Getting an Old HVAC System Online

Standardization might sound boring, but it’s really a great underlying strength of modern society. Everyone agreeing on a way that a certain task should be done saves a lot of time, energy, and money. But it does take a certain amount of consensus-building, and at the time [JC]’s HVAC system was built the manufacturers still hadn’t agreed on a standard control scheme for these machines yet. But with a little ingenuity and an Arduino, the old HVAC system can be given a bit of automatic control.

The original plan for this antiquated system, once off-the-shelf solutions were found to be incompatible, was to build an interface for the remote control. But this was going to be overly invasive and complex. Although the unit doesn’t have a standard remote control system, it does have extensive documentation so [JC] was able to build a relay module for it fairly easily with an Arduino Nano Matter to control everything and provide WiFi functionality. It also reports the current status of the unit and interfaces with the home automation system.

While some sleuthing was still needed to trace down some of the circuitry of the board to make sure everything was wired up properly, this was a much more effective and straightforward (not to mention inexpensive) way of bringing his aging HVAC system into the modern connected world even through its non-standardized protocols. And, although agreeing on standards can sometimes be difficult, they can also be powerful tools once we all agree on them.