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How Does a Programmable Thermostat Work?

Mukul Deshpande Nov 23, 2018
A thermostat is that part of a control system which coordinates with the cooling and heating devices to maintain the correct temperature. The manual versions of this device are fast being replaced by programmable or clock ones.
A programmable thermostat can be a 7-day model facilitating different temperature settings for each day or a 5+2 model in which temperature can be set separately for weekdays (from Monday to Friday) and weekends (Saturday and Sunday).
It can also be a 5-1-1 model in which you have one temperature setting for weekdays, another for Saturday, and a third one for Sunday. The RiteTemp 6030 and the Honeywell RTH8500D come with a 7-day model. The Honeywell RTH230B has a 5+2 model. The RiteTemp 6022 and the Honeywell RTH6400D are 5-1-1 models.
If price is not a factor, the best option is the 7-day model. Some models are lockable, which means unauthorized persons cannot change the temperature. Some of them allow the temperature to be changed by a remote control, whereas some have Wi-Fi and voice control features.

How it Works

While using a programmable thermostat, you need to specify the start and end time of the period, and the equipment automatically changes the temperature for that particular span. You can specify up to 4 periods per day as morning, day, evening, and night.
The recommended temperature settings are between 70°F and 78°F so that the occupiers of the house are comfortable. The temperature can exceed this range when you're outside the house or sleeping.
The thermostat has a vacation feature which allows you to set a constant temperature in the house when you are out on a holiday. A device having the adaptive recovery feature may start cooling or heating the house so that the temperature is reached by the set time.
There are many factors that a clock thermostat is designed to check for, before starting to heat or cool the house:
  • The temperature of the furniture
  • The temperature of the wall, which depends on the construction of the building and the materials used
  • The weather patterns during summer, winter, and other seasons
These devices may be digital or electromechanical. The electromechanical ones use a dial or a slide to regulate the temperature. Some automatically compensate for daylight saving time.


Keep the machines away from direct sunlight or other sources of light such as bright lamps and skylights. Don't place them near doorways or windows; keep them away from drafts of wind. You may have more than one thermostat in the house.
The benefits are most obvious in moderate climates than in extreme climates. A clock or setback one should not be used with a heat pump.


You may need to call a HVAC (heating, ventilating, and air-conditioning) contractor to install your programmable thermostat. You should install it mainly if you're planning to install a new CAC (central air conditioning) system. If your old one contains mercury, take extra care while uninstalling it.
1. The first step in installing a clock thermostat is switching off the power.
2. While removing the old manual version, make sure that the wires don't go back into the wall. This can be done by wrapping the wires around a pencil.
3. Next, drill holes in the wall for the anchors that come with it and place the mounting plate on the wall.
4. Join the wires to the terminals. The new thermostat may have a configuration with two, three, four, or five wires. Connect the red wire into the red nut, and the white wire into the white nut, and so on.
5. Insert two double A batteries into the new device after ensuring that the polarity is correct and attach it to the mounting plate.
6. Press the reset button to clear the program memory. Finally, turn on the power, and your new equipment should function properly.


A clock thermostat is an energy-saving device that will help cut down on your energy usage in the house by reducing the difference between the outdoor and indoor temperatures. It will lower your energy bills, which is especially important at a time when energy prices are soaring.
It also helps in protecting the environment by reducing the carbon emissions that contribute to global warming. When choosing a model for your system, make sure that it has the Energy Star logo, so it contributes to making your home energy efficient.
When you compare programmable thermostats, you can choose one that does only heating or does both heating and cooling. Don't forget to read reviews that mention whether the thermostat is easy or difficult to use, so you can choose one having simple functionality.