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.
Do not start or
Dehydration can be done at room temperatures. Using a cold trap (Fig. 31) 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 m3/s] or larger is recommended) to the refrigerant charging valve (Fig. 2). 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)
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
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.
Fig. 31 — Dehydration Cold Trap
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.
Water must be within design limits, clean, and treated to ensure proper chiller performance and to reduce the poten- tial of tube damage due to corrosion, scaling, or erosion. Carrier assumes no responsibility for chiller damage result- ing from untreated or improperly treated water.
Check Optional Pumpout Compressor Water Piping — If the optional pumpout storage tank and/or pumpout system are installed, check to ensure the pumpout condenser water has been piped in. Check for
Check Relief Valves — Be sure the relief valves have been piped to the outdoors in compliance with the latest edition of ANSI/ASHRAE Standard 15 and applicable local safety codes. Piping connections must allow for access to the valve mechanism for periodic inspection and leak testing.
The 19XR relief valves are set to relieve at the 185 psig (1275 kPa) chiller design pressure.
Inspect Wiring
Do not check the voltage supply without proper equipment and precautions. Serious injury may result. Follow power company recommendations.
Do not apply any kind of test voltage, even for a rotation check, if the chiller is under a dehydration vacuum. Insula- tion breakdown and serious damage may result.
1.Examine the wiring for conformance to the job wiring di- agrams and all applicable electrical codes.
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