TK 56433-5-MM-EN
61
3. Observe the oil level. The oil should be 1/4 to 1/2 up
in the sight glass.
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Ester P/N 203-513 is required for R-404A or R-
452A.
1. Pump down the compressor and equalize the
pressure to slightly positive.
2. Disconnect the compressor oil filter return line or
remove the oil fill plug from the top of the
compressor and add the oil.
3. Reattach the oil filter return line to the compressor
or reinstall the oil fill plug.
4. Evacuate the compressor before opening the
service valves.
High Pressure Cutout Switch
(HPCO)
The High Pressure Cutout Switch (HPCO) is located on
the compressor discharge manifold. If the discharge
pressure rises above 470 psig (3241 kPa), the HPCO
opens the HPCO circuit to the run relay and stops the
unit. To test the HPCO, rework a gauge manifold as
shown (
) and use the following
procedure:
1.
Connect the gauge manifold to the compressor
discharge service valve with a heavy duty, black
jacketed thick wall #HCA 144 hose with a 900 psig
(6204 kPa) working pressure rating.
2.
Use the Service Test Mode to run the unit (or host
unit) in high speed cool.
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3.
Raise the discharge pressure of the compressor by
blocking the condenser coil air flow by covering the
condenser grilles with pieces of cardboard. This
should increase the discharge pressure enough to
cause the HPCO to cut out.
4.
If the HPCO does not open to de-energize the run
relay and stop the unit, it must be replaced.
Figure 70.
High Pressure Cutout Manifold
1.
Relief Valve (66-6543)
2.
O-Ring (33-1015)
3.
Adapter Tee Weather Head No. 552X3
Three-Way Valve Condenser
Pressure Bypass Check Valve
A three-way valve condenser pressure bypass check
valve is used in this unit. This check valve controls the
bypass flow of refrigerant gas between the condenser
inlet line and the compressor discharge line.
The check valve is closed when the unit is running on
cool, or whenever the discharge pressure is higher
than the condenser pressure.
When the unit is running on defrost or heat, if the
condenser pressure is higher than the discharge
pressure, the check valve opens and the condenser
pressure is bled off until it drops to the level of the
discharge pressure. The purpose of the valve is to
improve the three-way valve response time when
shifting from heat to cool.
If a three-way valve does not shift back to cool
immediately after the pilot solenoid closes, and finally
shifts to cool when the temperature rise puts the unit
into high speed, the three-way valve end cap should be
checked. See
“Three-Way Valve Repair,” p. 74
in
Refrigeration Service Operations.
Check the operation of the condenser pressure bypass
