Wet rotor & dry rotor circulator pumps- what’s the difference?

Depending on the design, all the pumping units of the heating systems are divided into two types:

-Wet rotor circulator pump
-Dry rotor circulator pump

Wet rotor circulator pump

Wet rotor circulator pump is characteristic that the rotor is located directly in the fluid that is being pumped. The electric motor is located in a sealed part, where water does not get. The principle of operation of this mechanism is as follows: a rotating rotor accelerates the movement of water. The fluid in which the rotor is located is a coolant and lubricant for the mechanism.

To prevent air from entering the rotor area, the pump is equipped with exhaust bends. The upper one is designed for the operation of an automated system, and gas is released through the front of the case during commissioning or adjustment.

Wet rotor mechanisms are used in heating systems with a relatively small piping length.

Advantages of the wet rotor circulator pumps:

  • low noise level;
  • no need for lubrication;
  • effective way of cooling;
  • ease of installation;
  • lack of need for maintenance.
  • relatively low price of the unit and spare parts;
  • long period of service;

IMPORTANT! THE OPERATION OF THE PUMP WITH A WET ROTOR, PROVIDED THAT AIR ENTERS THE PIPELINES, CAUSES SHARPLY INCREASING WEAR OF MOVING PARTS, OVERHEATING, JAMMING OR IRREPARABLE DAMAGE TO EQUIPMENT. THE PRESENCE OF ABRASIVE PARTICLES IN THE COOLANT IS NOT RECOMMENDED. THEREFORE, A WET ROTOR WATER PUMP SHOULD ONLY BE INSTALLED IN A CLOSED HEATING SYSTEM.

Dry rotor circulator pump

In a dry rotor circulator pump, the rotor does not come into contact with the coolant. Its working part is isolated from the engine by means of O-rings, which are made of coal sinter, ceramic or stainless steel. To eliminate friction, between the elements of the seal(O-ring) is constantly a thin film of liquid, which plays the role of a lubricant.

In the process, the O-rings self-adjust and rub against each other. The period of their service is not less than 3 years. The efficiency is about 80%. But at the same time, running pumps with a dry rotor make a lot of noise, which is why they need to be installed in separate rooms with sound insulation. You also need to consider the environment of the room in which such units are located. In the process, they create air turbulence, dust can rise up and penetrate into the system, which leads to damage to the surface of the seal rings. The overall reliability level of dry rotor pumps is lower due to the greater number of seals and the lack of constant lubrication. Cons also include cleanliness requirements and the need for periodic maintenance and lubrication of the rolling seal.

However, the main advantage of dry type blowers is that they are not afraid of airing. They are also less affected by the abrasive suspension in the water – only the turbine suffers from it, in which the yield to failure is much higher than that of the rotor block with its sliding bearings. Therefore, such superchargers should be chosen if an open heating system with a circulation pump is being built.