IBC AHU Series, Installation & Operating Manual, Page: 69 / 75

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5.0 Troubleshooting
This section includes a table of warning and error messages that may appear on the appliance as well
faults that may appear on the air handling appliance app.
A problem that does not prevent the operation of the air handler is declared as a "warning". A problem
that prevents the appliance from operating is declared as an "error" and the appliance is shut down.
5.1 Measuring voltage on AHU boards
The control voltage transformer is not bonded to the AHU cabinet. When measuring the voltage supplied
to the individual control circuit, you must reference the common post of the circuit. If you measure to
ground or to another common terminal, misleading readings of approximately 14V will occur.
To test for nominal 24V, reference the adjacent COM connection. For example, to test voltage at
Compressor S1 terminal, measure for VAC between Compressor COM and Compressor S1.
5.2 Pump not energized
If the pump is not energizing:
In the
IBCconnect
app, go to Advanced Settings , and check that Pump Enabled is set to "on".
In the
IBCconnect
app, go to Basic Settings , and check that Heat Mode is not set to "Heat
Pump": During Stage 1 heat pump heating, the AHU pump is not energized by design, to avoid
interfering with circulation through the heat pump. AHU pump is energized at Stage 2 call for
heat.
Check the AHU board for blown pump fuse—the only fuse rated for 10A.
5.3 Fault Codes
Fault Code/Error Message Description Possible Fix
Inlet Temperature Sensor Sensor not connected or
faulty. Check the sensor. For resistance
reading, see Table 13.
Outlet Temperature Sensor Sensor not connected or
faulty. Check the sensor. For resistance
reading, see Table 13.
Aux Air In Temperature Sensor Sensor not connected or
faulty. Check the sensor. For resistance
reading, see Table 13.
Air Out Temperature Sensor Sensor not connected or
faulty. Check the sensor. For resistance
reading, see Table 13.
Cool Air Temperature Sensor Sensor not connected or
faulty. Check the sensor. For resistance
reading, see Table 13.
A/C Temperature Sensor Sensor not connected or
faulty. Check the sensor. For resistance
reading, see Table 13.