Break your circuit, L N E through your contactor. Link a permanent live and a neutral from your supply to your coil (Al + A2) then use your switch feed to your photocell from A1, and switch the wire to the switched phase of your contactor load. This should now open when light, close when dark.

How do you set up a contactor?

Break your circuit, L N E through your contactor. Link a permanent live and a neutral from your supply to your coil (Al + A2) then use your switch feed to your photocell from A1, and switch the wire to the switched phase of your contactor load. This should now open when light, close when dark.

Does a contactor need a neutral?

In general, no, a it is not necessary that a lighting circuit, of which a contactor is a part, have a neutral conductor in all cases. The contactor must open all UN-grounded conductors. If the contactor is a single pole, then one of the current carrying conductors must be a groundED (not the groundING) conductor.