Alarms and Troubleshooting
46 RRU-SVX02F-EN
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
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 9. 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
Table 8. TOAU UC600 alarms (continued)
Point Diagnostic Possible Cause
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.
Unit Trips Heater
High Limit
High fire gas manifold pressure too high
Supply fan speed too low
Dirty or clogged filters
Restricted discharge air duct
Temperature of air entering heater too high
Defective high limit
Protonode Not
Communicating
Change Baud rate on UC600 to 38,400
Table 9. TOAU UC600 troubleshooting (continued)
Trouble Possible Cause
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