Example

We explain the calculations based on following heat exchanger, in which :

• the secondary side is a fully domestic cold and hot water circuit

• the primary side is a fully central heating circuit

• both circuits are connected with a heat exchanger

Calculations

step1 - step 2

First we calculate the diversity flow and the diversity factor, as explained in Step 2 : calculation of the diversity factor and the diversity flow

step 3

Calculate the secondary power, based on the formula (in which m is the massflow, T1 the cold water temperature, T2 the hot water temperature, and c the heat capacity for water)

step 4

Calculate the primary return temperature.

In case of a heat exchanger, both variables are determined by the UA value of the heat exchanger, and 3 equations that apply (see ).

In case of other regime changing base circuits like a storage tank, the primary return temperature can be a design parameter chosen by the user).

The primary supply temperature is always a design parameter chosen by the user.

Now that we know the primary

step 5 :

Heat exchanger

In the example above, a system of three equations determines the primary