Operating instructions
38
4. Leak determination - If an electronic leak detector
indicates a leak, use a soap bubble solution to locate the
leak. Total all leak rates for the entire chiller. Leakage
at rates greater than 0.45 kg/year for the entire chiller
must be repaired. Note total chiller leak rate on the
start-up report.
5. If no leak is found during initial start-up procedures,
complete the transfer of refrigerant gas from the pump-
out storage tank to the chiller. For machines with the
optional storage tank refer to the transfer unit installa-
tion manual, document order no. 19999, chapter
“Pumpout and refrigerant transfer procedures” and
chapter 4.12 “Chiller equalization with pumpout unit”).
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 chapter 4.3.
b. If the chiller fails this test, check for large leaks
(step 2b).
c. Dehydrate the chiller, if it passes the standing
vacuum test, as described in chapter 4.4 “Chiller
dehydration”. Charge chiller with refrigerant.
7. If a leak is found, pump the refrigerant back into the
pumpout storage tank, or if isolation valves are present,
pump into the non-leaking vessel (refer to the transfer
unit installation manual, document order no. 19999,
chapter “Pumpout and refrigerant transfer procedures”).
8. Transfer the refrigerant until chiller pressure is at 40 kPa
absolute.
9. Repair the leak and repeat the procedure, beginning
from step 2h to ensure a leaktight repair. (If chiller is
opened to the atmosphere for an extended period,
evacuate it before repeating leak test.)
10. The circuit openings must be plugged during repair, if
this does not take longer than one day. If it takes longer,
the circuits must be charged with nitrogen.
When performing the standing vacuum test or chiller dehy-
dration, use a manometer or a wet bulb indicator. Dial
gauges cannot indicate the small amount of acceptable
leakage during a short period of time.
1. Attach an absolute pressure manometer or wet bulb
indicator to the chiller.
2. Evacuate the vessel to at least 41 kPa, using a vacuum
pump or the pumpout unit (refer to the transfer unit
installation manual, document order no. 19999, chapter
“Pumpout and refrigerant transfer procedures”).
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 0.17 kPa in 24 hours,
the chiller is sufficiently tight.
b. If the leakage rate exceeds 0.17 kPa in 24 hours,
repressurize the vessel and test for leaks. If refri-
gerant is available in the other vessel, pressurize by
following steps 2 to 10 of chapter 4.2.2 “Leak test
chiller”. If not, use nitrogen and a refrigerant tracer.
Raise the vessel pressure in increments until the
leak is detected. If refrigerant is used, the maximum
gas pressure is approximately 483 kPa for R-134a at
normal ambient temperature. If nitrogen is used,
limit the leak test pressure to 1103 kPa maximum.
5. Repair leak, retest, and proceed with 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.
WARNING: 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.
Dehydration is readily accomplished at room temperatures.
Use of a cold trap (see Fig. 30 - “Dehydration cold trap”)
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 for boiling off any moisture. If the
ambient temperatures are low, contact a qualified service
representative for the dehydration techniques required.
Perform dehydration as follows:
1. Connect a high-capacity dehydration pump (0.002 m
3
/s
or larger is recommended) to the refrigerant charging
valve. Tubing from the pump to the chiller should be
as short and as large a diameter as possible to provide
least resistance to gas flow.
2. Use an absolute pressure manometer or a wet bulb
vacuum indicator to measure the vacuum. Open the
isolation valve to the vacuum indicator only when taking
a reading. Leave the valve open for 3 minutes to ensure
pressure equalization between detector and chiller.
3. Open all isolation valves (if present), if the entire
chiller is to be dehydrated.
4. With the chiller ambient temperature at 15.6°C or
higher, operate the vacuum pump until the manometer
reads -100.61 kPa or a vacuum indicator reads 1.7°C.
Operate the pump an additional 2 hours.
5. Do not apply greater vacuum than 100.97 kPa (757.4
mm Hg) or go below 0.56°C on the wet bulb vacuum
indicator. At this temperature/pressure, isolated pockets
of moisture can turn into ice. The slow rate of evapora-
tion (sublimination) of ice at these low temperatures/
pressures greatly increases dehydration time.
6. Close the valve to which the vacuum pump is connected,
stop the pump, and record the instrument reading.
7. 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.
8. If the reading continues to change after several attempts,
do a leak test up to the maximum 1103 kPa pressure.
Locate and repair the leak, and repeat dehydration.
1. To vacuum pump
2. Mixture of dry ice and
methyl alcohol
3. Moisture condenses
on cold surface
4. From system