York YVAA, Installation, Operation & Maintenance Instructions Manual, Page: 124 / 178

JOHNSON CONTROLS
124
SECTION 7 - OPERATION
FORM 201.28-NM1.1
ISSUE DATE: 1/31/2018
TABLE 19 - DISCHARGE PRESSURE LOAD
LIMITING/UNLOADING
DISCHARGE PRESSURE UN-LOADING
Discharge Pressure Cutout- 20
PSIG and Discharge Pres-
sure Cutout- 15 PSIG
0 Hz
Discharge Pressure Cutout- 13.5 PSIG 1 Hz
Discharge Pressure Cutout- 12 PSIG 2 Hz
Discharge Pressure Cutout- 10.5 PSIG 3 Hz
Discharge Pressure Cutout- 9 PSIG 4 Hz
Discharge Pressure Cutout- 7.5 PSIG 5 Hz
Discharge Pressure Cutout- 6 PSIG 6 Hz
Discharge Pressure Cutout- 4.5 PSIG 7 Hz
Discharge Pressure Cutout- 3 PSIG 8 Hz
Discharge Pressure Cutout- 1.5 PSIG 9 Hz
Discharge Pressure Cutout- 0 PSIG 10 Hz
Suction Pressure Load Limiting/Unloading
Suction pressure load limiting helps to protect the
evaporator from freezing. A system is permitted to load
normally as long as the Suction Pressure is above the
Suction Pressure Cutout plus 2 PSIG. Between Cut-
out plus 2 PSIG and the Cutout, loading is inhibited,
even though increased loading is required. Between the
Suction pressure Cutout and Suction Pressure Cutout
minus 10 PSIG, forced unloading is performed every 2
seconds according to Table 20 on Page 124 . This situ-
ation would occur if the suction pressure cutout tran-
sient override control is in effect (Refer to Low Suction
Pressure Cutout (Software) Fault on Page 122
). The
suction pressure cutout is programmed under the PRO-
GRAM key. The default Suction Pressure Cutout is set
at 24.0 PSIG.
Suction pressure load limiting is active at startup, to
only prevent loading of the compressors. Suction pres-
sure limit unloading will not occur until the system run
time reaches 5 minutes of operation to allow the sys-
tem to stabilize.
TABLE 20 - SUCTION PRESSURE LOAD LIMITING/
UNLOADING
SUCTION PRESSURE UN-LOADING
Suction Pressure is between
2 PSIG and Suc-
tion Pressure Cutout
0 Hz
Suction Pressure Cutout- 1 PSIG 1 Hz
Suction Pressure Cutout- 2 PSIG 2 Hz
Suction Pressure Cutout- 3 PSIG 3 Hz
Suction Pressure Cutout- 4 PSIG 4 Hz
Suction Pressure Cutout- 5 PSIG 5 Hz
Suction Pressure Cutout- 6 PSIG 6 Hz
Suction Pressure Cutout- 7 PSIG 7 Hz
Suction Pressure Cutout- 8 PSIG 8 Hz
Suction Pressure Cutout- 9 PSIG 9 Hz
Suction Pressure Cutout- 10 PSIG 10 Hz
Sensor Failure Cutout Fault
The Sensor Failure Cutout prevents the system from
running when a critical sensor (transducer, level sen-
sor, or motor winding temp sensor) is not function-
ing properly and reading out of range. This safety is
checked at startup and will prevent the system from
running if one of the sensors has failed.
The sensor failure safety will also fault and shutdown
a system while in operation, if a safety threshold is ex-
ceeded or a sensor reads out of range (high or low).
Following is the Status display fault message.
SYS X YYYYYYYY SENSOR FAILURE:
ZZZZZZZZZZZZ
The X indicates the specific system.
YYYYYYYY will either indicate the system
is in a “FAULT” condition and will restart
when the fault clears, or “LOCKOUT”
after 3 faults and will not restart until the
operator clears the fault using the keypad.
ZZZZZZZZZZZ indicates the failed sensor below:
• SUCT PRESS
• OIL PRESS
• DSCH PRESS
• MOTOR TEMP X *
The Unit Setup Mode allows a specific motor tempera-
ture sensor to be ignored, if it fails.