Thermo King 919180, Руководство пользователя

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Refrigeration Maintenance
92
High Pressure Cutout (HPCO)
The high pressure cutout is located on the
discharge line. If the discharge pressure rises
above 470 psig (3241 kPa), the switch opens the
8H circuit to stop the unit. To test the switch,
rework a gauge manifold per illustration.
1. Connect the gauge manifold to the discharge
service port with a heavy duty, black jacketed
thick wall #HCA 144 hose with a 900 psig
(6204 kPa) working pressure rating.
2. Set the thermostat well below the box
temperature so that the unit will be in High
Speed Cool.
3. Raise the discharge pressure of the
compressor by blocking the condenser coil air
flow by covering the roadside condenser grille
with a piece of cardboard.
NOTE: The discharge pressure should never
be allowed to exceed a pressure of 470 psig
(3241 kPa) on R-404A systems.
4. Failure of the HPCO system to stop
compressor operation should be investigated
first by checking the control circuit operation
and secondly by HPCO switch replacement.
Low Side Pump Down
NOTE: Operate the unit in COOL for 2 to 5
minutes before performing the low side pump
down.
1. Install a gauge manifold to the suction service
valve and the discharge service port.
2. Operate the unit in low speed cool.
3. Close the receiver tank outlet valve and allow
the low side to pump down to 0 to 5 in. Hg
vacuum (0 to -17 kPa).
4. Turn the unit Off.
5. Prepare to perform service on the low side by
equalizing the high side and low side
pressures through the gauge manifold.
6. Equalize low side pressure to 1 to 2 psig (7 to
14 kPa).
NOTE: Repeat the pump down procedure if
the pressures equalize above 20 psig
(138 kPa). If acceptable low pressures
cannot be achieved after the third pump
down, the refrigerant must be recovered to
perform service on the low side.
1. Relief Valve
2. O-ring
3. Adapter Tee Weather Head
Figure 52: High Pressure Cutout Manifold
CAUTION: Do not pull scroll compressor
into a deep vacuum to perform routine
maintenance procedures.
CAUTION: Do not run scroll compressor
in a vacuum for more than a few seconds.