York MILLENNIUM YCAS, Installation Operation & Maintenance

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137
YORK INTERNATIONAL
FORM 201.18-NM2
Low Ambient Temperature Cut-Out
The Low Ambient Cutout is used to select the ambient
temperature below which the chiller may not operate.
If the ambient temperature falls 1ºC (1ºF) below this
point, the chiller will shut down. Restart will occur auto-
matically, when temperature rises more than 1ºC (1ºF)
above the cutout and cooling demand is present (see
also Section 2.5 page 111). This programmable value is
password protected.
If the SW1 Dip Switch on the Microprocessor Board
is set for "Standard Ambient Control" (see Section 3.7)
the low ambient cutout is set at -4°C (25ºF) and is
NOT programmable. If the Dip Switch is set for “Low
Ambient Control”, programming of the cutout between
8 - 10°C (00.0 - 50.0ºF) is allowed. This allows higher
values than -4°C (25º F) to be programmed to shut
down the chiller when other cooling methods become
operational. Values below -4°C (25ºF) can be used for
applications requiring chiller operation at lower tem-
peratures. If operation is occasionally needed below
-17°C (1ºF), the cutout should be set at -18°C (-0.4ºF).
This will allow operation at any temperature, as
the micro will only recognize temperatures above
-17ºC (1ºF). Temperatures below -17ºC (1ºF) will not
be displayed.
To program the Low Ambient Cutout, key in the re-
quired setting and press the Enter key to store the value
into memory and scroll to the next display.
Operation below -17°C (1ºF) may oc-
casionally cause nuisance low pres-
sure safety shutdowns. This will gen-
erally not cause a problem provided
ambient temperature is not expected
to be below -17ºC (1ºF) for more than
a short time.
This cutout value increases with time, until after 90 sec-
onds, it equals the programmed cutout value. If the suc-
tion pressure rises to more than 0.3 bar (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 0.3 bar (5 PSI) above the
cutout, the timer will remain at zero and if the pressure
then falls below 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 3-5 bar (44 - 70 PSIG) for both
R22 and R-407C models. In this mode, settings of 3 bar
(44 PSIG) for R22 and R-407C are recommended. If
the Switch is set for "Brine Cooling" (glycol) the cutout
is programmable between 0.3 bar (5 - 70 PSIG) for
R22 and R-407C models. In this mode, the cutout should
be set to the saturated refrigerant pressure equivalent
to 10°C (18ºF) below the temperature of the chilled liq-
uid. 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 the next display.
High Ambient Temperature Cut-Out
The High Ambient Cutout is used to select the ambient
temperature above which the chiller may not operate.
If the ambient temperature rises 1ºC (1ºF) above this
point, the chiller will shut down. Restart will occur auto-
matically, when temperature falls more than 1ºC (1ºF)
below the cutout and cooling demand is present.
This cutout is normally set at 54ºC (130ºF) to allow op-
eration to the absolute maximum temperature capability
of the electromechanical components; however, values
between 38 - 54ºC (100.0 - 130.0ºF) are accepted. This
programmable value is password protected.
To program the High Ambient Cutout, key in the re-
quired setting and press the Enter key to store the value
into memory and scroll to the next display.
H I G H A M B I E N T T E M P
C U T O U T = 5 4 . 4 ° C
L O W A M B I E N T T E M P
C U T O U T = – 3 . 9 ° C
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