shown below.
If you’re working with Trane or American Standard equipment, you may not need to add the relay. These brands have mitigation boards with extra contacts that you can use to wire the mitigation board to the Arzel Zoning board. Here’s how you can wire the Arzel Zoning board to A2L mitigation boards that have these extra contacts.
We are working on adding a circuit to our new products that will directly connect to the mitigation board in the equipment without the need for a relay. Right now, you’ll need to use the wiring diagram above to add that functionality.
If you have additional questions about A2L refrigerants and Arzel Zoning, give us a call at 1-800-611-8312 or send a message to tech support. You can also refer to this list of Arzel wiring diagrams.
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