York YCAS Installation Operation & Maintenance Download

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144

YORK INTERNATIONAL

FORM 201.19-NM6 (804)

1.13 ANTI-RECYCLE

TIMER

The programmable Anti-Recycle Timer allows the user
to select the compressor anti-recycle time to best suit
their needs. Motor heating is a result of inrush current
when the motor is started. This heat must be dissipated
before another start takes place or motor damage may
result. The anti-recycle timer assures that the motor has
suffi cient time to cool before it is restarted.

An adjustable timer allows for the motor cooling, but
gives the user the ability to extend the anti-recycle
tim er to cut down on cycling. In some applications,
faster com pres sor start response is necessary and shorter
anti-recycle times are required. These needs should be
kept in mind, but whenever possible the timer should
be ad just ed for the longest period of time tolerable.
600 sec onds is recommended, although 300 seconds
provides adequate motor cooling time. Longer periods
will al low more heat dissipation, reduce cycling, and
pos si bly in crease motor life. See Section 8.2, page 178
for pro gram ming of the anti-recycle timer.

1.14 ANTI-COINCIDENCE

TIMER

The Anti-Coincidence Timer assures that 2 systems
do not start simultaneously. This assures that inrush
cur rent is kept to a minimum. A 60 second time delay
will al ways separate motor starts. This timer is not
pro gram ma ble.

1.15

EVAPORATOR PUMP CONTROL

Dry contacts are provided which transition (close) when
the Daily Schedule is calling for chiller operation, the
unit switch is on, and power has been applied to the
Micro Panel for 30 sec onds. If for some reason the
evaporator pump contacts have been closed to run the
pump and a power loss or Daily Schedule shuts the pump
down (contacts open), the contacts will not reclose for
any reason until 30 sec onds has elapsed after power re-
application or 30 sec onds have elapsed between a Daily
Schedule shut down and restart. If the daily schedule is
not used (ON/OFF times equal 00:00) the contacts will
be closed at all times.

1.16

COMPRESSOR HEATER CONTROL

Each compressor has its own heater. The heater will be
off whenever the compressor is running. As soon as the
compressor shuts off, the heater will turn on and stay on
for 5 minutes. After 5 minutes has elapsed, the heat er will
shut off if the discharge temperature rises above 150

(66°C) and will turn on when the dis charge tem per a ture
is equal to or less than 150

F (66°C).

1.17

EVAPORATOR HEATER CONTROL

The evaporator heater is controlled by ambient tem-
per a ture. When the ambient temperature drops below
40

F (4°C), the heater is turned on when the com pres sors

are turned off. When the temperature rises above 45°F
(7°C), the heater is turned off. An under voltage condi-
tion will keep the heater off until full voltage is restored
to the system. The heater will provide freeze protection
to -20°F (-28°C).

115VAC power must remain “ON”
through CB4 (3 System chillers) or
CB5 (4 System chillers) for freeze
pro tec tion. Oth er wise, the evap o ra tor
must be drained.

1.18

PUMPDOWN (EEV) CONTROL

Each compressor undergoes a pump down on shut-
down. This as sures that liq uid re frig er ant does not
enter the com pres sor on start-up, elim i nat ing the need
for recycling pump down, sav ing en er gy and re duc ing
com pres sor starts and wear.

On start-up, the controls unload the com pres sor and im-
mediately energize the pilot solenoid on the electronic
expansion valve. Normal operation commences without
pumpdown.

On shutdown, the microprocessor controls unload the
compressor, the pilot solenoid on the electronic expan-
sion valve is de-energized, and the Econ o miz er Liquid
Supply Solenoid Valve is de-energized. The compressor
continues to op er ate until it either pumps down to the
low suction pres sure cutout setting or for 180 seconds,
whichever comes fi rst. Pump down occurs on “normal”
shut downs where cool ing demand has been satisfi ed or
when a system switch is turned off, a fl ow switch opens,
run per mis sive is lost or a Daily Schedule or a Remote
Shut down is called for.

No pumpdown will occur on a safety shutdown. See
page 150 for the pumpdown display message.

Remote evaporator applications equipped with ther-
mostatic TXV and liquid line solenoid will also pump
down on shutdown.

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