Problem

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."

Solution

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.