Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual page 69

CHILLER EQUALIZATION WITHOUT A PUMPOUT
UNIT
When equalizing refrigerant pressure in the 19XRV chiller
after service work or during the initial chiller start-up, do
not use the discharge isolation valve to equalize. Either the
motor cooling isolation valve or a charging hose (con-
nected between the refrigerant charging valves on top of
the cooler and condenser) should be used as the equaliza-
tion valve. Damage to the float valve could result.
To equalize the pressure differential on a 19XRV chiller
with the refrigerant isolated in one of the heat exchangers, use
the terminate lockout function of the CONTROL TEST on the
SERVICE menu. This helps to turn on pumps and advises the
operator on proper procedures.
The following steps describe how to equalize refrigerant
pressure in an isolated 19XRV chiller without a pumpout unit.
1. Access terminate lockout function on the CONTROL
TEST screen.
2.
IMPORTANT: Turn on the chilled water and con-
denser water pumps to prevent freezing.
3. Slowly open the motor cooling isolation valve. The
chiller's cooler and condenser pressures will gradually
equalize. This process takes approximately 15 minutes.
4. Once the pressures have equalized, the cooler isolation
valve, the condenser isolation valve, and the hot gas isola-
tion valve may now be opened. Refer to Fig. 30 and 31,
for the location of the valves.
Whenever turning the discharge isolation valve, be sure to
reattach the valve locking device. This prevents the valve
from opening or closing during service work or during
chiller operation, which could result in serious personal
injury.
CHILLER EQUALIZATION WITH PUMPOUT UNIT —
The following steps describe how to equalize refrigerant
pressure on an isolated 19XRV chiller using the pumpout unit.
1. Access the terminate lockout function on the CONTROL
TEST screen.
2.
IMPORTANT: Turn on the chilled water and con-
denser water pumps to prevent freezing.
3. Open valve 4 on the pumpout unit and open valves 1a and
1b on the chiller cooler and condenser, Fig. 30 and 31.
Slowly open valve 2 on the pumpout unit to equalize the
pressure. This process takes approximately 15 minutes.
4. Once the pressures have equalized, the discharge isola-
tion valve, cooler isolation valve, optional hot gas bypass
isolation valve, and the refrigerant isolation valve can be
opened. Close valves 1a and 1b, and all pumpout unit
valves.
The full refrigerant charge on the 19XRV will vary with
chiller components and design conditions, as indicated on the
job data specifications. An approximate charge may be deter-
mined by adding the condenser charge to the cooler charge as
listed in Table 14.
Ensure that the condenser and chilled water pumps are
operating whenever charging, transferring, or removing
refrigerant from the chiller. Failure to do so could result in
serious personal injury or equipment damage.
Use the CONTROL TEST terminate lockout function to
monitor conditions and start the pumps.
If the chiller has been shipped with a holding charge, the
refrigerant is added through the pumpout charging connection
(Fig. 30 and 31, valve 1b). First evacuate the nitrogen holding
charge from the chiller vessels. Charge the refrigerant as a gas
until the system pressure exceeds 35 psig (141 kPa) for
HFC-134a. After the chiller is beyond this pressure the refrig-
erant should be charged as a liquid until all the recommended
refrigerant charge has been added. The charging valve (Fig. 30
and 31, valve 1a or 1b) can be used to charge liquid to the cool-
er or condenser. Do not charge liquid through the liquid line
service valve.
TRIMMING REFRIGERANT CHARGE — The 19XRV unit
is shipped with the correct charge for the design duty of the
chiller. On most 19XRV chillers the design LTD (Leaving
Temperature Difference) between the leaving chilled water
temperature and the cooler refrigerant temperature is so low
that the traditional method of trimming the charge to achieve a
minimum LTD is not practical. In the case where leaks have
been found and corrected and the LTD is greater than about
4° F (2.2° C) above design, add refrigerant until the full load
design LTD is approached, and then charge for proper oil
return at low load. (A high cooler LTD can also be caused by
dirty tubes, water box division plate bypass, a partially closed
liquid isolation valve, or a sticking float valve.)
If low load oil loss is experienced, operate the chiller at low
load with the guide vanes nearly closed and observe the flow
through the sight glass in the oil skimmer line. Under low load
operation one should be able to see a flow of bubbly oil and
refrigerant in the sight glass. If there is no visible flow, add
refrigerant. If the sight glass shows a flow of nearly clear fluid,
remove refrigerant.
The preferred location at which refrigerant should be added
directly into the chiller is through the service valve at the top of
the condenser. If that valve is not accessible due to presence of
an attached pumpdown unit which does not have a storage
tank, add charge through the valve connected to the side of the
condenser drain float sump. Adding charge through the drain
valve at the base of the chiller (off the liquid line) is NOT
recommended.
Table 14 lists the 19XRV chiller refrigerant charges for each
cooler and condenser code. Total refrigerant charge is the sum
of the cooler and condenser charge.
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