YORK INTERNATIONAL
42
FORM 201.25-NM1 (302)
Micropanel
where the cooling load has been met, or when a system
switch is turned ‘OFF’. Only one compressor could be
pumping down, as shown in the following display:
Incorrect Refrigerant Warning:
This message should never appear, if it does consult
your local YORK office. This message is a warning
that the setting for the type of refrigerant used with the
unit has been tampered with and the unit will not run.
Incorrect Unit Type:
This message should never appear, if it does consult
your local YORK office. This message is a warning
that the setting for the unit type has been tampered with
and the unit will not run.
Power Failure Warning:
The power failure warning will only be displayed on
‘power restoration’ after a ‘power loss’, if manual re-
start on power failure is selected under the ‘PRO-
GRAM’ key.
If manual restart on power failure has been selected,
the warning message is displayed indefinitely on power
restoration and the chiller will not run until the unit
switch is cycled ‘OFF’ and ‘ON’ to restart the unit.
3.4 ANTICIPATION CONTROL STATUS MESSAGES
Anticipation controls are built into the software to pre-
vent safety shutdowns by automatically overriding the
controls, if system conditions approach safety thresh-
olds. This avoids total loss of cooling resulting from a
lock-out by a safety control.
Anticipation controls monitor discharge pressure, mo-
tor current and suction temperature for each compres-
sor and if maximum limits are approached, the slide
valve loading of the respective compressor will be re-
duced to avoid exceeding the limit.
Discharge Pressure Limiting:
Discharge pressure limiting takes effect when compres-
sor discharge pressure nears the point at which the high
pressure cutout would shut the system down.
The message indicates the discharge pressure has ex-
ceeded the programmable threshold and the compres-
sor is being unloaded to prevent nuisance shutdown on
the high pressure cutout.
The operation of this safety is important if condenser
coils become dirty, if there is a problem with the con-
denser fan operation, or if extreme ambient or load con-
ditions occur.
Compressor Motor Current Limiting:
The message indicates that a compressor motor cur-
rent has reached a programmable, BAS, or remote limit
and the system is being unloaded to assure that motor
current does not become excessively high causing a
fault, during initial high load conditions.
Suction Temperature Limiting:
The suction temperature limiting message applies only
when the chiller is set for Water Cooling Mode (S1-1).
The message indicates that saturated suction tempera-
ture on a system has dropped to 28°F (-2°C) and that
any further temperature reduction could cause some
icing of the evaporator tubes. Saturated suction tem-
perature is calculated by the microprocessor by con-
verting suction pressure to temperature.
For the first 3 minutes that the saturated suction tempera-
ture is at or below 28°F (-2°C) any further compressor
loading is inhibited to allow time for the temperature to
rise. If the condition persists for more than 3 minutes, a 5
minute timer is started. As this timer counts down to zero,
a 1 second unload pulse will be sent to the slide valve of
the affected compressor every 5 seconds as long as the
temperature is below 30°F (-1°C). If the temperature rises
above 30°F (-1°C), the microprocessor will inhibit load-
ing for the remainder of the 5 minute period.
S Y S
1
P U M P I N G
D O W N
S Y S
2
C O M P
R U N N I N G
R E P R O G R A M
T Y P E
O F
R E F R I G E R A N T
T O
R U N
R E P R O G R A M
U N I T
T Y P E
! !
P O W E R
F A I L U R E
! !
C Y C L E
U N I T
S W I T C H
S Y S
#
D S C H
L I M I T I N G
S Y S
#
D S C H
L I M I T I N G
S Y S
#
C U R R
L I M I T I N G
S Y S
#
C U R R
L I M I T I N G
S Y S
#
S U C T
L I M I T I N G
S Y S
#
S U C T
L I M I T I N G
