Alarms and Troubleshooting
54
OAU-SVX02F-EN
Table 14. TOAU UC600 alarms
Point Diagnostic
Possible Cause
1
Indoor Fan
Failure
VFD not operating
Outdoor and/or Return Air Dampers not
Operating Properly
Indoor Fan Motor Failure
Indoor Fan Failure Switch IFFS (pressure)
Failure
IFFS Tubing damaged or not properly
connected
Refer to startup procedure
3
OAD Proving
Switch
No voltage at actuator
Failed OAD power transformer
No continuity thru end switch (check at UC)
Note: If unit optional RA damper is
installed, send switch on OAD is always
proven
6
Discharge Air
Temp Source
Failure
BAS communication down
Failed sensor or improper sensor
installation
8
Fire Shutdown
BAS ONLY
10
Low Temp
Lockout
Heat Overridden OFF
Compressor(s) Overridden ON
Setpoint Failures Incorrect
DAT sensor malfunction
Reference
for heat failure
issues
11
Space Temp
Source Failure
BAS communication down
Failed sensor or improper sensor
installation
13
OA Temp Source
Failure
BAS communication down
Failed sensor or improper sensor
installation
14
OA Humidity
Source Failure
BAS communication down
Failed sensor or improper sensor
installation
Humidity Wiring is polarity sensitive
15
High Temp
Lockout
Heat Overridden ON
Low discharge air volume
Dirty air filters
High gas heater manifold pressure
OA/RA damper position incorrect
High temp limit not properly installed or
wired
DAT sensor malfunction
17
System Lockout
Check all Alarms
External safety device failed open
19
Space RH Source
Failure
BAS communication down
Failed sensor or improper sensor
installation
Humidity Wiring is polarity sensitive
32
ERV Leaving Air
Condition Failure
Failed RH or temperature sensor
Incorrectly installed or connect RH or Temp
sensor
42
Heat Failure
Applies to 5:1 and 10:1 Gas Heaters Only
Trips after heat command “ON” and no GV
status offer 1 minute
Refer to unit “Service Facts” heat control
LED status legend
No gas, low gas pressure or high gas
pressure to unit
Unit Manual shutoffs closed
Heater inducer failure
Heat relay failure
Loose or incorrect wiring
Table 15. TOAU UC600 troubleshooting
Trouble
Possible Cause
Unit Not Running
No power supply to unit disconnect switch
Power disconnect tripped
Lockout alarm mode
Emergency Stop condition exists
Unit in Unoccupied mode
Discharge air sensor failed or not installed and
connected to unit
No Heat
No gas supply to unit
Unit manual gas valve(s) closed
Heater high limit tripped
Heat relay not energized
Conditions do not warrant call for heat
Heater control module malfunction
Roll out switch trip
Main gas on-off switch OFF
Inducer fan failure
Heater air proving switch not making or failed
No Compressor
Compressor limit switch(es) open
Compressor relay not energized or failed
Conditions do not warrant call for cooling or
dehumidification
Wide Discharge
Temp Swings
Discharge air sensor position must be at least
4 ft.-0 in. away from unit outlet
Min and Max gas heater manifold pressures not set
correctly
Space too Hot,
Cold or Humid
Setpoints not adjusted properly
Space sensors not correctly located or wired
Malfunctioning space sensor
IFM or PEX VFD OC
Trip
Overcurrent alarm requires max Hz setting on VFD
be checked and set to not exceed motor
nameplate amps
EX VFD only run to
Min HZ Setting
If supplied with RA pressure transducer and
modulating damper setup is not installed or
properly wired.
ERV Will Not Run
ERV leaving air temp below 34°F low temp cutout
Interlocked with Exhaust fan if exhaust is not
running ERV will be OFF
Table 14. TOAU UC600 alarms (continued)
Point Diagnostic
Possible Cause
