54 YORK INTERNATIONAL
DUAL CIRCUIT UNITS
ducers. From this, the micro computes the Differential
Oil Pressure (PSID) (kPaD). This PSID (kPaD) = Oil
Pressure PSIG (kPaG) – Suction Pressure PSIG (kPaG).
The affected system shuts down if <10 PSID (68.9 kPaD)
at run time 4-30 seconds: if < 25 PSID (172.2 kPaD) at
run time 30 seconds – 4 minutes: or if < 20 PSID (137.8
kPaD) at run time > 4 minutes. An F2 (Sys 1) or an F6
(Sys 2) will be displayed for this safety.
F3 (System 1) or F7 (System 2) Fault
Low Evaporator (Suction) Pressure
During the first 30 sec. of run time the micro ignores
suction pressure (low pressure bypass). At run time =
30 secs. to 4 min. the micro checks to see that the sig-
nal from the suction pressure transducer to the Analog
Input Board is 80% cut-out. After 4 min., the suction pres-
sure must remain above cutout. An F3 (Sys 1) or an F7
(Sys 2) will be displayed for this safety.
Compressor suction pressure cutout is an adjustable
setpoint (R3) on the Combo Board. It will be factory set
at 44 PSIG (303 kPaG). If Glycol or Brine is utilized,
then the cutout can be varied according to mixture.
F4 (System 1) or F8 (System 2) Fault
High Discharge Pressure
An analog signal is sent to the Analog input Board and
from there to the Micro Board by the Discharge Pres-
sure Transducer. The unit shuts down when the dis-
charge pressure exceeds the pressure cutout setpoint
of 395 PSI (2721 kPa) set in software. An F4 (Sys 1) or
an F8 (Sys 2) will appear for this safety. Normally the
manual H.P. cutout (primary safety) will open before this
safety (back-up safety) is activated causing an F1 or F5
Fault.
AUTOMATIC RESET FAULTS
Both systems will shut down instantly and display an “F”
code when an Automatic Reset Fault is sensed. The
compressors will automatically restart, if load demands,
when the condition causing the shutdown clears.
F9 Fault
High Ambient Temperature (HAT)
Both systems shut down when the ambient tempera-
ture is above 130°F (54.4°C). Upon a decrease in tem-
perature below 130°F (54.4°C), the unit will restart
automatically providing the anti-recycle timer has timed
out and a minimum 2-minute delay has passed. An “F9”
code will be displayed while the temperature is high. The
“F” will automatically disappear when temp. drops be-
low cutout.
F10 Fault
Low Ambient Temperature (LAT)
Both systems shut down when the ambient tempera-
ture is below the 0°F to 50°F (–17°C to 10°C) adjustable
cutout (Adjustable on the Combo Board resistor R1.)
This is factory set at 35°F (1.7°C). Upon a rise in tem-
perature above setpoint, the unit will restart provided the
anti-recycle timer has timed out and a minimum 2-minute
delay has passed. An “F10” code will be displayed while
the temperature is low. The “F” will automatically disap-
pear when temp. rises above cut-out.
MANUAL RESET FAULT
(1 Fault and Lockout)
This type safety is applicable to the low leaving water
temperature safety only. Both systems will shut down
and lockout when this fault is sensed.
F11 Fault
Low Leaving Water Temperature (LWT)
An Analog signal is sent by the Leaving Chilled Water
Sensor to the Analog Board and then to the Micro. If the
temperature drops below the freeze point as set by R2
on the Combo Board, both systems shut down. Typical-
ly with water, the LWT cut-out is set at 36°F (2.2°C) (fac-
tory setpoint). For Brine applications, the setpoint can
be varied from 0°F (–17.8°C) to 40°F (4.4°C) on the
Combo Board by adjusting R2. An F11 code will appear
for this safety.
AUTOMATIC RESET SAFETIES
Shutdown Safety Controls
A. These software safety controls in the Micro Board shut
the system down and automatically reset allowing
restart of the system, without operator intervention
(auto-restart), when the condition causing the shut-
down clears. After the condition causing the shutdown
clears, the unit will restart in a minimum of 2 minutes,
or a maximum of 10 minutes, depending upon the
remaining time on the anti-recycle timer. Restart will
occur only if cooling demand is present.
1. Power Failure: After power has been restored, the
unit will automatically restart after a 2 minute time
delay. System acts as it does any time power is
applied. Restart is dependent on cooling demand
after the 2 minute start-up timer has completed its
cycle.
F
3
F
4
F
9
F
0
1
F
1
1
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