York Millennium YCAS 310, Установка, эксплуатация и обслуживание

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6.1 GENERAL
The Microprocessor monitors leaving chilled liquid tem-
perature and adjusts the chiller cooling capacity to main-
tain this temperature within a programmed range. The
capacity is controlled by switching compressors on or
off, and by sending a series of load and unload pulses
to each compressor slide valve to adjust the capacity
of the compressors. Internal algorithms are used to
combine temperature control zones and timers, maxi-
mizing efficiency by spreading the cooling load between
compressors and minimizing compressor cycling. This
method of control is suitable for both water and brine
cooling. Control setpoints can be programmed into the
chiller to establish the desired range of leaving chilled
liquid operating temperatures. A description of the op-
eration and programming follows.
6.2A CHILLED LIQUID TEMPERATURE CONTROL
YCAS Models:
The Setpoints keys are used to program the required
chilled water leaving temperature, called the Target tem-
perature, for the application. This is done by program-
ming the acceptable deviation or range of leaving tem-
peratures around the desired Target temperature. This
range is called the Control Range and has the Target
temperature at its midpoint.
The minimum acceptable temperature in the Control
Range is referred to as the Low Limit Water Tempera-
ture which is the lowest user acceptable leaving tem-
perature, and the High Limit Water Temperature which
is the highest user acceptable leaving temperature. For
example, if the desired Target temperature is 44.0°F
and the allowable deviation from this temperature is
2.0°F, then the programmed acceptable Control Range
limits are 42°F and 46°F. This can be viewed pictorially
as follows:
To assure that the chilled liquid leaving temperature stays
within the Control Range, the micro will attempt to con-
trol the leaving temperature with an even tighter tem-
perature band than the low and high limits of the Control
Range. This smaller band is called the Neutral Zone.
When the chilled liquid leaving temperature is within the
Low Limit Water Temperature
46.0°F
44.0°F
42.0°F
High Limit Water Temperature
TARGET
temp.
CONTROL
RANGE
(User
acceptable
leaving
chilled liquid
operating
range)
➤
➤
28164(b)A
6. SETPOINT KEYS
“SETPOINTS”
KEYS