Deck 4 Flashcards
What does the compressor do?
Pump refrigerant Vapor and raises refrigerant pressure and temp
Reciprocating compressor
Transfer of the direction of force
Up and down of pistons
Intake Stroke
Pulled down
Pressure drops
Suction valve opens
Vapor enters cylinder
End of Intake Stroke
Piston at bottom
Cylinder pressures equalizes
Intake valve closes
Pistons rises
Increases pressure in cylinder
Discharge valve opens
Compression Stroke- Piston at top
Pressures equalize, discharge valve closes, discharge Vapor trapped on “clearance volume”
Vapor must re-expand before
Suction valve can open
Downwards Stroke
Suction Vapor pulled in, pressures equalize, ready for compression
In each cycle there is
Suction, compression, discharge
Hermetic Compressor
Airtight container
Welded steel shell
Internal springs
Suction cooled motor
Tare weight
Weight of tank when empty
Water capacity
Amount of water it can hold in pounds
Nominal tank sizes 25 and 50 lbs
80%
Reinspect
5 years
Tanks have
One valable for liquid and another for gas
Remove Vapor
Condense into liquid and discharge into recovery tank
Pushing out liquid first saves time
Vapor recovery on large systems is slow
A chilled tank
Speeds liquid recovery
Louis must be changed to
Vapor to recover
An orifice in the inlet
Vaporizes the liquid
Appointment does
0.6 pounds per minute
6 pounds per minute liquid recovery
16 pounds per minute of push pull recovery
Only recover
CFC HCFC AND HFC
Compression ratio
High side divided by low
Absolute discharge divided by absolute suction
What are compression ratios used for?
To compare pumping conditions for compressor. Higher than 12 to one is bad because it may become overheated.
The main types of compressors are…
Reciprocating screw rotary scroll in centrifugal
Reciprocating
Is used in medium size commercial refrigeration system
Screw is
In industrial systems
Rotary reciprocating and centrifugal
Are used in residential and light commercial air-conditioning 
Electrical
Motor overlaid and terminals
Mechanical
Crankshaft pistons valves and lead
Lubrication
There must be oil film on every surface
Connecting rods
Connect shaft to the piston
Too high oil
Can’t see top of oil
Too low oil
Can’t se any oil
Good oil level
Anywhere in sight glass per Copeland
Air cooled compressor
Motor is pressed right into housing: external air flow cools compressor motor
Suction and discharge service valves
Next to cylinders
Valve plate
Holds reeds in place
The head
Holds valve plate in place
Separates suction and discharge Vapor
Copeland design is more efficient
Due to discharge valve design
Discharge valve looks like disc
Less clearance volume, less re expansion more efficient
For mid seat position: Opens service port (gauge port)
For reading system pressure, also for charging recovery and evacuation
