Tail Pipe
Outlet pipe from the evaporator.
Tandem
A term used to identify a system that connects two motor compressors at the motor end.
Tank, Supply
Separate tank connected directly or by a pump to the oil-burning appliance.
Tap (screw thread)
Tool used to cut internal threads.
Temperature
1-Degree of hotness or coldness as measured by a thermometer. 2-Measurement of the speed of motion of molecules.
Temperature Humidity Index
Actual temperature and humidity of air Sample compared to air at standard conditions.
Temperature Sensing Bulb
Bulb containing a volatile fluid and bellows or diaphragm. Temperature increase on the bulb causes the bellows or diaphragm to expand.
Test Light
Light provided with test leads. Used to test or probe electrical circuits to determine if they are working properly.
Therm
Quantity of heat equal to 10.0,000 Btu.
Thermal Conductivity
The ability of a material to transfer heat.
Thermal Precipitation
The collection of dirt around warm air grilles.
Thermal Relay (hot wire relay)
Heat-operated electrical control used to open or close a refrigeration system electrical circuit. This system uses a resistance wire to convert electrical energy into heat energy.
Thermal Resistance
See R-value.
Thermistor
A semiconductor with electrical resistance that varies with temperature.
Thermocouple
Device that generates electricity, using the principle that if two unlike metals are welded together and the junction is heated, a voltage will develop across the open ends.
Thermo-disc Defrost Control
Electrical switch with bimetal disc controlled by temperature changes.
Thermodynamics
Part of science that deals with the relationship between heat and mechanical action.
Thermo-electric Refrigeration
Refrigerator mechanism that depends on Peltier effect. Direct current flowing through an electrical junction between unlike metals provides heating or cooling effect, depending on direction of current flow.
Thermometer
Device for measuring temperatures.
Thermo-modoule
Number of thermocouples used in parallel to achieve low temperatures.
Thermopile
Number of thermocouples; used in series to create a higher voltage.
Thermostat
Device that senses ambient temperature conditions and, in turn acts to control a circuit.
Thermostat Droop
Added heat in line-voltage thermostat }, produced by the thermostat itself.
Thermostatic Control
Device which operates system or part of system based on temperature change.
Thermostatic Expansion Valve (TEV)
Control valve operated by temperature and pressure within evaporator. It controls flow of refrigerant. Control bulb is attached to outlet of evaporator.
Thermostatic Motor Control
Device used to control cycling of unit through use of control bulb. Bulb reacts to temperature changes.
Thermostatic Switch
A switch controlled by temperature changes.
Thermostatic Valve
Valve controlled by temperature change response elements.
Thermostatic Water Valve
Valve used to control flow of water, actuated (made to work) by temperature difference. Used in units such as water-cooled compressors and condensers.
Three-phase
Operating by means of combination of three alternating current circuits that differ in phase by one-third of a cycle.
Three-way Valves
Flow control valve with three fluid flow openings.
Throttling
Expansion of gas through orifice or controlled opening without gas performing any work as it expands.
Throw
the distance air travels from a grille before slowing to 50 ft./minute.
Time-delay Fuse
A fuse that does not blow until the overload has persisted for a set duration of time (normally about 10 seconds).
Timed On-Off Control
Control needed when the existing differential is too great.
Timers
Clock-operated mechanism used to control opening and closing of an electrical circuit.
Timer-thermostat
Thermostat control which includes a clock mechanism. Unit automatically controls room temperature and changes temperature range depending on time of day.
Ton of refrigeration
Refrigerating effect equal to the melting of 1 ton of ice in 24 hours. This may be expressed as follows: 288,000 Btu/24 hr., 12,000 Btu/1hr., 200 Btu/min.
Ton Refrigeration Unit
Unit that removes same amount of heat in 24 hours as melting of one ton of ice.
Torque
Turning or twisting force.
Torque Fu11 Load
Maximum torque delivered without overheating.
Torque, Stall
Torque developed when starting.
Torque, Starting
Amount of torque available to start and accelerate the load.
Torque wrenches
Wrench which may be used to measure torque or pressure applied to a nut or bolt.
Torr
A unit of pressure equal to 1/760 of an atmosphere (1 mm Hg), normally used for measuring vacuum, pressure.
Total Air Balance (TAO)
In an air circulation system, adjusting the system, so that all rooms receive the proper amount of air.
Total Energy Management (TEM)
Conservation concept where a building is looked at in terms of its total energy usage, rather than analyzing the requirements separate systems.
Total heat
Sum of both the sensible and latent heat.
Toxicity
A measure of the amount of poison in a substance or the amount of harm it can cause.
Tranducer
Device turned on by a change of power from one source for the purpose of supplying power in a other form to a second system.
Transformer
Electromagnetic device that transfers electrical energy from the primary circuit into variations of voltage in a secondary circuit.
Transformer Rectifier
Combination transformer and rectifier in which input ac current may be varied and rectified into dc current.
Transistor
Electronic device commonly used for amplification. Similar in use to electron tube. Depends on the conducting properties of semiconductors in which electrons moving in one direction are considered as leaving holes that serve as carriers of positive electricity in opposite direction.
Transmission
Heat loss or gain from a building through exterior components such as windows, walls, floors, etc.
Triac
Three-lead semiconductor that allows current flow in two directions when a preset voltage is applied at one of the leads.
Trichlorotrifluoroethane
Complete name of R-113. Group. A1 refrigerant in common use. Chemical compounds that make up this refrigerant are chlorine, fluorine, and ethane.
Triple Point
Pressure-temperature condition in which a substance is in equilibrium (balance) in solid, liquid, and vapor states.
Troposphere
Part of the atmosphere immediately above the earth's surface in which most weather changes occur.
Troubleshooting
The analysis of a problem.
Truck, Refrigerated
Commercial vehicle equipped to maintain cool temperatures.
Tube-within-a-tube condenser
Water-cooled condensing unit in which a small tube is placed inside a large unit. Refrigerant passes through the outer tube, water passes through the inner tube.
Tubing
Fluid-carrying thin-walled pipe
Twin parallel
Two or more units installed in line by piping.
Two-pipe system
A heating system in which one pipe delivers steam to radiators and a second pipe is used to return condensate.
Two-position On-Off control
A control system in which the control device can only start and stop the equipment.
Two-stage vacuum pump
A vacuum pump used to remove vapor and moisture from a system.
Two-temperature valve
Pressure-opened valve used in suction line on multiple refrigerator installations that maintains evaporators in system at different temperatures.
Two-way valve
Valve with one inlet port and one outlet port.