Carrier WEATHERMASTER 48/50Z030-105 - Manual (Page 97)

97
DIAGNOSTIC ALARM CODES AND POSSIBLE
CAUSES
T051 (Circuit A, Compressor 1 Failure)
T052 (Circuit A, Compressor 2 Failure)
T055 (Circuit B, Compressor 1 Failure)
T056 (Circuit B, Compressor 2 Failure)
NOTE: These alerts only occur on units with a current sensor
board (CSB) (48/50Z105 only).
If the current sensor board reads OFF while the compressor
relay has been commanded ON for a period of 4 continuous
seconds, an alert is generated.
Any time this alert occurs, a strike will be called out on the
affected compressor. If three successive strikes occur the com-
pressor will be locked out requiring a manual reset or power re-
set of the circuit board. The clearing of strikes during compres-
sor operation is a combination of 3 complete cycles or 15 con-
tinuous minutes of run time operation. So, if there are one or
two strikes on the compressor and three short cycles (ON-
OFF,ON-OFF, ON-OFF) occur in less than 15 minutes, the
strikes will be reset to zero for the affected compressor. Also, if
the compressor turns on and runs for 15 minutes straight with
no compressor failure, the compressor's strikes are cleared as
well.
NOTE: Until the compressor is locked out, for the first two
strikes, the alert will not be broadcast to the network, nor will
the alarm relay be closed.
The possible causes are:
• High-pressure switch (HPS) open. The high-pressure switch
is wired in series with the compressor relays off of the
MBB. If the high-pressure switch opens while the MBB is
commanding the compressor on, the compressor stops and
the CSB no longer detects current, causing the control to
activate the alert.
• Circuit breaker trip.
• Wiring error.
To check out alerts T051, T052, T055, T056:
1. Turn on the compressor in question using Service Test
mode. If the compressor does not start, then most likely
the problem is one of the following: HPS open, circuit
breaker trip, incorrect safety wiring, or incorrect com-
pressor wiring.
2. If the compressor starts, verify that the indoor and
outdoor fans are operating properly.
3. If the CSB is always detecting current, then verify that the
compressor is on. If the compressor is on, check the
contactor and the relay on the MBB. If the compressor is
off and there is no current, verify CSB wiring and replace
if necessary.
4. Return to Normal mode and observe compressor opera-
tion to verify that compressor current sensor is working
and condenser fans are energized after compressor starts.
A051 (Circuit A, Compressor 1 Stuck On Failure)
A052 (Circuit A, Compressor 2 Stuck On Failure)
A055 (Circuit B, Compressor 1 Stuck On Failure)
A056 (Circuit B, Compressor 2 Stuck On Failure)
NOTE: These alarms only occur on units with a current sensor
board (CSB) (48/50Z105 only).
If the current sensor board reads ON while the compressor
relay has been commanded OFF for a period of 4 continuous
seconds, an alarm is generated. These alarms are only moni-
tored for a period of 10 seconds after the compressor relay has
been commanded OFF. This is done to facilitate a service tech-
nician forcing a relay to test a compressor.
In addition, if a compressor stuck failure occurs and the cur-
rent sensor board reports the compressor and the request off,
certain diagnostics will take place.
1. As A1 and B1 both have 1 unloader, the control will ener-
gize the particular unloader for these compressors if the
failure occurs.
2. If any of the 4 compressors are diagnosed as stuck on and
the current sensor board is on and the request is off, the
control will request the supply fan which will automati-
cally start building air flow control.
3. Heating will be disabled while any one of the compres-
sors has this problem.
The reset method will be manual for these alarms.
The possible causes are:
• Welded contact on compressor relay or contactor.
• Frozen compressor relay on MBB.
To check out alerts A051, A052, A055, A056:
1. Place the unit in Service Test mode. All compressors
should be Off.
2. Verify that there is not 24v at the contactor coil. If there is
24v at the contactor, check relay on MBB and wiring.
3. Check for welded contactor.
4. Verify CSB wiring.
5. Return to Normal mode and observe compressor opera-
tion to verify that compressor current sensor is working
and condenser fans are energized after compressor starts.
T057 (Circuit A, High Pressure Switch Failure)
T058 (Circuit B, High Pressure Switch Failure) — These
alerts occur on all units except the 48/50Z105 units (current
sensor board units).
If the high-pressure switch trips on a circuit with compres-
sors commanded on, the discharge pressure is sampled. If the
discharge pressure is between 368 and 418 psig, then the
discharge pressure trip point (Configuration → Cool → HPS.A,
HPS.B) is adjusted to the previously sampled trip point minus
3 psig. This is done to make a rough calibration of the high
pressure trip point which is used by the high discharge pressure
diagnostics.
When the trip happens, all mechanical cooling on the circuit
is shut down for 15 minutes. After 15 minutes, the circuit will
be allowed to come back on. An internal flag is set which needs
to sense the lead compressor on a circuit go from on to off, in-
dicating the circuit came back on after the 15-minute delay and
successfully completed a cooling cycle. If the high-pressure
switch trips again, the high pressure alarm occurs which will
then require a manual reset of the unit.
T072 (Evaporator Discharge Reset Sensor Failure) — This
sensor is responsible for third party reset of the cooling supply
air set point. If the unit is configured for “third party reset”
(Configuration → EDT.R → RS.CF=3) and this alert occurs, no
reset will be applied to the cooling supply air set point. Recov-
ery from this alert is automatic. Reason for error is either a
faulty sensor, wiring error, or damaged input on the CEM
board.