ZONEFIRST Solutions for NEW A2LRequirements for Zone Damper Systems
Underwriters Laboratories
UL's Code for HVAC Units using A2L refrigerants must have built-in leak detection. Upon a leak detection the heating and cooling must be shutoff and the fan turn on, if not already. When ZONING, all Zone Dampers MUST OPEN. All HVAC units will provide auxiliary normally open and closed contacts for activating external devices, such as a zone damper systems. Depending on the ZONEFIRST dampers used and for older zoning systems, such as Trol-A-Temp, we have you covered. Below are the solution for each, in order to meet this code.
24V Spring Return Damper Systems
When using 24V Power Closed, Spring Return Open dampers with the H32, MMZ3 and MZS4 zone panels, one leg of the panel's power transformer is wired thru the normally closed contact of the HVAC units leak detection auxiliary contact. This will break power to the zone panel and all zone dampers will spring open. The unit's leak detection circuit will drop the heat/cool calls and turn the fan on when a leak is detected. See Diagram #1 below.
Plug-In and 3-Wire Power Open-Closed Damper Systems
When using the Plug-In and 24V, 3-Wire, Power Open-Closed dampers with their respective zone panels, a 4PDR relay is used to break the R wire from each zone thermostat to the zone panel. This will break the calls on all zones and the panel will drive all dampers open. The 4PDR will be energized by the unit's auxiliary leak detection contracts. The unit's leak detection circuit will drop the heat/cool calls and turn the fan on when a leak is detected. See Diagram #2 below.
Wiring A2L
Diagram 1
24V Spring Return Dampers
OPERATION
When zoning with 24V AC Spring Return Dampers, use the Common and Normally Closed contacts on the A2L Leak Detection device, to break one leg of the 24V Transformer that powers the panel. Upon leak detection the A2L contact will open removing power to the zone panel.When power is removed from the panel all dampers will spring open. NOTE: The zone panel's Power LED will go out as well.
Diagram 2
Plug-In And 24V. Power Open-Close Dampers
OPERATION
When zoning Power Open and Closed dampers, both 24V 3-Wire and Plug-In Dampers, use the Common and Normally Open contacts on the A2L Leak Detection device. Upon leak detection the A2L contact will close to energize the 4PDR Relay.The 4PDR is used to break each thermostat's R wire to the zone panel Upon a leak detection, the contacts close to energize the 4PDR and removing the calls from all zone thermostats therefore opening all zone dampers.
NEW Z3 Zone Panels - Available in the Summer of 2025
ZONEFIRST has A2L covered going forward also. Our NEW Multi-Function Z3 and Z3P zone panels have A2L operation built-in. Wire the HVAC Units A2L contacts to the sensor connections on the panel. This simplifies installation even more. These new panels eliminate the need for determining the panel and simplify set-up with a NEW web-based set-up. Scan the QR code on panel and see the menu driven set-up on your phone. A2L functionality is built-in by wiring the A2L contacts to the sensor contacts on the panel.