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.
24V Spring Return Dampers
OPERATION
When using the RDS, RTS, ZDS, ZDB and other two-wire, spring return zone dampers, with the MMZ3, H32 and
MZS4 zone panels, the transformer power to the zone panel is wired through the Normally Closed contact
auxiliary contacts in the air handler. Upon leak detection these contacts OPEN, breaking the transformer power
to the zone panel and all dampers will spring return to the open position.
Plug-In and 3-Wire Power Open-Closed Damper Systems
When using either of these dampers and their respective panels, all zone thermostats’ R wires are wiredtogether and all are wired to one side of the normally open auxiliary contact in the HVAC unit. The other side ofthe normally open contact will wire to any one of the zones’ R thermostat connection on the zone panel. During detection, this breaks the call for all zones and all dampers will open.
Note: The zone panel’s test jumper, or DIP Switch, should be set to the 'on' position, for immediate opening of the zone dampers.
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.