My thermostat reads error message “ER2” on the display?
3iE Energy-Monitoring Thermostat
The ER2 message will occur if the floor sensor has a failed, not be connected or if there is a loose connection.
Your electrician must make sure all connections are secure and test the probe using a multi meter set to 20K ohms scale. The resistance reading should be between 8 and 12K ohms.
If a short is found and a backup sensor probe was not installed, you can bypass the error message by setting the thermostat to read the air temperature instead.
Menu > Settings > Set Heating Target > Target Air Temperature
Please note this feature cannot be used when installing under delicate floor covering such as vinyl or wood, a new sensor will need to be fitted if the original one has failed.