In the entry way of my 1935 home, there is a double switch box. One switch is a basic,two wire light switch controlling the indoor entry light. The other switch is a mechanical Intermatic EJ351 timer switch controlling the porch light. Each switch uses only two wires.
Coming from the conduit attached to the box are three cloth covered wires. They are old and very dirty, but, appear to be in good condition. The colors don't make sense to me. One appears to be red, one green and one black. Using a meter set at 200 VAC, I put the black probe to the junction box (as ground) and tested each wire with the red probe. The black and red wires showed no voltage, but, the green wire has full line voltage. The black wire is connected to the simple light switch, the red wire is connected to the mechanical timer and the green wire is connected to both. My limited knowledge of house wiring thereby suggests that the red and black wires are both neutral and the green is "hot". Not withstanding the colors, I would have thought there would be two hot, one neutral and a ground wire. At least the box appears to be a good ground.
The question is, how do I wire the Smart Switch KS-602 or can I even use it? It requires four wire connections which they label load, line, ground and neutral. I assume ground I can connect to the box, the red to the neutral, the green to line, but, what do I connect to load, another neutral?
Thank you for any help.
Allan
Best Answer
From your description, it sounds like the green wire is live, the black wire is connected to the entry light and the red wire is connected to the patio light. There is no ground or neutral coming to the box. The EJ351 timer switch is specifically advertised as not requiring a neutral connection.
Try turning on either light and then measuring the voltage on the black/red wires. These wires will now "appear" to be hot wires since they will be connected to live through the switch. When the lights are off the wires will "appear" as neutral since there is a (relatively) low-resistance path to neutral through the lights. They are the switched hot wires going to either light.
You cannot use your smart switch without a neutral wire.