3. Operate the vacuum pump to evacuate the system to the best attainable vacuum. The
vacuum must be less than 500 μm but if that cannot be attained, a vacuum at 1,000 μm or
lower is acceptable.
4. Close the system charging valve connection to the vacuum pump to start the 8-hour vacuum
hold test. Note the time and pressure.
5. Hold the vacuum obtained in Step 4 in the system for 8 hours. Any rise that exceeds the limits
in Step 6 can indicate a leak, the presence of moisture, or both. It is important to check for
pressure change with the chiller at the same temperature. Pressure changes proportional to
temperature and affects results. To determine if it is moisture or a leak, a pressure rise test
must be conducted. Evacuate the system to 5,000 μm again and perform another hold test. If
the pressure rise goes to 0 psig, that indicates that a leak is present. During the hold period,
if moisture is present, the pressure stabilizes at some level below atmosphere and should
correspond to room ambient temperature or the heat being applied to the vessel. See Table 2
for values.
6. An acceptable vacuum pressure rise is 150 μm per 60 minutes:
- 1000TR 1,000 μm
- See factory standard
7. If the vacuum does not hold within the limits defined in Step 6, you must locate the leak
and repair it. For cases where leaks cannot be identified while pressurized but vacuum hold
tests indicate that there is a leak, in most cases this can be traced to an elastomeric (O-ring
sealing) issue.
8. When the 500 μm hold test is successful, you can charge the system using the steps
described in Refrigerant charging.
Refrigerant charging
Before beginning, it is critical to establish that the vapor portion of the refrigerant container or
cylinder has not been contaminated with other gases that are not R-134a or R-513A, including air.
Use the appropriate saturation property table Table 3 or Table 4 to determine that the saturation
pressure and ambient temperature of the refrigerant in the container indicate that the gas
pressure coincides with the corresponding temperature.
You must only admit refrigerant vapor from the top of the drum or cylinder to the system until
the system pressure is raised above the corresponding saturation pressure at the highest freezing
point of the chiller liquids. This is to avoid the possibility of freezing liquid within any of the chiller
tubes when charging an evacuated system. For water with R-134a at 32°F, that pressure is 28 psig.
See Table 3. For water with R-513A at 32°F, that pressure is 32 psig. See Table 4.
Before charging, establish the starting weight for the refrigerant cylinder. After the chiller is vapor
charged to the appropriate saturation pressure, it may be necessary to use a refrigerant pump to
draw vapor from the chiller and discharge it to the vapor connection of the refrigerant cylinder.
This process aids in creating a pressure differential for pushing the refrigerant liquid from the
cylinder to the chiller.
While charging, every precaution must be taken to prevent air from entering the system. Make
up a suitable charging connection from new copper tubing or from properly selected flexible
charging hoses to fit between the system charging valve and the fitting on the charging drum. This
connection must be as short as possible but long enough to permit sufficient flexibility for changing
drums. It must also contain a tee fitting with a valve to serve as a connection point to a vacuum
pump to evacuate the charging lines. Evacuate the charging connection each time the lines are
disconnected for changing cylinders or any of the components of the charging process.
Model YK (Style H), R-134a and R-513A36
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