121
T098 (Circuit A Liquid Thermistor Failure)
T099 (Circuit B Liquid Thermistor Failure) — Failure of
this sensor (Temper ature s
REF.T
LT.A, LT.B) will disable
any elements of the control which requires its use. Elements of
failure include charge determination and prognostics. Recov-
ery from this alert is automatic. Reason for error is either a
faulty sensor, wiring error, or damaged input on one of the
EXV control boards.
T100 (Circuit A Liquid Pressure Transducer Failure)
T101 (Circuit B Liquid Pressure Transducer Failure) —
Failure of this sensor (Pressures
REF.P
LP.A, LP.B) will
disable any elements of the control which requires its use. Ele-
ments of failure include charge determination and prognostics.
Recovery from this alert is automatic. Reason for error is either
a faulty sensor, wiring error, or damaged input on the SCB con-
trol board.
T110 (Circuit A Loss of Charge)
T111 (Circuit B Loss of Charge) — Alert codes 110 and 111
are for circuits A and B respectively. These alerts occur when
all the compressors on a circuit are OFF and the suction pres-
sure is less than 18 psig, if the OAT is above –5 F for 1 contin-
uous minute. The alert will automatically clear when the suc-
tion pressure transducer reading is valid and greater than
54 psig. The cause of the alert is usually low refrigerant pres-
sure or a faulty suction pressure transducer.
T112 (Low Circuit A Charge Detected)
T113 (Low Circuit B Charge Detected) — Alert codes 112
and 113 are for circuits A and B respectively. These alerts oc-
cur when a charge determination using liquid sensors test has
been run and the charge has been calculated to be less than
Configuration
IAQ
PROG
AC.CL. This result typically
indicates charge should be added to the system. The alert will
automatically clear when the test is re-run and the charge is cal-
culated to be greater than AC.CL. The cause of the alert is usu-
ally low refrigerant charge.
T114 (High Circuit A Charge Detected)
T115 (High Circuit B Charge Detected) — Alert codes 114
and 115 are for circuits A and B respectively. These alerts oc-
cur when a charge determination using liquid sensors test has
been run and the charge has been calculated to be greater than
Configuration
IAQ
PROG
AC.CH. This result typically
indicates charge should be removed to the system. The alert
will automatically clear when the test is re-run and the charge is
calculated to be less than AC.CH. The cause of the alert is usu-
ally high refrigerant charge.
P120 (Circuit A Low Saturated Suction Temp. Comp Shut-
down)
T120 (Circuit A Low Saturated Suction Temperature Alert)
A120 (Circuit A Low Saturated Suction Temperature
Alarm)
P121 (Circuit B Low Saturated Suction Temp. Comp Shut-
down)
T121 (Circuit B Low Saturated Suction Temperature Alert)
A121 (Circuit B Low Saturated Suction Temperature
Alarm) — This alert/alarm is used to keep the evaporator coils
from freezing and the saturated suction temperature above the
low limit for the compressors.
When Tem per atu res
REF.T
SST.A or Temp era tures
REF.T
SST.B is less than 20 F for 4 minutes, less than 10
F for 2 minutes, less than 0° F for 1 minute, or less than –20 F
for 20 seconds continuously, a compressor of the affected cir-
cuit will be shut down with a local pre-alert (P120, P121) and a
15-minute timeguard will be added to the compressor. If the
saturated suction temperature continues to be less than 20 F for
4 minutes, less than 10 F for 2 minutes, less than 0° F for 1
minute, or less than –20 F for 20 seconds continuously, another
compressor of the affected circuit, if it exists, will be shut down
with a local pre-alert (P120, P121) and a 15-minute timeguard
will be added to the compressor. This sequence will continue
until the last compressor on the circuit is shut down, at which
time the circuit will be shut down with alert (T120, T121).
This failure follows a 3-strike methodology. When the cir-
cuit is shutdown entirely, an alert (T120, T121) is generated
and a strike is logged on the circuit. The Alert and strikes
logged will automatically reset if the saturated suction tempera-
ture remains above 29.4 F for 15 minutes. On the third strike,
alarm (A120, A121) will be generated which will necessitate a
manual reset to get the circuit back running. It is important to
note that a strike is called out only if all compressors in the cir-
cuit are off at the time of alert.
To prevent nuisance alerts, P120 and P121 show up in the
alarm history and locally at the display, but are never broadcast
to the network. To recover from these pre-alerts, both a 15-
minute hold off timer and saturated suction temperature rising
above 29.4 F must occur. If recovery occurs, staging will be al-
lowed on the circuit once again. A strike is tied to the circuit
going off entirely, not reducing capacity and recovering. There-
fore it is possible that multiple P120 and P121 alerts may be
stored in alarm history but not broadcast.
T122 (Circuit A High Saturated Suction Temperature)
T123 (Circuit B High Saturated Suction Temperature) —
This alert is for display purposes only. No action is taken by the
control when the alert occurs.
When Temper ature s
REF.T
SST.A or Temperatures
REF.T
SST.B is greater than 70 F for Configuration
COOL
H.SST minutes, local alert T122 or T123 will oc-
cur. The alerts automatically reset when the corresponding sat-
urated suction temperature drops below 70 F.
P126 (Circuit A High Head Pressure, Comp Shutdown)
T126 (Circuit A High Head Pressure Alert)
A126 (Circuit A High Head Pressure Alarm)
P127 (Circuit B High Head Pressure, Comp Shutdown)
T127 (Circuit B High Head Pressure Alert)
A127 (Circuit B High Head Pressure Alarm) — This alert/
alarm is used to keep the saturated condensing temperature be-
low the compressor operating envelope outlined in Fig. 22.
This alert/alarm also attempts to prevent the saturated condens-
ing temperature from reaching the high pressure switch trip
point by reducing the upper horizontal portion of the compres-
sor operating envelope to a level slightly below the saturated
condensing temperature recorded upon a high pressure switch
trip (T057, T058).
When Tem per atu res
REF.T
SCT.A or Temperatures
REF.T
SCT.B rise above the compressor operating enve-
lope for the corresponding Temperatures
REF.T
SST.A or
Tempe ratur es
REF.T
SST.B, a compressor of the affected
circuit will be immediately shut down with pre-alert (P126,
P127) and a 10-minute timeguard will be added to the
compressor. If the saturated condensing temperature remains
above the envelope for 5 more seconds, another compressor of
the affected circuit, if it exists, will be shut down with pre-alert
(P126, P127) and a 10-minute timeguard will be added to the
compressor. This sequence will continue until the last compres-
sor on the circuit is shut down, at which time the circuit will be
shut down with alert (T126, T127).
This failure follows a 3-strike methodology. When the cir-
cuit is shut down entirely, an alert (T126, T127) is generated
and a strike is logged on the circuit. On the third strike, alarm
(A126, A127) will be generated which will necessitate a manu-
al reset to get the circuit back running. It is important to note
that a strike is called out only if all compressors in the circuit
are off at the time of the alert.
To prevent nuisance alerts, P126 and P127 show up in the
alarm history and locally at the display, but are never broadcast
to the network. To recover from these alerts, both a 10-minute
hold off timer and saturated condensing temperature returning
under the compressor envelope must occur. If recovery occurs,
staging will be allowed on the circuit once again. Again, a
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