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APPENDIX A — TROUBLESHOOTING
Table A — Operating Issues and Concerns
SYMPTOM REASON SOLUTION
An alarm is displayed on
the LCD
Sensor, damper, or the whole working
system may not work properly
Check sensor, damper, or the whole working system following the detailed alarm
information.
DAC LED is blinking RED Damper slippage Check whether the damper works properly.
DAC LED is blinking
RED quickly
Damper unplugged Check whether the damper is connected.
DAC LED is OFF
Terminal ACT-FB is configured but
there is no available feedback signal
Check whether the feedback signal is connected; check if ACT-FB is faulty.
Economizer controller
has no alarm, but the
Free Cooling LED will
not turn on when the OA
seems to be suitable for
Free Cooling
Shutoff SP setting error
Shutoff temperature and/or enthalpy set point is incorrectly set up. Consult an
HVAC professional to set up the shutoff set point correctly.
OA temp is too low
The OA temperature is too low; therefore, there is no cooling demand. This could
possibly enable anti-freeze protection.
OA temp is too high or too humid
In DIFF mode, even though OA temperature is lower than RA temperature, if both
OA and RA temperatures exceed the high limit, then Free Cooling turns off.
In Differential Enthalpy control mode, even though OA enthalpy is lower than RA
enthalpy, if both OA and RA enthalpy exceed the high limit, then Free Cooling turns
off.
Economizer controller/
mechanical cooling is
not operating
No input power
Use a multi-meter to check whether there is 24 vac ± 25% (18-30 vac) at the
POWER terminals. If there is no voltage or if the voltage is significantly low, then
check the transformer output voltage at the RTU. If 24-v is not present at the
transformer secondary side, then check the primary line voltage to the transformer.
If the line voltage is not present at the transformer primary side, then check the
primary power to the RTU, fuses, circuit breaker, and so on.
Brownout
If voltage is below 17-v, then the economizer controller may be in Brownout
Protection mode. This mode disables all of the relay outputs. When the power is
19 vac or higher, the economizer controller and RTU operate normally.
Y1/Y2 signal is missing from the
thermostat
Mechanical cooling does not run until there is cooling demand (Y1/Y2 Active).
Check the wiring from Y1I and Y2I terminals to the commercial thermostat. 24-v
should be present between Y1I/Y2I and Y1O/Y2O respectively.
24 vac~ and 24 vac
are incorrectly wired
24 vac power supply has polarity when all devices are powered by the same 24 vac
transformer; reversing polarity may cause a short circuit that can damage the
system.
Follow the transformer polarity mark, check the wiring of 24-v~ (or G or 24-v+), and
ensure that they are tied to the same polar of 24 vac power supply; while checking
the wiring of (or G0 or 24-v- or COM), ensure that they are all tied to another polar
of 24 vac power supply.
Firmware Update Failure
Application file is damaged, operation
is incorrect, and/or USB flash disk
does not work properly.
Reload a BIN file, restart the controller, update firmware following “Firmware
Update” on page 19, or change a USB flash disk. Contact service provider if failure
still exists.
Free Cooling LED is solid
RED
Sensor, damper, or whole working
system may not work properly
Check sensor, damper, or the whole working system following the detailed alarm
information.
Free Cooling LED is
blinking RED
Not economizing when it should
Check the whole economizer working system, such as the sensor, damper, and
thermostat.
Incorrect controller
password error on
mobile application
The password has changed from
default
Performing a factory reset on the controller will reset the password to OneBT.
RS485 communication
failure
RS485 signal or configuration error
Check wiring, configuration, Baud Rate (using mobile application), and other
network communication parameters.
Sensor LED is blinking
RED
Excess outdoor air
Check the whole economizer working system, such as the sensor, damper, and
thermostat.
Sensor LED is solid RED
Mixed Air (MA) sensor error Check the MA sensor. It must be either a Type II NTC 10K or 0-10 vdc sensor.
Outside Air (OA)/Return Air (RA)
sensor error
Check the wiring and signal of the OA sensor. If in Differential (DIFF) mode, also
check the RA sensor. The following sensor signals are valid:
Type II NTC 10K or 0-10 vdc temperature.
0-10 vdc or 4-20 mA humidity.
Air temperature failure/fault
Check the air temperature sensor signal. The valid signal must be Type II NTC 10K
or 0-10 vdc.
Sensor LED is OFF
CO
2
sensor error
Check CO
2
sensor connection, sensor signal (under range or over range), and
sensor signal type.
Sensor LED is YELLOW Humidity sensor error
Check humidity sensor connection, sensor signal (under range or over range), and
sensor signal type.
Wi-Fi connection failure
Wi-Fi/WLAN stick error or wrong user
name and password
Unplug and re-plug in the Wi-Fi/WLAN stick, enter a correct user name and
password, restart the controller, or replace the Wi-Fi/WLAN stick. If the Wi-Fi/
WLAN stick is POL903.00/100, then the default user name and password are
Siemens-WLAN-Stick and SIBPAdmin. DNS name is siemens.wlanstick. Contact
Application Engineering for information on this accessory.
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