JOHNSON CONTROLS
75
SECTION 5 – SEQUENCE OF OPERATION
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
5
TABLE 28 -
COMPRESSOR MODEL (HP/TONNAGE)
70 TON
75 TON
80 TON
90 TON
105 TON
COMPRESSOR
SYSTEM
1A
ZP137 (12)
ZP154 (13)
ZP154 (13)
ZP182 (15)
ZP235 (20)
1B
ZP137 (12)
ZP154 (13)
ZP154 (13)
ZP182 (15)
ZP235 (20)
2A
ZP120 (10)
ZP137 (12)
ZP154 (13)
ZP182 (15)
ZP182 (15)
2B
ZP120 (10)
ZP137 (12)
ZP154 (13)
ZP182 (15)
ZP182 (15)
3A
ZP120 (10)
ZP137 (12)
ZP137 (12)
ZP154 (13)
ZP235 (20)
3B
ZP120 (10)
ZP137 (12)
ZP137 (12)
ZP154 (13)
ZP235 (20)
TABLE 29 -
COMPRESSOR STATUS MENU
STATUS
MESSAGE
NORMAL – BOTH OFF
These compressor status messages show the compressor system status is normal, there are no
faults, and the ON/OFF operating status of each compressor
NORMAL – #A ON,
#B OFF
NORMAL – #A OFF,
#B ON
NORMAL – BOTH ON
SAFETY TRIP
AUTO RESET LPCO TRIP 1
AUTO RESET LPCO TRIP 2
AUTO RESET COMP SAFETY CHAIN TRIP 1
AUTO RESET COMP SAFETY CHAIN TRIP 2
SAFETY LOCKOUT
LOCKOUT-COMP SYS #
LOCKOUT-COMP SYS # TIME-OUT
LOCKOUT-COMP SYS LPCO #
LOCKOUT-OAT SENSOR
SAFETY FAULT
AUTO RESET-LOW SUCT TEMP #
LOW-AMB INHIBIT
Mechanical cooling is not permitted due to OAT lower than the mechanical cooling lockout temperature
HIGH DP UNLOAD #
A compressor circuit shuts down one of the compressors due to high discharge pressure
• The IPU board starts/stops compressors accord-
ingly to achieve and maintain the active cooling
SAT setpoint when all of following are true:
• The unit is in Active Cooling mode
• OAT is above the mechanical cooling lock-
out temperature (50.0°F)
• Low ambient package not installed
• See
for details on the compressor HP/
tonnage for each compressor system.
Compressor Status
• The IPU board provides different messages for
the status of a compressor system.
• These status messages can be helpful in trouble-
shooting the unit.
• The messages can be seen under the Status menu
or the Comp Sys # menu.
•
shows the different messages that can be
displayed.
Compressor Safety Circuits
• Each compressor system contains the following
safeties:
a. Compressor safety chain
b. LPCO
c. Suction line temperature sensor
• These safeties is constantly monitored whenever a
compressor system is in operation.
• These safeties cause the shutdown and possible
lockout of a compressor system if any abnormal
conditions exist.
•
The first two faults of the compressor safety chain
or LPCO is an Auto-Reset Fault. The third trip in
a 120 minute time period results in a Safety Lock-
out, which requires a manual reset.
• Once a safety chain or LPCO trip occurs, the IPU
board starts a 60 minute timer where the fault needs
to clear. If the fault does not clear within 60 min-
utes, a Lockout-Comp System Timeout displays.