I don’t see this documented anywhere, and if I hadn’t noticed, my pipes might have frozen (because I rely on these to activate a relay which powers a hot water recirculation system). When I moved the temperature sensor terminal block from my 2022 Cerbo to a 2024 Cerbo (MK2), all four temperatures were way off. I’m not talking about the Offset being reset to 0º. I’m talking about the “Sensor voltage”, which (using GUI v2) is shown in Settings > Device list > [sensor name] > Setup.
While parked in a heated garage I collected data points from several Cerbos, moving the same terminal block from one Cerbo to another, without removing any individual GX temperature sensor from the block. All these hardwired sensors are properly inserted using ferrules, and I was careful to ensure the block was fully seated into each Cerbo.
2022 Cerbo readings:
- input 1: 2.78V
- input 2: 2.79V
- input 3: 2.77V
- input 4: 2.78V
Brand new 2024 Cerbo MK2:
- input 1: 2.88V
- input 2: 2.89V
- input 3: 2.87V
- input 4: 2.88V
Another brand new 2024 Cerbo MK2:
- input 1: 2.88V
- input 2: 2.89V
- input 3: 2.87V
- input 4: 2.88V
Spare unopened 2023 Cerbo:
- input 1: 2.99V
- input 2: 3.00V
- input 3: 2.98V
- input 4: 2.99V
Thus, it appears the Cerbo MK2s are consistent with how they interpret GX temperature sensor voltage, but the older Cerbos are not. The 2022 Cerbo thinks all sensors are 100mV lower, and the 2023 Cerbo thinks all sensors are 110mV higher. Fortunately, each Cerbo seems internally consistent, which means you should be able to look at the voltage difference of one input and update your Offsets for all sensors accordingly. Each degree Celsius is 10mV, so in my case I changed my offsets from about -6º to +4º to account for the 100mV increase.
As a side note, my 2022 and 2023 Cerbos treat the temperature sensors as instances 24-27, whereas my 2024 MK2s treat the temperature sensors as instances 20-23. This meant I had to update my widgets and alarms accordingly. Also, don’t make the mistake I did by deleting the old instances from VRM, because in doing so I lost my history. Fortunately I export all data every 2 weeks and can use a spreadsheet app (like Microsoft Excel or macOS Numbers) to graph the CSV data if need be.