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what is a programmable thermostat

A programmable thermostat is a thermostat which is designed to adjust the temperature according to a series of programmed settings that take effect at different times of the day. Programmable thermostats may also be called setback thermostats or clock thermostats.

Programmable thermostats save energy by permitting occupants to set temperatures according to whether the house is occupied. These thermostats can automatically store and repeat settings daily with allowance for manual override. By eliminating manual setback, which is easy to forget, they allow the setting of more comfortable temperatures in the morning before occupants wake. Temperature setback can be adjusted for both heating and cooling seasons.

Programmable thermostats can be set to adjust the temperature setting according to a user's schedule. These thermostats typically have a digital interface that allows more precise temperature control and a wider range of options or features.

Programmable thermostats typically offer a number of programming options:

  • Daily programming that allows one schedule to be used each day.
  • Weekday/Weekend (5/2) programming that allows adjustment of timing for setbacks with different settings for weekdays and weekends, and with 5/1/1 programming that permits separate schedules for Saturday and Sunday.
  • Full seven-day programming that permits a different setback schedule for each day of the week.

Other special features depend on manufacturer and model and may include the following:

  • Vacation Override, which allows temporary override of the programmed settings.
  • Keyboard Lock, which prevents unauthorized changes to the preprogrammed settings.
  • Low Battery Indicator indicates whether the battery used to hold the programmed schedule is low.
  • An Energy Monitor that can keep track of how many hours the HVAC system has run for any selected time period.
  • An Auto Season Changeover that automatically provides heat or cooling at the onset of the heating and cooling season.
  • A Filter Change Indicator that goes on after a pre-set time period to remind when it is time to clean or replace the filter.

Different types of heating/cooling systems may require different types of programmable thermostats. For example, heat pumps require programmable thermostats that minimize the use of less efficient auxiliary electric resistance heating. Only a few companies manufacture line-voltage setback thermostats that directly control 120 volt or 240 volt line-voltage circuits connected to electric baseboard electric heaters. When purchasing a programmable thermostat, it is necessary to insure the thermostat is compatible with the HVAC system.