York Millennium YCAS Series Скачать руководство пользователя страница 142

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142

YORK INTERNATIONAL

This message indicates that both refrigerant systems
are in a pumpdown cycle. Pumpdown display messages
occur on shutdowns where the cooling load has been
met, or when a system switch is turned OFF. Note that
only one compressor could be pumping down, as shown
in the following display:

See Section 1.18 (page 138) for details of pumpdown
control.

Anticipation controls monitor discharge pressure, motor
current and suction temperature for each compressor
and if maximum limits are approached, the slide valve
loading of the respective compressor will be reduced to
avoid exceeding the limit.

Displays of anticipation safety control messages and
their meanings are as follows:

Discharge Pressure Limiting:

Discharge Pressure Limiting takes effect when com-
pressor discharge pressure nears the point at which the
high pressure cutout would shut the system down. When
the above message appears, discharge pressure has ex-
ceeded the programmable threshold and the compres-
sor is being unloaded in an effort to prevent shutdown
on the high pressure cutout. The operation of this safety
is important if condenser coils become dirty, if there is
a problem with the condenser fan operation, or if ex-
treme ambient or load conditions occur (see Section
8.2 / High Discharge Pressure Unload Point [page 168]
for more details).

Compressor Motor Current Limiting:

The Motor Current Limiting message indicates that a
compressor motor current has reached a programmable,
Bas, or remote limit and the system is being unloaded
to assure that motor current does not become exces-
sively high causing a fault (see also Section 8.2 / High
Motor Current Unload Point, page 170; Section 3.5, Mo-
tor Current Key, page 149; Section 1.10, page 134).

Suction Temperature Limiting:

The Suction Temperature Limiting message applies only
when the chiller is set for Water Cooling Mode (see page
150). The message indicates that saturated suction tem-
perature on a system has dropped to -2°C (29°F) and
that any further temperature reduction could cause some
icing of the evaporator tubes. Saturated suction tempera-
ture is computed by the micro by converting suction pres-
sure to temperature.

For the first 3 minutes that the saturated suction tem-
perature is at or below -2°C (29°F) any further compres-

Incorrect Refrigerant Warning:

The incorrect Refrigerant Warning will occur if the DIP
Switch setting for refrigerant type and the type pro-
grammed into the micro “at the factory” are not the
same. This message will be displayed until the non-
programmable “factory” programmed refrigerant type
and DIP Switch setting agree.

Power Failure Warning:

The Power Failure Warning will only be displayed on
“power restoration” after a “power loss,” if manual re-
start on power failure is selected under the PROGRAM
key (page 172). If manual restart on power failure has
been selected, the following warning message is dis-
played indefinitely on power restoration and the chiller
will not run until the UNIT Switch is cycled OFF-and-
on to restart the unit. This safety is available for users
who desire a chiller lock-out on power failure.

This is typically not a desirable feature.

When this message appears, the chiller will not run and
the Unit Switch must be cycled OFF and ON to start
the unit.

2.4

ANTICIPATION CONTROL STATUS
MESSAGES

Anticipation controls are built into the software to
prevent safety shutdowns by automatically overriding
the temperature controls, if system conditions approach
safety thresholds. This avoids total loss of cooling
resulting from a lockout by a safety control.

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