Provided are embodiments for a heating, ventilation, and air conditioning (HVAC) system for providing sensor information and sensor communication over relay-controlled power line. The system can include a controller of the HVAC system and a first power line converter coupled to the controller. The first power line converter is configured to receive data over a serial bus, convert the data into a communication message for transmission onto a power line, wherein the power line is configured to transmit power and communication messages, and transmit the communication message over the power line. Also provided are embodiments for transmitting and receiving a communication message over relay-controlled power line.