You can install the MTS200(for electric system version) with your system according to the diagram and video below. Connecting to terminals 1-4 is required, the sensor connected to terminals 6,7 is optional. You can also follow up on the Meross APP step by step to set up the MTS200 with your system.
It means overheat protection triggered, and the device has stoped heating. You can check the floor sensor temperature and adjust the settings in meross app —＞Device Settings —＞Floor overheat protection. Or you can check the floor sensor on the corresponding port of your thermostat.
Yes, you can use the internal sensor to control the temperature and the external sensor to do the floor overheating protection(optional). Or you can use the external sensor to control the temperature, at which point it will no longer be used for floor overheat protection detection. This sensor option function is supported by Meross app.