York Millennium YCAS 316, Installation Operation & Maintenance

Page: 113 / 144

FORM 201.10-NM1
113
YORK INTERNATIONAL
If the anti-recycle timer is preventing a start, the timer
position in seconds may be viewed by pressing the “STA-
TUS” key. A sample display follows:
Anti-Coincidence Timer
The Anti-Coincidence Timer assures that 2 compressors
can never start simultaneously which limits excessive
current demand. A one minute time delay will always
separate compressor starts.
The Anti-Coincidence Timer can be viewed, when it is
active, by pressing the “STATUS” key. A sample display
is shown below:
Pumpdown Controls
Each compressor has a pumpdown on start-up and a
pumpdown on shutdown feature. Pumpdown is incorpo-
rated into the control scheme to assure that liquid does
not enter the compressor on start-up, which could cause
damage to the compressor.
The pumpdown on start-up control eliminates the need
for recycling pumpdown. Eliminating recycling pumpdown
saves energy, reduces the number of starts, and saves
wear on the compressor/motor.
On start-up, the Compressor Slide Valve Unload Sole-
noid will be energized to unload the compressor and the
system will be pumped down to the programmed cut-out
or will pump down for 30 seconds, whichever comes first,
before the Liquid Line Solenoid and Economizer Liquid
Supply Solenoid is energized.
Pumpdown on normal shutdown is incorporated to fur-
ther assure that liquid does not accumulate in the evapo-
rator. On shutdown, the Compressor Slide Valve Unload
Solenoid will be energized to unload the compressor and
the Liquid Line Solenoid and Economizer Liquid Supply
solenoid will de-energize. The compressor will continue
to operate until the suction pressure reaches the suction
pressure cut-out or a period of 30 seconds elapses.
Pumpdown on shutdown will occur on “normal” shutdowns.
Normal shutdowns include non-safety shutdowns where
cooling demand has been satisfied or when a system
switch on the Microprocessor Board is turned off (does
not apply to the UNIT Switch).
Pumpdown on shutdown will also occur when a flow switch
opens or run permissive is lost and when a Daily Sched-
ule or a Remote Shutdown is called for.
The following message will be displayed on the STATUS
display when a non safety shutdown due to cooling de-
mand, micro board system switch shutdown, or a run
permissive/flow switch shutdown occurs. After pumpdown
is complete, the respective shutdown message will be
displayed for the system.
No display indicating a pumpdown will be viewed when a
Daily Schedule or a Remote Shutdown occurs. Shutdown
messages for Remote and Daily Schedule shutdown will
be displayed during pumpdown and after shutdown for
these two messages.
Manual pumpdown from the control panel is not possible.
S Y S 1 A R T M R 1 0 2 S
S Y S 2 A R T M R 1 0 2 S
S Y S 1 C O M P R U N N I N G
S Y S 2 A C T M R 5 6 S
S Y S 1 P U M P I N G D O W N
S Y S 2 P U M P I N G D O W N