Turns the boiler on and off via OpenTherm or a relay contact, with galvanic isolation through optocouplers — the module that actually executes the heat command for the whole underfloor heating zone system.
Bridges the boiler and the home's Zigbee network: automatic on/off through a relay contact, or full communication via OpenTherm where the boiler supports it. Two dedicated optocouplers (TX/RX) provide complete galvanic isolation between the control electronics and the boiler's circuit.
OpenTherm communication runs through two dedicated optocouplers (TX/RX), which provide complete galvanic isolation between the control electronics and the boiler's circuit — an essential safety requirement for this type of connection. Where the boiler supports the protocol, the controller reads and sends real data, not just on/off.
A switching relay also allows classic control through a dry contact, for boilers without OpenTherm — giving flexibility regardless of the boiler's age. Underfloor heating automation doesn't depend on having the latest equipment; it adapts to what you already have installed.
The module runs on an ESP32-C6, with native Zigbee 3.0 connectivity and power from an industrial Mean Well supply. The board includes overvoltage protection (MOV) and a 2A time-delay fuse, for added safety in a residential installation wired directly into the boiler.
An addressable LED ring shows the system's state at a glance. It integrates directly with the ZAO Thermostat for Underfloor Heating Automation and the ZAO Control Center for Underfloor Heating for a complete underfloor heating automation system, controlled locally through Home Assistant — from reading the temperature per zone to actually driving the boiler.
Yes, in two ways. If the boiler supports OpenTherm, the controller communicates with it digitally (requested temperature, status, errors). If not, a switching relay allows classic control through a dry contact — on/off — for older boilers. The choice depends on which protocol the boiler supports, not on its age.
OpenTherm communication runs through two dedicated optocouplers (TX/RX), which completely electrically separate the Zigbee control electronics from the boiler's circuit. A fault in the boiler circuit can't propagate into the rest of the underfloor heating automation.
It receives the command over Zigbee from the ZAO Control Center for Underfloor Heating, which decides when heat is needed based on readings from the ZAO Thermostat for Underfloor Heating Automation in each room. The controller actually executes turning the boiler on or off — a complete chain, controlled locally through Home Assistant.
It gives instant visual feedback on the system's state — whether the boiler is on, whether there's an OpenTherm communication error, or whether the module is connected to the Zigbee network — without opening Home Assistant for a quick status check.
Want to see the whole automation system together? Check the complete underfloor heating automation guide.
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