Water pump for heating: types, specifications and selection rules
Gravitational natural phenomena are not always able to provide a sufficient level of coolant circulation, especially in complex systems with several rings. Stimulate the movement of coolant will help the water pump for space heating.
When choosing circulation equipment, it is necessary to take into account its technical characteristics and parameters of the installed heating system.
Types of pumps for heating systems
Modern circulating pumps are divided into two principal types: “dry” and “wet”. They are somewhat different internal device and the scheme of work, but the movement of fluid in them is still provided by the circulation processes in the system. Some models are equipped with devices for automatic control of their work.
General structure of equipment
The water pump is built into the heating circuit to ensure the forced circulation of the coolant.
It consists of the following basic elements:
- housing with working chamber;
- screw for bleeding;
- terminal box.
The terminal box can be equipped with additional mechanical and electronic equipment designed to regulate the mode of operation of the engine. The simplicity of the device provides high reliability of pumps, thanks to which they can function efficiently for about 5-10 years.
The principle of operation of devices "dry" type
The design of the dry circulation pump does not imply contact of the coolant with the rotor. Its working area is separated from the parts of the electric motor by special rings.
They are made from the following types of material:
- tungsten carbide;
- of stainless steel;
The principle of the "dry" pump is to rotate the wheel in the environment of the coolant.The water supply hole is located in the center of the main chamber, and the diverting system of channels - on the periphery.
Rotation of the impeller of the functional wheel leads to the appearance of centrifugal forces, which move the coolant from the center of the body to its edges. This principle of operation of the circulation pump provides a constant movement of water through its internal chamber.
Positive features of dry-type heating equipment are:
- high level of efficiency - 70-80%;
- minimum water hammer when starting;
- the possibility of horizontal and vertical engine layout;
- pumping large volumes of coolant due to high power.
Due to the combination of efficiency and noise, “dry” pumps are used mainly in heating systems of industrial, administrative buildings and large residential buildings.
Therefore, the following negative aspects can be distinguished in devices of this kind:
- The high level of noise that does not allow them to be used in apartments.
- The need to replace the sealing discs every 2-3 years.
- High probability of coolant leakage to the outside in violation of the tightness of the working chamber
- The need for external engine cooling.
Because of the large weight, such equipment is installed on the floor or suspended on brackets.
There are two options for the structural performance of "dry" pumps:
- Monoblock. The motor and the metal housing of the device are combined into one design with specific mounts.
- Cantilevered. With the help of universal fasteners, an engine of any power can be connected to the body of the equipment.
“Dry” circulating devices for heating systems with appropriate maintenance are more durable, so they are gradually pushing the model with a wet rotor out of the market.
The device of the pump with a rotor of the wet type
The principle of a circulating device with a wet type rotor is similar to its counterpart in the “dry” version: as the impeller rotates, the coolant supplied to the center moves to the periphery of the working chamber, from where it collects into the discharge channels.
The rotor of the "wet" pump is in contact with the coolant, which provides cooling of the engine. Such devices should not work in the dry mode, because they quickly overheat and burn.
Components of the equipment are usually located in the same housing and constitute a single structure, therefore, when individual elements break down, they are not replaced, but a new pump is purchased.
The advantages of the unit with the "wet" type of rotor:
- noiseless operation;
- compact size;
- negligible power consumption (30-50 W);
- the duration of work without maintenance;
- relatively low cost;
- easy installation
Devices are often embedded directly in the design of domestic boilers, facilitating the consumer to choose equipment when installing a heating system.
In this type of heaters there are also disadvantages:
- design limits on maximum power;
- low maintainability;
- small efficiency (40-60%);
- the need for a strictly horizontal arrangement of the axis of the engine.
Because of the low power, the “wet” type of pumping machines is used mainly in the heating systems of apartments and single-story houses.
Non-standard equipment for heating
Most household circulating devices for heating do not require adjustment. To start them, it is enough to connect the nozzles to the pipeline and plug the device into the electrical network. And also sold models with non-standard structure, which gives additional functionality.
If constant heating of the fluid is critical for the heating system, a pair of pumps that are sequentially arranged in the circuit can be installed. The second engine in such a system can be turned on when there is insufficient power or a breakdown of the first motor.
To automate the operation of the boiler with heating from the heating circuit, you can use pumps with a thermostat and a timer.The built-in mechanism provides switching the engine on and off depending on the temperature of the coolant and the time of day.
In extensive heating networks, you can use circulation pumps with a thermostat and a smooth adjustment of the impeller speed. With their help, autonomous regulation of the velocity of the coolant occurs in different loops, depending on its temperature.
Pumps with automation are many times more expensive and are rarely used in apartments and small apartment buildings.
The advantages of circulating devices
Until 1990, heating systems in private buildings were designed and built mostly without pumps. The coolant moved through the pipes by gravity, and its circulation was provided by convective flows of the liquid when it was heated in the boiler.
Now the movement of the coolant is carried out by force with the help of water pumps, which have several advantages:
- Reduced load on the boiler by reducing the temperature difference in the incoming and outgoing pipe.
- Uniform distribution of heat in the rooms due to the same temperature of the coolant along the entire length of the heating rings.
- The possibility of operational control of the temperature of the coolant.
- Rapid heating of the heating system at start-up of the cold boiler.
- Lack of need for the device of pipelines with a bias to the boiler, providing spontaneous movement of the coolant.
- The possibility of using thin pipes, which occupy a little internal space of the apartment.
- The power of the pump makes it possible to inject in the heating circuit a pressure sufficient to deliver coolant up to several floors.
- The use of valves on separate hinges of heating networks.
- The possibility of integrating the pump into the automatic control system of the boiler.
With a lot of advantages in circulating devices, there are two drawbacks - it is a dependence on power supply and additional energy costs.
But the disadvantages are easily compensated - the installation of a water pump saves 10-20% of fuel, and the share of the cost of electricity in the total heating costs is only 3-5%.In addition, with the frequent absence of electricity, you can install a UPS, which will provide for a certain period of autonomous operation of the boiler and pump.
Features marking equipment
Unfortunately, there are no unified requirements for labeling circulation pumps. Manufacturers independently choose the list of technical characteristics that are indicated on the device case.
The front panel usually displays this information:
- the direction of movement of the coolant;
- diameter of the attached pipes;
- maximum allowable pressure;
- manufacturer and model;
- maximum working temperature;
- degree of protection;
- power grid operating parameters;
- marks of compliance with national technical regulations.
Manufacturers may specify other information at their discretion. Detailed technical characteristics of devices are specified in the instruction manual.
Units of measurement vary from country to country, so numerical designations on the body can be deceptive.It is better to open the instruction once again, where, along with the characteristics, their units of measurement are indicated.
Technical parameters of pumps
Circulating equipment has a number of characteristics that are especially important to consider when purchasing. These include:
- Efficiency- the ratio of the amount of electricity consumed to the useful work done on pumping coolant.
- Head pressure- the pressure difference between the outgoing and inlet ports of the pump.
- Water supply- the maximum volume of the coolant pumped through the working chamber with the minimum resistance of the heating circuit.
- Powerelectricity consumption.
- Pipe diameter- nominal value of the equipment to be attached.
- Maximum pressure rating(denoted by PN) in the working circuit at 20 ° C, which still guarantees the long-term operation of the device within the warranty period.
This data is usually sufficient to confirm the sufficiency of the technical characteristics of the pump to the parameters of the heating system.
Calculation of power heating devices
The choice of a specific model of circulation equipment is influenced by the technical characteristics, as well as the financial possibilities of the buyer and the properties of the heating system.If you want to save, it is important that the pump capacity is sufficient for the normal operation of the boiler. After all, the level of water supply indicated in the instructions is always significantly higher than the actual one.
To independently determine the power adequacy of the device, three stages of calculations will be carried out.
First step. Determination of the required pump performance by the formula.
For apartments in multi-storey buildings, the heating power is assumed to be 75-80 W / sq. m., for homes - 100-120 W / sq. The temperature difference at the boiler inlet and outlet is usually 10 ° C.
It turns out that for an apartment of 60 square meters. m. will be enough real pump performance in (80 * 60) / (1.16 * 10) = 414 (l / h).
Second phase. Determination of the pressure to overcome the total hydraulic resistance of the system by the formula.
This formula requires complex calculations using reference data, so for home and apartment heating systems you can use a simplified schedule.
According to the schedule, the pressure loss in an apartment with a pipe diameter of 20 mm will be 70 mm / m, and taking into account the length of the pipeline at 50 m. - 3.5 meters. This figure should be multiplied by a factor of 1.3-2.2, taking into account the resistance of the water-pressure fittings.
Stage Three. Determination of the sufficiency of the pump power according to the schedule of pressure-flow characteristics.
Such a schedule is indicated in the instruction manual, and it is unique for each pump model. If the intersection point of the parameters calculated above is below the B curve, then the device is suitable for the heating system, and if it is higher, then no.
Rules for the selection of the circulation pump
The choice of a separate pump for the heating circuit must be carried out taking into account many parameters.It is important that the equipment not only performs its function, but also works for a long time, without causing inconvenience to residents of a house or apartment.
Therefore, when choosing a device should follow the following rules:
- Choose well-known pump manufacturers: Calpeda, Grundfos, WILO. The price of their equipment is 20-40% more, but the probability of breakage is much less.
- Take the device with the characteristics that are 20-30% higher than estimated. This stock will reduce the operating load and increase equipment life.
- Pay attention to the dimensions so that the pump fits in its intended place.
- The device should be as silent as possible so as not to disturb the residents at night.
- No need to strive to buy a model with a capacity that greatly exceeds the calculated parameters. This will only lead to excessive energy consumption, but also to unnecessary noise.
- Choose a pump specifically for heating systems, because they are designed for operating temperatures up to 130-150 ° C.
- It is desirable that the device has a built-in mesh for filtering solid particles suspended in the coolant.
The performance of the equipment must necessarily match the parameters of the heating system, it is impossible to save on this.In addition, you will have to pay only for a reliable manufacturer, enhanced security of the case and a system of automatic control of work.
Conclusions and useful video on the topic
How to choose a good circulation pump for heating:
DAB circulating equipment:
Comparison of two Grundfos devices: UPS and Alpha2 models:
It is better to coordinate the choice of the circulation pump with experts. If the power of equipment for a standard apartment can be prompted by the sellers in the store, then before buying a heater for a country house you will have to turn to professionals for complicated calculations. It should be remembered that it is impossible to exchange it in the store after the start of operation, therefore it is better to immediately buy a suitable model.