Selection of a circulation pump: device, types and rules for choosing a pump for heating

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Antonina Turyeva
Last update: November 2019

Self-flowing heat supply systems fully function only in one-story private houses with an area of ​​up to 100 square meters. m. If it is necessary to heat an apartment building or a spacious mansion, then you can not do without a forced circulation system. The best solution is to select a circulation pump and install the unit in the heating circuit.

We suggest figuring out what tasks the pump performs in the heating system, how the device is arranged and works. We described the features of operation of different types of pumps and identified the main criteria for a competent choice. The information provided will help you choose the right circulation pump model and not be disappointed in your purchase.

Why does a heating system need a pump?

Circulation pumps - hydraulic equipment that provides forced movement of a heated coolant in a closed circuit. Such devices contribute to a uniform and quick heating of the entire system.

Circulation pumps set:

  • in order to increase the energy efficiency of boiler equipment;
  • in cases where it is not possible to ensure the natural circulation of a liquid substance;
  • in the absence of a mounted pump unit in the heat generator;
  • for heating systems with a two-pipe scheme, allowing you to adjust the parameters of each individual radiator;
  • to overcome the inertia of autonomous systems with natural fluid circulation, used to transfer thermal energy.

The coolant must move along the closed circuit of the heating system pipe at a certain speed to ensure heat transfer to the radiators.

At natural circulation this condition is not always feasible - as a result, the heating equipment does not heat up or does not heat up evenly.

Therefore, circulation pumps are installed in the heat supply systems. Such devices provide transportation of the coolant over the network at high speed, minimizing the load on the boiler. When you return to the heating element, the water remains warm, which means that less energy is required for heating.

Design and principle of operation of the pump

By design, the circulation pump resembles a drainage installation. The pump consists of a robust housing made of stainless steel / cast iron / aluminum and an electrical part that includes a stator winding with an integrated ceramic / steel rotor.

Heating pump
Installation of a pumping device for forced circulation significantly increases the efficiency of hot water supply systems and autonomous heating

The impeller is fixedly fixed on the shaft of the rotating part of the electric motor.

The impeller is two parallel discs connected by radially curved blades. On one of them is a hole for the flow of coolant, on the other a small hole for fixing the impeller on the shaft of an electric motor.

The structure of the circulation pump
The body parts of the circulation pumps are made of steel and durable alloys. Under the walls of the housing is a hidden rotor with a fixed impeller

The motor itself is equipped with a special control board and terminals for connecting wires. For circulation pumps without electronics, a capacitor is installed instead of the board, and a speed switch is located on the terminal box.

When power is supplied, the wheel with blades rotates, creating a vacuum in the nozzle and pumping the coolant. The rotor creates a movement of the working fluid in the direction from the inlet to the outlet valve.

The pump constantly draws water on one side and pushes it into the heating system on the other. Centrifugal force facilitates fluid transportation throughout the line.

The created pressure overcomes the resistance in different parts of the circuit and ensures the circulation of the coolant.

Judging by the intensity of sales, the most popular in the domestic market are devices from the following manufacturers:

Types and advantages of circulation pumps

According to the design features, pumps for forced circulation are divided into pumping units with a wet rotor and high-performance devices with a dry rotor.

Wet type pumps. The rotor and impeller of such pumps are in direct contact with the working fluid, which simultaneously performs two critical functions: the role of lubrication and cooling the device. The rotor and stator in such pumps are separated by a special vessel responsible for the tightness of the elements of the electric motor under voltage.

Wet-type circulation pumps are equipped with a step speed controller. This allows you to choose the optimal mode of operation, and therefore to control energy consumption.

Pump internals
The rotor of the electric motor and the impeller in the pumps are in the pumped water, which moistens the supporting elements and constantly cools the motor (+)

Wet rotor units have a modular design. Separate modules are selected depending on the required pressure and performance. The prefabricated design greatly simplifies the repair of the pump, since a failed module can be easily and quickly replaced with a new one.

This type of circulation pump is used in small heating systems. They operate almost silently, and therefore are excellent for installation in residential premises.

The electric motor of the pumps with a wet rotor does not need additional cooling, since it is constantly in contact with water.There is a small number of working parts inside the pump, which minimizes the need for frequent maintenance.

The main advantages of using "wet" type pumps:

  • low noise level;
  • small overall dimensions and small weight;
  • minimum electricity consumption;
  • easy parameterization, maintenance and repair;
  • long term of operation.

Wet rotor units also have disadvantages. They are very sensitive to the quality of the working fluid. The presence of fine abrasive particles in water leads to accelerated wear of the hydraulic part of the pump.

In addition, the efficiency of such circulation pumps does not exceed 55%. However, this indicator is quite sufficient for small pipelines, and therefore pumps that are in direct contact with water are often used in individual heating systems.

For trouble-free functioning of wet-type units, it is necessary that pump installation was performed correctly. The main requirement is a strictly horizontal spatial orientation of the shaft. Only with this configuration is a complete lubrication of the bearings with fluid provided.

Proper installation of the circulation pump
Proper installation of the circulation pump is the key to the stable operation of the heating system throughout the entire period of operation

Dry rotor pumps successfully used for pumping large volumes of coolant in large installations. The rotor assembly of such devices does not come into contact with water.

The body part of the circulation pumps of the "dry" type is made of durable cast iron or galvanized steel. The surface is coated with special protective compounds to prevent corrosion phenomena.

Dry rotor units are suitable for collective use in residential high-rise buildings, entertainment centers and offices, and industrial facilities.

Dry rotor pump
The design of the pumps of the "dry" type provides increased power. Such pump models are able to create a lot of pressure in heating circuits (+)

Between the electric motor and the pumping part of the pump there is a special sliding seal (2 protective rings) that isolates the basic functional elements from liquid.

These rings are well polished and are in close contact with each other. One of them (dynamic) is mounted on a rotating shaft. The static wheel is firmly fixed in the pump casing.

A thin water film reliably seals the connection of the protective rings due to differences in pressure indicators in the circuit and the external environment.

For the manufacture of o-rings using coal obtained by oil sintering. Some modifications of pumps designed for use in extreme conditions have metal / ceramic protection rings.

The efficiency of dry rotor devices reaches 85%.This is an excellent indicator compared to wet pumps. However, “dry” units make a lot of noise due to the cooling fan, and therefore they are mounted in separate rooms with good sound insulation.

Dry type circulation pulsers come in 3 types:

  • monoblock;
  • cantilever;
  • "In-line".

One-piece pumps belong to the category of low pressure units. The electric motor and pump in such devices are mounted in one unit. They are easy to operate and maintain. Suitable for use in public utilities and apartment buildings.

Cantilever Pumping Devices collected on a single basis, while the axes of the pump and motor are on the same line. The suction pipe is located on the outer part of the cochlea, and the discharge pipe is on the opposite side of the housing.

In-line pump
If cantilever units are installed at production facilities, as well as in urban water supply systems, then In-line pumps are installed directly on the pipeline

In-line pumps mounted directly on the pipeline. The suction inlet and discharge outlet pipes are located on the same line, an automatic compensation mechanism for the production of o-rings is provided.

Advantages of using dry rotor circulation pumps:

  • high performance;
  • energy efficiency
  • low requirements for energy quality - the pumped liquid may contain neutral impurities;
  • simple repair and replacement of spare parts.

In addition, today, manufacturers of heating equipment offer potential customers dual models of pumps. Such devices are used to reserve power and additional safety in emergency situations.

Twin pump motors can function together or separately. If one pump breaks down, the second device continues to operate normally, ensuring uninterrupted operation of the boiler.

Twin circulation pumps
Reliable and trouble-free operation of the heat supply system will be ensured by dual circulation pumps, in which two impellers are connected in parallel

With proper operation, the life of the circulation pump is at least 10 years.

How to choose the right pumping equipment?

The efficiency of the pump depends on the basic parameters - productivity and pressure. Productivity shows the amount of heat transfer fluid that the unit must pump per unit of time. This parameter is determined from the conditions of maximum load.

Head - a value that expresses the energy of the fluid flow used as a heat carrier. It takes into account the hydraulic resistance of the entire system.

Also pay attention to the maximum temperature. Since the pump will pump hot water, it must withstand temperatures up to 110 ° C.

It is very important to choose the right capacity of the circulation pump. A low-power device can not cope with pumping the coolant fluid in the right volume. Pump parameters are selected based on performed calculations.

If you install a more powerful unit, an unpleasant noise will appear in the pipeline. Also in this case, the functional elements of the boiler equipment will wear out much faster than stated by the manufacturer.

Proper installation of the circulation pump
The power of the circulation pump must be sufficient to cope with the hydraulic resistance in a closed circuit

Experts recommend choosing a circulation pump at the design stage of the heat supply system. If the length of the pipeline does not exceed 80 m, just install one pump. With a greater length, it is advisable to mount several pumping devices at once.

When buying, you should pay attention to the materials from which the functional elements of the pump are made. Most parts are directly / indirectly in contact with heated working fluid, and therefore subject to rapid wear.

Therefore, it is advisable to give preference to circulation pumps with ceramic bearings and a rotor assembly.

An important role is played by electronics. To regulate the temperature indicators inside the premises in the heating circuits set thermostatic valves. With increasing temperature, they overlap, the pressure in the pipes increases.

As a result of these processes, an unpleasant noise appears. In order to get rid of it, it is necessary to transfer the circulation pump to lower revolutions, and doing it manually is inconvenient.

Pumps with integrated electronics will help you quickly and efficiently cope with this task. Such units smoothly regulate pressure drops in the pipeline depending on changes in the amount of liquid.

Compact overall dimensions of the pump
The main advantages of modern pumps are efficiency and durability, compact overall dimensions, low noise level, automatic operation mode, convenient control panel

It is worth noting the additional functionality of the pumps, namely:

  • smooth adjustment;
  • speed control;
  • automatic operation mode;
  • built-in informative display.

The simplest circulation pump models - without the ability to adjust the speed of transportation of the liquid. Modern multifunctional pumps are two / three-speed units with infinitely adjustable. They are highly accurate settings.

Equipment operating in automatic mode is equipped with a control panel. The settings of such devices are extensive and depend only on the modification of devices.

This can be automatic speed control depending on changes in temperature indicators of indoor air, an electronic timer for turning off / on, automatic pump startup at a minimum flow rate.

The presence of a digital display makes it possible to obtain all the necessary information about the operation of the pumping device: temperature of the heat-transfer fluid, resistance in a closed loop, performance, errors, etc.

Conclusions and useful video on the topic

Rules for choosing circulation equipment in the video:

The subtleties of calculating the pressure and performance in the video clip:

Video about the device, the principle of operation and installation of the circulation pump:

A modern heat supply system with a built-in pump for forced circulation allows you to heat residential premises in a matter of minutes after starting the heat generator.

Rational selection of the circulation pump and high-quality installation significantly increase the efficiency of the use of boiler equipment due to energy savings of about 30-35%.

Looking for a circulation pump for a heating system? Or have experience operating such installations? Please share your experiences with readers, ask questions and participate in discussions. The comment form is located below.

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Visitors Comments
  1. Victor

    For a private house or cottage with an area of ​​up to 200 sq.m. take Grundfos, you won’t regret it, of course, in fact it’s Danish, but it is produced in both China and Russia, there is no difference. The only thing is, do not take power vrytyk, you need at least a little bit, but more.
    Place it on the bypass circuit, immediately behind the boiler exit, so that in the event of a pump breakdown, boiler shutdown, power outage or gas shutdown, you could turn the valve and the coolant would go straight through the system. This will save your pipes from defrosting or air congestion, and in the case of freezing, then from breaking pipes.
    Put a special generator for it, and preferably a battery, since during power surges or when the lights turn off, the pump is turned off and it can only be started manually. In this case, the boiler itself may turn off.
    But if there is a generator, then there is no price for the reliability of this pump.