Selection of a circulation pump for a heating system - methods, calculation

The heating system in a private house, as a rule, comes in two types - with natural and forced circulation. If in the first case water moves due to thermal expansion, then during forced circulation the coolant is pushed into the pipeline by the impellers of electric pumps, and for efficient operation, the correct selection of a circulation pump for the heating system is important.

The task of selecting a suitable model includes choosing its operating principle and calculating the main parameters - the volume of pumped coolant and pressure (supply height). You can carry out the necessary calculations yourself using formulas, tables or online calculators - for this you need to know what initial data to enter and how to make the calculations correctly.

Fig. 1 Circulation pumps for a private house in operation

What is a circulation pump for?

Open heating systems, in which the coolant circulates in a circle, operate according to the following scheme: cooled water enters the boiler, and after heating due to thermal expansion, it rises up through the heating pipes, heating the radiators. Then, along a closed circuit, it goes down and through a horizontal pipeline with a slight slope again reaches the heating elements of the boiler.

The main disadvantage of natural circulation is the small size of the circuit, the length of which does not exceed 30 meters, therefore forced circulation is used in most household heating systems.

To move water through pipes into the main, an electric pump is installed, which pushes the coolant with the blades of its impeller. The temperature in heating radiators is adjusted by changing the temperature of the water in the heating boiler; the second method is by regulating the speed of water flow through the pipes.

Many types of circular heaters have 2 or 3 (less often 4) speeds, which make it possible to increase the heating properties of radiators by increasing the speed of coolant movement.

Fig.2 Heating system with forced circulation of coolant

Grundfos

The devices of the Danish company are characterized by small sizes and almost silent operation. They cope well with water circulation in heating and water supply systems.

The line of devices includes more than two dozen different models, and all of them are of high quality.

Circular pump device

In the domestic water supply, the leading place is occupied by electric pumps of the centrifugal principle of operation - during intake, the liquid enters the centrifugal wheel through the inlet located in the center of its axis and is pushed out through the side outlet pipe.

In circular machines, the coolant enters the working chamber through the central hole, and then is pushed out by the blades of the centrifugal wheel through the outlet pipe located in the side of its body. Thus, according to the principle of operation, circulation devices can be classified as centrifugal types, having an efficiency coefficient of no more than 80% and sensitive to solid impurities in water.

Structurally, the electric pump consists of a housing, inside which is placed a moisture-protected electric motor with an impeller on the shaft; generally, the wheels of closed-type pumps consist of two disks, between which feed blades are placed.

Rice. 3 Option for installing the pump in a single-pipe circuit with heated floors

Briefly about the main thing

The design of a circulation heating pump consists of a housing, a rotor, an impeller with blades, seals, and an electrical circuit. Due to the rotation of the turbine wheel, the coolant moves. Manufacturers produce pumps with a rotor in wet and dry versions. In the first type, the rotor parts operate in a heat-transferring environment, and in the second case, they have no contact with the coolant. Models with 1, 2, 3 and 4 speeds are also available.

Such pumps are used in closed and open heating circuits, as well as in underfloor heating. Supercharger calculations are performed to determine their performance and pressure. These parameters are calculated using an online calculator and special formulas. When selecting equipment, operating temperature and pressure are also taken into account, as well as the number of speeds, the presence of protective systems and design. Basic parameters can always be found from the device labeling.

What types of circulation pumps are there?

The pumps in the heating main are designed to move the coolant; their task is not to increase the pressure (booster pumps are installed for this), it is created only to overcome the hydraulic resistance.

The supply volume depends on the speed of movement of the liquid, and accordingly the speed of rotation of the impeller on the electric motor shaft.

Circular pipes belong to the In-Line type, in which the inlet and outlet pipes are located on the same line, and the nominal passage has the same cross-section along the entire length.

A distinctive feature of circular electric pumps is the dependence of the pressure on the design of the wheel blades on the electric motor shaft and the frequency of its revolutions, while all types are divided into two groups: with a frequency N of more than 1500 rpm. units are classified as high-speed; if the speed is less than 1500 rpm, they are called low-speed. By changing the power, you can regulate the flow Q, which is directly proportional to the rotation speed of the impeller N.

When operating the equipment, it should be taken into account that the change in power consumption P1\P2 is proportional to the square of the change in pressure H1\H2 and the cubic degree of the change in the rotation speed N1\N2 of the engine shaft.

When the rotation speed is doubled, the pressure increases 4 times, and the power consumption increases 8 times; the same proportion is maintained when the speed decreases.

Fig.4 Domestic circulation electric pumps for water supply and heating

It should be taken into account that low-speed types have a more complex design and a high price, which is fully compensated by the savings in electricity consumed by the electric drive when choosing this modification. If a unit is installed with stepless control of the rotation speed of the electric motor shaft depending on the temperature of the conductive body, then the energy savings will be even greater.

The optimal efficiency of electric pumps is obtained when its operating point is located in the middle third of the characteristics; for each brand, the manufacturer indicates the optimal parameter.

When choosing a circulation pump for heating, two main design options are considered - with a dry or wet rotor.

With dry rotor

In samples with a dry rotor, only the impeller on the electric motor shaft is immersed in the coolant flow, rotating on bearings that are separated from the rotor and stator of the motor by sliding mechanical seals. A high degree of sealing is created through the use of two tightly fitted ceramic and high-strength graphite spring-loaded rings, one of which rotates on the shaft and the other is statically fixed in the housing.

When rotating, a thin film of water is formed between the surfaces of the sealing washers, which acts as a lubricant and performs cooling functions. The devices are equipped with air-cooled electric motors; powerful samples have an impeller to supply air to the motor.

The efficiency of units with a dry rotor depends on the power and is 30% - 65% for devices with a power of up to 1500 W, 35% - 75% for modifications with a power of 1500 - 7500 W, and 40 - 80% for power models of 7500 - 45000 W .

Typically, the power indicator required for a household unit rarely exceeds 1500 W, while the maximum efficiency ceiling for equipment with a dry rotor is 65%.

Dry rotor circulation pumps are designed to supply liquid with high pressure; they are more often used in hot water supply (DHW) systems.

Fig. 5 Circular electric pump with a dry rotor for a heating system - structural device

With wet rotor

Models with a wet rotor are used only in closed heating circuits; they ensure rapid movement of liquid through pipes, which makes it possible to reduce the cross-section of the pipeline and reduce the amount of coolant in the system - these factors help reduce the overall costs of the heating system.

A relatively small amount of heat-conducting fluid increases the speed of response to changes in settings and facilitates adjustment.

In the design of the model, the rotor is separated from the stator by a thin-walled glass and rotates in liquid on bearings, which are lubricated and cooled by a coolant. The glass is usually made of non-magnetic stainless steel or carbon fiber, its wall thickness is 0.1 - 0.3 mm, the bearing material is pressed ceramic or sintered graphite alloy.

Electric pumps with a wet rotor do not have seals or cooling fiber - due to this they are characterized by silent operation. Their rotation speed is adjusted in steps manually or using automatic equipment in continuous mode, monitoring changes in pressure difference or temperature; if desired, the automatic system is configured to turn on the unit at a given time.

Modern devices are structurally built according to a modular principle, which facilitates their repair and operation; the models have a screw plug in the body to remove air when setting up the system.

Imported models of electric pumps and their parameters are designed to operate from a single-phase network with an alternating voltage of 230 V or from a three-phase network with a voltage of 400 V.

The efficiency of units with a wet rotor is lower than that of dry models due to the larger distance between the stator and the rotor, and as in all types, it increases with increasing power and overall dimensions of the unit. For modifications with a power of up to 100 watts, the efficiency is 5% - 25%, from 100 to 500 watts. - 20% - 40%, from 500 to 2500 W. - 30% - 40%.

It should be noted that at the highest power of an electric pump for a private home, about 1000 W, the efficiency of types with a dry and wet rotor differs by less than one and a half times.

This factor does not have a strong influence on the selection of a pump for the heating system due to the significant advantages of models with a wet rotor (silence, high throughput, small pipeline cross-section) over dry rotor units.

Fig.6 Glandless rotor pumps - design

Pump design and operating principle

The design of 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.

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

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

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

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

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

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

The pump constantly takes water from one side and pushes it into the heating system on the other. Centrifugal force promotes the transport of liquid throughout the pipeline.

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

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

Image gallery

Photo from

Grundfos circulation device

Equipment line with Wilo logo

Heating devices from DAB

Circulation pump from Gilex company

Technical specifications

When deciding how to choose a circulation pump for a heating system, consider its physical and technical characteristics, the main of which are:

• Bandwidth. Measured in cubic meters per hour or liters per minute, it shows the volume of liquid that the electric pump pumps per unit time; the higher the flow rate, the greater the flow rate. The indicator depends on the diameter of the pipeline used and can reach values ​​of up to 15 cubic meters per hour.
• Pressure The value is measured in meters of water column and indicates the height to which the electric pump can push liquid through a vertically installed pipeline. The maximum pressure of a circulating electric pump for varieties with a wet rotor is about 17 meters, although units with higher pressure characteristics may be found, but they are ineffective in operation (they have large overall dimensions and are too expensive).
• Temperature Range. It is clear that in a heating system, pumping equipment must withstand the maximum heating temperature of the coolant with a margin; commonly used modifications are designed for a maximum temperature of up to 110º C; some types can work with liquids with temperatures up to +130º C.
• Noise level. Basically, for use in individual homes, devices with a low noise level are chosen; such features have pumping equipment with a wet rotor, the noise characteristics of which do not exceed 35 - 40 dB.
• Compound. In residential individual houses, a heating main with a small cross-section of up to 1.5 inches is used - in this case, all pumping equipment is installed in the main using threaded connections (designed for pipelines with a diameter of up to 2 inches). The outlet fittings of most household electric pumps are equipped with external threads and are easily integrated into the line using American couplings.
• Dimensional parameters. The installation length is the main indicator of the device when built into a pipeline (for circular types, standard sizes are 130 and 180 mm), the diameter of the inlet and outlet pipes is also taken into account (standard 1 and 1.25 inches).
• Protection class. According to the international classification, the standard protection class for pumping equipment of heating systems is IP44 - this means that the unit is protected from the entry of solid mechanical particles with a diameter of more than 1 millimeter (the first digit in the marking) into the housing, and its electrical part is completely closed from drops and splashes, flying at any angle.

Rules and nuances of equipment operation

A circulation pump is not bought for a year or even two. Therefore, every owner of a country house must ensure that the equipment is in good working order for many years. Reliability and correct operation of the device can only be achieved through correct and timely maintenance.

The list of basic rules for operating a heating pump must include the following aspects:

• it is prohibited to turn on the device with zero supply;
• make sure that the equipment is grounded;
• make sure that the electric motor does not heat up above the permissible norm;
• check the connection in the terminal box for the presence/absence of damage, and all cables must be completely dry;
• make sure that there is no extraneous noise or vibration when the device starts;
• the equipment must operate at the coolant flow level recommended by the manufacturer;
• It is forbidden to run the circulation pump without water.

If the equipment is idle for a long time, it is recommended to turn it on for 10-30 minutes every month. This simple rule will help avoid oxidation and, as a result, shaft blocking.

If any malfunctions or problems occur in the operation of the pump, you should call a specialist as soon as possible. This will help get rid of many problems and unplanned financial expenses.

Particular attention must be paid to the temperature of the coolant. It should not exceed 60-65 degrees Celsius. If you neglect this rule, sediment will appear in the pipes and inside the pump, which will negatively affect the operation of the entire heating system.

Marking

Pumping equipment from different manufacturers has its own markings, most often the pressure (nominal or maximum value), flow volume (in cubic meters per hour or liters per minute, also nominal or maximum values) and the nominal diameter of the passage channel in millimeters are indicated on the body.

In Grundfos models, the body material, type of connection and installation length are indicated; in the Wilo model range, the main indicators are the internal diameter of the nominal diameter and the maximum pressure.

Video description

An example of automation for a circulation pump is shown in this video:

Structural design

This concept refers to the material of manufacture, the dimensions of the pipes and the housing as a whole. In the production of circulation pumps today, cast iron and plastic are used. Both materials are used to make housings. Cast iron models are characterized by a long service life, high strength and good heat dissipation from the electric motor. Devices in a plastic case are usually installed in places where there is a low probability of mechanical damage.

On a note! Circulation pumps are selected with fittings whose diameter corresponds to the same size of the connected pipes.

Selection of a circulation pump for a heating system - criteria

When choosing a circulation pump for the heating system of a private home, they almost always give preference to models with a wet rotor, specially designed for operation in any household lines of varying lengths and supply volumes.

These devices have the following advantages compared to other types:

• low noise level,
• small overall dimensions,
• manual and automatic adjustment of the number of shaft revolutions per minute,
• pressure and volume indicators,
• suitable for all heating systems of individual houses.

Selection of a circulation pump for a heating system by the number of speeds

To increase operating efficiency and save energy resources, it is better to take models with stepwise (from 2 to 4 speeds) or automatic control of the electric motor speed.

If automation is used to control the frequency, then energy savings compared to standard models reach 50%, which is about 8% of the electricity consumption of the entire house.

Rice. 8 The difference between a fake (right) and an original (left)

What else to pay attention to

When purchasing popular Grundfos and Wilo models, there is a high probability of counterfeiting, so you should know some of the differences between the originals and their Chinese counterparts. For example, German Wilo can be distinguished from a Chinese counterfeit by the following characteristics:

• The original sample is slightly larger in size and has a serial number stamped on its top cover.
• A raised arrow in the direction of fluid movement in the original was placed on the inlet pipe.
• The de-airing valve on the fake is yellow in brass color (the same color in the Grundfos analogues)
• The Chinese analogue has a bright shiny sticker on the reverse side indicating energy saving classes.

When purchasing Grundfos electric pumps, the original package must include two union nuts with gaskets, the passport itself is made in black and white colors - the Chinese counterfeit passport is colored and there are no fastening fittings.

Rice. 9 Criteria for selecting a circulation pump for heating

DAB

Circular pumps DAB and Aguario, located in the middle price segment, are in great demand on the product market.

The first device, subject to systematic prevention, works flawlessly. The company pays a lot of attention, and not without success, to reducing the noise level of dry-type pumps.

Selection of a circulation pump for a heating system - calculation based on pump parameters

When determining the parameters of circulation pumps for heating systems, their following main indicators are taken into account:

• Pressure When a heat-conducting liquid moves along the line, it overcomes the hydraulic resistance of pipes, heating radiators, and plumbing fixtures. The pressure created by the pump allows the coolant to move through the pipes, overcoming this resistance; the parameter is measured in meters of water column and shows to what vertical height the working fluid can be raised.
• Feed volume. This indicator indicates the amount of coolant that is supplied to heating radiators per unit of time; the parameter is directly related to the speed of rotation of the impeller.

All other characteristics of pumping equipment (power, motor shaft speed) are derived from the basic parameters. The power and frequency are selected according to the best indicators from the model range of units from different manufacturers after calculating the required pressure and supply volume.

If you do not seek help from specialists, then the parameters of electric pumps are calculated manually, using tables, using online calculators that are available on the websites of some well-known manufacturers, or using computer programs - the latter method is the most accurate.

It is not too difficult to calculate the main technical parameters yourself manually using formulas; the result can be compared with the data indicated in the table, which is provided by some manufacturers. The table (Fig. 11) indicates the power of the heating boiler and the volume of the heated room; a suitable pump model is selected based on these data. The tabulated results are not very accurate - they do not take into account the hydraulic resistance corresponding to losses in the forward and return lines, but they can be used to check the results obtained manually or using online calculators.

Rice. 10 Calculation of the heating power of the house

Why do you need to do the calculation?

The answer to this question is obvious; for the optimal selection of pumping equipment, a preliminary calculation of the circulation pump for the heating system is necessary; the more accurate the calculations, the more optimal the choice will be. A properly selected heating pump will operate within the operating area that provides the highest efficiency - this will save energy resources.

Also, many circular machines have several speeds for adjusting the rotation speed - if the calculations are correct, choose a model with the optimal speed so that switching to other speeds allows you to comfortably use heating or save energy resources without worsening living conditions.

Calculation of pump performance

The supply volume of the electric pump is calculated using several formulas, one of which is:

Q = P/(1.163 x (Tf – Tr)) or Q = 0.86R/(TF–TR) (m3/h)

Where:

• Q is the volume of pumped coolant in cubic meters per hour;
• P – thermal consumption of heated premises (thermal power) in W;
• (Tf - Tr) - the temperature difference in the pipes leaving the boiler and supplying water back (for long pipelines with water heated floors, the difference is about 20 C; if short circuits with a small number of heating radiators are used, the value is taken about 10 C; if only a small area underfloor heating is heated, the temperature difference is taken equal to 5 C.);
• 1.163 – coefficient of specific heat capacity of water in W.*h./kg.*K. (for antifreeze, the indicator has a different meaning, determined from reference literature).

Another formula that allows you to select a circulation pump for a heating system is as follows:

Q = 3.6 x P/(C x (Tf - Tr)), (m.cub./h.)

where: C is the heat capacity (for water it is 4.2 kJ/kg*C), the remaining symbols are similar to those given in the previous formula.

When calculating the thermal power of a room that is being heated, we are guided by SNiP 2.04.07-86 for heating networks; in them, for one- or two-story buildings at an external temperature of -20 to -30º C, a heat consumption indicator of 173 - 177 Watts per square meter is accepted, for For larger buildings with three or four floors, this parameter is 97 - 101 W/sq.m.

It is clear that the total thermal power of energy consumed by the entire house, which is necessary for calculations, consists of summing up the areas of all rooms in which heating radiators are installed.

The above formulas are used in the initial calculations of the heating main - on their basis, depending on the heat consumption of the premises, a heating boiler is selected. If it is installed, instead of the required thermal power, the boiler parameters are used in the formula, example (boiler power 50 kW.):

How to calculate hydraulic losses of a heating system

The choice of a circulation pump based on its power and the pressure it creates, as mentioned above, is also influenced by such an important parameter of the heating system as the hydraulic resistance, which is created by all elements of its equipment. Knowing the hydraulic resistance created by individual elements of the heating system, you can calculate the suction height of the pump and, guided by this parameter, select the equipment model according to the power and pressure created. To calculate the suction height of the pump, which is designated by the letter H, the following formula is needed:

H = 1.3x(R1L1+R2L2+Z1……..Zn)/10000.

The parameters used in this formula are shown in the table.

Table 3. Parameters for calculating suction lift

The values ​​of R1 and R2 used in this formula should be selected using a special information table.

The values ​​of hydraulic resistance created by various devices that are used to equip heating systems are usually indicated in the technical documentation for them. If there is no such data in the device passport, then you can use the approximate values ​​of hydraulic resistance:

• heating boiler – 1000–2000 Pa;
• sanitary mixer – 2000–4000 Pa;
• thermal valve – 5000–10000 Pa;
• device for determining the amount of heat - 1000–1500 Pa.

There are special information tables from which you can determine the hydraulic resistance for almost any element of heating system equipment.

Knowing the suction height, which is calculated using the above formula, you can optimally select pumping equipment based on its power, and also determine what the pump pressure should be.

Number of pump speeds

Well-known manufacturers of pumping equipment for heating equip their units with shaft rotation speed switches; in some models, the speed of the device is automatically adjusted. During operation, this creates additional convenience: since heating the liquid takes quite a long time, to quickly warm up the premises, you can set the maximum speed of the electric pump or save energy by setting the minimum speed of the electric motor when the room is heated.

The number of speeds, depending on the manufacturer, can be from 2 to 4 - the more there are, the more effectively you can use the circular in the heating system, and the most economical option is electronic speed control.

Fig. 13 Selection of electric pump according to pressure characteristics

How to choose the right pumping equipment?

The efficiency of the pump depends on the basic parameters - performance and pressure. Performance shows the amount of coolant that the unit must pump per unit time. This parameter is determined from the conditions of maximum load.

Pressure is a quantity that expresses the energy of the flow of liquid used as a heat carrier. Takes into account the hydraulic resistance of the entire system.

Image gallery

Photo from

Heating with five circulation pumps

Selection of equipment according to pipeline length

Relationship between radiator and pump power

Selection of pump according to boiler power

You should also pay attention to the maximum temperature. Since the pump will pump heated water, it must withstand temperatures up to 110°C.

It is very important to select the appropriate power of the circulation pump. A low-power device will not cope with pumping coolant fluid in the required volume. Pump parameters are selected based on the calculations performed.

If you install a more powerful unit, 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.

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 heating system. If the pipeline length does not exceed 80 m, it is sufficient to install one pump. For larger lengths, it is advisable to install several pumping devices at once.

When purchasing, you should also pay attention to the materials from which the functional elements of the pump are made. Most parts come into direct/indirect contact with the heated working fluid and are therefore subject to rapid wear.

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

Electronics play an important role. To regulate indoor temperatures, thermostatic valves are installed in heating circuits. As the temperature rises, they overlap, and the pressure in the pipes increases.

As a result of these processes, unpleasant noise appears. To get rid of it, you need to switch the circulation pump to lower speeds, and doing this manually is inconvenient.

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

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

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

• smooth adjustment;
• speed control;
• automatic operating mode;
• built-in information display.

The simplest models of circulation pumps are without the ability to regulate the speed of liquid transportation. Modern multifunctional pumps are two/three-speed units with continuous adjustment. They are distinguished by high precision 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 the devices.

This can be automatic speed adjustment depending on changes in indoor air temperature, an electronic off/on timer, automatic pump start at 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: coolant fluid temperature, closed-loop resistance, performance, errors, etc.

Manufacturers and prices

Heating is the main system of a private home; unlike water supply and sewerage, its stop can cause significant financial damage if it breaks down in winter and defrosts. Even if the owners are present in the house and the circular device is out of order, you will have to urgently buy a new device, and this is not always possible in remote rural areas. Also, high-quality pumping equipment for heating increases living comfort and saves energy resources - so it is better to choose models from well-known manufacturers, avoiding the Chinese counterfeits described above.

Wilo is a well-known German manufacturer that supplies the market with a wide range of household circular saws of the RS, Stratos, Smart, Top series, all modifications have the following features:

• Manufactured in accordance with the European energy saving directive EnEV for heating circuits with a thermal power of more than 25 kW, according to which only automatic control of the operation of pumping equipment and the presence of at least 3 stages of regulation of electricity consumption are allowed.
• Designed for European AC voltage of 230/400 V with a tolerance of 10%.
• The housings are mainly made of cast iron.
• The power of the units, depending on the pressure and volumetric characteristics, ranges from 40 to 200 watts; the previously selected electric pump for a one-inch pipe Wilo - Star RS 25\6 has a power of 99 watts.
• The cost of Wilo circular electric pumps ranges from 50 to 100 USD.

Rice. 14. Selection of a circulation pump for a heating system from popular brands Grundfos, Wilo, DAB

Grundfos is a world-famous Danish manufacturer of pumping equipment; the market offers models UP, UPS, UPSD, Solar and their more modern analogues Alpha2, which have the following features:

• The cases are made of cast iron, brass and stainless steel (marked with the letter N).
• UPS models are equipped with 3 shaft rotation speeds; in Alpha2 the frequency is automatically adjusted.
• There is a wide range of powerful models with a supply volume of up to 15 m3/cu.m. and pressure up to 15 m.
• The cost of Grundfos electric pumps is 70 - 100 USD, the price of powerful devices can reach up to 500 USD.

If we compare the power of Wilo and Grundfos units, then the Grundfos UPS 25-60 180, similar to the previously reviewed Star RS 25\6 device from Wilo, consumes one and a half times less electricity - its power is 60 W. In addition, Grundfos has a maximum supply volume of 4.35 m3/h. versus 3.5 m.cub./h. at Wilo.

DAB is a well-known Italian manufacturer that supplies the market with household circular pumps of the A and VA series, their distinctive features:

• Single-phase models have 3 rotation speeds and built-in overload protection.
• The operating temperature of the coolant is from -10 to +110 C.
• For domestic use, the VA line is most suitable, the maximum productivity of which is 3.5 cubic meters per hour and the maximum pressure is 6.5 m (for the A series, the corresponding maximum values ​​are 16 cubic meters per hour and 11 m.) .

The choice of DAB models is the best option in terms of price and quality ratio, the DAB VA 35/180 circular machine with a maximum productivity of 3 m3/h. and a head of 4.3 m costs about 60 USD. - this is for 40 USD cheaper than Grundfos and Wilo.

Rice. 15 DAB options

Example as a check

The correctness of calculations using the presented methodology can be verified by comparing their results with the results of accurate calculations in a real project, carried out in accordance with SNiP.

The assignment required calculating a circulation pump for a two-pipe heating system with floor-by-floor piping from the collector. It was previously determined that the building's heat requirement is 45.6 kW, and the coolant flow required for heating is 2.02 cubic meters per hour. The piping diagram to the most distant radiator includes four sections and a heat control valve.

The total pressure losses in them are equal to:

DP = 0.63 + 0.111 + 0.142 + 0.289 = 1.178 m

According to SNiP 2.04.05-91*, 10% should be added to this value for unaccounted pressure losses:

DP = 1.178 x 1.1 = 1.296 m

Thus, the circulator for this system must provide a supply of 2.02 cubic m/h of coolant and a pressure of 1.3 m. The HZ 401 (Deutsche Vortex) or UPS 25-40 (Grundfos) pump meets these conditions.

When calculating using the method outlined in the article, we obtain: H = 0.015 x (3.2 + 4.4 + 8.9 + 21.7) x 1.3 x 1.7 = 1.266 m,

Recommendations for installing pumps

When installing pumps in the heating main, the following rules must be observed:

• The unit is installed in such a way that its shaft is in a horizontal position; the direction of movement of the coolant must correspond to the arrow on the device body.
• The selected device is fastened with an adjustable plumbing wrench using threaded fasteners (socket nuts from American fittings) with gaskets.
• Connection to the power supply system is made according to the electrical connection diagram, using three wires with a cross-section of at least 0.75 mm. sq. and an outer diameter designed for the sealing coupling in the box.

Before turning on for the first time, check the pipeline for the absence of foreign objects, the tightness of threaded connections, the correct connection of wires and the parameters of the power supply network, and make sure that the shut-off valves are open.

When turned on, remove air from the pump by unscrewing the screw plug, check the current strength in the electric motor winding with an ammeter (it must correspond to the data given on the housing marking), and make sure that there is no increased vibration and noise during operation of the unit.

Rice. 16 Connection and installation of a Grundfos circular distributor with a bypass branch

Video description

This video describes how to calculate the pressure and performance of a circulation model of an electric pump:
To ensure trouble-free operation of the heating system, professionals recommend that homeowners install high-quality and reliable equipment for coolant circulation. Such blowers are capable of moving fluid with temperatures ranging from 110 to 130 °C. Their price is higher than budget models, but their service life is much longer.

Number of speeds

If the preliminary calculation is done correctly, then it does not matter what number of speeds the circulation pump has. Despite this, experts advise choosing three-mode devices. With their help, you can reduce energy consumption and even reduce noise levels.

Protective systems

Circulation pumps that are equipped with automatic protection work the longest. Such systems prevent overheating of the superchargers, as they turn them off if the temperature of the electric motors rises significantly.

Automation also prevents dry running of devices with a wet rotor. By stopping the pump, its electric motor does not fail, the impeller does not break, and the seals remain intact.

Installation features

As a rule, circular electric pumps are installed in the main using a bypass - a parallel pipeline with a ball valve through which coolant is supplied when the pump branch is turned off. This design allows you to remove the circular valve for adjustment, repair or replacement without draining the coolant from the system.

Choosing the right circulation pump for heating is a responsible task, the solution of which is best left to specialists. The comfort and efficiency of the heating system (optimal efficiency of the device), as well as energy consumption, the savings of which, with the right solution, can reach 80%, depend on the selected unit.

If you wish, you can independently select a circulation pump for the heating system, make calculations using formulas; the highest accuracy of calculations is obtained when using computer programs. When working with programs, you need to understand how to enter data correctly - in many cases this requires special technical knowledge, which will take some time to obtain

Performance calculation

One of the control parameters is the performance of pumping equipment, which is calculated from the ratio:

– the amount of thermal energy consumed in a specific room;

– the performance value of the pumping device;

– specific heat capacity, if water is used as the coolant; for other types (transformer oil, antifreeze, etc.) the corresponding data are used;

– the temperature difference between the forward and return branches of the heating system, which can be:

• 20 o C – with a normal heating system for residential areas;
• 10 o C – temperature level in non-residential areas with low-temperature heating;
• 5 o C – temperature of the coolant in the heated floor system.

The performance indicator is a passport characteristic; in technical documentation it is reflected as cubic meters per hour. In order for the calculation result to correspond to the form we are familiar with, it must be divided by the specific gravity of water.

Let's give an example of a calculation: the area of ​​the heated room is 200 square meters, therefore, to heat it, an energy expenditure of 20,000 W will be required. The room is equipped with a normal heating system with a temperature difference of 20 o C. Using these numerical values ​​in the above formula, we obtain:

20000/(1.16 x 20) = 862 kg/hour,

recalculation into usual values ​​gives the result

862 / 971.8 = 0.887 m 3 / hour.

To heat the specified room, you will need a pump with a capacity of at least 0.9 m 3 / hour. This indicator must be looked for in your passport.

To calculate this characteristic, you can use the following formula:

G = 3.6Q/(cx dT) kg/hour, where

c is the specific heat capacity of the medium used in heating.

The easiest way to choose a pump is if the boiler power is already known. In this case, you can apply the relation:

Q – unit productivity;

N – boiler power;

dT – temperature difference at the boiler outlet and return.

The photo above shows the correct connection of the unit for a heating system using a bypass. This placement allows the liquid to flow in a roundabout way if it is necessary to carry out repair work or replace the pump without stopping the functioning of the heating system. See how to make heating in an honest house yourself.

Important! The rotor is only positioned horizontally! The direction of flow is indicated by an arrow on the housing.