York YCRS Series Installation, Operation And Maintenance Manual page 45

This type of oil failure will not be picked up by the High
Oil Differential Safety since no flow will cause the dif-
ferential through the oil piping to drop to zero.
Example:
For ambients above 50°F (10°C), the cutout will be
activated (and system shutdown) after 1 minute of com-
pressor operation if the oil pressure differential is not
greater than 10 psi (0.7 bar). After 2 minutes it must be
greater than 20 psi (1.4 bar); after 3 minutes, 30 psi (2
bar); after 4 minutes, 40 psi (2.7 bar); and after 5 min-
utes of operation and onwards, oil pressure must re-
main higher than 50 psi (3.4 bar).
For lower ambient temperatures the ramp times are as
follows:
AMBIENT TEMP
>50°F (10°C)
>45°F (7°C)
>40°F (4°C)
>35°F (2°C)
>30°F (1°C)
<30°F (1°C)
High Oil Temperature Cutout:
This cutout assures oil temperature does not exceed a
safe operating temperature which affects compressor
lubrication. Typical oil temperature during normal op-
eration will be approximately 130 to 150°F (54 to 66°C).
S Y S # H I G H
S Y S # H I G H
The cutout will be activated (and system shutdown)
after 2 minutes of compressor operation, when the oil
temperature is above 225°F (107°C) for more than 3
seconds.
Low Suction Pressure Cutout:
This cutout aids in protecting the evaporator from dam-
age due to ice build up caused by operation at low re-
frigerant charge or restricted refrigerant flow. A num-
ber of transient timer features prevent nuisance trips
during start-up, compressor loading, etc. The cutout is
programmable.
S Y S # L O W
S Y S # L O W
The suction pressure cutout is ignored for the first 45
seconds of operation. During the next 180 seconds of
YORK INTERNATIONAL
RAMP TIME
5 Minutes
6 Minutes
7 Minutes
8 Minutes
9 Minutes
10 Minutes
O I L T E M P
O I L T E M P
S U C T P R E S S
S U C T P R E S S
running, suction pressure may be lower than the cutout,
but must be greater than:
SUCTION
PRESSURE = PROGRAMMED CUTOUT * (RUN TIME - 25)
CUTOUT
This cutout value increases with time until after 225 sec-
onds it equals the programmed cutout value. If suction
pressure falls below the calculated cutout value before
225 seconds of run time, the system will be shutdown.
The following graph shows a typical programmed suc-
tion pressure cutout of 44 psi (3 bar) and its change
from time = 0 sec of compressor run time to 225 sec-
onds of compressor run time.
45
40
35
30
25
20
15
10
5
0
0 30 60 90 120 150 180 210 240 270 310
Run Time (seconds)
FIG. 15 – SUCTION PRESSURE CUTOUT WITH
44 PSIG (PROGRAMMED CUTOUT)
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 suction pressure drops below the cutout point after
225 seconds of operation, the transient timer is acti-
vated. While the transient timer is active, suction pres-
sure must not drop below 10% of the cutout initially
programmed and must be greater than:
C.O. = PROGRAMMED C.O. X ( TIME + .1 )
33.3
This transient cutout value increases with time until
after 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
shutdown on a low suction pressure fault. If the suc-
tion pressure rises above the programmed cutout value,
the 30 second timer will be reset.
FORM 201.25-NM1 (302)
25
LD03525
45
7