Installation and Maintenance Manual

Diagnostics
106 SCXG-SVX01H-EN
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.
UCM Reaction: Off or close requests are issued as
appropriate to the following functions;
a. Compressor staging/chilled water cooling control
b. Heat operation
c. Supply fan control and proof of operation
d. Exhaust fan control and proof of operation.
e. Exhaust actuator control
f. Outside air damper control
g.On VAV units, VFD control
Reset Required: (PMR) A manual reset is required after the
emergency stop input recloses.The diagnostic can be
reset by the HI.
Entering Cond WaterTemp Sensor Fail
Problem:
Activation Conditions: temperature < -50°F or temperature
> 209°F, and unit configured for water cooled condenser
c.Time to React: 10 sec <T < 20 sec
d. DiagnosticText (Human Interface Display) “ENT COND
WATERTEMP SENSOR FAIL”
e. Actions to be Initiated: A “Lockout All Ckts ” request is
issued to the “Compressor Staging Function”
f. Reset: An automatic reset occurs after the entering
condenser water temperature input returns to within
range continuously for 15 seconds.
Entering WaterTemp Sensor Fail
a. Data used (module, packet, byte, bit): WSM, 01,18,05
b. Activation Conditions: temperature < -50°F or
temperature > 209°F, and unit configured with water
cooled condenser and/or economizer
c.Time to React: 10 sec <T < 20 sec
d. DiagnosticText (Human Interface Display) “ENTERING
WATERTEMP SENSOR FAIL”
e. Actions to be Initiated: A “Disable Water Side
Economizer” request is issued to “Water Side Economizer
Temperature Enable Function”
f. Reset:An automatic reset occurs after the EnteringWater
Temp. input returns to within range continuously for 10
seconds.
Evap Temp Sensor Failure - Circuit 1, 2, 3, or 4
Problem:The evaporator temperature sensor (ckt #1, 2, 3,
or 4) is out of range.
Check: Sensor resistance should be between 830 ohms
(200°F) and 345.7Kohms (-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 evaporator temperature
sensor input (temp < -55°F or temp > 209°F).
UCM Reaction:The coil frost protection function for the
refrigeration circuit (#1, 2, 3, or 4) only is disabled.
Reset Required: (PAR) An automatic reset occurs after the
#1, 2, 3, or 4 evap temp input returns to its allowable range
for 10 seconds.
G
GBAS 0-5 VDC Module Comm Failure
Problem:The RTM has lost communication with the GBAS
module.
Check: Field/unit wiring between RTM and GBAS.
Reason for Diagnostic:The RTM has lost communication
with the GBAS module.
UCM Reaction: The UCM will initiate the following actions;
a. If the demand limit input was closed prior to the
communications loss, then the demand limit commands
issued to the heat operation function (if applicable) and the
compressor staging/chilled water cooling function will be
cancelled.
b. If any of the GBAS setpoint control parameters are the
HI-selected setpoint sources, then those setpoints will
revert to the default HI setpoints.
c. Any active GBAS output control parameters will be
ignored.
d. A failsafe function in the GBAS module will cause all
GBAS outputs to be zeroed and deenergized.
Reset Required: (PAR) An automatic reset occurs after
communication has been restored.
H
Heat Failure
Problem:The heat has failed.
(Electric heat unit)Typically, this is because the electric
heat section became too hot.
Reason for Diagnostic:The heat fail input on the heat
module was closed:
a. for more than 80 seconds,
b. for ten consecutive occurrences (each lasting five
seconds or more) within a 210 second period.
UCM Reaction: An information only diagnostic is set.
Reset Required: (INFO) An automatic reset occurs after the
heat fail input remains open for 210 seconds continuously.