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FORM 160.67-O2
ISSUE DATE: 10/9/2020
SYSTEM SHUTDOWN
The following are methods for stopping the YST sys-
tem;
• Normal (Controlled) Stop - The chiller is un-
loaded prior to the actual de-energizing of the tur-
bine trip solenoid to shutdown the turbine. This
is done by pressing the SOFT SHUTDOWN key
on the HOME screen.
• Immediate Stop - The turbine trip solenoid is de-
energized as soon as the keypad switch is put in
the (O) STOP/RESET position.
Refer to STOPPING THE SYSTEM in Section 2 of
this manual for more detailed instructions.
PROLONGED SHUTDOWN
If the chiller is to be shut down for an extended pe-
riod of time (for example, over the winter season), the
following instructions outline the procedures to be fol-
lowed.
1. Test all system joints for refrigerant leaks with a
leak detector. If any leaks are found, they should
be repaired before allowing the system to stand
for a long period of time.
During long idle periods, the tightness of the sys-
tem should be checked periodically.
2. If freezing temperatures are encountered while
the system is idle, carefully drain the cooling wa-
ter from the cooling tower, refrigerant condenser,
steam condenser, condenser water pump, and the
chilled liquid system-chilled liquid pump and
coils.
Open the drains on the evaporator and condenser
liquid heads to assure complete drainage.
3. On the SETUP Screen, disable the clock. This
conserves the battery.
4. Open the main disconnect switches on the Power
Panel, condenser water pump, and chilled liquid
pump motor starters. Turn the compressor oil
heater protector disconnect switch and all motor
protector disconnect switches in the Power Panel
to the "OFF" position.
Turbine Off-Season Storage
Many YST chillers are used as "seasonal machines",
being out of service for as many as six to eight months
of the year. During the off-season, many turbines
JOHNSON CONTROLS
SECTION 2 - PRE-STARTUP AND SYSTEM OPERATING PROCEDURES
are subjected to moisture and contaminants that will
shorten the life expectancy of the machine. The tur-
bine must be protected from corrosion internally with a
vapor type of corrosion inhibitor introduced in crystal
form or clean dry air/nitrogen purge.
The following suggested preventative maintenance
procedures will greatly reduce the possibility of dam-
age to the turbine due to off-season storage. Frequent
inspections, both internal and external, for evidence of
rust should be made. Cleaning and reapplication of
preventatives may be necessary.
Turbine Steam Path
The following procedures are recommended to prevent
off-season deterioration of the steam path:
• Gland cases should be opened, dried and inspect-
ed. If gland cases do not have removable covers,
low pressure air may be blown through drain lines
to assist in drying the gland area.
The Gland leak-off connection should be capped
to prevent moisture from re-entering the turbine.
For extended storage, the carbon rings should be
removed to prevent pitting of the shaft that may
occur due to any condensation.
• Warm, dry air may be circulated through the tur-
bine to remove moisture from the steam path. Air
may be introduced through some other casing
opening such as a hand-valve boss.
The air can be exhausted through the exhaust
flange, vacuum breaker, port or casing drains.
• Steam inlet and exhaust valves (non-condensing
turbine only) must be tightly closed to provide a
positive shut-off or disconnected to prevent steam
entering the turbine.
A pressure relief valve must be installed
between the exhaust flange and exhaust
line positive shut-off valve on non-con-
densing turbines.
• Several types of rust preventatives are available
and can be placed into the turbine casing to help
keep the turbine dry. If this type of corrosion in-
hibitor is used the main steam inlet and exhaust
connection must be sealed off with blank flanges
(wood or metal) to prevent the loss of the vapor
inhibitor.
2
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