Thermostat; Ecm Motors - Trane VUV Installation, Operation And Maintenance Manual

Diagnostics and Troubleshooting

Thermostat

Table 67. Thermostat troubleshooting
Probable Cause/Symptom
No display
System fan does not come on
properly
Thermostat turns on and off too
frequently
Room temperature is not correct Calibrate thermostat (see Configuration Mode Setting 14). If remote sensor is used, check connections.
Displays Lock symbol when any
button is pressed
Displays -- instead of room
temperature
Heat or cool not coming on (No
pipe sensor)
Heat or cool not coming on (Pipe
sensor is connected)

ECM Motors

WARNING
Hazardous Voltage w/Capacitors!
Failure to disconnect power and discharge capacitors
before servicing could result in death or serious injury.
Disconnect all electric power, including remote
disconnects and discharge all motor start/run
capacitors before servicing. Follow proper lockout/
tagout procedures to ensure the power cannot be
inadvertently energized. For variable frequency drives
or other energy storing components provided by Trane
or others, refer to the appropriate manufacturer's
literature for allowable waiting periods for discharge of
capacitors. Verify with a CAT III or IV voltmeter rated per
NFPA 70E that all capacitors have discharged.
An electronically commutated motors (ECM) is a closed loop
system that has equipment protections and envelope
enforcements. Do not assume that the motor has failed without
first consulting the VelociTach™ engine status/diagnostics
screen. In many cases, the engine shuts down the motor
operation and locks it out to prevent equipment damage.
Electric heat operation and changeover coil control on CSTI
units are coordinated by the VelociTach™ motor control board.
Changeover function on Tracer® ZN units can also be affected
by incorrect configuration of the VelociTach™ motor control
board or improper wiring of terminals to analog input 1 on the
Tracer® ZN controller (polarity sensitivity).
The mini-access lid on the front of the main control panel lid
has the VelociTach™ troubleshooting/setup guide affixed to
the back of the lid. This guide is unit-specific and should be
consulted before determining the disposition of a unit.
The adapter boards contain high voltage. Configuration
adjustments to the VelociTach™ board should be made
through the SMALLER of the two low-voltage lids on the front
of the control panel, through the low-voltage insulation/
shielding.
114
Explanation
Check for voltage at thermostat; display is blank when voltage is not present.
Verify wiring is correct. Check connections are correct (see Configuration Mode Setting 5).
Adjust temperature differential (see Configuration Mode Setting 10).
Thermostat has the button lockout function activated (see Lockout feature and Configuration Mode Setting 15).
Check for bad connection if remote sensor is used (see Configuration Mode Setting 4).
Verify wiring is correct. Gently pull on each wire to verify there is a good connection, verify configuration settings.
Check pipe sensor temperature by pressing up and down buttons in. If out of range, outputs may not turn on (see Configuration
Mode Settings 6-9).
WARNING
Hazardous Voltage!
Failure to disconnect power before servicing could
result in death or serious injury. Disconnect all electric
power, including remote disconnects before servicing.
Follow proper lockout/tagout procedures to ensure the
power can not be inadvertently energized. Verify that
no power is present with a voltmeter.
General Information
The VelociTach™ motor control board oversees and monitors
all motor operations and changes to speed resulting from:
• Direct fan speed requests
– Customer fan speed switches
– Thermostat fan speed, On or 0–10V requests
– Automatic fan request from Tracer® controllers
• Indirect fan speed requests
– Electric heat requests will bring the fan to the proper
speed.
• Conflicting fan speed requests
– If two or more commands are received (direct or
indirect), the fan will honor the higher speed requested.
Note: In some cases, indirect requests will result in fan
behavior change regardless of whether the end-device
fails to actuate (due to device failure, or safety/down-
stream lockouts).
The VelociTach™ motor control board also coordinates the
operation of electric heat, electric/hydronic heat lockouts, and
CSTI changeover coil operation.
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