Greetings - here is the response:
To answer the Intesis engineer’s question: the Mitsubishi unit has an option for an external mitsubishi temperature sensor that lives in the wall of the room instead of the return duct. When this optional sensor is installed, the mistubishi unit will send via CN105 the temperature at the external sensor, instead of the one in the return air. I have verified that this is happening as intended and the right value is being sent to the Intesis gateway.
My original problem and why I reached out to you was that in heating mode, the temperature sent to Intesis was several degrees off from the actual temperature in the room. After speaking to Mitsubishi engineers, I found out that the mitsubishi units have an offset that is enabled by default, that will manipulate the reported temperature to account for the fact that it is being read in the return duct and not in the room (the idea being that the temperature high up in the ceiling would be different from the actual temperature in the room). This “feature” should be disabled when using the external sensor, and once I disabled it, the temperature reported to intesis became correct.
Now the remaining problem that I have is the following: I noticed that the temperature readings are not very granular. They will jump up and down by several degrees Farenheit at one time. After digging around, I found that the Mitsubishi unit natively talks in degrees celsius, which are less precise than Farenheit to begin with. When reading values in intesis, it looked like only full degrees celcius were being reported by Mitsubishi, which is not very granular at all. I reached out to Mitsubishi and they stated that the “old” CN105 protocol was indeed communicating only in full degrees celsius (so the reported temp could be either 25 degrees celsius or 26 degrees celsius, but not in between). The “new” CN105 protocol however is reporting temperatures in half degrees celsius, and so are my Mitsubishi units. I was able to verify this using a Mitsubishi MAA remote controller.
Now it appears that the intesis boxes are not setup for this, and are always rounding the temperature down to the fullest degree celsius. I was able to verify this by telneting into the intesis box and using the ascii query protocol, while watching the temperature reported by the same mitsubishi unit on the mitsubishi MAA controller. The Mitsubishi controller would report 25.5 degrees celsius while the intesis would report a value of 250.
So I am wondering if there is a setting or firmware update available that would allow the intesis boxes to read and report temperature in half degree celsius increments as they are being received through this newer CN105 protocol, and if not, whether this could be fixed by a patch?
The reason for needing the half degree celsius increment is that I need to build a dual setpoint thermostat in software (which is also what mitsubishi does in their own thermostat and Kumo cloud that they sell to customers), as this feature is lacking in mitsubishi’s residential equipment natively, and the full degrees celcius plus deadband of the mitsubishi unit make this much too imprecise to achieve a constant temperature in the house.