Hvac Flashcards
Definition
React to heat by changing resistance, often to modify an electrical signal being measured by an instrument
Thermistor
React to heat by producing a voltage that generates a current in a completed circuit
Thermocouple
React to heat by changing pressure, usually with diaphragm or bellows.
Sensing bulb
A circuit that responds to change in the signal from sensors and issues signals to devices
Controller
A device that change an input energy into mechanical motion
Actuator
A device commonly use to start and stop another operation of another system component such as motor
Relay
Relay that uses electronic devices for switching
Solid state
Heavy duty relay with built-in overload protection
Motor starter
Heavy duty relay with parts that can be replaced
Contactor
Whose operation is based on CEMF
Potential relay
The present condition as it is measured
Control point
The difference between the desired and present condition
Offset
The desired conditions
Set point
This motor is not commonly found in AC units, it has a centrifugal switch or start relay to remove the start capacitor and start winding from the circuitry once it reaches 75% of it rate RPM’s
CSIR
This motor is basically a PSC motor with a start capacitor and relay to drop out the start cap. It has a high starting torque
CSCR
This motor has a run capacitor wire in series with start winding. Start relay or centrifugal is needed, the run capacitor reduce the current flow through the start winding so it can stay in the circuit
PSC motor
This motor has a run and start winding and start winding must be protected. It has a low running and starting torque
Split phase motor
This motor is single speed or multi speed motor. It has low running and starting torque and has a run winding only
Shaded pole motor
This compressor is a piston type compressor use in domestic commercial system
Reciprocating compressor
This compressor is use in large commercial refrigeration systems over 50 tons. It use impeller or wheels and has no valve or piston and operated at high speed
Centrifugal compressor
This compressor is the newest type of compressor and has no intake or discharge valve except a check valve on the discharge. It has very little wear and tear because it has so few moving parts
Scroll compressor
This compressor is used on large chill water systems 20 tons and up. It uses to spacing between the lobes of screws to compres the refrigerant and will operate smoothly even when it’s capacity is reduced to as low as 10%
Screw compressor
This compressor is small and light weight and uses blades or vane to move the refrigerant
Rotary compressor
