In some applications, like in the Cooling modality, increasing or decreasing the number of circuits, even of just one point, can affect drastically the performances of the coil.

For example, it may happen that a cooling coil gives you 13,3 kW with 7 circuits, and jut increasing the nr. of circuits by one, you get 7 kW, which is half.

This happens because the Nr of Reynolds have decrease below the limit of 2200, which means that the coil is working in laminar flow.

As you can see below, in this case the software gives a warning that we are working in laminar flow, because the Reynolds number is less than 2200.

In the original calculation with 7 circuits, the Reynolds number is just higher that 2200. That is why increasing by one circuit you got the difference.

The Reynolds number affects highly the heat transfer coefficients, so a decrease of such number yields the big difference.