Installation and Maintenance Manual

Diagnostics
110 SCXG-SVX01H-EN
Supply Air Pressure Sensor Failure
Problem:The supply air pressure sensor voltage input 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 supply air pressure sensor voltage
input (input < 40mV or input > 4.75V)
UCM Reaction:The supply fan is de-energized, and the
following functions are disabled;
a. SA pressure control
b. SA static pressure limit
Reset Required: (PAR) An automatic reset occurs after the
SA temp heating setpoint input returns to within range for
10 continuous seconds, or after a different SA temp
heating setpoint selection source is user-defined.
Supply Air Pressure Setpoint Failure
Problem:The SA pressure input signal is out of range.
Reason for Diagnostic:The SA pressure setpoint input is
sending a signal that is out of range (Input < 1.0 iwc or input
> 4.3 iwc)
UCM Reaction:The default SA pressure setpoint will
become the active SA pressure setpoint.
Reset Required: (PAR) An automatic reset occurs after the
designated SA pressure setpoint source sends a signal
within range for 10 continuous seconds, or after a different
SA pressure setpoint source is user-defined.
Supply Air Temp Cool Setpoint Fail
Problem:The active supply air temperature cooling
setpoint is out of range.
Reason for Diagnostic:The input designated as the SA
temp cooling setpoint is out is out of range (temp < 35°F or
temp > 95°F).
UCM Reaction:The default HI-set SA temp cooling
setpoint becomes the active SA temp cooling setpoint.
Reset Required: (PAR) An automatic reset occurs after the
SA temp cooling setpoint input returns to within range for
10 continuous seconds, or after a different SA temp
cooling setpoint selection source is user-defined.
Supply Air Temp Heat Setpoint Fail
Problem:The active supply air temperature cooling
setpoint is out of range.
Reason for Diagnostic:The input designated as the SA
temp heating setpoint is out is out of range (temp < 35°F
or temp > 185°F).
UCM Reaction:The default HI-set SA temp heating
setpoint becomes the active SA temp heating setpoint.
Reset Required: (PAR) An automatic reset occurs after the
SA temp heating setpoint input returns to within range for
10 continuous seconds, or after a different SA temp
heating setpoint selection source is user-defined.
Supply Air Temperature Failure
Problem:The supply 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 supply air temperature input on the
RTM (temp. < -55°F or temp > 209°F).
UCM Reaction:These unit functions are disabled:
• supply air tempering
• economizing
• supply air temperature low limit function (CV units)
• supply air temperature control heating and cooling
functions (VAV units)
Reset Required: (PAR) an automatic reset occurs after the
designated S/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.
Supply Fan Failure
Problem:There is no supply airflow indication after the
supply fan is requested on.
Check: Check belts, linkages, etc. on the supply fan
assembly. If these are ok, check field/unit wiring between
RTM and supply fan. If the supply fan runs in service mode,
then verify airflow proving switch and wiring.
Reason for Diagnostic:The supply airflow input is detected
OPEN for 40 continuous seconds during any period of time
in which the supply fan binary output is ON. between 830
ohms (200°F) and 345.7 ohms (-40°F). If so, check field/unit
wiring between the sensor and MCM.
This input is ignored for up to 5 minutes after the supply
fan starts, until airflow is first detected.
UCM Reaction: “Off” or “Close” requests are issued as
appropriate to the following functions;
a. Compressor staging/chilled water control
b. Heat operation
c. Supply fan control & proof of operation
d. Exhaust fan control & proof of operation
e. Exhaust actuator control
f. Economizer actuator control
g. VFD control
Reset Required: (PMR) A manual reset is required anytime
after the diagnostic is set.The diagnostic can be reset at
the HI, Tracer Summit, or by cycling power to the RTM.
Supply Fan VFD Bypass Enabled
a. Data used (module,packet,byte,bit): RTM