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.
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).
systems use two wires and typically connect to older wall or floor
furnaces; units that heat only one area.
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
such as a baseboard or wall heater.
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.
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.