System operating procedures
Pre-starting
Before starting the chiller, make sure that the display reads SYSTEM READY TO START.
The panel can boot up only when line power is available to the VSD transformers and the UPS
battery in the power panel is present and connected with its disconnect closed.
CAUTION
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
2
chiller is designed to use less power 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.
The minimum entering condenser water temperature for other full and part-load conditions is
provided by the following equation:
where:
ECWT = entering condensing water temperature LCHWT = leaving chilled water
temperature
At initial startup, entering condensing water temperature 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 standby return chilled water temperature. Cooling tower fan cycling normally provides
adequate control of the entering condenser water temperature on most installations.
Start-up
If the chilled water or condenser water pumps are manually operated, start the pump. The control
center does not allow the chiller to start unless chilled liquid flow is established through the unit.
If the liquid pumps are wired to the microcomputer control center pump run contacts, the pump
automatically starts. As a result, this step is not necessary.
Note: The coolant temperature inside any liquid-cooled motor starter supplied by Johnson
Controls must be maintained above the dewpoint temperature in the equipment room
to prevent condensing water vapor inside the starter cabinet. As a result, 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, 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 operations screen. You can start the chiller in several ways:
• Locally by using only the keypad when the chiller is set to local mode
21
YMC
2
Mod B with OptiView Control Center
To Next Page
Loading...
Need help?
General
