Thermo King T-1000R, Maintenance Manual

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Refrigeration Maintenance 10-41
HIGH PRESSURE CUTOUT SWITCH (HPCO) TEST
The HPCO is located on the compressor discharge manifold. 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/R-452A
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. Pump down the low side to a 20 in. Hg vacuum (-68 kPa) then stop the unit.
2. Front seat the discharge and suction service valves.
3. Open both service manifold hand valves to bleed the pressure in head into the compressor crankcase. If the pressure balances
in a vacuum, raise the pressure to 1 to 3 psig (7 to 21 kPa) by cracking the discharge service valve.
4. Disconnect the wires and remove the HPCO from the compressor discharge manifold.
1. Relief Valve
2. O-ring
3. Adapter Tee Weather Head
High Pressure Cutout Manifold