Do you have to wire the floor sensor probe that comes with the 3iE thermostat?

Yes, the system will operate without a sensor probe. However, for efficient use and to validate Warmup’s product warranty, installations must be completed with a Warmup floor sensing controller. If the sensor is missing or damaged, it can be repaired or replaced. If you encounter the ER1 error code, unhook the thermostat from the wall and make sure the sensor is properly connected in slots 1 and 2 of the sensor terminal. You may have to reset/reboot the thermostat to get rid of the Error Code. In the not uncommon instance where the sensor was not installed at all, you can purchase a new sensor and connect it to the thermostat, leaving it hanging in the wall. This will reduce your thermostat to AMBIENT control only, but it will bypass the ER1 code.