Thermostats: Tools That Manage HVAC Performance
In basic definition, thermostats and advanced A/C system controls function as simple on/off switches. The switch trips whenever changes in the indoor air temperature of a structure nears the associated thermostat’s set point. But modern HVAC performance involves much more the simplicity of an on/off thermostat control function.
The following overview reviews the power of thermostats and advanced A/C system controls.
Basic Thermostat and A/C System Control Processes
In 1883, Warren S. Johnson invented the first electric room thermostat. The Johnson Controls technology used mercury and electrodes inserted directly through the glass. The systems were accurate within one degree of temperature.
Skip ahead. In modern technology, most 2014 air conditioning and heat pump thermostats operate on low voltage control circuits that pull 24 volts AC from a control transformer installed within the home’s heating or cooling equipment. Low voltage control technology provides a safety advantage that enables the thermostat to operate multiple electromechanical contractors, relays and sequencers at inherently safe voltage. Modern systems also include an integrated “anticipation” function that activates the contacts in a manner that prevents room temperatures from overshooting the desired temperature settings. And all this excludes the growing range of features associated with modern programmable thermostats & controllers.
Pre-digital Heating and Air Conditioning Thermostats
In 1953, Honeywell introduced the T-86 “Round” thermostat technology. This bimetallic-spring regulated room thermostat still controls millions of home heating and cooling systems throughout the world.
Typically mounted on a central wall within the home, the traditional Honeywell thermostat uses a basic dial-type round-controller design that includes two temperature scales and two temperature pointers. The top scale and pointer provides the adjustable components of the system. The bottom scale shows the actual physical temperature in the chosen area of the home. Rotating the pointer in the top scale to the right increases the desired heating requirements. Rotating the pointer in the top scale to the left decreases the desired temperature setting.
In the early years, thermostats designed to control both cooling and heating included a manual setting switch at the base of the unit. This switch, also seen in rectangular units of the pre-digital era, can be moved from heat-to-off-to-cool or back again. The temperature sensor within the units compare the air temperature near the thermostat to the settings of the system and turn on or off the associated heating or cooling equipment as appropriate. The heat/cool/off control switch assures that only the selected equipment can activate at any one time.
Digital Era Thermostats and Controllers
By the year 2005, nearly 97% of U.S. households used installed heating systems. During the same time frame, only 75% of the U.S. households used air conditioning. But the world is changing and the changing climates associated with global warming continue to press upward the demand for installed air conditioning.
Modern programmable thermostat and controller technology bestows a dramatic increase in features and capabilities. From simple on/off heating and cooling to controlled ventilation systems and from manual settings to controllers that respond to electricity price-signals the home air conditioning and heat pump management system engages in a whole new arena of thermal comfort and energy savings.
And then along come thermostats and advanced air conditioning controls that link directly into the home Internet networking system. Wonder what comes next?