120
YORK INTERNATIONAL
FORM 150.52-NM2 (1001)
New C.O.= Programmed C.O. x
(33.3 - Time Remaining)
33.3
This transient cutout value increases with time until af-
ter 30 seconds it equals the programmed cutout value.
If the suction pressure falls below the value as calcu-
lated by the formula relative to time, the system will
shut down on a low suction pressure fault. If the suc-
tion pressure rises above the programmed cutout value,
the 30-second timer will be reset.
If the Dip Switch on the microprocessor board is set
for “Water Cooling” (see page 124), the cutout is pro-
grammable between 3-5 bar (44-70 PSIG) for both R-
22 and R-407C models. In this mode, settings of 3 bar
(44 PSIG) for R-22 and R-407C are recommended. If
the Switch is set for “Brine Cooling” (glycol) the cut-
out is programmable between 0.3 - 5 bar (5 - 70 PSIG)
for R-22 and R-407C models. In this mode, the cutout
should typically be set to the saturated refrigerant pres-
sure equivalent to 10°C (18°F) below the temperature
of the chilled liquid. The sludge point of the glycol
MUST be at least another 11°C (20°F) below the
equivalent cutout temperature. This programmable
value is password protected.
High Compressor Motor Current Cutout:
The High Motor Current Safety protects against exces-
sively high motor current and shuts a system down and
locks it out after only a single occurrence of a rise in
average motor current above the cutout point. Motor
current is monitored through the 3 Current Transform-
ers (CTs) per motor, one on each phase, in the motor
protection module.
Average motor current is monitored after 4 seconds of
compressor operation. The system will be shut down if
average motor current exceeds 115% FLA.
FLA (full load amps) is approximately
1.2 x RLA (rated load amps). RLA is
specified on the motor / chiller name-
plate and is typical current demand
under rated operating conditions in a
fully loaded system. When a system is
fully loaded, typical motor currents
may be at 60 - 85% FLA depending on
operating conditions.
frigerant flow. A number of transient timer features pre-
vent nuisance trips during start-up, compressor loading,
etc. The Low Suction Pressure Safety is programmable
(see Section 9 [8.2] / Page 143, Low Suction Pressure
Cutout for more details).
The suction pressure cutout is ignored for the first 45
seconds of operation. During the next 180 seconds of
running , suction pressure may be lower than the cutout,
but must be greater than:
SP Cutout =
Programmed Cutout * (Run Time - 25)
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 of run time, the system will be shut
down.
The following graph shows a typical programmed suc-
tion pressure cutout of 3 bar (44 PSIG) and its change
from time = 0 sec of compressor run time to 225 sec-
onds of compressor run time.
After 225 seconds of operation with suction pressure
operating above the cutout, a 30-second transient timer
prevents short term fluctuations in suction pressure due
to loading or fan cycling from causing shutdown. If suc-
tion pressure drops below the cutout point after 225 sec-
onds of operation, the transient timer is activated. While
the transient timer is active, suction pressure must not
drop below 10% of the cutout initially programmed and
must be greater than:
Suction Pressure Cutout With
3 bar Programmed Cutout
LD03525
0 30 60 90 120 150 180 210 240 270 310
45
40
35
30
25
20
15
10
5
0
Run Time (seconds)
Suction Pressure Cutout
FIG. 38 – SUCTION PRESSURE CUTOUT
SYS # H I GH MTR CURR
SYS # H I GH MTR CURR
Micro Panel
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