Komatsu 830E-AC Shop Manual page 939

Trinary™ Switch
This switch is mounted on the receiver-drier and has
three functions, as implied by the name:
1. Disengage the compressor clutch when system
pressure is too high.
2. Disengage the compressor clutch when system
pressure is too low.
3. Engage and disengage the radiator fan drive
clutch during normal variation of system pres-
sure.
The Trinary™ switch performs three distinct func-
tions to monitor and control refrigerant pressure in
the system. This switch is installed on the receiver-
drier. The switch functions are:
Terminals 1 & 2 are connected internally through
two, normally closed pressure switches in series, the
low pressure switch and the high pressure switch.
Terminals 3 & 4 are connected internally through a
normally open switch that is used to control the
clutch that drives the radiator fan. This switch closes
and causes the cooling fan clutch to engage when
system pressure rises to 1379-1586 kPa (200-230
psi). When pressure falls to 965-1344 kPa (140-195
psi), the switch contacts open, and the cooling fan
clutch disengages.
• Low Pressure - This
disengages the compressor clutch if system
pressure drops into the 103-207 kPa (15-30 psi)
range. When pressure rises above 276 kPa (40
psi), the switch contacts close, and the clutch
engages the compressor. Since temperature has
a direct effect on pressure, if the ambient
temperature is too cold, system pressure will
drop below the low range, and the pressure
switch will disengage the clutch.
N04031 10/06
switch opens and
Operator Comfort
• Fan Clutch - The mid-range function actuates the
engine fan clutch, if installed.
• High Pressure - This
disengages the compressor clutch if system
pressure rises above the 2068-2413 kPa (300-
350 psi) range. After system pressure drops to
1448-1724 kPa (210-250 psi), the switch
contacts will close and the clutch will engage.
The switch functions will automatically reset when
system pressure returns to normal.
OPENS
Low 103-207 kPa
Pressure (15-30 psi)
descending
pressure
High 2068-2413 kPa
Pressure (300-350 psi)
241-414 kPa
Fan Clutch (35-60 psi)
below closing
pressure
The pressures listed above are typical of pres-
sures at the receiver-drier. Due to normal system
flow losses and the distance between the service
port and the receiver-drier, it is expected that
actual system pressure displayed on the gauge
will normally be approximately 20 psi higher.
This factor should be observed when checking
for proper operation of the switch.
NOTE: One other pressure controlling device is
installed within the compressor. A mechanical relief
valve is located on the back of the compressor. The
relief valve will open at 3447-3792 kPa (500 - 550
psi). The purpose of this valve is to protect the
compressor in the event that pressure should be
allowed to rise to that level. Damage to the
compressor will occur if pressure exceeds 550 psi.
switch opens and
CLOSES
276 kPa
(40 psi)
rising pressure
1448-1724 kPa
(210-250 psi)
1379-1586 kPa
(200-230 psi)
rising pressure
N4-13