Carrier AquaEdge 19XR series, Start-Up, Operation And Maintenance Instructions Manual, Page: 71 / 212

71
6. If no leak is found after a retest:
a. Transfer the refrigerant to the pumpout storage
tank and perform a standing vacuum test as out-
lined in the Standing Vacuum Test section, below.
b. If the chiller fails the standing vacuum test, check
for large leaks (Step 2b).
c. If the chiller passes the standing vacuum test,
dehydrate the chiller. Follow the procedure in the
Chiller Dehydration section. Charge the chiller
with refrigerant.
7. If a leak is found after a retest, pump the refrigerant back
into the pumpout storage tank or, if isolation valves are
present, pump the refrigerant into the non-leaking vessel.
See the Transfer Refrigerant from Storage Tank Vessel
to Chiller section on page 91.
8. Transfer the refrigerant until the chiller pressure is at
18 in. Hg (40 kPa absolute).
9. Repair the leak and repeat the procedure, beginning from
Step 2h, to ensure a leak-tight repair. (If the chiller is
opened to the atmosphere for an extended period, evacu-
ate it before repeating the leak test.)
Standing Vacuum Test —
When performing the
standing vacuum test or chiller dehydration, use a manometer
or a wet bulb indicator. Dial gages cannot indicate the small
amount of acceptable leakage during a short period of time.
1. Attach an absolute pressure manometer or wet bulb indi-
cator to the chiller.
2. Evacuate the vessel to at least 18 in. Hg vac, ref 30-in. bar
(41 kPa), using a vacuum pump or the pump out unit.
3. Valve off the pump to hold the vacuum and record the
manometer or indicator reading.
4. a. If the leakage rate is less than 0.05 in. Hg (0.17 kPa) in
24 hours, the chiller is sufficiently tight.
b. If the leakage rate exceeds 0.05 in. Hg (0.17 kPa) in
24 hours, repressurize the vessel and test for leaks if
refrigerant is available. If not, use nitrogen and a
refrigerant tracer. Raise the vessel pressure in incre-
ments until the leak is detected. If refrigerant is
used, the maximum gas pressure is approximately
70 psig (483 kPa) for HFC-134a at normal ambient
temperature. If nitrogen is used, limit the leak test
pressure to 160 psig (1103 kPa) maximum.
5. Repair the leak, retest, and proceed with dehydration.
Chiller Dehydration —
Dehydration is recommended if
the chiller has been open for a considerable period of time, if
the chiller is known to contain moisture, or if there has been a
complete loss of chiller holding charge or refrigerant pressure.
Dehydration can be done at room temperatures. Using a
cold trap (Fig. 34) may substantially reduce the time required
to complete the dehydration. The higher the room temperature,
the faster dehydration takes place. At low room temperatures, a
very deep vacuum is required to boil off any moisture. If low
ambient temperatures are involved, contact a qualified service
representative for the dehydration techniques required.
Perform dehydration as follows:
1. Connect a high-capacity vacuum pump (5 cfm [.002 m
3
/s]
or larger is recommended) to the refrigerant charging
valve (Fig. 2 and 3). Tubing from the pump to the chiller
should be as short in length and as large in diameter as
possible to provide least resistance to gas flow.
2. Use an absolute pressure manometer or a wet bulb vacu-
um indicator to measure the vacuum. Open the shutoff
valve to the vacuum indicator only when taking a read-
ing. Leave the valve open for 3 minutes to allow the indi-
cator vacuum to equalize with the chiller vacuum.
3. If the entire chiller is to be dehydrated, open all isolation
valves (if present).
4. With the chiller ambient temperature at 60 F (15.6 C) or
higher, operate the vacuum pump until the manometer
reads 29.8 in. Hg vac, ref 30 in. bar (0.1 psia)
(–100.61 kPa) or a vacuum indicator reads 35 F (1.7 C).
Operate the pump an additional 2 hours.
Do not apply a greater vacuum than 29.82 in. Hg vac
(757.4 mm Hg) or go below 33 F (.56 C) on the wet bulb
vacuum indicator. At this temperature and pressure, iso-
lated pockets of moisture can turn into ice. The slow rate
of evaporation (sublimation) of ice at these low tempera-
tures and pressures greatly increases dehydration time.
5. Valve off the vacuum pump, stop the pump, and record
the instrument reading.
6. After a 2-hour wait, take another instrument reading. If
the reading has not changed, dehydration is complete. If
the reading indicates vacuum loss, repeat Steps 4 and 5.
7. If the reading continues to change after several attempts,
perform a leak test up to the maximum 160 psig
(1103 kPa) pressure. Locate and repair the leak, and re-
peat dehydration.
8. Once dehydration is complete, the evacuation process can
continue. Evacuate the vessel or chiller with the vacuum
pump set to at least 18 in. Hg vac, ref 30-in. bar (41 kPa).
Inspect Water Piping —
Refer to piping diagrams pro-
vided in the certified drawings and the piping instructions in
the 19XR Installation Instructions manual. Inspect the piping to
the cooler and condenser. Be sure that the flow directions are
correct and that all piping specifications have been met.
Piping systems must be properly vented with no stress on
waterbox nozzles and covers. Water flows through the cooler
and condenser must meet job requirements. Measure the pres-
sure drop across the cooler and the condenser.
CAUTION
Do not start or megohm-test the compressor motor or oil
pump motor, even for a rotation check, if the chiller is
under dehydration vacuum. Insulation breakdown and
severe damage may result.
WARNING
Starters must be disconnected by an isolation switch before
placing the machine under a vacuum. To be safe, isolate
any starter before evacuating the chiller if you are not sure
if there are live leads to the hermetic motor.
Fig. 34 — Dehydration Cold Trap