LightwaveRF LW921 Instruction Manual page 13

Device setup
Linking the Thermostat to LightwaveRF heating devices
To use a LightwaveRF Home Thermostat with other
LightwaveRF heating devices, such as the Boiler Switch, you
will need to 'link' them. The thermostat can be linked to other
LightwaveRF heating devices using the following method.
1.
Press and release the 'link' button on the thermostat. 'link'
should appear on the display.
2.
Press the Link button on the heating device you wish to
link. 'Link OK' should appear to indicate that the Thermostat
is linked.
To unlink a heating device from the Thermostat, press and
release the linking button and then press the Standby button.
This activates 'unlinking' mode. Press the linking button on the
heating device you wish to unlink. The 'deleted' should be
displayed to indicate that the devices have been unlinked.
To completely clear the memory of the Thermostat, press
and release the linking button. Then hold the linking button
until 'clear' is displayed. Finally, press and release the linking
button once more. 'Cleared' should be displayed.