Wattio THERMIC Manual Del Usuario página 36

In case of a two wire thermostat circuit, the other wire needs to be placed in one of the other
two holes of the terminal block. The correct one will depend on the type of heater system,
normally opened or normally closed. The following scheme indicates it graphically:
Another way to identify the heater system type is as follows:

In case that the heating system does not work when the wires
are not connected, the missing wire must be placed in the
position1.

If the heating system works even if the wires are not
connected, the missing wire will be placed in the position2.
For a three wire thermostat circuits annul "Neutral"
(N) wire or "Ground lead". Cover the end of the cable
with insulating tape.
The phase cables must be connected to the terminal
block.
For a four wire thermostat circuits, it is highly recommendable to keep the old thermostat-label,
as there is a high variability in the wire set up, depending on the thermostat model.
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