Section 2 - System Operating Procedures; Pre-Starting; Condenser Water Temperature Control; Start-Up - York YMC2 Operation And Maintenance

FORM 160.84-OM1
ISSUE DATE: 9/21/2017

SECTION 2 - SYSTEM OPERATING PROCEDURES

PRE-STARTING

Prior to starting the chiller, make sure the display reads
"SYSTEM READY TO START".
The Panel can only boot up when line power is avail-
able to the VSD transformers and the UPS battery in
the power panel is present and connected with its dis-
connect 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 YMC chiller is designed to use less power
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by taking advantage of lower than design temperatures
that are naturally produced by cooling towers through-
out the operating year. Exact control of condenser wa-
ter such as a cooling tower bypass, is not necessary for
most installations. The minimum entering condenser
water temperature for other full and part-load condi-
tions is provided by the following equation:
where:
ECWT = entering condensing water temperature
LCHWT = leaving chilled water temperature
At initial startup, entering condensing water tempera-
ture may be as much as 30°F (16.66°C) colder than the
standby chilled water temperature.
Min ECWT = LCHWT -30°F (16.66°C)
At start-up, the entering condenser water temperature
may be as much as 30°F (16.66°C) colder than the stand-
by return chilled water temperature. Cooling tower fan
cycling will normally provide adequate control of the en-
tering condenser water temperature on most installations.

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 temperature
in the equipment room to prevent condens-
ing water vapor inside the starter cabinet.
Therefore, an additional temperature-
controlled throttle valve is needed in the flow
path for the starter heat exchanger to regu-
late cooling above the equipment room dew-
point for applications using cooling sources
other than evaporative air-exchange meth-
ods, such as wells, bodies of water, and
chilled water. 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 on a chiller
order by special quotation.
The Start/Stop control depends whether the chiller
Control Source is set to Local or one of the Remote
types from the chiller Setup - Operations screen. Start
is operated:
• only the keypad when the chiller is set to local
mode,
• remotely through digital inputs in digital or ana-
log remote mode but local keypad start must be
pressed initially to enable the run permissive, or
• by the SC-EQUIP in BAS (ISN) remote mode but
local keypad start must be pressed initially to en-
able the run permissive.
To start the chiller press the START key on the Home
Screen on the display panel. In LOCAL control source,
the chiller then starts. In remote ISN, ANALOG, DIGI-
TAL, or MODEM a remote start command must also
be provided to the proper 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 also located on the side of the panel.
The chiller will start if the following conditions are met:
• Leaving Chilled Liquid Temperature is above the
setpoint
• Chilled liquid flow is established
• Condenser liquid flow is established
• No uncleared faults or start inhibits exist
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