The Wilo Star-RS 25/4 surface circulation unit has a single-phase electric motor and a wet rotor centrifugal pump that is resistant to blocking currents.

The body is made of cast iron, the wheel is made of polypropylene, the shaft is made of stainless steel, and the bearings are made of metallographite. During installation, spring terminals are used. Characteristics: feed 3,5 m3 / h, head 4 m, power consumption 0,048 kW. The liquid distills at t from ‒10 to +110 ° С.

Pros:

energy efficiency: 3 steps of rotation speed are provided;
wear resistance and durability: used parts do not rust;
protection against voltage surges and overheating: bearings in a “wet” rotor are cooled independently by pumped water;
silent running of the water pump Wilo Star-RS 25/4 (5.0-5.8 thousand rubles): before the device for testing “works / does not work” sometimes you need to lean your ear;
ease of installation and ease of use: weight – 2.4 kg, insert length – 18 cm.

Minuses:

in the state of air removal, the pump can block: depending on the pressure in the circuit;
over time, noise appears selectively.