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.
Condenser water temperature control
The YORK 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 full and part load conditions is specified
in the chiller engineering guide, where:
• ECLT = Entering Condensing Liquid Temperature
• LCHLT = Leaving Chilled Liquid Temperature
• C Range = Condenser Leaving Liquid Temperature - Condenser Entering Liquid Temperature
at the load condition being calculated
At start-up, the entering condenser water temperature may be as much as 25°F (14°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.
Heat recovery chillers and chillers using optional head pressure control would use a signal provided
by the microprocessor to control main condenser bundle heat rejection or pressure, respectively.
Operating log sheet
A permanent daily record of system operating conditions (temperatures and pressures) recorded at
regular intervals throughout each 24 hour operating period should be kept.
An optional status printer is available for this purpose or Figure 4 shows a log sheet used by
Johnson Controls Personnel for recording test data on chiller systems. It is available from the
factory in pads of 50 sheets each under Form 160.54-MR1 and may be obtained through the nearest
Johnson Controls office. Automatic data logging is possible by connecting the optional printer and
programming the DATA LOGGER function.
An accurate record of readings serves as a valuable reference for operating the system. Readings
taken when a system is newly installed will establish normal conditions with which to compare later
readings.
For example, an increase in condenser approach temperature (condenser temperature minus
leaving condenser water temperature) may be an indication of dirty condenser tubes.
13Model YK (Style H), R-134a and R-513A
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