Tekmar 546 tekmarNet� 4 Thermostat Two Stage Heat, Two Stage Cool, Two Fan The tekmarNet 4 Thermostat 546 is designed to operate mechanical equipment to deliver 2 stages of heating and 2 stages of cooling to a single zone within a hydronic heating system while maintaining a programmable setback schedule. It can be used with any terminal unit type including radiant floor, baseboard, fan coils, and non-hydronic sources. This product is capable of controlling 2 zone valves or pumps directly or through a tekmarNet 4 Wiring Center or Zone Manager, 2 cooling devices, and 2 fans while reading up to 3 auxiliary sensors. These could be floor, outdoor, duct, or remote air sensors.