May 4, 2025

    Well, drat! We had a really tough bug to find and fix. We were using the dead band that the X-400 series of controllers provide in their conditional tasks, so the HVAC compressor wouldn’t be short cycled by noise on the temperature sensor. That wasn’t always working??!

     It’s impossible to explain without a graph and discussion from the X-400 series user manual:

So, what was the problem? We had two conditions on the turn off - temperature satisified or Evaporator Coil Freezeup detected. If we shut down on the freeze up condition, the temperature value did not go below the yellow line, the “Setpoint - Deadband” in the above chart. Therefor the deadband was never cleared and therefor the system never turned on. 

So, we had to implement the dead band ouselves because the freeze up condition made the deadband not work.

We now have the “deadband” explicitly defined on the control page. It’s the delta between the Cool On and Off temps. Not pretty, but it works. Almost ugly enough to resort to using the basic script the X-400 series have.

We won’t need to do this for the Infloor Heat because that only has one condition and the builtin dead band will work fine.