Owens Corning
How to Install a Setback Thermostat
The cost of heating or cooling a house is becoming a big ticket item in most everybody's budget. If you live in the South, your money is spent on air conditioning, and in the northern states keeping a house warm in the winter takes lots of energy dollars.

No matter where you live, one of the best ways to help you save energy and money is to install a setback thermostat. Now that's not exactly earth-shattering news for anybody. But what is newsworthy is the latest version of setback thermostats featuring multiple cycles. Older types of setbacks allowed for only one or at best two cycle changes. You can set back the temperature to a money-saving lower setting during the evening hours while everyone is sleeping and then automatically raise the temperature in the morning.

Newer programmable thermostats allow for more complex cycles that allow you to raise or lower the heating or cooling setting on the thermostat to fit your lifestyle. A typical program might run like this: At 6:30 a.m., the heat rises from an energy saving 55 degrees to 70 degrees for showering and breakfast. Everyone is on their way by 8:30 a.m., so the temperature is lowered to 65 degrees until 11:30 a.m., when some family members show up for a lunch break and want it 70 degrees. The thermostat sets back the temperature down to 65 until 4:00 p.m., when people start returning home from school and work. The thermostat then maintains the temperature in the house at 70 degrees until 10:30 a.m., when everyone is ready for bed.

A different program can be set for each day of the week. The new thermostats can also be programmed for a separate cooling cycle. Of course you can override the program any time you want.

Throughout the evolution of heating and cooling systems, there have been many types of thermostat controls installed. When you pull your old thermostat off the wall you will probably find that it has two, three, or even five or more thin wires connected it. The new setback thermostats are designed to work with most systems and come with specific, easy-to-follow wiring diagrams.

Installing a thermostat is safe because most heat control devices run on 24-volt circuits. This low voltage does not present a shock hazard. Some systems, especially electric heat, use standard house 120-volt house current. If your thermostat is connected to thin wires coming directly out of a hole in the wall, then have a safe 24-volt system. If the thermostat is connected to an electrical box, don't attempt to install a standard setback thermostat until you seek professional help.

Before you shop for a setback thermostat take a look at your old one. Remove the cover. Most of them snap off but some are held in place with a couple of screws. Look at the screw terminals and see how many wires are connected to them. If there are five or less, you will be able to make the swap yourself.

When shopping for a thermostat consider your present and future needs. If you don't have central air conditioning, then purchase a unit for heating only. But if you do plan to install air conditioning in the near future, consider this feature. The more features the thermostat has, the more expensive it is and the longer you will take to recover your investment. Don't skimp. If the thermostat can't handle your schedule, you might not be able to take full advantage of potential energy savings.

Step-by-Step Installation

Turn the power off to the furnace at the main switch or open the circuit breaker serving the furnace. If you haven't already removed the cover of your old thermostat, take it off. Before you remove any wires, make a diagram of the position of each wire and what terminal it is connected to on the thermostat. Most replacement setback thermostats come with stick-on wire identification tags that make this process easy. It is very important that you identify each wire before you remove it. With a two-wire system it does not matter which wire is attached, but it does on a five wire system and there are twenty-five possible combinations. If you miswire the thermostat, there is a possibility you will damage it.

After you have the wires identified, remove the old thermostat. You can sometimes detect how many layers of paint or wallpaper have been applied to the wall with the cover removed. Usually the new thermostat will cover up the wall area concealing mismatched paint or wallpaper discovered behind the cover. If the new thermostat is smaller than the old one, you may want to touch up this area with paint or wallpaper before you install the new one.

The new thermostat will most likely be of the solid state type and be powered by a 9-volt transistor radio battery. Most of these do not use a mercury switch, so it's not important that they be mounted perfectly level. If you are installing one with a mechanical check-type timer, you should take care to level the thermostat or you will not get accurate temperatures.

The thermostats come with mounting screws and wall anchors. Some manufacturers provide location templates, others direct you to use the base of the thermostat as a template. In either case, mark the location of the mounting screws on the wall and then drill a 3/16-inch hole for each wall anchor. Tap the wall anchor into the hole and then install the mounting plate or body of the thermostat with the screws provided.

Wiring up the thermostat is not difficult; the only requirement is that you follow the directions exactly. The two-wire systems are very easy to wire. Most thermostats have a row of screw terminals. Connect either wire to the terminal marked with a W and the other wire to the terminal marked R. Loosen the screw, push the wire under the terminal arm, and then tighten the screw. Of course, if the specific installation directions provided by the manufacturer instruct you to connect these wires differently, follow those directions.

Other systems are just as straightforward to wire up, but because there are so many different possibilities you should follow the specific directions that come with the thermostat.

After the thermostat is wired install the 9-volt battery if one is required. Return the power to "on" to the furnace. Follow the directions in the owner's manual, which should tell you that you turn the thermostat on by placing it in either the "heat" or "cool" mode. Then put the thermostat into its "manual" mode and set the temperature a few degrees above the present room temperature, or lower it if you're testing the thermostat in the 'cool' mode. If you experience any problems, refer to the trouble-shooting section of your owner's manual.

Written by the editors of HouseNet.

Copyright HouseNet, Inc.

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