Ingersoll-Rand 900829, Maintenance Manual

Page: 47 / 142

Refrigeration Maintenance
45
22. The above conditions MUST be established
each time the refrigerant level is checked, or if
refrigerant needs to be added for any reason.
NOTE: To prevent oil migration from one
compressor to another, and for proper oil
return when a compressor is operating,
operate a compressor for a minimum of 15
minutes. Do not operate a compressor for
shorter intervals.
Checking the Refrigerant
Charge
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. Also, an insufficient charge does not
circulate enough oil to properly lubricate the
compressor. The charge can be determined by
inspection of the refrigerant through the sight
glass with the following conditions established:
Testing the Refrigerant Charge with
an Empty Box
1. Place a test box over the evaporator.
2. Install gauge manifold set.
3. Run the unit in cool on engine driven
compressor operation until the thermometer
reads 32 F (0 C).
4. Establish head pressure of 180 psig (1241
kPa) for R-134a systems or 275 psig (1896
kPa) for R-404A systems. It may be necessary
to partially cover the condenser grille on the
front of the unit to create the desired head
pressure.
5. Look at the liquid line sight glass. Under these
conditions there should be no bubbles in the
flow of refrigerant through the liquid line sight
glass. Bubbles in the refrigerant indicate the
unit is low on refrigerant. Refer to “Charging
the Refrigeration System” for information
about adding refrigerant.
Testing the Refrigerant Charge with
a Loaded Box
1. Install a gauge manifold.
2. Run the unit in cool on engine driven
compressor operation.
3. Cover the condenser to drive any excess
refrigerant from the condenser into the
receiver tank.
4. As the head pressure rises, check the liquid
line sight glass. There should be no bubbles in
the flow of refrigerant through the liquid line
sight glass. Bubbles in the refrigerant indicate
the unit is low on refrigerant. Refer to
“Evacuating and Charging the Refrigeration
System” on page 43 for information about
adding refrigerant.
NOTE: If no bubbles are present, 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
Charge
The compressors are furnished with the amount of
oil shown in the Specifications chapter. The oil
level in the compressor will change after the
compressor is initially run, making any level
measurements inaccurate.
To ensure an adequate oil supply, the following
procedure must be followed whenever the
refrigerant charge is lost or removed from a unit:
1. Install a compressor on the system having a
residual oil supply and self-lubricating system
such as a TK 214 model. Connect an oil
separator on the discharge or suction line to
collect and drain out circulated oil.
NOTE: A suction line oil separator can be
improvised by installing a suction filter
upside down in the suction line near the
compressor. Cap off both access ports, and
use the lower one to drain off the
accumulated oil.
2. Place a normal amount of oil in the cleanup
compressor before operating.