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8.2 PROGRAM KEY –
USER PROGRAMMABLE VALUES
High Discharge Pressure Cutout:
D I S C H A R G E
C U T O U T
=
The Discharge Pressure Cutout is a microprocessor
backup for the mechanical high pressure cutout located
in each refrigerant circuit. This safety is bypassed for the
first 5 seconds of operation, after which if the cutout point
is exceeded for 3 seconds, the system will shut down.
Normally, air-cooled YCAR chillers should have
the cutout set at 27 bar (395 PSIG) for R-22 and
R-407C models. The micro will, however, accept val-
ues between 14 - 28 bar (200 - 399 PSIG). For this cut-
out to be functional, the Discharge Pressure Read-out
Option must be installed (fitted as standard on 50 Hz
models). This programmable value is password protected.
To program the Discharge Pressure Cutout, key in the
desired value and press the Enter key to store the value
into memory and scroll to the next display.
High Discharge Pressure Unload Point:
D I S C H A R G E
U N L O A D
=
The Discharge Pressure Unload point is used to avoid a
high pressure cutout shutdown by unloading a compres-
sor, if its discharge pressure approaches the cutout value.
The chiller can then continue to run automatically at
reduced capacity until the cause of the excessive pres-
sure is attended to (e.g. dirty condenser coils), or ceases
naturally (e.g. high ambient temperature).
For the first 60 seconds of operation, discharge pressure
limiting is disabled. After this time, if discharge pressure
exceeds the programmed limit, load limiting will occur
with the affected system being unloaded by one stage
until the discharge pressure drops below the programmed
limit. The message will be removed and reloading will
take place when discharge pressure has dropped 4 bar
(60 PSIG) below the threshold.
Typically, the unload point should be set 1.4 to 1.7 bar
(20 - 25 PSIG) below the discharge pressure cutout set-
ting. The micro will accept a range of programmable
YORK INTERNATIONAL
P R E S S U R E
2 7 . 2
B A R
P R E S S U R E
2 4 . 8
B A R
values between 14 - 28 bar (200 - 399 PSIG). This pro-
grammable value is password protected.
To program the Discharge Pressure Unload, 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:
S U C T I O N
P R E S S U R E
C U T O U T
=
The Low Suction Pressure Cutout protects the evapo-
rator from damage due to ice buildup caused by opera-
tion at low refrigerant suction pressure.
Forty-five seconds after the compressor starts, suction
pressure is monitored as long as the compressor runs.
For the first 225 seconds of running, suction pressure
can be lower than the programmed cutout, but must be
greater than:
Programmed
x
Cutout
Example: If Programmed Cutout = 3 bar (44 PSIG)
and Run Time = 150 seconds
150 – 25
New Cutout
= 44 x
200
This cutout value increases with time until, after 225
seconds, it equals the programmed cutout value. If suc-
tion pressure falls below the calculated cutout value
before 225 seconds, the system will be shut down.
After 225 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 30-second transient timer starts. Dur-
ing the 30-second time period, the suction pressure must
be greater than:
Programmed
33.3 – transient time remaining
x
Cutout
Example: If Programmed Cutout = 3 bar (44 PSIG)
and timer has run 10 seconds.
33.3 – 20
New Cutout
= 44 x
33.3
FORM 150.52-NM2 (1001)
3 . 0
B A R
(Run Time – 25)
200
= 1.9 bar (27.5 PSIG)
33.3
= 1.2 bar (17.6 PSIG)
143
9
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