Setback devices for furnaces and, in some cases, central air conditioning, evolved as a way of reducing energy consumption in the home with no loss in comfort. All of the units operate on the principle of a timer that turns the heat up or down automatically at predetermined times.
This allows the user to turn the heat down 10 degrees shortly after bedtime and back up to normal shortly before rising. More expensive units offer a double cycle or four settings, especially useful to those whose homes are empty during the day.
It is generally accepted that cutting back more than 10° on heating or air conditioning is not effective in saving energy. However, with 10° setbacks, the homeowner can expect to save 5-15 percent on energy bills each year, depending on location.
There are three basic types of units. The first is a replacement thermostat. It contains a timer with either single or dual cycle capabilities. Each setting allows users to set a reduction of 1°-10°. This type will control heat only, or both heating and cooling. The thermostat is automatically regulated up and back from the established "normal" setting at the times specified.
Electronic computerized devices allow consumers to program multiple settings for a given day or week. Some automatically switch between heating and cooling.
A second type of setback device is designed to integrate with an existing thermostat. It can be powered by a battery or screwed onto thermostat sub-base and contains a timer and a temperature change control. This unit, at the predetermined time, turns the dial up or back on the existing thermostat. It is available with both single and dual timing cycles.
The third type, the least expensive, controls heat by "fooling" the existing thermostat. It consists of a timer with a single cycle control that plugs into an AC outlet. This timer is wired to and controls an activator that is placed next to an existing thermostat. At a predetermined time, the activator heats a small element and raises the air temperature immediately around the thermostat, causing it to turn off.
Developed for forced air fossil fuel furnaces, these devices control the burner to cut overheating and waste. The control monitors the temperature of the duct next to the furnace. When it reaches maximum potential temperature, the device turns off the burner while the fan continues to distribute hot air. When the duct temperature drops, the control relights the burner until the desired room temperature is reached.
Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.
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