Circulation pump

Circulation pump is designed to create circulation of water in closed circuits of heating and hot water supply systems. The name 'circulation pump' defines the application scheme, not the structural features of the pump. All types of pumps that allow continuous operation can be used for water circulation.

In this section, you will find pumps with water-cooled motor of the pumped liquid, so-called pumps with a 'wet rotor', which are used only as circulation pumps due to their design features.

Application

The quietness and resistance to installation have led to widespread use of wet rotor pumps for circulation in boiler and heat transfer stations with a wide range of power.

Circulation pumps with a wet rotor are used in heating and hot water supply systems with the required head up to 15 meters and a flow rate of less than 100 m³/hour. If, according to the technological process, the circulation pump should provide higher parameters, pumps with air-cooled motors are used, as the limitations in productivity are imposed by the design features of the wet rotor pump.

Circulation pumps for hot water supply systems differ from pumps used in heating systems by the presence of rotor protection from scale and the body made of corrosion-resistant materials, such as bronze or stainless steel.

Installation of wet rotor pumps for pumping coolant in cooling systems is prohibited by regulations, as the motor is cooled by the pumped liquid. In other words, cooling the rotor with the pumped liquid will heat the coolant.

Advantages

• Practically silent
• Very low vibration level
• Compact design
• Does not require support frames
• Long service life
• No shaft seals
• No technical maintenance required
• Inlet and outlet pipes are located on the same axis

Disadvantages

• Low efficiency, up to 54%
• High requirements for the quality of the heat transfer fluid
• The motor shaft must be horizontal
• Installation in cold water supply systems is not allowed
• The design features of wet rotor pumps do not allow for a head that exceeds 15-20 meters (1.5-2.0 bar).
• The price of a circulation pump with a wet rotor is usually higher than that of a pump with a dry rotor with similar characteristics.

Alternatives

• In-line pump with a dry rotor (air-cooled motor) and pipes located on the same axis
• Monoblock pump with air-cooled motor, axial inlet and radial outlet pipe.