Specifications
55
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. Disconnect power from the VFD before placing the
chiller under a vacuum.
2. Connect a high capacity vacuum pump (5 cfm [.002 m
3
/s]
or larger is recommended) to the cooler or condenser
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.
3. Use an absolute pressure manometer or a wet bulb
vacuum indicator to measure the vacuum. Open the
shutoff valve to the vacuum indicator only when taking a
reading. Leave the valve open for 3 minutes to allow the
indicator vacuum to equalize with the chiller vacuum.
4. If the entire chiller is to be dehydrated, open all isolation
valves (if present).
5. 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 vacuum, referenced to 30 inches of
mercury barometric pressure (0.1 psia) (–100.6 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,
isolated pockets of moisture can turn into ice. The slow
rate of evaporation (sublimation) of ice at these low
temperatures and pressures greatly increases dehydration
time.
6. Valve off the vacuum pump, 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,
perform a leak test up to the maximum 160 psig
(1103 kPa) pressure. Locate and repair the leak, and
repeat dehydration.
Inspect Liquid Piping — Refer to piping diagrams
provided in the certified drawings and the piping instructions in
the 23XRV 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. Liquid flows through the cooler
and condenser must meet job requirements. Measure the pres-
sure drop across the cooler and the condenser.
Check Optional Pumpout Compressor Liquid
Piping — If the optional pumpout storage tank and/or
pumpout system are installed, check to ensure the pumpout
condenser liquid has been piped in. Check for field-supplied
shutoff valves and controls as specified in the job data. Check
for refrigerant leaks on field-installed piping. See Fig. 30-33.
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 23XRV relief valves are set to relieve at the 185 psig
(1276 kPa) chiller design pressure.
Identify the VFD — The LiquiFlo
™
2.0 AC drive is a
PWM (Pulse Width Modulated), liquid-cooled drive that
provides vector and general purpose regulation for a wide
range of applications. Identify the drive from the Drive Part
Number on the drive’s nameplate and the model number
matrix in Fig. 35 and 36.
CAUTION
Do not start or megohm-test the compressor motor, even
for a rotation check, if the chiller is under dehydration vac-
uum. Insulation breakdown and severe damage may result.
Fig. 34 — Dehydration Cold Trap
a19-661
CAUTION
Liquid must be clean and treated to ensure proper chiller
performance and to reduce the potential of tube damage
due to corrosion, scaling, or erosion. Carrier assumes no
responsibility for chiller damage resulting from untreated
or improperly treated cooler or condenser liquid.
Fig. 35 — VFD Nameplate
a23-1553