Acme How To Logo Acme How To Logo
Related Articles
HVAC Section





Energy Ideas


Sign up to receive our free Maintenance Reminder Newsletter

Learn More

How To Choose a Thermostat

Before replacing a thermostat, you must first select the proper replacement. A vast majority of home heating systems use a low-voltage thermostatic control. However, there are two other types of controls, so you must determine which type thermostat you need.

If you are looking for instructions on how to install a thermostat, take a look at this article.

Beyond the type of control, you must decide what features you want. Honestly, to get to the heart of the matter, choose a digital thermostat with 5-1-1 or 24 hour programming. This will allow you to set temperatures for different times of day and a different schedule for the week and each day of the weekend. The 24 hour model allows you to set a different schedule for every day of the week.

More expensive models have a PID controller built-in that will decide when to start the system based upon the current temperature and the desired temperature at an appointed time. For instance, if you wanted the temperature to be 68 degrees when you wake up at 7am, the basic unit would turn on at 7am and start heating, the programmed temperature would be reached sometime after 7am. The unit with the PID would start the system so that 68 degrees is the ambient temperature when you wake up at 7am. On an extra cold morning the system would start heating even earlier so that it could have the temperature up to 68 at the appointed time.

Is a programmable thermostat the cheapest option? No, but it isn't expensive either. Plus, the programming allows you to save money by heating your home to a comfortable when you are home, a lower temperature while you sleep and an even lower temperature (or not at all) while you are away from home. This thermostat will pay for itself in fuel savings and convenience, tests suggest a 30% fuel savings over standard thermostats.

Now to the matter of determining which type is needed. There are essentially three types of thermostats: millivolt (75mv), low-voltage (usually 24v) and line voltage (110v or 220v).

Millivolt systems use two wires and typically connect to older wall or floor furnaces; units that heat only one area.

Line Voltage systems can be recognized by the heavier gauge wires used. Instead of the thin doorbell or telephone wire, they use large wires similar to those in your home's electrical system. They typically control an electric heater such as a baseboard or wall heater.

Low Voltage systems are the most common and use small gauge wire, similar to telephone wire. There may be anywhere from two to seven wires, depending upon the equipment controlled.

Electromechanical thermostats use a bimetal wire that shrinks and expands with temperature changes, to shift the position of a mercury switch. They can be used with all three types of systems described above (although you must match the voltage of the system). While you can replace your old thermostat with a new electromechanical, we recommend choosing a digital model.

Once you select the replacement, we can show you how to install your new thermostat, its easy.

Search for Articles on Acme How To

Ask a HVAC Technician Now
