Installing a Room Thermostat

Before attempting to install the thermostat, read the manufacturer’ s installation instructions. These instructions should be followed as closely as possible to ensure efficient thermostat operation.

Always handle the thermostat carefully. Rough handling may decrease its accuracy. Inspect the thermostat carefully when you unpack it. Report any damage to the shipper if the damage was caused after it left the factory or distribution center. Their insurance should pay for any replacement. Any other damage or malfunction should be reported to the thermostat manufacturer or his field representative. The thermostat is the basic controller in any heating and/or cooling system. It must operate accurately and efficiently.

Make sure the thermostat selected for the heating and cooling system is the appropriate one for the job. Heat pumps require twostage thermostats. Furnaces and boilers used with air-conditioning systems commonly require thermostats with extra terminals. Thermostats with changeover terminals are required for many zoned systems. Check the manufacturer’ s specification sheet before making a final selection.

The installation instructions differ from one thermostat manufacturer to another, usually on the basis of design and construction; however, the following points are common to all:

1. Mercury-switch thermostats are usually shipped with some form of protection around the mercury tube to prevent breakage. This must be removed before operating the thermostat.
2. Disconnect the power supply before connecting the wiring to the thermostat in order to prevent electrical shock and/or equipment damage. Low-voltage thermostats are used in heating and cooling systems. These low voltages are not fatal, but they can deliver a nasty shock and may damage the system controls.
3. All wiring must be done in accordance with local electrical codes and ordinances. Be sure to follow the thermostat manufacturer’ s wiring diagram when making the connections.
4. Use a plumb line or spirit level to accurately level the subbase or wall plate when mounting it on the wall (see Figure 4-26). Thermostat control deviations are often caused by inaccurate leveling.
5. Follow the manufacturer’ s instructions for making any internal wiring connections (e.g., connecting lead wires to terminal screws), connecting a heating thermostat to a cooling base, and so on.
6. Check out the installation to make sure the thermostat is operating correctly.