A pump for a solid fuel boiler how to choose

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

Gravity heat supply systems fully functional only in single-storey private houses up to 100 square meters. м. If you need to heat an apartment building or a spacious mansion, without a system with forced circulation is not manage. The best solution is to choose a circulation pump and install the unit in the heating circuit.

We propose to understand what tasks performs the pump in the heating system, how the device is designed and works. We have described the peculiarities of operation of different types of pumps and identified the main criteria for a competent choice. The above information will help you choose a suitable model of circulation pump and not be disappointed in the purchase.


In the description of any circulating pump you can meet such parameters as performance, heat output and flow capacity. They are all measured in cubic meters per hour and are the same characteristic, just called differently. If the performance is calculated correctly, then all the batteries in the house will be the same temperature, as well as hot water at the intake points.

To calculate uses a complex scheme, presented in the relevant regulations. But there is a simplified formula. To calculate, multiply boiler output by 0.86 and divide by 20. The result will be the value to be selected in the parameters of the pump.

The formula is quite simple, but if your house has underfloor heating it will not work. Here you already have to calculate the length of the line and other nuances.

How to choose a circulation pump

Each circulation pump has a set of technical characteristics. They are selected for the parameters of each system individually.

Selecting the technical characteristics

Let’s start with the selection of technical characteristics. For professional calculation there are a lot of formulas, but for the selection of a pump for the heating system of a private house or apartment you can do with averaged norms:

  • The pump capacity is assumed to be equal to the capacity of the installed heating boiler. That is, if the boiler is 35 kW, then the pump is selected with a capacity of 35 l / min.
  • Next you need to calculate the required head (lifting height). On average it is considered that for 10 meters of piping there should be a pump head of 0.6 m. To determine which head of circulation pump is needed for the system, you need to divide its total length by 10 and multiply by 0.6 m/s. For example, if the total length of the heating system is for example 80 m, the required head is: 0.6 m 8 = 4.2 m. That is the technical characteristics of the head should not be less than.

You can choose a circulating pump for your heating system by yourself

Choose a circulating pump for heating following these rules is easy. Calculations are elementary. But I must say that these figures are statistical averages. If your house in some point is very different from the “average performance”, it is necessary to make adjustments either to increase or to decrease the technical characteristics. For example, you have well insulated the house, the power of the previously bought boiler was excessive. In this case it makes sense to take a pump with a smaller capacity. In reverse situation. it is chilly in the house in severe cold. you can put a more productive circulator. It will temporarily solve the problem (in the future it is necessary either to insulate or to change the boiler).

Model selection

When selecting a particular model pay attention to the graph with the pressure characteristics of the pump. On the graph find the point of intersection of head and capacity. It must be in the middle third of the curve. If it does not fall into any of the curves (there are usually several of them characterizing different models), then they take the model, the graph of which is closer to the temperature of. If the point is in the middle, take the less productive (the one that is located below).

The operating point should be in the middle of the graph

What else to pay attention to

There are some more positions in technical specification of circulation pumps to pay attention to. The first is the admissible temperature of the pumped medium. That is the temperature of the coolant. In quality products this value is in the range from 110 ° C to 130 ° C. In the cheaper ones may be lower. up to 90°C (and in fact 70-80°C). If you have a system designed as a low-temperature, it is not terrible, but if it is a solid fuel boiler. the temperature to which can be heated coolant is very important.

Choose a circulating pump should be first based on the characteristics

You should pay attention to the maximum pressure at which the pump can work. In the heating system of a private home, it is rarely above 3-4 atm (this is for a two-story house), and the norm is 1.5-2 atm. But still, pay attention to this indicator.

The difference between wood & multi-fuel stoves

What else you should pay attention to. the material of which the casing is made. optimal. cast iron, cheaper. from a special heat-resistant plastic.

Type and size of connection. Circulation pump can be threaded or flanged connections. There are male and female threads. the appropriate adapters are selected for it. Connection sizes can be: G1, G2, G3/4.

It is also worth paying attention to the presence of protection. There can be a dry run protection. In circulating pumps with wet rotor it is very desirable, as the cooling of the motor occurs at the expense of the transported medium. If there is no water, the motor overheats and fails.

One more type of protection. overheat protection. If the motor reaches a critical temperature the thermostat switches off the power supply and the pump is stopped. These two functions will prolong the lifetime of the equipment.

Calculation and choice of circulating pump

Most heating systems in private houses have a forced or combined circulation of water. An inseparable part of such a system is a circulation pump which ensures water flow through the radiators and pipes. In order for its work to be as effective as possible, it is necessary to make the correct calculation and selection of the circulating pump for the heating system.

Technical parameters

Among the main ones are 3 indicators:

pump, solid, fuel, boiler, choose

These parameters are reflected in the technical documentation of the pump, so it is important to read them correctly and make the necessary lining.


The entire line of pumps for the heating system is identical in structure. The main difference that affects the performance and quality of the system is the principle of operation of the rotor. Thus, there are 2 main groups:

There are 2 varieties of circulation pumps according to the type of activity of the rotor. in contact with the coolant (wet) and out of it (dry).

The dry operating principle means that the rotor is completely isolated from the coolant. These types of pumps belong to the category of industrial, more powerful, but also noisier samples.

When selecting such equipment it is necessary to provide a separate isolated room.

The fundamental difference between the “dry” and “wet” rotor is the presence of ceramic clamping rings that protect the electric motor. The rings are made of stainless steel and lubricated with a very thin layer of water. Tight connection of the rings to each other is provided by a spring, which compresses more as the elements wear, thereby sealing them.

The “wet” variant involves the location of the rotor directly in the coolant and the electric motor is reliably protected from the penetration of moisture by a special sealed metal sleeve.

This is an almost silent type of pumps, but with low efficiency, which, in principle, is enough to heat even large houses, provided the correct selection of equipment.

Among the main advantages of such equipment include:

  • compact size;
  • absolutely silent operation;
  • No need for maintenance due to the fact that the coolant itself acts as a cooling element and lubricant at the same time.

Calculation of pump capacity with forced circulation

There are several ways to calculate the pump capacity for a particular heating system.

Carrying out calculations and layout of the different parameters should be carried out by a specialist who can accurately determine the required capacity and provide recommendations on the type of boiler.

Compliance with SNiP

It is no secret that there are certain standard parameters for determining the sufficient amount of heat for a certain area. According to these parameters, boilers and pumps are installed in multi-storey buildings, production facilities and public buildings.

Providing heat to a residential house should also comply with sanitary regulations, based on which you can calculate the approximate power of the pump.

Thus, according to SNiP 2.04.07-86 on 1 sq.m.м. rooms at ambient temperature.25-30 0 C should emit the following amount of heat.

In order to determine the required amount, it is enough to multiply the total area of the room by the corresponding figure.

Such a calculation formula is justified when choosing a universal pump, the automatic control system of which checks the design features and adjusts the operating characteristics by itself.

Photo 2 Table of heat output required for the different rooms

Calculation of working capacity of the heating system

It is much more effective to calculate the capacity of the circulation pump, based on the characteristics and capacity of the boiler. In this case, the following formula should be used:

  • N. calculated pump power;
  • Nc. power of the boiler equipment;
  • T1-T2. temperature difference between return and supply side. As a rule, this figure is up to 15 0 C.

The power calculation is also influenced by the hydraulic resistance in the pipe system, according to which the appropriate coefficient is applied (decreasing or increasing the reference value). The main resistance of the coolant occurs in indirect sections of the pipe or with connecting elements.

For example, even in a straight pipe section, the hydraulic resistance is up to 1.5 cm/m. Based on this figure, you can independently calculate the resistance throughout the pipeline to the following indicators:

The increase in resistance is not affected by the number of floors in the building. The movement of the coolant through the pipes is carried out on the communicating vessel principle, where in the system there are two columns with an equal level of fluid.

Calculate the total resistance can only be if the entire heating system was installed in the presence of the customer or there is a wiring diagram of the pipes. If such a scheme is absent or part of the pipe system is hidden, it is better to use the universal type of pump, based on the total area of the premises.

After obtaining the appropriate calculations, you can choose a pump from the catalog presented by all manufacturers of equipment. In this case please note that all the technical parameters of circulating pumps are always given based on the load of the heating system at maximum. You should choose the unit, the power of which is an order of magnitude lower. In this case it will be possible to save not only on purchase but also on further service and electricity payment.

Operating parameter of the circulation pump, as well as of any other equipment, is always lower than the design one.

What to pay attention to when mounting?

All circulating pumps pass the coolant strictly in a certain direction, which can be determined by marking on the body of the unit itself.

pump, solid, fuel, boiler, choose

This is a necessary parameter, respecting which provides long and efficient operation of the pump. All devices are equipped with rubberized gaskets and seals, which deform and deteriorate when exposed to hot environment. Installation of the pump on the flow pipe where the temperature of the heat carrier is always higher leads to the fact that at the end of the season the pump will break down.

Selection Criteria of a reserve power source

Backup power supplies designed to work with the heating system pumps should be selected according to several characteristics:

pump, solid, fuel, boiler, choose
  • Power;
  • The capacity of the battery pack;
  • The permissible autonomy time;
  • The possibility of using external batteries;
  • Input voltage variation;
  • Output voltage accuracy;
  • Transition time to standby;
  • Output voltage distortions.

UPS for a circulation pump should be selected according to several basic parameters, the most important of which is the power.

Determination of required capacity of UPS

The electric motor, which is part of the heating system pump, is an inductive type reactive load. This is the basis for calculating the power of the UPS for the boiler and the pump. The technical documentation of the pump may indicate the power in watts, e.g. 90 W (W). Heat output power is usually stated in watts. To know the total power, divide the heat output by Cos ϕ, which can also be found in the documentation.

For example, the power of the pump (P) is 90W, andCosϕ 0.6. The total power is calculated according to the formula:

Hence the total power of the UPS to operate the pump correctly must be 90/0.6=150W. But this is not the final result. At the moment of starting the motor, its current consumption increases by about three times. Therefore the reactive power must be multiplied by three.

As a result, the UPS power for the heating circulation pump will be equal:

In this example the power supply will be 450 watts. If the power factor is not listed in the documentation the heat output in watts is divided by a factor of 0.7.

The capacity of the batteries

The capacity of the battery determines the time during which the heating pump will operate in the absence of mains. The batteries integrated in the UPS usually have a small capacity, determined primarily by the size of the device. If the backup power supply will operate in conditions of frequent and prolonged power outages, you should choose models that allow the connection of additional external batteries.

A very informative video about the personal experience of someone who has been confronted with the purchase of an inverter for a boiler and heating pump, see:

Input Voltage

The 220-volt line voltage standard allows for a tolerance of ±10%, i.e., from 198 to 242 volts. This means that all the devices which are used on the territory of the Russian Federation must operate correctly within these limits. In fact, in different regions, and especially in rural areas, voltage deviations and surges can significantly exceed these values. Before purchasing a UPS for the heating pump, it will be very useful to perform measurements of the mains voltage repeatedly, throughout the day. The passport of the redundant power supply indicates the allowable input voltage limits, at which the device provides a voltage at the output close to the nominal.

Output voltages and their shape

If the voltage parameters at the output of an uninterruptible power supply unit are within the limits of 10 percent, then this device is quite suitable for powering a heating system pump. The time it takes the control board to switch to battery power is usually less than tens of microseconds. This is not critical for the motor.

A very important parameter of UPS, necessary for correct operation of the heating system pump, is the shape of the output signal. The pump motor requires a smooth sine wave, which of all models of backup power supply can provide only a double conversion device or on-line UPS. In addition to a perfect output sinusoid, this source also provides an accurate value of voltage and frequency.

There are some rules to follow when installing a UPS for a heating pump:

  • The temperature in the room must correspond to the values specified in the documentation;
  • The room must be free of caustic vapors and flammable liquids
  • Grounding circuit must be made in accordance with the rules of operation of electrical installations.

Choice of size

You have probably noticed that there are units in our product range with the same characteristics but with different sizes and spigot sizes. How to choose the external parameters of the pump:

  • For installation in pipes, bypasses and mixing stations for underfloor heating, standard blowers with a length of 180 mm are used. “The 130 mm short pieces are installed inside heat generators or on highways in very confined spaces.
  • The diameter of the process fittings is matched to the diameter of the base pipe. Larger sizes are possible, smaller sizes are strictly not recommended. This means that a unit with connections of 32 mm can be installed on a DN 25 pipe.
  • Pumps with 32 mm nipples are used in primary rings and boiler circuits, as well as in upgraded gravity-flow systems.

The pumps performance is not affected by the installation length of 130 or 180 mm

Note. The sizes of readymade bypasses, sold in stores, are matched to a standard 18 cm pump.

The number of speeds of the blower does not play a special role. In home conditions 3 modes are enough, the optimal speed. the second. Air is bled from the units through a side screw, so do not buy units with a separate air vent.

Pumps with dry rotors

All the internal work unit of dry units is completely isolated from water. These products are slightly larger, heavier. There is noise, vibration. There is more often a need for a separate place, enclosure, installation on the floor with larger piping, distribution. But also devices can be plugged as standard, as well as wet ones. directly into the pipe, bypass on the line.

“Dry” pumps are put to transport large masses of coolant through the circuits with a long length, for example, for a large number of apartments in multi-storey buildings, facilities with several floors, entertainment centers, administrative, industrial buildings.

Design features are as follows. Insulating gaskets (2 rings) between the electric motor and the hydraulic working segment. There are 2 discs with a tight fit. One movable on the shaft, the other. static, firmly fixed inside the body. A thin film of pumped resource is created between the wheels, putting pressure on the elements, increasing tightness.

The efficiency of dry pumps. 85%, by this parameter they are the best, but for home systems are used less often because of the noise, vibration created by the cooling fan.

Dry circulating pumps are available in the following sizes:

  • monoblock. motor, all pump parts in one piece. Advantages: easy to service and install. But such devices, as well as cantilever, are more often put for MCD, on large objects, and these products are usually with a stand-foundation;
  • cantilever version. Assembled on a single base, the axes of the elements on 1 line, but the shaft, spigots removed from the drive;
  • in-line. Compact, placed directly on the pipe. Single line pipes (no snail, as in the previous version). There is an auto-compensation of sealings output. Exactly such variants are popular, they are usually put on not particularly demanding standard home heating.

Advantages and disadvantages of dry circulation pumpsDadvantages of dry pumps:

  • performance, power is higher, efficiency of 85%;
  • more energy efficient;
  • does not require horizontal positioning;
  • low requirements to the cleanliness of the coolant, abrasive particles will not damage the working parts of the mechanism, as they do not come into contact with it. It is possible to put on all systems. open, closed. The filter can not be mounted, although it is desirable;
  • dimensions, weight is a little more. For high performance, the characteristic option of installation on the floor (not directly on the pipe, as with most dry pumps). Accordingly, the installation is more complicated, the cost increases. But such a need does not often arise, as for home systems enough compact, not particularly powerful model, in most cases the device is mounted directly on the pipe;
  • Large units require lubrication. For compact sizes, this procedure may not be required or may be required very rarely, but it must be prescribed in the manual;
  • if the cooler breaks, the device will overheat, with a high probability of failure;
  • the cooling impeller is noisy, vibration occurs. Quite a significant disadvantage, as extraneous sounds, making users nervous, will nullify all the advantages. Noise isolation will be required, at least a box/baffle with it or installation on a remote segment;
  • repair, replacement of parts is somewhat more labor-intensive: the design is complicated by the cooling impeller, there are features associated with the isolation of internal parts;
  • more expensive.

This type of equipment productive, unpretentious to the heat transfer fluid, works with high head, does not require horizontal location. But the device is noisy, with vibration, is often made in oversized sizes, this sometimes entails the need for installation on a foundation, a frame of metal.

Presenting: DIY Solid Fuel Boiler 50 kW with full process control

Features of installation

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

To choose the right circulating pump for heating. a responsible task, the solution of which is better to entrust to professionals. The selected unit determines the comfort and efficiency of the heating system (the optimal efficiency of the device), energy consumption, savings which, with the right solution can be up to 80%.

If you want to independently conduct the selection of circulating pump for the heating system, to make calculations according to formulas, the highest accuracy of calculations are obtained by using computer programs. When working with programs, you need to understand how to properly enter data. in many cases, this requires special technical knowledge, which you will have to spend some time to obtain

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