Thermo King 914970, Руководство пользователя, Страница: 120 / 186

Refrigeration Maintenance
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4. Back seat (close) the receiver outlet valve.
Back seat the discharge service valve. Open
the suction service valve.
5. Open the refrigerant supply valve for liquid.
Open the gauge manifold hand valve.
6. Start and operate the unit with the thermostat
set for cool. Add liquid through the suction
service valve until the correct charge is
attained. Make sure that the liquid level does
not rise above the sight glass. Refer to the unit
serial plate for the correct amount of charge.
Refrigerant Charge
Testing the Refrigerant Charge with
an Empty Box
If the unit has an insufficient charge of refrigerant,
the evaporator will be “starved” and the box
temperature will rise even though the unit is
operating. The suction pressure will drop as the
refrigerant charge decreases. The charge may be
determined by inspection of the refrigeration
through the receiver tank sight glass with the
following conditions established:
1. Place compartment bulkheads to separate
zones.
2. Install the gauge manifold.
3. Run the unit on High Speed Cool until the air
in the box indicates 0 F (-18 C). By allowing
the box to leak a small amount, you will be
able to maintain 0 F (-18 C).
4. The discharge or head pressure gauge should
read 275 psig (1896 kPa).
If the pressure is below this, it can be raised by
covering a portion of the condenser coil with a
piece of cardboard.
5. The compound gauge should be indicating 13
to 18 psig (90 to 124 kPa) gauge pressure.
If there is any doubt about the unit gauge,
check the calibration.
6. Under these conditions, the ball in the receiver
tank sight glass should be floating. If there is
no indication of refrigerant in the receiver tank
sight glass, the unit is low on refrigerant.
Testing the Refrigerant Charge with
a Loaded Box
1. Install a gauge manifold (optional).
2. Run the unit on the Cool cycle.
3. Cover at least three quarters of the condenser
to drive any excess refrigerant from the
condenser into the receiver tank.
4. As the head pressure is rising, check the
receiver tank sight glass. The ball should be
floating. If there is no indication of refrigerant
in the receiver tank sight glass, the unit is low
on refrigerant.
NOTE: If the ball floats, there is sufficient
refrigerant in the unit for that load at that
particular box temperature. This test does
not determine if the unit contains a full
charge of refrigerant.
Checking Compressor Oil
The compressor oil should be checked when there
is evidence of oil loss (oil leaks) or when
components in the refrigeration system have been
removed for service or replacement.
To check compressor oil level with an ambient air
temperature above 50 F (10 C):
Install a gauge
manifold on the compressor.
Operate the unit on Cool with a 10 psi (69 kPa)
minimum suction pressure and a 100 psi
(689 kPa) minimum discharge pressure for 15
minutes or more.
1. Sight Glass
Figure 46: X426 Compressor
SP2001
1