Unit installation

Diagnostics
SCXF-SVX01K-EN 97
Check: Sensor resistance should be between 1 ohm and 40
ohms. If so, check field/unit wiring between sensor and
RTM.
Reason for Diagnostic:The mode input signal on the RTM
is out of range (resistance < 1 ohm or resistance > 40
ohms).
UCM Reaction:The system mode reverts to the default (HI
set) system mode.
Reset Required: (INFO) An automatic reset occurs after the
mode input returns to its allowable range for 10 seconds.
N
NSB Panel Zone Temperature Sensor Failure
Problem:The NSB panel's zone temp sensor input is out of
range. (This input is at the NSB panel, not on the unit
itself).
Check: If have an external sensor connected to the NSB
panel zone sensor input, then the internal NSB panel zone
sensor should be disabled. Verify sensor resistance. If in
valid range, check wiring between the sensor and NSB
panel.
NSB Panel Comm Failure
Problem:The RTM has lost communications with the night
setback panel (programmable zone sensor).
Check: Field/unit wiring between RTM and NSB Panel.
Reason for Diagnostic:The RTM has lost communication
with the NSB panel.
UCM Reaction:The unit reverts to the next lower priority
mode switching source (typically the HI default mode). If
the NSB panel zone sensor is the designated sensor source
for any functions, those functions are disabled.
Reset Required: (PAR) An automatic reset occurs after
communication has been restored.
O
O/A Humidity Sensor Failure
Problem:The outside air humidity sensor data is out of
range.
Check: Check field/unit wiring between the sensor and
RTM.
Reason for Diagnostic:The unit is reading a signal that is
out of range for the outside air humidity sensor (humidity
< 5% or humidity > 100%).
UCM Reaction:The economizer enable enthalpy function
reverts to dry-bulb temperature changeover (“Level 1”)
control.
Reset Required: (PAR) An automatic reset occurs after the
OA humidity input returns to its allowable range for 10
seconds.
O/A Temp. Sensor Failure
Problem:The outside air temperature sensor input is out
of range.
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 RTM.
Reason for Diagnostic:The unit is reading a signal that is
out of range for the outside air temperature input on the
RTM (temp. < -55°F or temp > 209°F).
UCM Reaction:These unit functions occur:
• low ambient compressor lockout disables
• O/A damper drives to minimum position
• on VAV units with S/A temp. reset type selected as O/A
temp. reset, the reset type reverts to “none” for the
duration of the failure
Reset Required: (PAR) an automatic reset occurs after the
O/A temperature input returns to its allowable range.To
prevent rapid cycling of the diagnostic, there is a 10 second
delay before the automatic reset.
Occupied Zone Heat Setpoint Failure
Problem:The occupied zone heat setpoint input is out of
range.
Reason for Diagnostic:The input designated as occupied
zone heating setpoint source is out of range for the outside
air temperature input on the RTM (temp. < 45°F or temp >
94°F).
UCM Reaction:The active occupied zone heating setpoint
reverts to the default value.
Reset Required: (PAR) an automatic reset occurs after the
occupied zone heating setpoint input returns to its
allowable range for 10 continuous seconds, or after a
different occupied zone heating setpoint selection source
is user-defined.
R
Return Air Humidity Sensor Failure
Problem: On units with both airside economizer and
comparative enthalpy installed, the return air humidity
sensor input is out of range.
Check: Check field/unit wiring between the sensor and
ECEM.
Reason for Diagnostic:The unit is reading a signal that is
out of range for the return air humidity sensor (humidity
< 5% or humidity > 100%).
UCM Reaction:The economizer enable r.e. enthalpy
function reverts to reference enthalpy changeover (“Level
2”) control.
Reset Required: (PMR) An automatic reset occurs after the
RA humidity input returns to its allowable range
continuously for 10 seconds.