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water temperature to save on compressor kilowatt
requirements but, not be below 55 F (12.8 C).
6. Cooler pressure and temperature also will vary with
the design conditions. Typical pressure range will be
between 60 and 80 psig (410 and 550 kPa) [30 to
40 psig (204 to 260 kPa)] with temperature ranging
between 34 and 45 F (1 and 8 C).
7. The compressor may operate at full capacity for a short
time after the pulldown ramping has ended, even
though the building load is small. The active electrical
demand setting can be overridden to limit the compres-
sor IkW, or the pulldown rate can be decreased to
avoid a high demand charge for the short period of
high demand operation. Pulldown rate can be based on
load rate or temperature rate. It is accessed on the
Equipment SERVICE screen, RAMP_DEM table
(Table 3, Example 20).
To Stop the Chiller
1. The occupancy schedule starts and stops the chiller
automatically once the time schedule is configured.
2. By pressing the STOP button for one second, the alarm
light blinks once to confirm the button has been
pressed. The compressor will then follow the normal
shutdown sequence as described in the Controls sec-
tion. The chiller will not restart until the
softkey is pressed. The chiller is now in the
LOCAL
OFF control mode.
If the chiller fails to stop, in addition to action that the
PIC will initiate, the operator should open the slide
valve to reduce chiller load by overriding the slide
valve count to –20. Then, the operator should open the
main disconnect.
IMPORTANT: Do not attempt to stop the chiller by
opening an isolating knife switch. High intensity arcing
may occur.
Do not restart the chiller until the problem is diagnosed and
corrected.
After Limited Shutdown —
should be necessary. Follow the regular preliminary checks and
starting procedures.
Preparation for Extended Shutdown —
refrigerant should be transferred into the pumpout storage tank
(if supplied; see Pumpout and Refrigerant Transfer Procedures)
to reduce chiller pressure and the possibility of leaks. Maintain
a holding charge of 5 to 10 lbs (2.27 to 4.5 kg) of refrigerant or
nitrogen to prevent air from leaking into the chiller.
If freezing temperatures are likely to occur in the chiller
area, drain the chilled water, condenser water, and the pumpout
condenser water circuits to avoid freeze-up. Keep the waterbox
drains open.
Leave the oil charge in the chiller with the oil heater and
controls energized to maintain the minimum oil reservoir
temperature.
After Extended Shutdown —
tem drains are closed. It may be advisable to flush the water
circuits to remove any soft rust which may have formed. This
CCN
or
No special preparations
The
Ensure the water sys-
is a good time to brush the tubes and inspect the Schrader fit-
tings on the waterside flow devices for fouling, if necessary.
Check the cooler pressure on the CVC default screen and
compare it to the original holding charge that was left in the
chiller. If (after adjusting for ambient temperature changes) any
loss in pressure is indicated, check for refrigerant leaks. See
Check Chiller Tightness section, page 49.
Recharge the chiller by transferring refrigerant from the
pumpout storage tank (if supplied). Follow the Pumpout and
Refrigerant Transfer Procedures section, this page. Observe
freeze-up precautions.
Carefully make all regular preliminary and running system
checks. Perform a Control Test before start-up. If the oil level
appears abnormally high, the oil may have absorbed refriger-
ant. TD frame 4 chillers are able to start with an abnormally
high oil level. Ensure that the oil temperature is above refriger-
ant temperature plus 35º F (19º C) (TC frame 1 and 2 chillers
only).
NOTE: TD frame 4 chillers do not have an oil heater.
Cold Weather Operation —
denser water drops very low (55 F [13 C] minimum), the oper-
ator should automatically cycle the cooling tower fans off to
keep the temperature up. Piping may also be arranged to by-
pass the cooling tower. The PIC II controls have a low limit
tower fan output that can be used to assist in this control (termi-
nal 11 and 12 on ISM).
Slide Valve Operation —
slide valve to check control operation, or to control the valve in
an emergency operation, is possible by overriding the manual
slide valve count. Access the Status COMPRESS table on the
CVC and highlight MANUAL SLIDE VALVE. To control slide
valve movement, enter a desired count value. The MANUAL
SLIDE VALVE LOAD/UNLOAD has an allowable input range
of plus or minus 10 to provide up to 10 seconds of slide valve
movement in the selected direction. If the counts are positive
then the slide valve position will increase to load the compres-
sor and vice versa. To release the valve to PIC II control press
the
softkey.
RELEASE
NOTE: The valve can be increased with manual control to
override the pulldown rate during start-up. However, motor
current above the electrical demand setting, capacity overrides,
and chilled water below control point will override the manual
count and decrease the slide valve position. For descriptions of
capacity overrides and set points, see the Controls section.
Entering a 0 count value will cause the slide valve to main-
tain a HOLD state. In this condition, the slide valve will re-
spond to maintain the chilled water (∆T) temperature when the
override occurs.
Refrigeration Log —
one shown in Fig. 37, provides a convenient checklist for rou-
tine inspection and maintenance, and provides a continuous
record of chiller performance. It is an aid in scheduling routine
maintenance and in diagnosing chiller problems.
Keep a record of the chiller pressures, temperatures, and liq-
uid levels on a sheet similar to that shown. Automatic record-
ing of PIC II data is possible through the use of CCN devices
such as the Data Collection module and a Building Supervisor.
Contact your Carrier representative for more information.
67
When the entering con-
Manual operation of the
A refrigeration log, such as the
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