Overcontrolled error messages usually occur when the flow rate, either in a single system loop or in the entire system, has been overspecified.  Three situations where overcontrolled errors can occur are shown below.  While these three examples do not cover all of the situations where an overcontrolled error message would be displayed, they do represent the most common situations that cause users to run into this problem.

Situation 1
An overcontrolled error can occur when two or more flow control valves are installed in series. In the figure below, the total flow rate to the section shown is 600 gpm.  This flow rate has been specified twice – once with FCVT set at 600 gpm, and also by the 3 FCVs set at 200 gpm in each of the branches.  To perform the system calculation, either one of the FCVs in one of the branches should be removed, or FCVT should be removed.
NOTE:  PIPE-FLO 2007 has an balancing orifice sizing routine that calculates the differential pressure needed across an orifice for a given flow rate.  If the flow meter has not been sized then this can cause a an overcontrolled problem similar to a flow control valve.
 
Situation 2
An overcontrolled error can occur when a pipeline upstream or downstream of a control is closed, such that the flow rate in the loop is zero.  For example, in the figure below, the flow rate in the last loop in the model has been set to zero by closing pipeline R PIPE01.  However, FCV4 is set to 250 gpm.  As a result, two different flow rates have been specified for this loop.  If you try to perform a lineup calculation for this configuration, the program issues an overcontrolled error message.  This problem can be resolved by closing both the pipeline upstream and downstream of the FCV.
NOTE:  You can quickly close the inlet and outlet pipelines on a device by selecting the Open/Close tool and clicking on the device.
 
Situation 3
An overcontrolled error can occur when the total system flow rate is overspecified by setting a pump to operate at a fixed flow rate and then also specifying the total system flow rate by setting a flow control valve (FCV) in every system loop.  In the figure below, the flow rate out to the system of 1100 gpm is set with the Secondary Pump.  The total system flow rate is also set by the FCVs in all of the building loops.  Since the total system flow rate was set with the Secondary Pump operating at 1100 gpm, it is not necessary to set an FCV in every building loop - one of these loops must be left uncontrolled.  The loop that you want to leave uncontrolled is the loop that is the most hydraulically remote.
NOTE:  To leave a loop uncontrolled, set the FCV in the loop to fully open.