Thermo King MD-MT, Operator'S Manual

Page: 114 / 192

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
charge 70% of the recommended charge as
liquid, or charge it until the system will take
no more liquid. The remainder of the charge
will be added as a vapor through the suction
service valve.
3. After the liquid refrigerant is added, close the
gauge manifold hand valve.
4. Back seat (close) the receiver outlet valve.
Back seat the discharge service valve. Open
the suction service valve.
5. Connect the HGSA wire and the RHGS wire
to the relay board. Connect the condenser inlet
solenoid wires (2 pin connector) to the main
wire harness. Replace the front and rear fan
relays. Connect the 20A wire to the low oil
pressure switch.
6. Open the valve on the refrigerant supply bottle
set for liquid. Open the gauge manifold hand
valve.
7. Start and operate both units with the
thermostats set to cool. Add liquid through the
suction service valve until the ball in the
receiver sight glass rises to the top of the sight
glass. Make sure that the liquid level does not
rise above the top of the sight glass. Refer to
unit serial plate for the correct amount of
charge.
8. When the ball rises to the top of the sight
glass, close the gauge manifold hand valve.
Continue to operate both units in Cool for 10
minutes and then check the position of the ball
in the receiver sight glass. If the liquid level
has dropped, add liquid until the level
stabilizes near the top of the sight glass.