Trane SCXG-SVX01B-EN manual Maintenance diagnostics, NSB Panel ZoneTemperature Sensor Failure

Maintenance diagnostics

occurs after the mode input returns to its allowable range for 10 seconds.

N

NSB Panel ZoneTemperature 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

•onVAV 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.

Return Air Temp Sensor Failure Problem: On units with the comparative enthalpy option, the return 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 the sensor and ECEM.

Reason for Diagnostic: The unit is reading a signal that is out of range for the return air humidity sensor (temp < -55°F or temp > 209°F).

UCM Reaction: The economizer enable r.e. enthalpy function reverts to reference enthalpy changeover (“Level 2”) control.

Reset Required: (PAR) An automatic reset occurs after the RA temp input returns to its allowable range continuously for 10 seconds.

SCXG-SVX01B-EN 109