Of course, you can use a two-wire timer even if you have four wires available. These are super simple to install: just remove the existing switch and connect the timer to the two wires that used to be connected to the switch. Many two-wire timers require a battery, so watch out for that!!! There is at least one that is purely mechanical and doesn’t require a battery (the Intermatic EJ351 note that the instructions for this say it only works with incandescent bulbs, not fluorescent). Two-wire timers don’t use wall power to run. Okay, now that that painful step is out of the way, I can start talking about the pros and cons of the different types of timers.

So, the question is, does your switch box only have two types of wires (“hot” and “load”), or does it have a neutral wire as well?

Ground: usually bare copper or green, often tied to other wires of the same type, sometimes comes from a cable containing AC and Neutral.Neutral: usually white, often tied to other white wires, sometimes comes from a cable containing AC and Ground.If you measure the voltage using a volt meter, you will find 115V AC when the switch is on, and 0V when the switch is off. Power to the light bulb or “load”: goes from the other pole of the existing switch to your light, sometimes black also, usually a single wire not tied to any other wires.If you measure the voltage using a volt meter (after carfully turning the power back on at the switchbox), you will find about 115V AC. AC power or “hot” wire: goes to the existing switch, sometimes red, blue, or black, often bundled together with other wires of the same type, sometimes comes from a cable or conduit with Neutral and Ground wires in it.The summary of the four possible types of wires you might have are as follows: The ground wire is often bare copper or sometimes green. Note that neutral is different than ground. One of these wires is power (“hot”), and the other goes to the light, or the “load”, as it is called. The answer will be at least two, since the switch needs a wire coming from power and a wire going to the light in order to work. You then need to figure out how many different types of wires are available inside that box. Once the switch box is exposed, unscrew the switch and pull it out slightly so that you can see the wires that are available inside the box. Next, unscrew the cosmetic wall plate and put it aside. Turn on the light and go through your switches to find the one that controls that light. Some experimentation might be necessary to find the right circuit breaker switch controls the light. To find out, first shut off power to the switch you’re working on by turning off the respective switch on your circuit breaker. New homes are required to have a neutral wire, but if your home is old, it might not have it. Before buying anything, you need to find out if your switch box has the neutral wire available. This is actually the trickiest part of the project, but doing this before you go out and buy a timer can save you the hassle of going back and returning it. Do you have a neutral wire in the switch box? But, double check to be sure, and note which type you have so you buy the right kind of timer.

Luckily, most things that you would want to put a timer on, like a porch light, only have one switch controlling them. Three-way switch wiring is more complicated and will require a timer that is specifically for three-way switches. The options I discuss in this article only cover the case where one switch controls the light, or a “single pole” switch. This is often the case in a long hallway or staircase, where you can control the hallway light from either end. A three-way switch is when two switches control the same light. The first thing to determine is whether the existing switch that you want to replace is a three-way switch or not. Is the existing switch a three-way switch?

Smart timer switch