Model ST series panels are for single stage heating and cooling with manual changeover. Zone 1 is the "master" zone which controls the heating and cooling mode and also the fan operation. The ST-3 is a 3 zone panel. Zones 2 and 3 will only operate in the same mode that the zone 1 thermostat is in. Each thermostat can turn the system "on" and "off ", but only in the same mode. It is recommended that zones 2 and 3 have no switching subbases for the thermostats. The ST panels can be used with mechanical or digital programmable thermostats that are non-power stealing.
Open-Close switches on the control panels near the damper terminal blocks allow for continuous air circulation. This switch controls the damper position when the heating and air conditioning system is at rest. The ST panels can be wired together to create larger zoning systems up to 6 zones.