Now, with the development of technology, the hot water circulation pump means many families have learned, but also in our hotels, villas where even repair need to install a hot water circulating pump, and in order to achieve the cold water cycle, effect of hot water supply. Let us use the time more convenient, the following eleven can, for example, let small for everyone to look at science hot water circulating pump selection, selection from the flow rate and lift the main consideration of these two aspects. 
Hot water circulating pump flow
Circulation pump circulation pump is to be used for heating, the heat pump that is used to heat the water tank. This pump is not used for domestic hot water supply directly. Therefore, the pump flow is your host side of the water heat recovery matches head is resistance heat recovery unit + pipe resistance of the condenser, and then consider the vascular resistance of the tank.
If the water is hot water circulation pump, then it would consider cycling resistance line, balance-story hot water to overcome water pressure, and water pressure needed for domestic hot water water points, as well as the cold water pressure .
Hot water circulating pump head
The heat pump cycle H = SQ ^ 2 head
Wherein: the total friction S-- circulation line; circulating pump head - the circulation flow rate.
For selected pumps and piping, total head loss if the pipeline is equal to the pump head,
The flow rate Q = (H / S) ^ (1/2)
If the total head loss is not equal to the line head pump, should be established by the characteristic equation and the characteristic equation of a pump duct:
Tube H = SQ ^ 2
Pump H = Ho-SoQ ^ 2
Simultaneous solution to give Q = [Ho / (So + S)] ^ (1/2)
Wherein: the friction So-- pump; HO- when the pump head when the flow rate is zero, may be found Pump curves. H-- head loss or tubing pump head.
Water pumps point height of +10 and -10 meters and flow meters head when there is no difference, but must be careful not line head excessive negative (negative pressure) to prevent cavitation of the pump or tubing, or even normal work.