You Are Here: Home > Thermostat FAQ > Thermostat Glossary
Thermostat Glossary
115/230VAC or Line Voltage
The control voltage for line voltage systems (like baseboard heat) takes a special line voltage thermostat.

24VAC
The control voltage for low voltage systems (gas, elec, oil, etc).

accuracy
How close the thermostat reads the actual room temperature.

air handler
The circulating fan inside the house.

anticipator
A device in mechanical thermostats to heat the thermostat when the heat is running to shut the thermostat off early.

autochangeover
A thermostat mode that automatically switches to the HEAT or COOL program as needed.

auxiliary heat
Separate 2nd source of heat, generally electric strips.

back plate
The back part of some thermostats that mounts to the wall and also where the HVAC system wires connect.

backlight
Lights up the thermostat display for use in the dark. Electro luminescent panel behind the LCD display that glows a gentle blue white when the backlight button is pressed.

C wire
The Common side of a 24VAC system often used to run the thermostat instead of or with batteries.

calibration
Allows the changing of the room temperature reading on most digital thermostats.

compressor
A pump that moves the refrigerant in an A/C or heat pump.

compressor delay
The minimum time the thermostat allows a compressor to cycle off and back on to prevent compressor stall.

compressor stall
A compressor must be off for a few minutes (approx. 5) before it can be turned back on or the compressor might not start.

dehumidifier
A device that removes moisture from the air. An air conditioner naturally removes moisture from the air during normal operation.
See Also: humidifier

dual stage
Two stages of heat and/or two stages of cool, LOW and HIGH.
See Also: multi stage

heat pump
Heats and Cools using a single heat exchanger.

humidifier
A device on the furnace that adds moisture to the air.

humidity
The volume of water vapor is in the air.

HVAC
Heating, Ventillation, Air Conditioning.

jumper
The small plastic devices that connect pins on the back of the thermostat circuit board for making various selections shown in the manuals.

jumper wire
The wire connecting the RC and the RH terminals.

long cycling
The HVAC system is not cycling on and off enough.
See Also: short cycling

millivolt
The control voltage for some gas fireplaces, heaters, etc.

multi stage
A multi stage thermostat can control multiple sources of heating and/or cooling.

Nema Code
Standards for wiring thermostats.

set point
The requested temperature set on the thermostat.

short cycling
The HVAC system is cycling on and off too often.
See Also: long cycling

swamp cooler
A device which cools by adding moisture to the air via evaporation.

swing
Sets the temperature spread between the heat or cool on and off temperatures.
Swing is the temperature difference between where a system comes on and then goes off. EXAMPLE: The thermostat is set at HEAT, a target temperature set at 70F, and the swing number set at 3 (+/-1F). The heat would typically come on at 69 and go off at 71. Most thermostats have the ability to set swing.

target temperature
Desired temperature.
See Also: set point

thermostat
A thermostat controls one or more of the HVAC functions.

time slot
A Time Slot is one of the four parts the thermostat divides the progam day into: Morning(MORN), Day(DAY), Evening (EVEN), and Night (NITE). All 4 time slots must reside in the same 24 hour day.

touch screen
A unit with a display screen that can be changed and programmed by touching the displayed icons on the screen.

trim plate
A piece of plastic that mounts at the wall in back of the thermostat to help cover a whole in the wall.

wiring
Connecting thermostats to HVAC systems.

zoned HVAC
A zoned HVAC system uses a series of dampers to selectively heat/cool different areas (zones) when necessary.
Questions/Comments? Contact Us