Thermo King 920000, Manual

Page: 114 / 190

Refrigeration Maintenance
114
Unit Charging
NOTE: The electrical system must be energized
throughout this procedure.
1. Before charging the system, make sure that
the refrigerant lines from the gauge manifold
to the refrigerant supply bottle have been
evacuated or purged, that the suction service
valve is still back seated, and that the
discharge service valve and receiver outlet
valve are still open.
2. Set the refrigerant supply bottle for liquid.
Open the gauge manifold hand valve and add
a partial charge of 9.0 lb (4.1 kg). Do not add
more than this. The remainder of the charge
will be added through the suction service
valve while the unit is running.
3. Close the gauge manifold hand valve. Turn the
unit On/Off switches Off.
4. Back seat (close) the receiver outlet valve.
Back seat the discharge service valve. Open
the suction service valve.
5. Attach the high pressure gauge on the gauge
manifold to the discharge service valve. Open
the discharge service valve to monitor the
discharge pressure.
6. Connect the HGS wires and the RHGS wires
to the relay board. Connect the condenser inlet
solenoid wires (2 pin connector) to the main
wire harness. Connect the 20A wire to the low
oil pressure switch. Replace the
CYCLE-SENTRY module.
7. Start the condensing unit. Run the condensing
unit in high speed with the thermostats in both
zones set to Cool.
8. Observe the suction pressure and slowly open
the gauge manifold hand valve to allow liquid
refrigerant to flow into the suction service
valve. Control the liquid flow so the suction
pressure increases approximately 20 psi
(138 kPa). Maintain a discharge pressure of at
least 275 psi 1896 kPa).
9. Add refrigerant until the ball in the receiver
tank sight glass rises to the middle of the sigh
glass, then close the gauge manifold hand
valve. Make sure the liquid level does not rise
above the top of the sight glass.
10. Continue to operate the unit with both zones
in Cool for another 10 minutes and check the
refrigerant level in the receiver tank sight
glass. If the level has dropped, add liquid
refrigerant until the level stabilizes near the
middle of the sight glass. Do not exceed the
recommended refrigerant charge for the unit
mode.
11. Back seat the discharge service valve.