HVAC/R COMPRESSORS AND CAPACITORS Flashcards
Run Capacitor
In the circuit, always
Improves running efficiency
Start Capacitor
In the circuit for a few seconds
Start relay cuts it out after reaching 75% speed
Provides starting torque
Cheapest motor
RSIR RESISTIVE START INDUCTION RUN
RSIR AD CSIR
Start winding doesn’t stay in the circuit
PSC motor
Has no start relay
Most hermetic compressors
Respond to heat and current
So they are Inherent
Devices used for defrost
Pressure-operated method
See constant cut in
See dixell controllers
Frost sensors defrost on demand
Brine spray defrost
KOOL gas like reverse cycle hot gas
Coolers
Fan never turns off
Freezers
Fans turn off in the off cycle
Type of mechanical compressors failure
Lubrication
Flooding and slugging
Flooded start
Over heating
Lack of Lubrication causes
Damage to bearings that support crankshaft
Lubrication problems
Too much oil: can cause noise and vibration
Someone added too much oil
Too much oil from multiple compressor changes
Look for signs of slugging but with oil accumulated in the piston area
Too little oil in the compressor
Can seize because of friction between metal parts
Too little oil causes?
*Low refrigerant charge or low load not returning oild
*improper installation
*no defrost or frozen evap
* short cycling
Flooding
Is a continous stream of liquid refrigerant returning to the compessor
Flooding what to look for
Center and rear bearings worn or seize
Dragging rotor, shorted stator
Progressively scored shaft
Fixed metering devices
Are critically charged means manufacturer has set an exact amount of refrigerant to be in the unit and hermetic compressors used mostly in critically charged systems
PSC and CSCR
Keep the start winding in the circuit at all times
CSIR AND RSIR
Remove start winding after it gets up to 2/3 RPM
