Air Conditioning System Components

1
Air Conditioning System Components

• Compressors
• Compressor Clutches
• Condensers
• Expansion Devices
• Evaporators
• Receiver-Driers/Accumulators
• Switches and Evap. Temperature Controls
• Rear AC Systems

2
Compressors
There is a large variety of compressors. Some of
variations are The compressor manufacturer Piston
, vane, or scroll type The piston and cylinder
arrangement How the compressor is mounted Style
and position of ports Type and number of drive
belts Compressor displacement Fixed or variable
displacement
3
Compressor Operation
Out/Discharge High Pressure, about 200 psi
High Temperature, above ambient
In/Suction Low Pressure, about 30 psi
Low Temperature, close to freezing
The compressor increases the refrigerant pressure
about five to ten times. This increases the
temperature so heat can leave the refrigerant in
the condenser.
4
Piston Compressors
Reed Valve Plate
Piston
This two-cylinder compressor uses a crankshaft to
move the pistons up and down. Refrigerant flow is
controlled by the suction and discharge reeds in
the valve plate.
Connecting Rod
Crankshaft
Shaft Seal
Animation Piston Compressor
5
Reed Valves
Evaporator Pressure Condenser Pressure
Discharge Reed Open
Suction Reed Open
Suction Discharge
Refrigerant flow can be controlled by reed
valves. Pressure on one side of the flexible reed
forces it to close the port. Pressure on the
opposite side forces the reed open.
6
Scotch Yoke Compressors
Discharge Reed
Suction Reed
A Scotch yoke compressor has two pairs of pistons
that are driven by a slider block on the
crankshaft. The pistons are connected by a yoke.
Pistons with Yokes
Crankshaft
Slider Block (hidden)
Animation Scotch Yoke Compressor
7
Scroll Compressors
Orbiting Scroll
Clutch
The orbiting scroll is driven by the crankshaft
and moves in a small circular orbit. The fixed
scroll remains stationary.
Fixed Scroll
Shaft Seal
Crankshaft
Animation Scroll Compressor
8
Scrolls
Orbiting Scroll
Fixed Scroll
The fixed scroll is secured to the case so it
does not move. The orbiting scroll moves in a
circular motion as it is driven be the crankshaft.
9
Swash Plate Compressors
Piston Valve Plate
Swash Plate
Shaft Seal
Valve Plate
10
Swash Plate Compressors
Pistons
Reed Plate
The swash plate is mounted at an angle onto the
drive shaft. It drives three double-ended
pistons. Two sets of reeds control the
refrigerant flow in and out of the cylinders.
Swash Plate
Shaft Seal
Clutch Assembly
Animation Swash Plate Compressor
11
Wobble Plate Compressors
Wobble Plate Drive Hub
Valve Plate
Piston Connecting Rod Shaft Seal
Animation Wobble Plate Compressor
12
Variable Displacement
Low Angle Minimum Stroke
The evaporator pressure has dropped, and the
control valve has increased crankcase pressure
High Angle Maximum Stroke
Normal operation when cooling is required.
Crankcase pressure is low.
Control Valve
13
Variable Displacement Wobble Plate Compressors
Pivot
Control Valve Valve Plate Piston
Shaft Seal
Connecting Rod
14
Vane Compressors
Rotor Vane
The rotor is driven by the clutch and driveshaft.
The vanes move in and out of the rotor to follow
the outer wall to pump refrigerant.
Shaft Seal
Discharge Reed
Animation Vane Compressor
15
Vane Compressor, Cutaway
Discharge Check Valve
Clutch Pulley Plate Coil
Rotor Vane
Shaft Seal
16
Clutch Assembly
Pulley
Coil
Drive Plate
The three major parts of a clutch assembly.
17
Compressor Clutch
V-belt Pulley
Most compressors use a three-part clutch the
hub, rotor, and coil. The hub is attached to
the compressor drive shaft. It has a plate that
is pulled against the rotor when the clutch is
applied. The rotor is driven by the accessory
drive belt it is mounted over the front of the
compressor using a bearing so it can rotate.
The coil becomes an electromagnet when current is
sent through it.
Multi-Vee Pulley
Hub Pulley/ Magnetic Rotor
Coil
18
Clutch Operation
Pulley
Current is sent to the clutch coil to energize
the magnet and apply the clutch. Shutting off the
current flow releases the clutch and stops
compressor operation.
Coil
Clutch Hub/Plate
Animation Clutch Control
19
Condenser Types
Condensers A and C are round tube, serpentine
condensers. Condenser B is an oval/flat tube,
serpentine condenser. Condenser D is an oval/flat
tube, parallel flow condenser. Flat tube
condensers are more efficient.
20
Serpentine Condenser
Refrigerant flows from the upper inlet to the
bottom outlet through two tubes. These tubes wind
back and forth though the condenser.
21
Parallel Flow Condenser
Refrigerant flows from the upper inlet to the
bottom outlet through groups of parallel tubes.
Some carry refrigerant from the right to the
left, and others move it back to the right side.
22
Expansion Devices

• The expansion device separates the high side from
  the low side and provides a restriction for the
  compressor to pump against.
• There are two styles of expansion devices
• The TXV can open or close to change flow. It is
  controlled by the superheat spring, thermal bulb
  that senses evaporator outlet temperature, and
  evaporator pressure
• Most OTs have a fixed diameter orifice

23
Thermal Expansion Valves, TXVs
The three major types of expansion valves
Internally balanced TXVs are the most common.
Externally balanced TXVs are used on some larger
evaporators. Block valves route the
refrigerant leaving the evaporator past the
thermal sensing diaphragm so a thermal bulb is
not needed.
Internally Balanced
Externally Balanced
Block Valve
Animation TXV Operation
24
Orifice Tubes, OTs
The OT used in a modern vehicle is a tubular,
plastic device with a small metal tube inside.
The color of the OT is used to determine the
diameter of the tube. A plastic filter screen is
used to trap debris that might plug the tube.
Some older General Motors vehicles used an OT
that resembled a brass fuel filter.
25
Orifice Tubes, OTs
26
Evaporator Types
Plate evaporators, top, are a series of stamped
aluminum plates that are joined together. Tube
and fin evaporators, bottom, have tubes for the
refrigerant that are joined to the fins.
27
Receiver Dryers
Barb Connections, Note Sight Glass
Male Flare Connections

• A receiver dryer is mounted in the liquid line of
  a TXV system. It is used to
• to store a reserve of refrigerant.
• hold the desiccant bag that removes water from
  the refrigerant.
• filter the refrigerant and remove debris
  particles.
• provide a sight glass so refrigerant flow can be
  observed.
• provide a location for switch mounting.

Male O-ring Connections, Note Switch
28
Accumulators

• Accumulators are used in the suction line of all
  OT systems.
• The accumulator
• separates liquid refrigerant so only gas flows to
  the compressor.
• Allows oil in the bottom of the accumulator to
  return to the compressor.
• provides storage for a refrigerant reserve.
• contains the desiccant bag for water removal.
• provides a place to mount low pressure switches
  and sensors.

29
Receiver Dryers/Accumulators
30
Switches

• Ambient temperature
• High pressure
• Low pressure
• Compressor rpm
• Compressor superheat
• Compressor high temperature
• Compressor cutoff

31
Switches

• ECT
• Evaporator pressure
• Evaporator temperature
• Pressure cycling
• Thermostatic cycling
• Trinary pressure

32
Switches
33
Switches
34
Switches
35
Evaporator Temperature or Pressure Controls

• EPRV
• EPR
• ETR
• POA
• STV
• VIR