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Micro Panel Contents
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 compressor 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 adjusted for the longest period of time tolerable.
600 seconds is recommended, although 300 seconds
provides adequate motor cooling time. Longer periods
will allow more heat dissipation, reduce cycling, and
possibly increase motor life. See Section 8.2, page 163
for programming 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 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
seconds has elapsed after power re-application or 30
seconds have elapsed between a Daily Schedule shut-
down 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 150 °F
(66°C) and will turn on when the discharge temperature
is equal to or less than 150 °F (66°C).
132
1.17
EVAPORATOR HEATER CONTROL
The evaporator heater is controlled by ambient tempera-
ture. When the ambient temperature drops below 40°F
(4°C), the heater is turned on when the compressors
are turned off. When the temperature rises above 45°F
(7°C), 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
-20°F (-28°C).
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 refrigerant
does not enter the compressor on start-up, eliminating
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, whichever
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 cooling 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 134 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 system
or if power is lost to the control panel. The internal
contacts are normally open (N.O.) and will close when
JOHNSON CONTROLS
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