"The root sought in BISECTWIN is not sufficiently close to the estimated root"

Product(s): HAMMER
Version(s): 08.11.XX.XX, 10.XX.XX.XX
Area: Analysis / Computation


The following messages appear when trying to compute a transient simulation:

"The root sought in BISECTWIN is not sufficiently close to the estimated root."

"There is no convergence for the solution of a variable-speed pump."


This message may be related to the general instability in the model and is dependent on the system, data entry issues. Things to check include:

  • Pump settings and demands in the system.
  • If the reservoir is cut off there is no boundary element in the model.
  • If pumps are trying to satisfy a small system demand, they may not be operating at the optimal operation point on the pump curve.
  • Make sure that model gives no error in initial conditions.
  • Reduce the transient simulation duration under the time when you receive this error and view the results for clues as to what is causing the instability.
  • Also, if there is a Discharge to Atmosphere element, make sure the input is correct, particularly for the "Pressure Drop (Typical)" and "Flow (Typical)" fields.