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There are five basic types of automatic
and programmable thermostats.
Types of Programmable Thermostats
The basic types of automatic and programmable thermostats
include:
- electromechanical,
- digital,
- hybrid,
- occupancy, and
- light sensing.
Most range in price from $30 to $100, except for occupancy
and light sensing thermostats, which cost around $200.
Electromechanical (EM) thermostats, usually
the easiest devices to operate, typically have manual controls
such as movable tabs to set a rotary timer and sliding levers
for night and day temperature settings. These thermostats
work with most conventional heating and cooling systems, except
heat pumps. EM controls have limited flexibility and can store
only the same settings for each day, although at least one
manufacturer has a model with separate settings for each day
of the week. EM thermostats are best suited for people with
regular schedules.
Digital thermostats are identified by their
LED or LCD digital readout and data entry pads or buttons.
They offer the widest range of features and flexibility, and
digital thermostats can be used with most heating and cooling
systems. They provide precise temperature control, and they
permit custom scheduling. Programming some models can be fairly
complicated; make sure you are comfortable with the functions
and operation of the thermostat you choose. Remember—
you won't save energy if you don't set the controls or you
set them incorrectly.
Hybrid systems combine the technology of
digital controls with manual slides and knobs to simplify
use and maintain flexibility. Hybrid models are available
for most systems, including heat pumps.
Occupancy thermostats maintain the setback
temperature until someone presses a button to call for heating
or cooling. They do not rely on the time of day. The ensuing
preset "comfort period" lasts from 30 minutes to 12 hours,
depending on how you've set the thermostat. Then, the temperature
returns to the setback level. These units offer the ultimate
in simplicity, but lack flexibility. Occupancy thermostats
are best suited for spaces that remain unoccupied for long
periods of time.
Light sensing heat thermostats rely on
the lighting level preset by the owner to activate heating
systems. When lighting is reduced, a photocell inside the
thermostat senses unoccupied conditions and allows space temperatures
to fall 10° below the occupied temperature setting. When
lighting levels increase to normal, temperatures automatically
adjust to comfort conditions. These units do not require batteries
or programming and reset themselves after power failures.
Light sensing thermostats are designed primarily for stores
and offices where occupancy determines lighting requirements,
and therefore heating requirements.
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