What is a Timer or Time Switch?

Time switch
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So what exactly is a time switch? Could it be some sort of time machine that takes you back in time and makes the switch from now to then? Of course not! The concept is really pretty simple. It is a device with a built-in timer that turns a circuit on and off automatically at preset times.

Time vs. Timer

If you're thinking that a time switch sounds a lot like a timer switch, you're not far off. In fact, the two names often are used interchangeably, but there are some differences.

A time switch typically is used for commercial- or industrial-grade switches that control things like HVAC (heating, ventilation, air conditioning) equipment, traffic lighting, commercial water heaters, and large pumps. Time switches often have detailed programming functions and are may be rated for 30 or more amps and 120 or 240 volts of electricity. Timer switches usually are residential-grade wall switches for controlling lights, and most are rated for standard 120-volt household electricity. 

Setting a Time Switch

A classic time switch is a dial-type that is set manually. You set the switching time by lifting up on the timer dial and turning it to the proper time. This is set by aligning the time of day on the dial with the silver time arm in the center of the dial. Caution! Do not turn the center time arm pointer! When power is applied to the time switch, the motorized dial will keep time, just like a clock or watch.

How Timers Work

As the dial advances, it triggers "on" and "off" trippers. These are bolted on the face of the dial and turn the switch "on" and "off" at the times you selected on the dial. You can set as many times as you want, which makes this a nice feature. The switch it controls is basically a single-pole switch, which is either "on" or "off".