Google Nest Protect How To Install page 4

6. Remove the
old
backplate
Unscrew the back plate from the ceiling or electrical box. Save
the screws for installing the Nest back plate later. You'll see one
or two wires coming from the ceiling.
Each wire in the ceiling or wall will have two to four differently
coloured conductors. Their colours may vary based on their age.
If you are in the Netherlands, the interconnect conductor is
usually coloured orange.
7. Attach the
Nest
connector
Match the live wires coming from the ceiling to the live wires in
the Nest 230V AC connector and put them into a connector
block. All the neutral wires go into another connector block, and
the earth wires into a third terminal block.