Electrical – Removing Outdoor Lights

From the looks of it, there are only black, white, and ground in the junction box. This most likely means it's set up as a switch, and the white wire is actually a switched hot (and should be marked with tape or marker with a black or red stripe).

Unfortunately, since your timer requires a neutral, this isn't quite going to work.

What you need to do is:

• Open the main panel
• You should find:
  • The black from this junction box goes to the breaker
  • The white is connected to a black wire that goes off to the fixture
  • The white wire that goes off to the fixture is connected to the neutral bus

If this isn't the case: stop. Update the post, as my instructions won't help.

• First, route the wire that goes off to the fixture into this junction box
  • Ideally, you would do this outside of the breaker panel
  • You may need to use wire nuts and run a new wire into the junction box
• Second, run a new wire from the panel to the junction box
  • Connect neutral (white) to the neutral bus in the breaker panel
  • Connect hot (black) to the breaker in question
  • You may be able to use whatever wire is there now for this, impossible to tell without opening the panel

You should now have in the junction box:

• Black + white + ground from the panel (black from the breaker, white from neutral bus)
• Black + white + ground going to the fixture.

Basically, just connect it up exactly as that diagram shows:

• Connect grounds together, and to the fixture
• Connect neutrals together (including the white wire on the timer)
• Connect black from the break to black on the switch
• Connect blue from the switch to black to the fixture

Assuming that it's twin and earth wiring (which it sounds like from your description), yes the earth wire in the cable is typically uninsulated once the outer sheath has been removed. It's usual to use a piece of yellow and green sleeving to slip over the earth wire to provide basic insulation.

I'd recommend that you run the outer sheath of the cable into the junction box, or you could likely run into water ingress issues in the future.

As to why it's exposed, I'd hazard a guess that it's a cost saving measure to avoid the additional insulation. Except in a fault condition, there should be no current in or potential on the earth conductor, so it doesn't need the same level of protection as the line conductors.