Types
A thermostat that can operate a cooling system and a heating system. Also called heating- cooling thermostat.
What is a combination thermostat?
An HVAC system designed to heat or cool different areas of a building to different comfort, humidity, and ventilation standards.
What is a zoned system?
In a thermostat, a high-value resistor wired in parallel with the bimetal coil temperature- sensing device that conducts current during the cooling system’s Off cycle to produce heat that will trip the cooling system on several minutes before the conditioned area reaches the cut-in temperature
What is a cooling anticipator?
A damper that opens and closes in reaction to static pressure.
What is a barometric damper?
An unwanted effect that occurs when electrical contacts close through high amounts of pressure and then rebound from each other due to the force. Contact bounce is undesirable because it can create secondary arcs and reduce contact life
What is contact point bounce?
The voltage of a building’s electrical wiring, which is usually 120 Vac or 240 Vac.
What is line voltage?
A thermostat that can operate a cooling system and a heating system. Also called a combination thermostat.
What is a heating-cooling thermostat?
In a zoned system, a room thermostat that measures temperature and issues calls for system operation to a master thermostat. See master thermostat and master-slave thermostat design.
What is a slave thermostat?
DIP switch Dual in-line package switches. Small switches grouped together in a single package. These are often used on circuit boards to manage system settings on a thermostat subbase or air handler control board
What is a DIP switch?
A damper in a bypass duct between supply and return plenums in forced-air zoned systems
What is a bypass damper?
A control term meaning to increase or decrease the intensity of operations. Examples include variable refrigerant flow or some thermostats controlling multistage heating.
What is modulate?
A thermostat that typically operates using either 120 Vac or 240 Vac
What is a line-voltage thermostat?
A thermostat that can remember an occupant’s desired set point and adapt the HVAC system operation to automatically program On and Off cycles and temperature set points.
What is learning thermostat?
A damper that requires electrical power to open and electrical power to close.
What is a power-open/power-closed damper?
A small resistance coil used by a thermostat to produce enough heat to keep the thermostat warmer than the ambient temperature so the thermostat will cycle off the heat before reaching the cut-out temperature and avoid system overshoot.
What is a heat anticipator?
The use of an air-side economizer to draw in cool outdoor air to reduce indoor air temperature
What is free cooling?
A temperature drop occurring between the time the heating system turns on and the time heat is delivered to the conditioned area
What is system lag?
A thermostat that operates at 24 Vac supplied by a step-down transformer. It often uses relays to switch line voltage circuits on and off.
What is a low-voltage thermostat?
A thermostat that typically operates using either 120 Vac or 240 Vac.
What is a line-voltage thermostat?
A damper that is in the open position when power is not applied to its motor.
What is a normally open damper?
An electrical switch consisting of a sealed tube containing a small puddle of mercury and two to four contacts made at the ends of wires that run outside the tube. Contact is made when a mercury switch is tilted, which causes the mercury puddle to slide down the tube and complete the circuit.
What is a mercury switch?
A damper that is in the closed position when power is not applied to its motor.
What is a normally closed damper?
Concerning control systems, when the temperature of a conditioned space exceeds the thermostat’s set point. It is a heat lag that occurs when a furnace shuts down and the amount of residual heat that has built up is sent by the blower through the ductwork and into the conditioned space, raising the temperature above the thermostat set point.
What is system overshoot?
An electrical switch consisting of a sealed tube containing a small puddle of mercury and two to four contacts made at the ends of wires that run outside the tube. Contact is made when a mercury switch is tilted, which causes the mercury puddle to slide down the tube and complete the circuit.
What is a mercury switch?
A thermostat that operates at 24 Vac supplied by a step-down transformer. It often uses relays to switch line voltage circuits on and off.
What is a low-voltage thermostat?
A damper that is in the closed position when power is not applied to its motor
What is a normally closed damper?
An electrical switch that has a pair of electrical contacts mounted on magnetic reeds sealed in a glass tube that are opened and closed by an outside magnet.
What is a reed switch?
A damper that is in the open position when power is not applied to its motor.
What is a normally open damper?
In a heating system, a safety control that ensures that a measured temperature does not exceed a certain level.
What is a temperature limit switch?
A heating thermostat that operates a small solenoid valve powered by a very small voltage produced by a thermocouple device sensing a standing pilot light. These may only be used in systems having a standing pilot.
What is a millivolt thermostat?
A heating thermostat that operates a small solenoid valve powered by a very small voltage produced by a thermocouple device sensing a standing pilot light. These may only be used in systems having a standing pilot.
What is a millivolt thermostat?
An older form of controlling a zoned system consisting of a master thermostat that operates based on the inputs from several slave thermostats
What is a master-slave thermostat design?
A damper that requires electrical power to open and electrical power to close.
What is a power-open/power-closed damper?
The total difference of the high and low temperature in a room.
What is temperature swing?
An electrical term meaning to measure the resistance of an electrical load. Only do this with electrical power disconnected and after checking with a voltmeter that no voltage is applied (0 V measurement).
What is ohm out?
A thermostat that can control a system’s heating and cooling capacity through various means, such as modulating compressor and fan operation or varying fuel combustion or electrical power
What is a multistage thermostat?
In a zoned system, this is the thermostat that governs system operation and receives temperature input and calls for operation from slave thermostats. See slave thermostat.
What is a master thermostat?
In basic terms, a sensing device that reacts to temperature change. More broadly, a temperature control that starts and stops an HVAC system when preset temperature conditions are reached
What is a thermostat?
An electrical switch that has a pair of electrical contacts mounted on magnetic reeds sealed in a glass tube that are opened and closed by an outside magnet.
What is a reed switch?
An electronic thermostat that draws a small amount of electrical power from the low- voltage side of an HVAC system’s control circuit to operate the thermostat’s electronics.
What is a power-stealing thermostat?
A damper in a bypass duct between supply and return plenums in forced-air zoned systems.
What is a bypass damper?
An electronic thermostat that draws a small amount of electrical power from the low- voltage side of an HVAC system’s control circuit to operate the thermostat’s electronics
What is a power-stealing thermostat?
A thermostat that contains a microprocessor that functions as a clock and allows the user to select different conditions for different blocks of time.
What is a programmable thermostat?
A safety control device used in forced-air zoned systems that functions as a open-on-drop thermostat set to open if air temperature right above the evaporator coil drops to around 33°F. This stops the compressor to prevent the formation of ice on an evaporator, which can occur when airflow is reduced (such as when a zone damper closes and a bypass damper does not compensate adequately).
What is a freezestat?
In a heating system, a safety control that ensures that a measured temperature does not exceed a certain level.
What is a temperature limit switch?
A thermostat that can be controlled wirelessly from anywhere in the home or the world.
What is a Wi-Fi enabled thermostat?
A thermostat that can be controlled wirelessly from anywhere in the home or the world.
What is a Wi-Fi enabled thermostat?