For closed hot water heating system with many kinds of hot users, in principle, it is necessary to draw the comprehensive heating regulation curve first, superposition the total network water flow curve of various heat loads, and get the maximum network design flow value under a certain outdoor temperature as the basis for selection.At present, the maximum design flow of the network is used as the basis for calculating the flow of the circulating water pump in the network for the common single heating load or the parallel closed hot water heating system with a variety of heat users, which adopts the centralized regulation.The flow rate of the circulating pump is calculated as follows [2] :

G= (1.1~1.2) G '(1)

Where G -- flow rate of circulating pump, t/h;

G '-- maximum design flow rate of heat network, t/h.