Unit 14 Vocabulary Flashcards
Air pressure control (switch)
Requires large diaphragms to sense very low pressure in air systems. Used in air duct to sense blower air before heat is activated
Boiler relief valve
Safety device used on boilers to release excess pressure
Cold anticipator
A fixed resistor in a thermostat that is wired in parallel with the cooling contacts. This starts the cooling system before the thermostat calls for cooling, which allows the system to get up to capacity before the cooling is actually needed.
Cut-in
Point or pressure setting at which the electrical circuit is made
Dual pressure controls
Two controls that are mounted in the same housing, typically low-and high-pressure controls together.
Snap disc
Bimetal device used to sense fast moving airstreams in duct work and furnace heat exchangers
Fluid
The state of matter of liquids and gasses.
Gas pressure switch
Detects presence of gas pressure in gas burning equipment before burners are allowed to ignite.
Helix coil
A bimetallic formed into a specific shape that provides longer travel when heated.
Line-voltage thermostat
Heavy duty but not as sensitive or as fast acting as low voltage type when larger current carrying capacities are needed
Low-voltage thermostat
Normally regulates other controls and does not carry much current (2A max)
Mercury bulb
A glass bulb containing a small amount of mercury and electrical contacts used to make and break the electrical circuit in a low-voltage thermostat.
Motor temperature sensing thermostat
A thermostat that monitors the motor temperature and shuts it off so it will not overheat
Pressure switch
Used to start or stop electrical loads such as motors
Snap or detent action
Mercury rapidly makes or breaks the electrical current flow
