Program of hydraulic calculation of heating and cooling loop (OFAF and ODAF). The purpose is to ensure normal operation of selected pumps. Also it defines the coolant flow rate through windings, radiators or coolers in order toclarify transformer heat mode. Program automatically creates equivalent hydraulic connection diagrams of windings from TDS. Results of coolant flow rates in windings are automatically transferred to TR-HEATING-W module for more precise calculation of cooling conditions whiting the Similarity Theory. User should input equivalent connection diagram which represents heating and cooling loop between windings and cooling system. It may be done by means of user friendly graphic editor or in a table form where all the elements are selected from editable database.