Unit installation
Diagnostics
94 SCXF-SVX01K-EN
the S/A static pressure limit setpoint for at least one
second continuously.
UCM Reaction: A "supply air pressure shutdown" signal is
sent to the following functions:
a. Compressor staging control,
b. Economizer actuator control,
c. Heat operation,
d. Supply fan control,
e. VFD control,
f. Exhaust fan control,
g.Exhaust actuator control
Reset Required: (PAR)The supply fan is not allowed to
restart for 15 seconds after the diagnostic occurs. An auto
reset will also occur if the unit cycles out of occupied mode
and back.
A pressure switch installed on the suction line that
prevents compressor operation below the switch’s
setpoint.
C
CO2 Sensor Failure
Problem:The VCM CO2 sensor input signal is out of range.
Check: Check field/unit wiring between sensor and VCM.
Reason for Diagnostic:The unit is reading a signal that is
out of range for the CO2 sensor transducer input.
UCM Reaction:The CO2 reset function disables.
Reset Required: (PAR) An automatic reset occurs after the
CO2 sensor transducer input receives a signal that is
within range for ten continuous seconds.
Compressor Contactor Fail - Circuit 1, 2, 3, or 4
Problem:The compressor contactor for Ckt. 1, 2, 3, or 4 has
malfunctioned.
Reason for Diagnostic:The circuit compressor proving
input is detected closed continuously for more than three
seconds while neither compressor output on that circuit
closes.
UCM Reaction: A "lockout ckt #1, 2, 3, or 4 request is issued
to the compressor staging control function.
Reset Required: (PMR) A manual reset is required after the
diagnostic is set. It can be reset by the HI orTracer Summit.
Compressor Trip - Ckt 1, 2, 3, or 4
Problem:The compressor ckt #1, 2, 3, or 4 has tripped.
Reason for Diagnostic:The ckt #1, 2, 3, or 4 compressor
proving input is detected open continuously for more than
3 seconds when either or both compressor outputs on that
circuit energize (as described in the compressor protection
function).
Reason for Diagnostic:The circuit compressor proving
input is detected open continuously for more than 3
seconds when either or both compressor outputs on that
circuit energize (as described in the compressor protection
function).
UCM’ Reaction: A “lockout ckt #1, 2, 3, or 4” request is
issued to the compressor staging control function.
Reset Required: (PMR) A manual reset is required after this
diagnostic occurs.The diagnostic can be reset by the unit
mounted HI module orTracer Summit.
Condenser Temp Sensor Failure - Circuit 1, 2, 3, or 4
Problem:The saturated condenser temperature input is
out of range for circuit #1, 2, 3, or 4.
Check: Sensor resistance should be between 830 ohms
(200°F) and 345.7 ohms (-40°F). If so, check field/unit
wiring between sensor and MCM/SCM.
Reason for Diagnostic:The unit is reading a signal that is
out of range for the circuit #1, 2, 3, or 4 saturated
condenser temperature sensor. (temp < -55°F or temp >
209°F).
UCM Reaction: A “Lockout Ckt # 1, 2, 3, or 4” request is
issued to the compressor staging control function.
Reset Required: (PAR) An automatic reset occurs after the
circuit 1, 2, 3, or 4 condenser temp input returns to its
allowable range within 10 seconds.
D
Dirty Filter
Problem:There is a dirty filter.
Reason for Diagnostic:The filter switch input on the RTM
is closed for more than 60 seconds continuously.
UCM Reaction: An information only diagnostic is set.
Reset Required: (INFO) An automatic reset occurs after the
dirty filter input reopens for 60 continuous seconds.
E
ECEM Communications Failure
Problem:The RTM has lost communication with the
ECEM.
Check: Field/unit wiring between RTM and ECEM module.
Reason for Diagnostic:The RTM has lost communication
with the ECEM.
UCM Reaction: If the unit has the comparative enthalpy
option, the economizer enable r.e. enthalpy function will
revert to level 2 enthalpy comparison.
Reset Required: (PAR) An automatic reset occurs after
communication has been restored.
Emergency Stop
Problem:The emergency top input is open.
Reason for Diagnostic: An open circuit has occurred on the
emergency stop input caused either by a high duct temp t-
stat trip, or the opening of field-provided contacts, switch,
etc.