Anti-Recycle Timer; Anti-Coincidence Timer; Evaporator Pump Control; Compressor Heater Control - York MILLENNIUM YCAS Installation Operation & Maintenance

Micropanel

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 sufficient 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 timer
to cut down on cycling. In some applications, faster com-
pressor 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-
justed for the longest period of time tolerable. 600 sec-
onds is recommended, although 300 seconds provides
adequate motor cooling time. Longer periods will allow
more heat dissipation, reduce cycling, and possibly in-
crease motor life. See Section 8.2, page 136 for pro-
gramming 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
current is kept to a minimum. A 60 second time delay
will always separate motor starts. This timer is not
programmable.

1.15 EVAPORATOR PUMP CONTROL

Dry contacts are provided which transition (close) when
the Daily Schedule is calling for chiller operation and
power has been applied to the micropanel 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 shutdown
and restart.

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 heater
will shut off if the discharge temperature rises above 66°C
(150 ºF) and will turn on when the discharge temperature
is equal to or less than 66°C (150 ºF).
106

1.17 EVAPORATOR HEATER CONTROL

The evaporator heater is controlled by ambient tem-
perature. When the ambient temperature drops below
4°C (40ºF), the heater is turned on when the compres-
sors are turned off. When the temperature rises above
7°C (45ºF), the heater is turned off. An undervoltage
condition will keep the heater off until full voltage is
restored to the system. The heater will provide freeze
protection to -29°C (-20ºF).
115VAC power must remain "ON"
through CB3 for freeze protection.
Otherwise, the evaporator must be
drained.
1.18 PUMPDOWN (LLSV ) CONTROL
Each compressor undergoes a pump down cycle on
start-up and shutdown. This assures that liquid refriger-
ant does not enter the compressor on start-up, eliminat-
ing the need for recycling pump down, saving energy
and reducing compressor starts and wear.
On start-up, the controls unload the compressor and the
system either pumps down to the low suction pressure
cutout setting or pumps down for 15 seconds, which-
ever comes first, after which the Liquid Line Solenoid
Valve is energized and normal operation commences.
On shutdown, the microprocessor controls unload the
compressor and the Liquid Line Solenoid Valve and
Economizer/Motor Cooling Liquid Supply Solenoid Valve
are de-energized. The compressor continues to operate
until it either pumps down to the low suction pressure
cutout setting or for 180 seconds, whichever comes first.
Pump down occurs on "normal" shutdowns where cool-
ing demand has been satisfied or when a system switch
is turned off, a flow switch opens, run permissive is lost
or a Daily Schedule or a Remote Shutdown is called
for.
No pumpdown will occur on a safety shutdown. See
page 110 for the pumpdown display message.

1.19 ALARMS

Internal contacts are provided in the Power Panel (See
Section 1.12) which can be used to remotely signal a
warning whenever a fault lockout occurs on any sys-
tem or if power is lost to the control panel. The internal
contacts are normally open (N.O.) and will close when
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