
FORM 201.10-NM4
115
YORK INTERNATIONAL
If the leaving chilled liquid temperature (water or glycol)
drops below the cutout point, the chiller will shut down.
The chiller will be restarted automatically when tempera-
ture rises more than 4°F above the cutout point and
cooling demand exists.
If the Dip Switch on the microprocessor board is set for
Water Cooling (See Section 3.7), the cutout is auto-
matically set at 36°F and cannot be reprogrammed. If
the Switch is set for Brine Cooling (glycol) the cutout
can be programmed between 8 - 36°F. The cutout should
normally be set to 4°F below the Low Limit Water Tem-
perature of the programmed Control Range (See Sec-
tion 6).
To program the Leaving Water Temperature Cutout, key
in the required setting and press the Enter key to store
the value into memory and scroll to the next display.
Low Suction Pressure Cutout
The Low Suction Pressure Cutout protects the evapo-
rator from damage due to ice build up caused by op-
eration at low refrigerant suction pressure.
After the compressor starts, and the pump down cycle
is completed (pump down to cutout or 30 seconds,
whichever comes first), suction pressure is monitored
as long as the compressor runs. For the first 270 sec-
onds of running, suction pressure can be lower than
the programmed cutout, but must be greater than:
Programmed
x
Run Time / 3 + 10
Cutout
100
Example: If the Programmed Cutout = 44 PSIG
and Run-Time = 60 seconds
New Cutout = 44 x
60 / 3 + 10 = 13.2 PSIG
100
This cutout value increases with time until, after 270
seconds, it equals the programmed cutout value. If suc-
tion pressure falls below the calculated cutout value
before 270 seconds, the system will be shut down.
After 270 seconds a transient timer system prevents short
term fluctuations in suction pressure from causing shut-
down as follows: If suction pressure drops below the
cutout point, a 90 second transient timer starts. During
the 90 second time period, the suction pressure must
be greater than:
Programmed
x
100 - transient time left
Cutout
100
Example: If Programmed Cutout = 44 PSIG
and the timer has run 30 seconds:
New Cutout = 44 x
100 60 = 17.6 PSIG
100
Again, this cutout value increases with time until, after
90 seconds, it equals the programmed cutout value. If
the suction pressure now rises to more than 5 PSI above
the programmed cutout value during the 90 second time
period, the timer will be reset. If the suction pressure
does not rise to more than 5 PSI above the cutout, the
timer will remain at zero. If the pressure then falls be-
low the cutout again, the system will shut down on a
low pressure fault.
If the Dip Switch on the microprocessor board is set for
Water Cooling (see Section 3.7), the cutout is pro-
grammable between 44 - 70 PSIG for R22 models and
19 - 36 PSIG for R134a models. In this mode, settings
of 44 PSIG for R22 and 19 PSIG for R134a are recom-
mended. If the Switch is set for Brine Cooling (glycol)
the cutout is programmable between 20 - 70 PSIG for
R22 models, 4.5 - 36 PSIG for R134a models. In this
mode, the cutout should be set to the saturated refrig-
erant pressure equivalent to 18°F below of the tempera-
ture of the chilled liquid. This programmable value is
password protected.
To program the Suction Pressure Cutout, key in the re-
quired setting and press the Enter key to store the value
into memory and scroll to the next display.
Lag Panel Start Point (YDAS only)
On rising demand for cooling, the Lag panel Start Point
% is the load level of the lead compressor group (%
FLA or % Slide Valve, whichever is programmed [see
Load Sharing Basis later in this section]) at which the
lag compressor group is allowed to start. A compressor
group is a pair of compressors operating on one evapo-
rator. The % FLA or % Slide Valve for a group is the
sum of the values for the two compressors in the group.
The micro will accept values between 30 - 99%, for this
control. Once the lag group of compressors has started,
equalizing loading and unloading for the two compres-
sor groups will occur until each has reached 100% load,
if demand allows. A setting of 40 - 60% is recommended
for the Lag Panel Start Point % for most applications.
S U C T I O N
P R E S S U R E
C U T O U T
=
4 4 . 0
P S I G
L A G
P A N E L
S T A R T
P O I N T
4 0 %
Содержание Millennium YDAS 410
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