Error for CellConst

[alexkey79]

I try to test the step_by_step Simulation but I have a Translation error:

[ThermoCycle.Components.FluidFlow.Pipes.CellConst: 77:1-77:64]: In sum(qdot), the expression is of type Real(quantity = "HeatFlux", unit = "W/m2"), but is required to be of builtin array type (of any number of dimensions).

the code is: Q_tot = Ai*sum(qdot) "Total heat flow through the thermal port";

whyt there is "sum(qdot)" and not simply "qdot"?

Thanks
Alexkey