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Thermostat Quick Guide -- All About Thermostats


Honeywell TH8110


Honeywell T8775-C1005


White Rodgers 1F72-151


Robert Shaw 8600


1. What is a thermostat?

A thermostat is a device that controls the temperature of an environment by adjusting the degrees to maintain a preferred temperature range. It will turn on heating if the temperature becomes chilly, or start-up the air conditioning if it gets too warm. Thermostats control the mechanisms of heating and/or cooling systems by directing energy to the right system when needed, bringing you a nice and cozy environment and saving you money!

2. What different types of systems can be regulated by a thermostat?

Thermostat Quick Guide -- All About ThermostatsSingle-stage heating indicates one gas or electric heating device for the system. It can consist of just a heater, or include an air conditioning device as well. Almost all systems that use natural gas are single-stage. Generally, a single-stage thermostat will need to accommodate five wires or less if the system handles heat and air conditioning. If the system is only for heat, only three or fewer are needed.

A multi-stage system will have both a standard gas or electric heating device as well as an auxiliary and/or emergency heating device. The auxiliary or emergency heating will engage when the temperature drops faster than the main heater can maintain, or, if there is a problem with the main heater. The wiring of a multi-stage thermostat is connected to a W2 terminal.

Heating systems are either conventional (gas or electric) or use a heat pump. Heat pumps are unique in that they consist of a single unit that provides both heating and cooling. In the Midwest heat pumps are a popular choice for most households. If you know that your system runs both heating and cooling entirely out of one unit, and features an auxiliary setting, it is likely that you have a heat pump.

Line voltage systems use direct current, and either use 120 or 240 volts for a household system. One telltale sign that your home can accommodate a line voltage thermostat is that wires are much thicker to handle additional conducted power. Line voltage, electric heat thermostats are common with older construction, especially where electric or baseboard heaters are present. Line voltage systems are not compatible with gas heating. The adjustment controls are usually mechanical, rather than digital programmable, and almost always have either two or four wires (single pole versus double pole).

3. How do electromechanical, manual, and programmable thermostats differ?

Electromechanical - or manual - thermostats are the old-fashioned mercury units that have internal coils to expand or contract in response to temperature change. This type is becoming obsolete for two reasons: digital thermostats are able to more accurately register and respond to temperature changes, and the purchase of products containing mercury has been restricted or banned in many states. However, manual thermostats remain popular due to their low cost, the familiarity of their controls' design, and the ease of their use.

Manual digital thermostats use an electronic temperature sensor to register changes in the room temperature that then compare these changes with the settings selected by the user. If there is a difference between the room temperature and the set temperature, a command is sent to the heating or cooling system that action is needed. For this type of unit, you will still have to physically adjust the setting of your preferences whenever you would like to adjust the room temperature.

Programmable digital thermostats are an upgrade from the digital manual thermostats as they are far more convenient and can help save energy costs. Once you program the thermostat to fit your lifestyle and schedule, all you have to do is relax and let it do all the work. To stay comfortable and save energy year-round, you simply must program the temperatures into the memory of the unit, along with the times of day that you would like the changes to occur. For example, you can set a thermostat to a comfortable temperature for when you wake up in the morning, have it go into energy-conservation mode - while you are away at work, and then have a temperature set to go before you return home! You only need to program your thermostat once - until your season, schedule, or lifestyle changes.

Depending on the model, a thermostat can be programmed in one of three ways:

  • 5 - 2 programming: Maintains a set schedule for five days (weekdays), then switches to an alternate schedule for the other two days (weekends).

  • 5 - 1 - 1 programming: Maintains a five day schedule (weekdays), then switches to first individual day (Saturday), then second individual day (Sunday).

  • 7 day programming: Allows the maximum flexibility for those with frequently-changing schedules by allowing you to program each day individually.

Special features to look for:

  • Automatic switchover - This allows the thermostat to control both heating and cooling without requiring that you manually switch between the heat and cool settings. Most digital programmable thermostats have this feature.

  • Manual override - Lets you manually modify your settings on a programmable thermostat. Your changes will remain in effect until the next programmed setting begins.

  • Vacation override - This function temporarily overrides any preprogrammed settings while you are away, saving money on unnecessary temperature maintenance. When you return, you can go back to your original settings without reprogramming from scratch!

  • Keypad lock - This prevents any changes to your system once you have programmed the settings.

  • Battery indicator - For the units that use a battery, this lets you know that the battery is low and needs to be replaced.

  • Filter change indicator - This indicator is triggered after a preset length of time to indicate that the system's internal filters need to be cleaned or replaced. Clean filters improve the efficiency of your furnace or air conditioner!

  • Auto season changeover - Changes settings as the seasons change.

  • Energy monitor - Maintains a record of how many hours your system has run for any period of time that you select.

  • Plus many other unique features to keep you comfortable!

If you are still unsure which thermostat will best suit your needs, feel free to contact our friendly customer service representatives at (800)734-0405 for more help! When you call, it is very helpful to have available the brand and model number of the thermostat that you are currently using. Most manufacturers print the model number of the thermostat on the inside of the wall casing, normally behind the easily-removed cover.

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Air & Water, Inc. serves Orange County, Los Angeles County, Riverside County, San Bernardino County.  If you live in any of the following zip codes, please feel free to come see our products in person: 92628, 90630, 92629, 92650, 92609, 92610, 92708, 92728, 92831, 92832, and 92833.

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