York Millennium YCAS 310, Установка, эксплуатация и обслуживание

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FORM 201.10-NM3
103
YORK INTERNATIONAL
Low Leaving Water Temperature Cutout
The Low Leaving Water Temperature Cutout protects
the evaporator from damage due to ice build-up caused
by operation below the chilled liquid freezing point.
If the leaving chilled liquid temperature (water or gly-
col) drops below the cutout point, the chiller will shut
down. The chiller will be restarted automatically when
temperature 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 starting pump down cycle is com-
pleted (pump down to cutout or 30 seconds, which-
ever comes first), suction pressure is monitored as long
as the compressor runs. For the first 270 seconds of
running, suction pressure can be lower than the pro-
grammed 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
shutdown as follows: If suction pressure drops below
the cutout point, a 90 second transient timer begins,
during which 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 so far
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, the 90 second
timer will be reset. If the suction pressure does not rise
to more than 5 PSI above the cutout, the timer will re-
main at zero. If the pressure then falls below the cutout
again the system will shut down on 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 tem-
perature of the chilled liquid. This programmable value
is password protected.
To program the Suction Pressure Cutout, key in the
required 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 compres-
sor group is a pair of compressors operating on one
evaporator. 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
L E A V I N G W A T E R T E M P
C U T O U T = 3 6 . 0 ° F
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 %