A Warning message in AFT Fathom

This warning alerts you to the fact that the converged results may be incorrect. Once a converged solution is obtained, AFT Fathom checks all junctions to ensure a flow balance exists. It compares the imbalance to the flow tolerance you specified, and when it appears to exceed the tolerance, it gives you this warning.

If the magnitude of the out of balance flow is close to the tolerance you specified, then it is generally safe to ignore this warning, although you may want to tighten your tolerances further and rerun the model.

If the magnitude of the flow out of balance is large, then you have a converged solution that is incorrect. This can occur in rare circumstances. When this happens, it is usually an indicator that your model is not realistic.

You should always review each of these warnings in detail, and perform hand calculations on the flow balance at the affected junctions to verify whether an acceptable solution exists.