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hoses only, to the vacuum pump, electronic vacuum
gauge, and refrigerant recovery system.
c.
With the unit service valves closed (back seated) and
the vacuum pump and electronic vacuum gauge valves
open, start the pump and draw a deep vacuum. Shut off
the pump and check to see if the vacuum holds. This
operation is to test the evacuation setup for leaks, repair
if necessary.
d. Midseat the refrigerant system service valves.
e. Then open the vacuum pump and electronic vacuum
gauge valves, if they are not already open. Start the
vacuum pump. Evacuate unit until the electronic vacuum
gauge indicates 2000 microns. Close the electronic
vacuum gauge and vacuum pump valves. Shut off the
vacuum pump. Wait a few minutes to be sure the vacuum
holds.
f.
Break the vacuum with clean dry refrigerant gas. Use
refrigerant that the unit calls for. Raise system pressure
to approximately 2 psig by monitoring it with the
compound gauge.
g.
Remove refrigerant using a refrigerant recovery
system.
h. Repeat steps e through g one time.
i.
Remove the copper tubing and change the
filter-drier. Evacuate unit to 500 microns. Close the
electronic vacuum gauge and vacuum pump valves. Shut
off the vacuum pump. Wait five minutes to see if vacuum
holds. This checks for residual moisture and/or leaks.
j.
With a vacuum still in the unit, the refrigerant charge
may be drawn into the system from a refrigerant
container on weight scales. The correct amount of
refrigerant may be added by observing the scales. (Refer
to section 4.4)
4.4
ADDING OR CHECKING THE
REFRIGERANT CHARGE
4.4.1 Checking the Refrigerant Charge
1.
Set the controller set point to ---25_C
(---13_F) to ensure that the modulating solenoid
valve is fully open when checking operation of unit.
2.
The refrigerant level should only be checked
when the unit is running with the modulating
solenoid
valve
temperature should be approximately 1.7_C
(35_F) or ---17.8_C (0_F).
a. Connect the gauge manifold to the compressor
discharge and suction service valves.
b. Units equipped with the optional water-cooled
condenser, check charge only on air-cooled operation.
Refrigerant level on water-cooled operation will be
normally above sight glass. Partially block the condenser
coil inlet air starting from the front of the condenser coil.
Increase the area blocked until the compressor discharge
pressure is raised to approximately 12 kg/cm@ (175 psig).
Refrigerant should appear at center line of sight glass on
the water-cooled condenser. If not, refer to section 4.4.3.
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Units equipped with air-cooled condenser only,
partially block the condenser coil inlet air starting from
the front of the condenser coil. Increase the area blocked
until the compressor discharge pressure increases to
approximately 13 kg/cm@ (190 psig) with the container
temperature about 2_C (35_F) or 11 kg/cm@ (160 psig)
with the container temperature about ---18_C (0_F).
Allow the system to stabilize for 5 minutes of continuous
operation maintaining the head pressure at the proper
level. Proceed to step c.
c.
For units with air-cooled condenser only, check the
liquid line sight glass. If the sight glass appears clear with
no bubbles visible or only occasional intermittent
bubbles, then the unit has an adequate charge. If the sight
glass appears to be flashing or bubbles are constantly
moving through the sight glass, then the unit may have a
low refrigerant charge, or the filter-drier could be
partially plugged. Refer to section 4.10. If it is determined
that the filter-drier is not restricted, then it will be
necessary to add some refrigerant to the system. Refer to
section 4.4.3.
4.4.2 Adding Refrigerant to System (Full Charge)
a. Evacuate unit and leave in deep vacuum. (Refer to
section 4.3.)
b. Place drum of R-12 on scale and connect charging
line from drum to liquid line valve. Purge charging line at
liquid line valve and then note weight of drum and
refrigerant.
c.
Open liquid valve on drum. Open liquid line valve
half-way and allow the liquid refrigerant to flow into the
unit until the correct weight of refrigerant has been
added as indicated by scales. Correct charge is noted in
Table 1-1.
It may be necessary to finish charging unit
through suction service valve in gas form, due to
pressure rise in high side of the system. (Refer to
section 4.4.3.)
d. Backseat liquid line valve (to close off gauge port).
Close liquid valve on drum. Crack connection on
charging line at liquid line valve to vent charging line.
e. Start unit in cooling mode. Run approximately ten
minutes and check the refrigerant charge. (Refer to
section 4.4.1.b.)
4.4.3 Adding Refrigerant to System
(Partial Charge)
a. Examine the unit refrigerant system for any evidence
of leaks. Repair as necessary. (Refer to section 4.2.)
b. Maintain the conditions outlined in section 4.4.1.
c.
Fully backseat (to close off gauge port) the suction
service valve (see Figure 1-3) and remove the 1/4" flare
cap.
d. Connect charging line between suction service valve
port and drum of refrigerant-12. Open VAPOR valve.
e. Partially frontseat (turn clockwise) the suction
service valve and slowly add charge until the refrigerant
appears at the proper level (refer to section 4.4.1).
4-2
NOTE
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