Thermo King T-1080S, Maintenance Manual

Page: 151 / 191

Refrigeration Service Procedures
150
5. Solder suction line connection to the
evaporator coil.
6. Solder the liquid line to the expansion valve.
7. Solder the equalizer line to the suction line.
8. Pressurize the system and check for leaks.
9. If no leaks are found, replace the liquid line
drier then evacuate and dehydrate the system.
10. Clean the suction tube to a bright polished
condition. Install the feeler bulb clamps and
feeler bulb on the side of the suction line in its
former position. The feeler bulb must make
good contact with the suction line or operation
will be faulty. Wrap with insulating tape.
11. Install the evaporator top panel.
12. Recharge the unit with refrigerant and check
the compressor oil.
High Pressure Cutout Switch
(HPCO) Test
The HPCO is located on the discharge line. If the
discharge pressure rises above 470 ± 7 psig (3241
± 48 kPa), the switch opens the HPCO circuit the
to run relay and stops the unit. To test the switch,
rework a gauge manifold per the following
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 condenser with a piece of
cardboard.
NOTE: The discharge pressure should never
be allowed to exceed a pressure of 477 psig
(3289 kPa) on R-404A systems.
4. If the HPCO opens too soon or does not open
to de-energize the run relay and stop the unit,
it must be replaced.
High Pressure Cutout Switch
(HPCO) Replacement
Removal
1. Recover the refrigerant charge.
2. Disconnect the wires and remove the HPCO
from the discharge tube.
1. Relief Valve
2. O-ring
3. Adapter Tee Weather Head
Figure 241: High Pressure Cutout Manifold