If, in the case of choosing a pump, the question arose which one is better - a pump with wet rotor or dry, then we will try to deal with such units using the example of circulation pumps. It is known that such equipment is successfully used to create excellent and uninterrupted circulation coolant in the heating system of a private house.
In working condition, a pump with any type of rotor pumps a volume of liquid through the pipes, forcing it to move constantly forward. As a result of such an impact on the coolant, we have the following advantages:
- Constant temperature indicator radiators in all parts of the heating system;
- Absence air locks in the system, which means eliminating the possibility of water hammer in it;
- Saving family money on fuel or electricity consumption for heating the coolant (now you do not need to intensively fire the boiler so that the desired water temperature reaches the radiators in the back room of the house and warms it up). Glanded or dry rotor pumps will make everything faster and more productive.
Important: pumps with rotors of all types have two openings in their design: suction and discharge. Thus, the unit performs its work, moving it along a closed circuit.
Circulation pumps are similar to drainage pumps device. The pump housing with a dry or wet rotor is most often made of durable alloys such as brass, cast iron, stainless steel or bronze. These metals interact well with water. high temperatures or with aggressive environments(in the case of a drain rotor).
The rotor itself is made from either durable stainless steel or ceramic. And the working unit (wheel with blades) is placed on the rotor shaft.
The principle of operation of such a device is to create centrifugal force inside the pump and looks like this:
When turned on, the rotor drives the impeller wheel, which rotates fast enough to create a pressure drop in the pump chamber. This encourages the flow of water into the tank. Further, the water that has entered the chamber increases the pressure and, at the same time, is pressed against the walls of the internal reservoir of the pump. As a result of this difference, water is pushed out into the outlet. The cycle repeats over and over until the unit is turned off.
Division of pumps with a rotor into types
Everything pump equipment with a rotor can be divided into two types:
- Units with a "wet" rotor;
- Pumps with a "dry" rotor.
In the first case, we are talking about a mechanism whose rotor does not have direct contact with the pumped water. The isolation of the rotor in the pump mechanism is supported by special ceramic or metal seals in the form of rings. They protect the rotor from direct contact of the nodes with the pumped medium. But here the principle of operation of a device with a wet rotor is that between the protective rings rubbing against each other there is a thin, barely noticeable water layer. It helps to maintain the pressure difference in the heating system and in working chamber, which means that it ensures the tightness of the rotor compartment. At the same time, at the moments of operation of the ring, the seals rub against each other more strongly, which ensures even greater tightness of the device.
Important: circulation units for heating or air conditioning systems with a "wet" rotor can be either single-phase or three-phase. That is, such pumps can be used both at home and in a large production or industrial enterprise.
Thanks to precisely these principles of operation, the unit with a “wet” rotor has a number of advantages:
- Low noise level when pumping water through the system;
- Modest weight and small dimensions;
- Possibility of long-term operation without stops;
- Economical power consumption;
- Ease of installation, configuration, maintenance and repair.
At the same time, monoblock devices with a “wet” rotor are more popular with modern consumers.
Important: but along with all the listed advantages, the efficiency of a pump with a “wet” type rotor is significantly lower and is about 55%. Thus, it is best to use a similar mechanism in homes. small area, where the closed circuit of the heating system has a small length.
If we talk about water pumps with a "wet" type rotor, then here the devices will be slightly inferior to their counterparts with a "dry" rotor. But this applies only to surface aggregates.
Important: Required quality work pumps with a "wet" rotor and compliance with the principles of pumping water is correct installation unit per circuit. Here, the equipment shaft must be located strictly horizontally relative to the closed circuit of the heating system. Only in this case, a high-quality flow of fluid to the bearings for lubricating the working units will be ensured through the sleeve.
Dry Rotor Pumps
With all their productive capacity, the units this type have a number of disadvantages:
- High noise level in operation.
- The need for constant monitoring of the quality of the processed medium, since pumps with a "dry" rotor do not tolerate the presence of impurities in the water or air molecules. Such "neighbors" are able to break the tightness of the sealing rings in the mechanism.
At the same time, the entire range of pumps with a "dry" rotor is divided into three types:
- Block devices;
- Vertical aggregates, in which the engine is in a vertical position, and both nozzles are located on the same axis;
- Console (horizontal), in which the engine is mounted horizontally, and the nozzles are perpendicular to each other.
Pump selection rules: dry or wet rotor
In order for the heating system to work as efficiently as possible, it is necessary to choose the right pump in accordance with the parameters of the house and characteristics heating system. Only in this case and under the condition correct installation mechanism in compliance with the principles of its operation, the heat in the house will be of high quality and long lasting.
So, when choosing a pump, consider the following points:
- The total area of \u200b\u200bthe house and the length of the closed circuit of the heating system;
- The number of radiators for the entire length of the heating system;
- The presence of "warm floor" systems, etc.;
- Quality and density of window metal-plastic packages;
- Insulation of walls, ceiling or roof in the house.
Important: calculations required amount heat should be carried out only by competent heat engineers who will take into account all important nuances and recommend a pump with nominal pressure characteristics for your premises.
It is important to consider that if you choose a pump for a heating system that already exists, but needs to be improved, then it is better to buy an adjustable unit. This device perfectly adapts to the operating parameters of a given circuit.
Mounting principles for units with any rotor
In order for the operation of the circulation equipment to be of high quality, it is better to invite specialists to install it. But if you want to install the pump yourself, then follow these rules:
- The installation of the unit is carried out at the boiler from the reverse type. That is, where the water that has passed the entire closed circuit of the system returns again. But this rule applies to premises whose area does not exceed 150-200 m2.
- It is important to follow the location of the arrow on the pump housing when installing it. The arrow should point in the direction of movement warm water by system.
- All flanged and threaded joints must be treated with sealant to avoid possible leaks.
- If you are dealing with a reverse circulation heating system, then it would be useful to install a bypass - a piece of pipe, which, in case of repair of the unit, will be able to close the heating circuit after removing the pump.
Popular Wet Rotor Pump Models
The most popular units for transporting water with wet rotors are products manufactured by German, Danish and Canadian companies. Special place among the product range is the Wilo pump.
Devices have threaded connection and are equipped with a speed control system to control the performance and power of the pump. Wilo units are used in heating and air conditioning systems, as well as in circulation systems cold water at enterprises.
Grundfos pumps
Another leader in the modern Russian and world markets of pumping equipment. These pumps are different. high performance and reliability. Thanks to careful assembly from scrupulous Danes, the units work without failures and breakdowns for a long time.
The salient features of these mechanisms are:
- Absolute inertness to water and anti-corrosion properties of the metal;
- No need for frequent preventive maintenance and repair (wet rotor does its job);
- Reliable tightness of the case.
Important: Grundfos pump casings are equipped with a special heat-shielding casing, which prevents the risk of possible user burns.
If necessary, heating large rooms with total area several hundred square meters system pressure autonomous heating with natural circulation (about 0.6 MPa) created heating heater, is usually insufficient.
To solve this problem, you can go two ways:
1. Build a closed system using large caliber pipes, which are expensive.
2. Connect the circulation pump to the system.
The second option is more economically feasible. By improving the circulation of the coolant in the system, the heating efficiency increases significantly.
Circulation heating pumps are divided into two types:
1. With a wet rotor.
They are used in the heating system of private households, where the length of pipelines is not so great.
The pump rotor, equipped with an impeller, rotates inside the housing, accelerates the movement of the coolant. The fluid inside which the rotor rotates cools and lubricates the mechanism.
When installing a "wet type" pump, attention should be paid to the horizontality of the shaft, then there will always be water inside the casing.
Advantages of wet rotor pumps:
- practically silent;
- stepless switching of the rotor speed;
- reliability in operation;
- long service life;
- no need for maintenance;
- ease of repair and adjustment of the pump;
- relative cheapness.
Flaws:
- not high efficiency(not higher than 50%)
2. With a dry rotor. Are applied in heating systems of big extent. O-rings are installed between the electric motor and the working part of the rotor, the service life of which is 3 years. There is no contact between the rotor and the coolant.
Advantages:
- high efficiency - about 80%;
Flaws:
- high level noise, in connection with which they are installed in separate room equipped with soundproofing;
- the need to control the absence of suspended particles in the coolant and dust in the air surrounding the engine in order to avoid damage to the surfaces of the sealing rings, which can cause damage and leakage.
When choosing the type and model of a circulation pump for a heating system, one should also take into account their performance, operating conditions, features of the coolant (its viscosity and density), recommendations and requirements of the manufacturer for installation and quality characteristics pumped liquid.
It's no secret what water heating most common in urban residential buildings and private cottages. And an integral part of the system, along with the boiler, is a circulation pump, the function of which is to ensure the movement of water along the “boiler-heating circuit-boiler” circuit. Of course, you can do without a circulation pump, thereby doing so, but this will entail an increase in pipe diameters, the presence of slopes during installation, which will only complicate the heating system.
When the term "circulation pump" is mentioned, a "wet rotor" pump immediately appears. And this is not accidental, since this species is the most suitable for providing heating in private houses and small rooftop boilers. The device of the circulation pump with a wet rotor determines its advantages such as compactness and noiseless operation.
Sectional view of a wet rotor circulation pumpThis type of pump got its name because of the presence of water cooling motor. The liquid pumped by the pump is also used for for parts lubrication.
Although there are currently a lot of manufacturers of pumping equipment, but principle device wet rotor circulation pump is the same as that of Wilo that u Grundfos.
AT cast iron or steel body attached to the motor shaft closed impeller made from heat resistant composite material. It represents two parallel drives which are interconnected by radially curved blades. One of the discs has a hole for the inlet of the working fluid, the second has a hole for mounting the impeller on the motor shaft.
In the pump housing along the periphery of the impeller, a spiral hole is made in the form confuser. Its purpose is to convert the kinetic energy of the fluid flow into static pressure, as well as to collect and drain water in the right direction.
The impeller is fixed on the shaft rotor, which is washed and cooled by pumped water. motor stator hermetically separated from the rotor separating glass with wall thickness 0.1 - 0.3 mm. The glass is made of ferritic stainless steel or carbon fiber.
The circulation pump rotor is fixed on end face graphite or ceramic plain bearings which are also cooled by the pumped water.
Also on the front wall of the engine housing there is screw plug to remove air from the pump.
The external difference between the design of a wet rotor circulation pump and air-cooled electric motor pumps (with a dry rotor) is the absence of fins on the motor housing and an impeller at its end.
The design of the Grundfos circulation pump with a wet rotor
Dry rotor pumps are used to pump liquids with high pressure. They are best suited for supplying coolant and aggressive media. Unlike wet rotor pumps, in these pumps the liquid does not come into contact with the motor.
Another difference from glandless pumps is the way the pump housing/shaft is insulated. This is achieved using stuffing box or sliding mechanical seals (STU).
Standard dry rotor pumps typically use three-phase, constant speed motors. They are usually controlled via an external electronic speed control system. Today, dry rotor pumps are available with a built-in electronic speed control unit, which, thanks to modern technology can be installed on motors with high output power.
General pump efficiency with a dry rotor is significantly higher than that of pumps with a wet rotor. Dry rotor pumps are divided into three main types:
In-line pumps
Pumps in which the suction and discharge pipes are on the same axis and have the same nominal bore are called in-line pumps. In-line pumps are equipped with standard air-cooled flange motors. This type of pump is considered the most suitable for building systems requiring high power output. These pumps are installed directly on the pipeline. In this case, the pipeline is fixed with brackets or the pump is installed on a foundation or a separate bracket.
Block pumps
Block pumps are low head, constant speed centrifugal pumps with a standard electric motor. air cooling. Fluid enters the pump in an axial direction and exits in a radial direction. Brackets or motor supports are standard on the pumps.
Console pumps
Data centrifugal pumps have an axial inlet and a radial outlet of the liquid from the pump. The pump and motor have independent attachment points. Therefore, they are installed on a foundation slab.
Depending on the fluid and operating conditions, they can be equipped with a STU or a stuffing box seal. The nominal passage of such pumps is determined by the discharge pipe. The suction pipe has a larger conditional passage.
Shaft seal
The shaft can be sealed (in standard equipment or as an option, in the case of cantilever pumps) from the atmosphere with the help of STU or stuffing box seal. Below is a description of these two types of seals.
STU pump with a dry rotor
Sliding mechanical seals
The mechanical seal is based on two rings with carefully polished surfaces. They are pressed against each other with a spring and work together. STUs are dynamic seals and are used to seal a shaft rotating in a liquid at high operating pressures. STU consists of two polished wear rings (eg silicone or graphite), which are pressed against each other by axial forces.
One ring (dynamic) rotates with the shaft, while the other ring (static) is fixed in the housing. A thin film of water forms between the sliding surfaces, serving as a lubricant and cooling agent. Depending on the mode of operation of the pump, several types of friction of the mating surfaces are possible: mixed friction, boundary friction or dry friction, the latter (occurring in the absence of a lubricating film) causes immediate destruction of the surfaces.
The service life depends on the operating conditions such as the composition and temperature of the working fluid.
Stuffing box seals
Good quality synthetic fiber yarns such as Kevlar® or Twaron®, PTFE, porous graphite yarn, synthetic mineral fiber yarn, and natural fibers such as hemp, wadding or ramie are used as materials for stuffing boxes.
Material for stuffing boxes is produced in the form of threads or compressed coils, in dry form or with special impregnation, depending on the purpose. If the material is purchased in the form of threads, you first need to form a ring and give it a shape. Then, the stuffing box ring is wrapped around the pump shaft and tightened with a ferrule.
Mounting types
Permissible mounting methods
In-line pumps are designed for horizontal and vertical installation directly on the pipeline.
Sufficient space must be left to dismantle the motor, pump elements.
When connecting the pipelines, stress and weight of the pipelines must not be transferred to the pump, and the pump must be installed on supports (if any).
Prohibited mounting methods
Mounting with the motor and terminal box pointing downwards is not permitted.
If the motor power exceeds a certain level, the manufacturer should be consulted before installing the pump in a horizontal position.
- Section of a centrifugal pump high pressure
- Characteristics of high pressure centrifugal pump
High pressure centrifugal pumps
These pumps are usually multistage. The flow rate of the pump depends on the size of the impeller and other factors. The pressure in high pressure centrifugal pumps is achieved by using several impellers installed in series. Kinetic energy is converted into pressure partly in the working, and partly in the straightening apparatus.
Due to the possibility of varying the number of stages, high-pressure centrifugal pumps develop a higher pressure compared to low-pressure single-stage centrifugal pumps.
Some pumps have up to 20 stages. Thus, they can provide heads up to 250 m. Almost all high pressure centrifugal pumps that we have described belong to the dry rotor pump family. However, in recent times manufacturers successfully equip them with wet rotor motors.
Special instructions for block pumps
Block pumps must be installed on suitable foundations or brackets.
Installation of a block pump with the motor and terminal box pointing downwards is not allowed. All other mounting methods are considered acceptable.
For details on installation methods, see the installation and operating instructions.
Heating systems with forced circulation increasingly popular with owners country houses. Earlier we already talked about - the main element of such a heating system, today we will talk about how to choose it correctly.
What are circulation pumps made of, their varieties
- corps on which the "snail" is installed;
- contour pipes attached to the "snail";
- electric motor , on which there are terminals for connecting to the network;
- rotor- a rotating structural element (on the one hand, the rotor sucks in the coolant, after which it pumps it into the loop pipes, as a result, the necessary pressure is formed at the pump outlet).
Using a circulation pump eliminates a number of problems. So, if at natural circulation the water in the last radiator is cold, and in the nearby ones it is a little warm, then when it returns, the coolant with a low temperature makes the boiler work more intensively, sometimes even at the peak of its capabilities. Moreover, if mistakes were made in the design of the heating system, then the difference in temperature will be even more noticeable.
Advantages of using circulation pumps
- The requirements regarding the slope of the pipes of the circuit are significantly reduced.
- All plugs caused by temperature differences are eliminated.
- The room is heated evenly, since the coolant will be equally warm in all elements of the system.
- The operation of the boiler is stabilized.
- The pipeline diameter may be smaller.
Types of pumps
Considering the design features circulation pumps were divided into two large groups - with dry and wet rotors.
Dry circulating pumps differ in that the rotor in this case during operation does not come into contact with the liquid - the heat carrier of the system. Such devices are isolated with a special ring, they are characterized by a fairly high efficiency (about 80-85%), as well as a low noise level during operation. Dry pumps are larger than their wet-type "relatives", and installation requires a special piping circuit.
You might be interested in information on how to install
Dry-type circulation pumps are installed mainly in separate boiler houses serving a couple of houses or one object industrial type. Dry rotor devices require regular maintenance.
Unlike them, wet pumps work for years without any maintenance. The rotor in them is in contact with the coolant, only the starter is isolated - a fixed element of the electric motor. The advantage of such pumps is that the coolant is also a lubricant for the rotor, which is the main "secret" of durability and lack of noise during operation. Despite the low efficiency (often no more than 60%), they are convenient and compact, which is why they are so widely used in domestic heating systems.
In addition, by way of connecting the electric motor, circulation pumps are divided into:
- pumps with coupling connection;
- flanged pumps.
Note! If all nozzles of the device (that is, pressure and suction) are located on the same axis, then this design is direct-flow. This means that the pump can be cut directly into the line using a special frame for fastening.
Industrial circulation pumps are somewhat different from household ones.
Prices for the circulation pump
circulation pump
We got acquainted with design features pumps and their varieties, but it's too early to rush to the store for a purchase. You should also decide on the parameters that you need to pay attention to when choosing a particular model. "P , you can read in our article".
Marking
The first thing we must to see, picking up the model you like - this is the marking, which will be under the name. It can be, for example, 32-50. The first number here is the connection dimensions, 32 mm or 1.25 inches. Often pumps are equipped with nuts required dimensions allowing for quick assembly/disassembly.
The second number is the lift height of the pump. In our case, this is 5 m of water column or 0.5 of the atmosphere. There are pumps designed for greater or lesser heights.
You may be interested in information on which one to choose
In addition, there should be a plate on the body that indicates what maximum load should be and at what parameters. The parameters mean performance - there are three positions for adjusting it in the pump. This is the second criterion for choosing a pump.
Performance
All requirements for a circulation pump are closely related. Under performance means the volume of coolant distilled by the pump at a minimum load on it. The higher the performance, the better the model.
In order to find out the required performance, we will use the popular formula:
N / (T 2 -T 1) \u003d Q, where
- T 1 - the temperature of the coolant in the return pipeline;
- T 2 - its temperature in the supply pipeline;
- N is the average power of the heating boiler;
- Q is the performance we need to calculate.
We take the average value of the water temperature in the "return" (T 1) 65–70 ° C, while the temperature in the supply pipeline (T 2) will be approximately 95 ° C. So we can approximately select the required parameters for the pump. It is believed that for every 10 m of pipeline you need 0.6 m pressure, or pump lift.
In addition, there are ready-made thermal standards. According to them, for every 10 m² of heated area, only 1 kW of power is needed. And if, for example, the power of one radiator battery is 200 W, then for 10 m² you will need five sections. But this number of sections is relative, since in most cases their number is larger, “with a margin”. Therefore, we need to take into account the fact that the circulation pump must cope with the supply of coolant to each radiator in the house.
Required power
The electrical power required to operate the pump is another parameter that you should pay attention to when buying. Often this power is negligible - no more than 200 watts. It matters only in cases where permanent use of the pump is planned.
How external factors affect performance?
In addition to these parameters, when buying, we need to take into account the influence of external factors on the operation of the pump, which, of course, take place. First of all, this is the ambient temperature, the amount of thermal energy needed to heat the house and the power of the device depend on it. Sometimes environment affects the pump itself: if it “freezes”, then it will work somewhat worse than if it were “warmed up”.
Note! If the circulation pump is not selected correctly, it may not be able to cope with the load and overheat. Therefore, before buying, we additionally study specifications heating system.
Also, the power of the pump depends on the diameter of the pipeline - the larger it is, the more powerful the device will be required. Moreover, if not water, but antifreeze is used as a coolant, then the circulation pump must be more powerful, because the viscosity of the antifreeze is different. It is good that the range of pumps today is quite wide and allows you to choose a device for literally every heating system.
In order for the device to cope with the load, we must know whether it will constantly work. If this is not the case and the pump will turn on only as a feed to the main system (or to correct pressure), then its high power is not prerequisite . Of course, if we are talking about cutting into a contour with natural ventilation, then the pump will fall high loads. Then, when choosing, we should be guided by the rule "the more powerful, the better." If the pump power is not enough, then the radiators will be barely warm, and the device itself may simply burn out.
Important point! If the pump is designed for a pipeline with a diameter of 1 inch, then you should not install it in pipes larger diameter, albeit with special adapters. Often this weakens the pressure of the water.
About the importance of the brand
There are a great many names of circulation pumps, but this does not prevent all of them from having almost identical characteristics. And if there are significant differences, then they relate mainly to reliability and service life.
The most popular brands today are Grundfos, Speroni, Wilo, ELSO-THERM and Wester. In addition to them, there are a lot of frank Chinese fakes and not only (meaning "real" Chinese goods). The brands indicated by us are considered by consumers to be the highest quality and most reliable. Circulation pumps from well-known manufacturers practically silent. You can make sure that the device is working only by touching it, or by ear, but from a distance of several centimeters. They are durable and can serve you for many years, but have a significant drawback - high cost(it is almost twice as much as less popular models).
Other brands are average. They work well, prices do not bite, breakdowns occur infrequently.
On pumps from China, the opinions of all buyers agree: sooner or later, the devices begin to make noise, the rotor begins to “walk”. Their service life sometimes reaches several years, but in most cases does not exceed several months. They are, of course, inexpensive.
What to choose?
The answer is obvious - anything but Chinese pumps. If funds allow, then buy products from well-known companies, if not, then pumps of the middle price category are quite suitable.
Video - How to choose the right circulation pump?
Frequently asked Questions
1. Will the pipes make noise when using the pump?
It can make noise in pipes only if the device is incorrectly selected or air has accumulated in the line. To remove air, do the following:
- fill the entire system with water;
- we remove the air, using for this purpose the valves on the radiators - “air vents”;
- start the heating boiler and pump;
- we wait for a while, after which we remove the air again;
- check the pressure, fill the circuit with water;
- start the pump and adjust it (if it can be adjusted at all).
2. Can a high pressure pump be used for water supply?
Definitely - no! Although they (pumps) look almost the same, but in the water supply, pumping equipment is used solely to maintain the right pressure if for one reason or another it is not enough.
3. What are pumps made of?
Some parts (shaft, ball bearings) modern pumps made from ceramics. This not only ensures quiet operation, but also significantly increases the service life.
4. Are there hot water pumps?
Yes, there are. This is, for example, circulation GRUNDFOS pump Comfort UP, thanks to which you do not have to wait for the tap to start flowing hot water. Of course, its use will increase the consumption of electricity and water itself.
5. How much energy do the pumps consume?
In most cases, circulation pumps are extremely economical devices that consume as much energy as an ordinary light bulb. Recently, all pump manufacturers have "agreed" to assign labels to products that notify them of their "gluttony", as is the case with household appliances. A classification was developed according to which A-class devices, for example, need no more than 6 watts.
Note! Variable pumps are more economical!
6. How often do the circulation pumps need to be changed?
If the pump is of high quality, then it will last about ten years. Although, as we have already said, a lot depends on the manufacturer itself. In order for your device to last longer, follow all the recommendations regarding operation: choose the right model and install it, avoid airing the line, use only specially purified water as a coolant.
Video - Installation of the circulation pump
