Carrier WEATHERMASTER 48/50Z030-105 - Manual (Page 98)

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T073 (Outside Air Temperature Thermistor Failure) — Fail-
ure of this thermistor (Temperatures → AIR.T → OAT) will dis-
able any elements of the control which requires its use. Econo-
mizer control beyond the vent position and the calculation of
mixed air temperature for the SumZ algorithm will not be pos-
sible. Recovery from this alert is automatic. Reason for error is
either a faulty thermistor, wiring error, or damaged input on the
MBB control board.
T074 (Space Temperature Thermistor Failure) — Failure of
this thermistor (Temperatures → AIR.T → SPT) will disable
any elements of the control which requires its use. If the unit is
configured for SPT 2 stage or SPT multi-stage operation and
the sensor fails, no cooling or heating mode may be chosen.
Recovery from this alert is automatic. Reason for error is either
a faulty thermistor in the T55, T56 or T58 device, wiring error,
or damaged input on the MBB control board.
T075 (Return Air Thermistor Failure) — Failure of this ther-
mistor (Temperatures → AIR.T → RAT) will disable any ele-
ments of the control which requires its use. Elements of fail-
ure include:
• the calculation of mixed air temperature for sumZ control
• the selection of a mode for VAV units
• economizer differential enthalpy or dry bulb control
• RAT offset control for dehumidification
• return air temperature supply air reset
• fan tracking for building pressure control.
Recovery from this alert is automatic. Reason for error is
either a faulty thermistor, wiring error, or damaged input on the
MBB control board.
T076 (Outside Air Relative Humidity Sensor Failure) —
Failure of this sensor (Inputs → REL.H → OA.RH) will disable
any elements of the control which requires its use. Elements of
failure include: economizer outdoor and differential enthalpy
control. Recovery from this alert shall be automatic. Reason for
error is either a faulty sensor, wiring error or damaged input on
the CEM control board.
T077 (Space Relative Humidity Sensor Failure) — Failure
of this sensor (Inputs → REL.H → SP.RH) will disable any ele-
ments of the control which requires its use. Elements of failure
include humidification and dehumidification. Recovery from
this alert is automatic. Reason for error is either a faulty sensor,
wiring error, or damaged input on the CEM control board.
T078 (Return Air Relative Humidity Sensor Fail) — Failure
of this sensor (Inputs → REL.H → RA.RH) will disable any ele-
ments of the control which requires its use. Elements of failure
include economizer differential enthalpy control, humidifica-
tion, and dehumidification. Recovery from this alert is auto-
matic. Reason for error is either a faulty sensor, wiring error, or
damaged input on the CEM control board.
T082 (Space Temperature Offset Sensor Failure) — When
this failure occurs, there is no offset available that may be ap-
plied to space temperature. Recovery from this alert is automat-
ic. Reason for error is either a faulty slider potentiometer, wir-
ing error, or damaged input on the MBB control board.
T090 (Circ A Discharge Press Transducer Failure)
T091 (Circ B Discharge Press Transducer Failure) — The
associated circuit becomes disabled whenever this transducer
(Pressures → REF.P → DP.A, DP.B) fails. Recovery from this
alert is automatic. Reason for error is either a faulty sensor, wir-
ing error, or damaged input on the MBB control board.
T092 (Circ A Suction Press Transducer Failure)
T093 (Circ B Suction Press Transducer Failure) — The as-
sociated circuit becomes disabled whenever this transducer
(Pressures → REF.P → SP.A, SP.B) fails. Recovery from this
alert is automatic. Reason for error is either a faulty sensor, wir-
ing error, or damaged input on the MBB control board.
T094 (Circ A Discharge Press exceeded 440 psig)
T095 (Circ B Discharge Press exceeded 440 psig) — Should
the discharge pressure read by a discharge pressure transducer
exceed 440 psig for any reason, the circuit will be stopped
which requires a manual reset for recovery. The unit high-
pressure switch should trip before the discharge pressure
reaches this value. Check for failed a high-pressure switch or a
discharge pressure transducer out of calibration.
T130 (Low Suction Pressure Circuit A)
T131 (Low Suction Pressure Circuit B) — If a circuit is
equipped with unloaders and the suction pressure drops below
48 psig for 15 seconds, then that circuit is staged down until ei-
ther the pressure remains above 48 psig or the compressor is
staged off naturally, due to lessening demand. Each subsequent
circuit stage will then be turned off every 15 seconds.
There will be a start-up delay if the outside-air temperature
is too low. When the outdoor ambient is below 60 F, during
initial start-up, suction pressure is ignored for a period of
5 minutes.
The alarm and recovery of the low pressure condition will
follow the basic three strike methodology.
If a low suction pressure condition is detected while the cir-
cuit is ON and action has been taken to lower capacity, a
“strike” is called out (only if the circuit is staged off in this con-
dition). If less than three strikes have occurred, the alarm will
show up in alarm history and locally at the display, but will not
be broadcast (just as in the high discharge pressure condition).
To recover (if the alarm is not manual), both a 10-minute
timer must expire and the suction pressure must recover above
54 psig. If recovery occurs, staging will be allowed on the cir-
cuit once again. A strike is tied to the circuit going off entirely,
not reducing capacity and recovering. Therefore it is possible
that multiple alerts may be stored but not broadcast in this con-
dition. If all compressors in the circuit go down twice due to
low suction pressure, the next low suction pressure condition is
a manual alarm and the circuit is locked out and the alarm
broadcast to the network.
If the circuit operates with capacity for 15 continuous min-
utes and the low discharge pressure alarm condition is not man-
ual, all strikes will be cleared.
T132 (High Suction Pressure Circuit A)
T133 (High Suction Pressure Circuit B) — During opera-
tion, the suction pressure cannot exceed 100 psig (60 F saturat-
ed). If after 5 minutes of operation, suction pressure exceeds
this value, then all compressors in that circuit are stopped and
the alarm is tripped. Reset method is automatic after time
guards have expired. The three strike rule applies which means
the third time is a manual reset and CCN broadcast for the
alert/alarm.
T134 (High Discharge Pressure Circuit A)
T135 (High Discharge Pressure Circuit B) — There is a con-
figuration for each circuit which monitors high discharge pres-
sure (Configuration → Cool → HPS.A, HPS.B). This configura-
tion is adjusted to compensate for calibration whenever a high
pressure switch fault occurs. If discharge pressure rises above
this trip point, the individual circuit starts staging down 1 stage
every 5 seconds. To recover, both a 10-minute timer must expire
and the discharge pressure must fall 25 psig below the trip point.
If the circuit recovers, the circuit will stage back up (if the alarm
is not manual), allowing one stage every 5 seconds. The timer
starts 10 minutes since the last circuit stage was decreased. The
alarming and recovery of the high discharge pressure condition
will follow the basic three strike methodology. A strike is tied to
the circuit going off entirely, not reducing capacity and recover-
ing. Therefore it is possible, multiple alerts may be stored but
not broadcast in this condition.
If the circuit operates with capacity for 15 continuous min-
utes and the high discharge pressure alarm condition is not
manual, all strikes will be cleared.