Section 2 - System Operating Procedures; Pre-Starting; Start-Up - York YZ MODEL A Operation And Maintenance Manual

FORM 161.01-OM1
ISSUE DATE: 6/8/2018

SECTION 2 - SYSTEM OPERATING PROCEDURES

PRE-STARTING

Prior to starting the chiller, the display should read
"SYSTEM READY TO START."
The Panel can only boot up when line power is avail-
able to the VSD transformers and the UPS battery is
present and connected with its disconnect closed.
After periods of waterside maintenance
or prolonged shutdown, vent any air from
the chiller water boxes prior to starting the
water pumps. Failure to do so can result
in pass baffle damage.
Condenser Water Temperature Control
The YORK YZ chiller is designed to lower power con-
sumption by taking advantage of lower than design
temperatures that are naturally produced by cooling
towers throughout the operating year. Exact control of
condenser water, such as a cooling tower bypass, is not
necessary for most installations.
At start-up, the entering condenser water tempera-
ture may be as much as 30°F (16.66°C) colder than
the standby return chilled water temperature. Cooling
tower fan cycling will normally provide adequate con-
trol of the entering condenser water temperature.

START-UP

If the chilled water and/or condenser water pumps are
manually operated, start the pump. The control cen-
ter will not allow the chiller to start unless chilled liq-
uid flow is established through the unit. If the liquid
pumps are wired to the microcomputer control center
pump run contacts, the pump will automatically start,
therefore, this step is not necessary.
JOHNSON CONTROLS
The coolant temperature inside any JCI-
supplied liquid-cooled motor starter must
be maintained above the dewpoint tem-
perature in the equipment room to prevent
condensing water vapor inside the starter
cabinet. An additional temperature-
controlled throttle valve is needed in the
flow path for the starter heat exchanger
to regulate cooling above the equipment
room dewpoint for applications using
cooling sources other than evaporative
air-exchange methods. The temperature
control valve should be the type to open
on increasing drive coolant temperature,
fail-closed, and set for a temperature
above dewpoint. It can be requested as
factory-supplied by special quotation.
Start/stop control depends on whether the chiller con-
trol source is set to Local or one of the Remote start
types on the chiller Setup - Operations screen.
The chiller is started:
• By pressing the Start key on the Home Screen
when the chiller is set to local mode.
• Remotely through digital input in hardwire re-
mote mode by closing a contact between TB3-1
and TB3-7. The local keypad start key must be
pressed initially to allow remote operation.
• Remotely by the SC-EQUIP in BAS remote
mode. The local keypad start key must be pressed
initially to allow remote operation.
In LOCAL control source pressing the START key on
the home screen will immediately start the chiller. In
remote ISN, ANALOG, DIGITAL, or MODEM, a re-
mote start command must also be provided to the prop-
er input connection.
When the control is changed to local mode from any
other source, it will remain in RUN if already running
or remain in STOP if already stopped. A hardware safe-
ty stop button is located on the side of the panel to stop
the chiller in an emergency situation.
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