WD Catalog 2018

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4-8
Chapter 4 – Air Conditioner Components
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0 1000 2000 3000 4000
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
COMPRESSOR SPEED IN RPM
REFRIGERANT CAPACITY IN BUT'S PER HOUR—R-12
YORK MODEL 210
COMPRESSOR OUTPUT
PSIG
SUCTION
40
30
20
0 1000 2000 3000 4000
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
COMPRESSOR SPEED IN RPM
ZEXEL
COMPRESSOR OUTPUT
PSIG
SUCTION
40
30
20
180 PSIG DISCHARGE
65° F RETURN
15° F SUBCOOLING
180 PSIG DISCHARGE
65° F RETURN
15° F SUBCOOLING
REFRIGERANT CAPACITY IN BUT'S PER HOUR—R-12
Clutch
The clutch is driven by the truck engine through a V-belt running in a grooved
clutch pulley. The clutch pulley rides on ball bearings and can turn without
driving the compressor shaft. Heavy duty clutches have double row ball bear-
ings. An electromagnetic coil is mounted inside the pulley housing and bolted to
the compressor body. The clutch drive plate is bolted to the compressor shaft.
There is a small amount of clearance between the plate, pulley and coil.
When the AC system thermostat control in the evaporator calls for cooling,
current flows through the coil inside the pulley. This sets up a magnetic field
between the drive plate and the pulley. The magnetic field locks the pulley to
the drive plate, causing the pulley to turn the compressor shaft. When the
clutch is not engaged the pulley spins free without turning the compressor.
Electrical connection to the clutch coil is made through lead and ground
wires. Figure 4-6 illustrates the clutch mounted on a compressor.
Figure 4-5
Each chart plots compressor
output curves at three
suction pressures or PSIG
(pounds per square inch
gauge). The three pressures
represent variations in
operating conditions for
these two compressors.