How do I connect an expansion unit/power module to the DITRA-HEAT-E-WIFI, DITRA-HEAT-E-RT or DITRA-HEAT-E-R thermostats? What is the maximum length of signal cable between a power module and the thermostat?

Connect a 2 conductor 20 AWG wire from terminal A on the thermostat to terminal C on the power module and from terminal B on thermostat to terminal D on power module.

The maximum length is 80 feet (25 meters), and with 20 AWG signal or communication wire (recommended). See the installation guide for further details.