Timer switches are used to control household appliances, saving energy and adding automatic capabilities to "dumb" devices. Popular brands include Intermatic and Leviton.
Wall switch timers are fixed to the wall and wired into the electricity mains. Plug-in timers are removable and fit into standard electrical sockets.
Mechanical (Analog) Timer Switches
These have a large rotating dial, with small pegs to set the on and off times. The dial rotates once in 24 hours.
Advantages
- Easy to use.
- Can be used with fluorescent bulbs.
Disadvantages
- Some models make ticking noises because of the electrical/mechanical clock. Only a problem in bedrooms.
- Might be less reliable because of mechanical parts.
- Difficult to set exact on and off times, 15 to 30 minutes accuracy is typical.
- The same settings are used every day. No separate settings for weekdays and weekends.
Electronic (Digital) Timer Switches
These have LCD displays, and buttons to program the settings.
Advantages
- Theoretically more reliable than mechanical timers. Some have internal plastic gears that can fail, and other reliability issues.
- Normally quiet.
- Can have complex features such as different programs for different days, automatic tracking of sunset times.
- Normally more accurate than mechanical timers, but some have analog electronic clocks (not quartz) that can drift as much as a minute a week.
Disadvantages
- Many are not suitable for use with fluorescent bulbs, causing the bulbs to fail after a few weeks or months. Unless specifically stated by the manufacturer, these timers should not be used with fluorescent lamps.
- Can be complicated to program.
- Small, hard-to-read LCD displays are a common complaint.
Battery Issues
Digital timers with battery backups are convenient as the timer settings will be preserved if the mains electricity supply is cut.
Some digital timers will run down their batteries even if there is no power cut. Their internal electronics always draw power from the batteries, never the mains supply. The batteries need to be replaced every few months, a significant disadvantage.
Battery backups for mechanical timers are rare, but not unknown. They are less necessary as after a power cut all that needs to be done is to turn the dial to the correct time.
Number of Conductors
Shoppers should check that the timer socket will fit their appliances.
Many timers have two-prong sockets (no Earth). An electrical appliance with a three-prong plug should never be used with a two-prong socket (using an extension cord to convert, for example) as this reduces protection against electrocution.
Number of Programs
Even digital timers can have a limited number of on/off times per day. Those who require more than one on/off program a day should check that this is supported by the timer.
Mechanical timers are limited by the number of on/off pegs supplied. Often only two sets are provided. Some mechanical timers have built-in sliding pegs for every 15 or 30 minutes in a day. This means that any combination of on/off settings can be programmed, in increments of 15 or 30 minutes.
Countdown (Preset) Timers
Instead of setting a fixed time of day, a delay of between 5 to 30 minutes is triggered. This is useful for water heaters, bathroom exhaust fans. Both mechanical and electronic countdown (or rundown) timers are available.
The Best Timer Switch
When choosing a timer, important points to note are:
- Both digital and analog timers can have reliability issues. Shoppers should search the Internet for user reviews of individual models.
- Fluorescent lamps need special digital timers. If in doubt, a mechanical timer should be used.
- Digital timers can be difficult to program. The simplest timer that can get the job done, should be selected.
Resources
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