The ecobee EB-PEK-01 Power Extender Kit simplifies the installation of a EB-SmartSi-01 or EB-EMSSi-01 thermostat in applications where there is no existing common wire available for installation.
ecobee Smart Si Power Extender Kit. Install in place of running a ‘C’ common wire. Simplifies 4-wire installs. Compatible with Smart Si and EMS Si only