model TwoPumpCode
  // Pump 1
  Modelica.SIunits.Frequency fPump1 "pump 1 frequency";
  Modelica.SIunits.Frequency fMax = 50 "maximum frequency";
  Modelica.SIunits.VolumeFlowRate v1;

  // Pump 2
  // Boolean runPump2(start=false) "true if pump 2 should run";
  Modelica.SIunits.VolumeFlowRate v2IfRunning = 30;
  Modelica.SIunits.VolumeFlowRate v2
    "actual flow through pump 2";

  Integer nPumpsRunning(start = 1) "number of pumps running";

  // Total flow
  Modelica.SIunits.VolumeFlowRate vTotal = 70;

equation
  // Calculate the flow through pump 1 as a function of frequency
  v1 = fPump1;

  // Calculate the flow through pump 2 based upon running state
  if fPump1 > fMax then
    nPumpsRunning = 2;
    v2 = v2IfRunning;
  else
    nPumpsRunning = 1;
    v2 = 0;
  end if;

  // Calculate the total flow
  vTotal = v1 + v2;

end TwoPumpCode;