72
YORK INTERNATIONAL
programmable from 5-10 minutes; however, it automati-
cally is set to 2 minutes after a power failure.
This safety assures that the motor has a minimum of 2
minutes to cool under any circumstances allowing much
of the internal heating due to starting to be dissipated
before another start occurs.
ANTICIPATION SAFETY CONTROLS
Anticipation controls are built into the software to pre-
vent safety shutdowns by automatically overriding tem-
perature controls if system pressures near safety thresh-
olds. This allows the chiller to continue to run under re-
duced capacity to avoid total loss of cooling resulting
from a lockout on a safety.
Anticipation safeties monitor suction and discharge pres-
sure and unload the compressors as needed. The micro
will display a message on the STATUS DISPLAY when-
ever these controls are in operation.
Suction Pressure Unloading
*
If suction pressure exceeds the value programmed by
the user (Page 53), the micro will unload the affected
compressor. Automatic reloading will occur when pres-
sure drops 10 PSI below the programmed value. This
value assures that the motor will receive proper cooling
from the refrigerant which promotes longer motor life.
An example of the message displayed when suction pres-
sure unloading is in effect is shown below:
Current Limiting
* *
If current exceeds the value programmed by the user (Page
42), the micro will unload the affected compressor.
Whenever Current Limiting is activated, the compressor
will stay in the unloaded state for 5 minutes. After the 5
minute time period, the micro will look at motor current
once again. If motor is 25% below the programmed Mo-
tor Current Unload point, the compressor will be allowed
to reload, if water temperature allows.
This safety assures that the motor will receive proper cool-
ing from the refrigerant which promotes longer motor life.
An example of the message displayed when Current Lim-
iting is in effect is shown below:
Discharge Pressure Unloading
If discharge pressure exceeds the value programmed by
the user (Page 52), the micro will unload the affected
compressor. Automatic reloading will occur when pres-
sure drops 60 PSI below the programmed value. This
feature reduces the chance of faulting on the high dis-
charge pressure cut-out.
On water cooled chillers, this safety reduces the chance of
tripping the relief valve due to a very high rate of rise in
pressure resulting from a controls problem which would cause
condenser water flow to be interrupted. In this case, the
pressure rise is so fast, refrigerant loss may occur through
the relief valve even though the high pressure cut-out has
opened and the compressor is in the midst of stopping.
An example of the message displayed when discharge
pressure unloadings in effect is shown below:
INTERNAL TIMERS AND PUMPDOWN CONTROLS
Anti-Recycle Timer
Anytime a compressor shuts down for any reason, re-
start cannot occur until the programmable Anti-recycle
Timer (Page 53) has timed out (timer starts with the com-
pressor start). Even though the Anti-recycle timer has
timed out, a minimum of 2 minute (2-minute start-up
timer) must always elapse after a compressor stop be-
fore it may restart.
If a power failure occurs, the anti-recycle timers will re-
set to 2 minutes after power is re-applied.
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 is shown below.
Anti-Coincidence Timer
The Anti-Coincidence Timer assures that 2 compressors
can never start simultaneously. This assures that ex-
cessive current demand will never result. 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 (Non-Recycling Pumpdown
EPROMS)
* * *
Each compressor is controlled by a pumpdown on start-
up feature which eliminates the need for recycling
pumpdown. On start-up, the compressor will pumpdown
to the programmed suction pressure cut-out before the
liquid line solenoid is energized. This assures that liquid
slugging does not occur. Manual pumpdown from the
keypad is not possible.
S Y S # 1
S U C T
L I M I T I N G
S Y S # 2
S U C T
L I M I T I N G
S Y S # 1
C U R R
L I M I T I N G
S Y S # 2
C U R R
L I M I T I N G
S Y S # 1
D S C H
L I M I T I N G
S Y S # 2
D S C H
L I M I T I N G
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
*
This safety applies to chillers with 031-01096-001 EPROMs only.
** This safety applies to chillers with 031-01652-001 EPROMs only.
*** Non-recycling pumpdown on start-up applies to chillers with 031-01096-001 and earlier versions of 031-01652-001 EPROMs.
Summary of Contents for YCWJ45EE0
Page 29: ...FORM 150 24 NM27 YORK INTERNATIONAL 29 CONTROL CIRCUIT With I O Expansion Board LD02106...
Page 30: ...30 YORK INTERNATIONAL FIG 9 SYSTEM WIRING...
Page 31: ...FORM 150 24 NM27 YORK INTERNATIONAL 31 LD02678...
Page 35: ...FORM 150 24 NM27 YORK INTERNATIONAL 35 LD02679...
Page 36: ...36 YORK INTERNATIONAL MICROPANEL CONNECTION DIAGRAM With I O Expansion Board LD02107...
Page 37: ...FORM 150 24 NM27 YORK INTERNATIONAL 37 LD02108...