How to choose a DHW circulation pump. Circulation pump for water supply: functions, connection diagrams, selection by parameters
- a device designed to pump liquid through the hot water supply system at home. Using this equipment, you can heat the room, supply all taps with hot water. The use of a circulation pump saves on electricity and avoids excessive consumption of water. The main thing is to take a responsible attitude to the choice of a model, choosing a unit that can fully satisfy your needs.
The use of a circulation pump for a hot water supply system (DHW) or heating in a private house
The essence of the circulation pump is the constant distillation of water through the system, which does not allow it to cool down. The installation of such a device will significantly improve the living conditions in a private house if there is a need for a constant availability of hot water, heating the water in the pool or heating.
In houses where water heaters are installed to obtain hot water, you have to drain a decent amount of liquid until hot water flows out, and this significantly increases its consumption. The optimal way out is the selection of a circulation pump that minimizes the differences between centralized and autonomous water supply.
Thus, there are three main tasks that can be solved by installing this equipment:
- Hot water supply;
- Air conditioning;
- Heating.
The principle of operation of the circulation pump: the main pipeline of a closed type running through the entire building, with pipes extending from it to all water supply points, is connected to the boiler.
Hot water circulates continuously through the system, which allows households to get water of the desired temperature at any time, simply by opening the tap. They do not have to drain cold water while waiting for the liquid to heat up. A return pipeline is connected to the tank, so that the unused liquid flows back.
The circulating pump with high performance, has a small size, affordable price, consumes little energy, does not make noise and is easy to install, which makes it more attractive to consumers.
What parameters should be guided by when choosing a pump for hot water in the house
The pump should be selected according to its characteristics, which is the dependence of two indicators on each other:
Pressure
The flow force must be sufficient to ensure all water supply points with good pressure taking into account possible hydraulic losses. The largest value of the hydraulic resistance of the system that the pump is able to overcome is called the maximum head. The head is measured in meters of water column.
Performance
Before choosing, it is necessary to calculate the maximum load of the system and compare it with the pump performance. Usually in the house the value of hydraulic resistance is in the range of 0.1 - 0.2 atm... The highest value of the pumped amount of the coolant per unit of time is the maximum productivity.
Not superfluous in the functions will be protection against lime deposits, low noise level during operation, low power consumption.
Also, when choosing the optimal model, it is worth considering the operating conditions: the type of boiler for hot water supply, the required liquid temperature, the diameter of the pipeline, etc.
The best choice is how to choose the right model
Water circulation device design
There are two types of this water circulation device: dry and wet rotor.
Units of the first type are distinguished by their large dimensions and noise, lack of natural lubrication, since the rotor remains dry (the device is separated from the pumped liquid). But pumps with a dry rotor are characterized by high performance (up to 70%), because the engine is less susceptible to heating from the coolant.
Pumps with a wet rotor, on the other hand, are small in size and practically do not make noise during operation. The impeller and rotor are installed directly in the pumped liquid, which provides both lubrication and cooling, and helps to absorb operating noise.
Due to the accumulation of deposits on the surface of the device, the rotor can jam, you need to regularly inspect the equipment.
The range of temperatures at which the unit is able to function normally is much wider for pumps with a dry rotor than with a wet one. In connection with these "dry" is more often used in industry, and "wet" in private houses, especially since the latter are cheaper.
In addition, there is a division according to the type of connection: with flange and coupling.
Models with suction and discharge nozzles in line can be flush-mounted into the system. Fastening takes place using special frames.
Unit performance
Pay attention to the following factors:
- You should not buy a unit whose performance is much higher than the value you need. In this case, energy overruns are possible. For a private house, a device with a pressure of 3-4 meters is sufficient.
- Choosing a model is from proven and well-established manufacturers on the market.
- When buying a device, you should take into account the ambient temperature, in order to avoid freezing, which will lead to malfunctions.
- The larger the diameter of the pipeline, the more powerful the pump will be required.
If it is assumed that the unit is not permanently used (seasonal or as a recharge of the main system), no great importance should be attached to its capacity. The load on it will be small, which means it makes no sense to overpay.
- the device must be installed on a pipeline of the diameter for which it is intended. Otherwise, you will have to sacrifice pressure;
- the presence of a timer will allow you to set the pump operation mode, and it will automatically turn on at the time of the greatest liquid consumption.
Modern models are equipped with special sensors that save water and energy: thermostat, timer, auto-settings.
Cost calculation
The circulating device can be purchased from 5000 rubles and more, depending on the technical characteristics and brand of the manufacturer.
Grundfos brand pumps - prices in the range of 8000 - 15000 rubles at a head of 1.20 m.w., DAB 7000 - 9000 rubles at a head of 1.60-5.70 m.w., Wilo 5000-7000 at a head 2-6 m.w.st. respectively. The price of the consumed energy is approximately 720 rubles or 200 kW per year.
These small costs will allow you to use hot water at any time, heat the room and even warm up the water in the pool.
The use of a circulation pump allows you to significantly reduce the overconsumption of water, because now you do not have to wait and drain the water while it warms up.
Learn more about the circular pump by watching the video:
Special functions allow you not only to save fluid consumption, but also the use of electricity: various thermostats, timers, sensors allow you to regulate the operation of the device, turning it on and off at the right time.
In a residential building, there is a need to circulate hot water. For the circulation of water in a closed circle, as well as for the efficient functioning of the hot water supply system, a pump for hot water supply is used. Thanks to DHW circulation pumps, there is no need to wait for the hot water flow from the boiler. This is especially effective if the distance between the water heater and the tap is large. Such a unit significantly saves water.
A circulating or recirculating pump ensures the constant movement of water through the pipes. With its help, the pressure in the main pipelines rises to the required level. The device allows you to receive hot water of the same temperature and pressure on all floors of the house, even if several taps are open at the same time.
1 Device
The DHW pump is manufactured according to the standards. The noise from the operation of the unit does not exceed 55 dB during the day, and 40 dB at night.
The DHW circulation pump is produced in small dimensions, which simplifies installation. Installation is carried out in a pipeline rupture, removal from the general system and the use of a bypass is not necessary.
The main elements of centrifugal pumps for water circulation are the shell, the impeller and the motor. Water is supplied to the center of the impeller, spun by the engine, as a result of which it moves with the outer edge of the shell to the outlet pipe.
Characteristics of pumps for DHW recirculation:
- performance;
- generated pressure, head;
- power;
- control method (timer or temperature sensor).
These units do not need high power and productivity, since water is pumped through pipes with a small internal volume, at a low speed. For pipes with a length of 40-50 meters, an apparatus capacity of 0.2-0.6 cubic meters is sufficient. meters per hour.
The operation of the pump in a stable mode is ensured by a power consumption of 5 to 20 W.
It is important to find the right head. For a one-story house or apartment, a pressure of 0.5-0.8 meters of water column is enough. For a multi-storey building, the pressure should correspond to the number of floors, and even with a margin.
1.1 How it works
The recirculation pump works according to the following principle:
- The main piping through the house is connected to the heating equipment.
- Pipes with a small diameter go from the heater to the parsing points.
- The installation of a circulation pump ensures constant circulation of heated water, as a result of which, when the tap is opened, a hot stream immediately flows.
To return unused water to the heater, a return line must be installed. Water heating equipment has three connections:
- from the first branch pipe, heated water enters the water supply circuit;
- the second branch pipe facilitates the flow of liquid from the DHW circuit to the tank;
- cold water flows through the third pipe, which replaces the used hot water.
1.2 Scope
Recirculation pumps are used not only in DHW systems. They are also used for:
- accelerating the circulation of liquid in radiator heating systems;
- liquid circulation of extended underfloor heating systems;
- in multi-storey buildings to maintain the required pressure of the heating system.
2 Control method
Constantly maintaining the circulation of hot water in the pipes is unjustified and uneconomical. Hot water is not used all the time, for example at night or when no one is at home.
If the piping is correctly performed, thermal insulation is necessarily applied. Therefore, water entering the pipes does not cool down quickly. So periodic operation of the pump is sufficient, it will also take the load off the pump and the DHW system.
There are two control methods - by the readings of the temperature sensor or by the timer. The principle of operation of these options is significantly different.
2.1 By temperature sensor
The temperature sensor is immersed in water inside the circuit pipe. The pump control unit is based on its readings. As soon as the water in the pipes cools down to the set temperature value, the pump turns on. Thus, the water remains constantly heated, and the load on the equipment is reduced.
2.2 By timer
The timer sets the time after which the control unit turns the mechanism on and off. In order to choose the right on and off mode, you need to know and take into account the parameters of the DHW system. These include the length of pipes, their volume, thermal insulation and heat loss.
The timer has another advantage - scheduling the pump for a day or for the whole week.
3 Varieties
There are two types of DHW circulation pumps:
- reverse (installed on the pipeline for the return water supply);
- supply (mounted on pipes for supplying hot water from the heater).
Both of these types are used in closed loop systems.
Due to the design features, the units providing hot water supply are divided into two types:
- Wet rotor units. In this type of recirculation pump, the pressure head is located inside the pumped liquid. Water acts as a lubricant and cooling agent. Such devices are distinguished by a long service life and low noise operation. Maintenance-free, affordable. The disadvantages of this equipment include low efficiency (40-45%), as well as the method of installation only in a horizontal position. Used in small houses for heating and water supply systems. Able to create pressure up to 1.5-3 atm.
- Dry rotor devices. In such pumps, the power plant and the pumped liquid are separated from each other. Dry rotor circulation pumps require periodic maintenance, during which lubrication is carried out. There is a built-in fan to cool the engine. The cost of maintenance and the device itself is higher than a unit with a wet rotor. But productivity is also higher, it is about 70%. The pressure is increased to 5-10 atm. The disadvantages include increased noise levels during operation and high cost. They are used in industry and for centralized heating and water supply systems.
Depending on the gearshift speeds, there are such models:
- multi-speed - perform switching of the operation algorithm. Used in houses with a large area, more expensive;
- single-speed - have reduced performance, suitable for domestic use. Easy to install, work independently.
3.1 Model selection
The main task of the recirculation pump is to maintain the optimal speed of hot water through the pipeline, at which the temperature of the water in the return pipe will be within the required range. The choice of the unit is made taking into account the following parameters:
- the maximum head of the liquid, which is measured by the height of the water column. The pressure affects the pressure and temperature of the water circulating through the pipeline;
- fluid consumption. The formula calculates the temperature difference between the supply and return water. The power of the heating equipment is divided by the received number;
- heat transfer of the heating system. It is calculated depending on the area of the room that is heated and the expected heat loss.
It is necessary to select a recirculation electric pump taking into account these parameters. This is the job of an experienced designer.
4 Equipment connection
This equipment is installed on direct or return pipes. For a warm floor, it is better to connect a pump on the return pipe to stimulate the movement of water.
For DHW pipes with a long length, it is recommended to install on a direct pipe. Then all residents of the house will receive hot water in the right amount.
Stages of installing the circulation pump:
- assembly of the mechanism using the attached instructions;
- choosing a place for installation;
- disconnection of water supply;
- cutting and removing part of the pipe;
- connection of the pump using flange or threaded connections;
- sealing joints;
- electrical connection;
- setting up the work and testing the mechanism.
For maximum system functionality, the pump is recommended to be installed in a pocket. This is a pipe bend cut off by shut-off valves. In this case, the system, if necessary, is easily turned off and dismantled, and the coolant is reoriented to the central branch.
When installing the pump, remember the following nuances:
- the device is mounted only after complete removal of air from the system and filling it with water. Dry running will damage the device;
- when installing devices with a wet rotor, the horizontal position of the shaft must be observed;
- it is impossible to install a pump with a higher than necessary performance. Otherwise, noise will appear in the pipes;
- the system is well rinsed before starting;
- you need to make sure that it is possible to remove air from the pipes and pump;
- equipment with a thermostat cannot be mounted near heating tanks, they will overheat the device;
- with a closed system, the unit is installed on the return line, where the water temperature is lowest.
4.2 Model for DHW WILO STAR-Z NOVA (VIDEO)
4.3 Launch rules
After the installation of the unit, start-up is carried out. To do this, follow these steps:
- water pipes are filled with water and static pressure is created in the system;
- an automatic air vent or valve removes air from the mechanism;
- the heater turns on;
- the pump turns on and the circulation of water through the pipes is checked;
- after a few minutes of operation, the pump turns off and the remaining air is removed from the system.
4.4 The most common types of breakdowns
Failure can occur for several reasons:
- dry running - it is forbidden to operate the pump without a coolant;
- hydraulic shock - to avoid it, the pump is filled with liquid before manually starting;
- freezing of water - when the device is not in use, the liquid is drained.
With proper installation and operation of the pump, it will work properly for a long time.
In an autonomous hot water supply (DHW) system, a circulation pump is often used. If the heat source is the boiler, and a significant portion of hot water accumulates in the boiler, then the pump constantly pumps water from the storage tank to the heat exchanger and vice versa. If we mean a recirculation pump for hot water, then it eliminates the greatest disappointment of autonomous DHW systems - it makes it so that when the tap is opened it does not have to wait long for hot water to go from the boiler to the consumer through the pipes.
Principle of operation
A recirculation pump is not necessary at all, but it significantly increases comfort and even the quality of hot water. Its main task is to pump water through a pipeline in a closed loop from the boiler to the intake points and back. For this purpose, devices with low performance, low noise and low power consumption are specially developed. The main requirement for pumps is resistance to high temperatures, stable operation, provided that the water is heated to 65 ° C.
Collectively, hot water recirculation pumps are still different from heating pumps. The latter are designed for temperatures up to 90 ° C and with significantly higher performance. At the same time, interchangeability is irrelevant. If desired, the pump from heating can be used in DHW recirculation, however, on the contrary, the pump cannot be used.
The circulation pump is especially in demand in houses with an area of more than 200 square meters, where the boiler is located in a separate room or basement, and there are several points of water intake located around the house. It will take a long time to wait for cold water to drain from the pipes, which significantly increases the consumption. If the water in the boiler heats up to 65-80 ° C, then almost all pathogenic bacteria die, but in the pipes where the water cools down, they are able to actively multiply.
Regular pumping of water through pipes eliminates these problems at the root. However, due to heat loss in the pipes, the load on the boiler or water heater increases, so that the installation of a recirculation pump has a lesser effect on savings and is primarily responsible for the comfort of the residents.
To use a recirculation pump, the domestic hot water distribution must be carried out in the form of a closed circuit, closed on the boiler. All water intake points are already connected from it. If you take water from the upper part of the boiler, then this will be considered the beginning of the circuit, then the pump is installed at the second inlet to the boiler, located in the lower part of the storage tank, on the same level with the inlet to the cold tap water supply.
The circulation pump must be installed in conjunction with a non-return valve, which will prevent the backflow of water in the circuit, because in this case only cold water will flow through the pipes, tied to the bottom of the boiler and the inlet water supply.
Specifications
In the list of the main characteristics of circulation pumps:
- productivity, m3 / hour (liter / min);
- head created pressure, meters or Pa;
- power consumption, W;
- control method (timer or temperature sensor).
The power and performance for the recirculation pump needs little. It is necessary to pump water only in tubes with a small internal volume, moreover, at a low speed. An apparatus with a capacity of only 0.2-0.6 cubic meters / hour is enough to constantly maintain the temperature of water in pipes up to 40-50 meters long.
The pump's consumption is also low at 5 to 20 watts. This is enough for stable work and the fulfillment of the assigned task.
It is more important to choose the correct pressure generated by the pump. More often, in a house or even more so an apartment, the wiring is performed on one floor at the same level, then a pressure equivalent to 0.5-0.8 meters of water is sufficient. However, if it is necessary to ensure trouble-free circulation of water in a house with several floors, then the pump must also cope with the rise of water to a given height, moreover, with a margin. The pump performance directly depends on the actual installed load.
Design
Centrifugal pumps are used to circulate the water. The main elements in them are the shell, the impeller and the engine. Water is supplied to the center of the impeller. It is spun by the engine, and under the influence of centripetal force, the water moves with pressure along the outer edge of the shell to the outlet.
For a recirculation pump, the advantages are quietness and small dimensions. Therefore, small pumps are used mainly with a wet rotor type. The rotor is the internal movable part of the engine mounted on the same shaft as the impeller. Under the influence of an alternating magnetic field from the stator coil, the rotor acquires a rotational motion.
The wet rotor is completely immersed in the pumped medium. Water acts as a heat sink and, at the same time, as a lubricant for the thrust bearings. The presence of water around the moving parts of the engine reduces noise and vibration during pump operation.
Control method
It is perfectly acceptable to constantly maintain the circulation of hot water in the pipes, but this is uneconomical and unjustified. Hot water is not used all the time. At night, while all the residents are sleeping, it is useless to maintain hot water in the pipes, the same applies to the time when everyone is at work or school.
If the piping is done correctly, then thermal insulation is necessarily applied, so that once it gets into the pipes, the hot water will not cool down instantly. Therefore, there is no need to pump water all the time from the boiler to the pipes and vice versa, periodic operation of the pump is enough, which reduces the load on it and the DHW system as a whole. There is no need to talk about saving electricity, since the consumption of the recirculation pump is low.
There are two main control methods used:
- according to the readings of the temperature sensor;
- by timer (schedule).
Both options are in demand, although they differ significantly in their principle of operation.
Temperature sensor
Grundfos UP 15-14 BT 80 In this case, the pump control unit relies on the readings of a temperature sensor immersed in water inside the circuit pipes. The pump resumes as soon as the water has cooled down to a certain temperature threshold. This approach significantly reduces the load on the equipment, constantly keeps the water in the pipes heated. In addition, the safety of DHW is increased. Having established a sufficiently large response threshold, water is more often pumped through the boiler, where it is additionally heated and disinfected.
By timer
Grundfos UP 15-14 BU The control unit alternately turns on and off the pump based on the time delays set in the settings. Knowing exactly the parameters of the hot water supply system, the length of pipes and their internal volume, thermal insulation and average heat losses, it is possible to choose the optimal time for which the water will not have time to cool down. The pump is switched on by a timer signal and pumps all the water. In this case, the duration of operation is also calculated based on their volume of pipes and pump performance.
Another advantage of the timer is the ability to schedule the operation of the recirculation pump for a day or even a week. It is in this case that the downtime is taken into account when hot water is not used.
Installation diagrams
Depending on the number of connection points and the length of the pipes, the method for connecting the circulation pump and the piping is selected:
- serial connection with one circuit;
- parallel connection with a collector.
In the first case, all points of water intake are connected in series and in one circuit. This is beneficial if you can easily combine bathrooms and a kitchen with one water pipe without unnecessary material costs and a fairly short route. There is only one feature that concerns the pressure pump more than the circulation pump. If several points of water intake are open at the same time, then the pressure in each of them will be divided equally. Alternatively, this is solved by installing a gearbox on each crane and choosing a more powerful pump.
Parallel connection solves the problem of water pressure and distribution with a manifold group and a compact arrangement of gearboxes. In this case, recirculation pumps must be installed in each separate circuit or one more efficient pump must be selected for all groups at once. Such a wiring is necessary if there are several bathrooms in the house, which are far from each other and from the kitchen, or when, with a serial connection, the total length of the route becomes too long.
The one who got up early is the first in the shower. Turn the handle of the mixer and wait for hot water to pour out of the watering can. A common situation for a private house. During the night, the water in the pipes had time to cool down, and until you get the right temperature, you will have to watch how the liters drain into the sewer. Clean, by the way, drinking water. In general, complete disrespect for nature, and for your own wallet. But everything is fixable.
As you know, hot water in a private house has its own circuit. And there is nothing surprising in the fact that the liquid cools down in the pipes while you sleep, or no one from the household is at home for a long time. But for thrifty owners, accustomed to counting every ruble, to drain cold water, expecting hot water, is a luxury. In order not to wait and save money, you can solve the issue by installing a circulation pump in the DHW system. But which one and how to choose it?
Devices can be either permanently running or automatic. With "wet" or "dry" rotors. Be that as it may, the main parameters when choosing it are flow rate and pressure. Plus, in units designed for the hot water system, there is another important indicator - power. It depends on how much electricity the pump will consume.
It is best to entrust the selection to a specialist. Of course, the consumer can calculate everything on his own, spending time on this. For example, use the norms and standards of the code of rules (SP), building codes and regulations (SNiP), Santechproekt standards and even DIN (German Institute for Standardization). Each of them calculates the instantaneous water consumption in a different way at the current time. Therefore, in our country, specialists use the standards that are closer to them.
However, when choosing a pump for hot water supply, it is necessary to know the height and length of the pipeline in order to understand what hydraulic resistance will be in the system along the length, as well as local resistances. The power of the pump and its ability to overcome resistance depends on this so that the water reaches each of the points of draw-off. We must not forget the maximum admissible value of the outlet head. As a rule, this is no more than 4.5 atmospheres for hot water supply in the plumbing area. Otherwise, the pressure will break your faucet, shower or mixer.
So. Which pump should you choose? It is difficult for the consumer to understand the wide range of models on the market. Professionals recommend starting from one criterion. And that's quality. Reliable, having thousands of positive reviews, and besides, not expensive - this is, without a doubt, a pump from the GRUNDFOS company (Russia). The manufacturer can offer several excellent models for high-quality hot water supply to your home.
First of all, a UP type pump with an asynchronous motor. The device has a built-in timer and thermostat. The user just needs to set the time 15 minutes before the time at which he usually takes a shower, for example, 7 in the morning, and not to worry about anything else. The pump will turn itself on at 6:45 and run hot water through the system. By the time the tap is turned on, hot water will already circulate throughout the system. But the thermostat is responsible for maintaining the water temperature you need in the system. If it becomes colder than usual, the pump will start automatically working and will do this until a comfortable value for a person is reached.
An even more interesting model from the GRUNDFOS company is the UP PM pump with a permanent magnet motor and its modification UP PM with AUTO function ADAPT. This is a unique feature developed by the engineers of the Danish concern GRUNDFOS. Its main feature is that the electronic unit of the pump memorizes the schedule of hot water consumption of people living in the house and builds work on its basis.
How does it work in practice? After installation - the pump must be installed on the return pipe, and the external temperature sensor on the hot water supply pipe - the device operates in temperature mode for two weeks. During this time, all events occurring with the cranes are recorded. Namely, how many times a day, and at what time the water points were involved. Whether it's the frequency of hot water consumption on weekdays, or how consumers use hot water on Saturday and Sunday. After this time, the information received is analyzed. Taking into account all possible nuances, electronics determines the optimal model of work. Subsequently, the pump starts working 15 minutes before the supposed opening of the tap. This way, the pump only starts up when really needed and provides instant hot water. Thus, real savings in energy resources and money are achieved.
Separately, it must be said about the UP PM engine. Compared to asynchronous UP, the permanent magnet motor consumes much less electricity. If UP consumes 25 watts, then UP PM is only 8. Three times less! In addition, it meets the European requirements for energy efficiency EuP 2015. It is practically silent and durable. The engine is able to work effectively with water, the hardness of which is estimated at 4.99 degrees of hardness. It has a spherical rotor and a self-aligning bearing that is lubricated by the pumped liquid. The pump body of this series is made of a material that is most suitable for working with drinking water - brass. Models are available with built-in check and shut-off valves.
The manufacturer also made sure that the consumer did not experience any inconvenience during routine inspection and cleaning of pump elements from scale and other debris. You do not need to dismantle the equipment for this. It is enough to block the water access with stopcocks and separate the electronic part of the pump with the impeller from the pump volute. This is not difficult to do, since the connection is threaded. In addition, it is even easier to carry out inspection in models with built-in check and shut-off valves - there is no need to install shut-off valves. The valves will automatically restrict water access to the pump.
Circulation pumps for hot water supply systems from GRUNDFOS (Russia) meet the highest safety and energy efficiency requirements in Europe. By purchasing any model of equipment, the consumer gets comfort, convenience, practicality and economy for a reasonable price. This is why the purchase of Grundfos pumps should rather be seen as a good investment that will soon pay off.
It remains to add that Grundfos (Russia) is one of the few on the market that takes care of customers throughout the entire warranty period of the equipment. The project of the SERVICE 24 company will help to solve all possible difficulties in the operation of pumps. In the event of a problem, the buyer just needs to call the hotline and the operator will solve your problem by phone. If this is not possible, a specialist from the nearest service center will be organized to the specified address. An expert will find out the cause of the problem. A minor problem will be eliminated on site, and in case of significant damage, the pump will be replaced with a new one. Of course, all work for the client is free. But only on condition if the case is recognized as a guarantee. Today the Service 24 program operates in 33 Russian cities. In the future, it is planned to expand the territorial zone.
Lack of hot water pressure when opening a tap is a fairly common phenomenon found in private and apartment buildings. One of the most effective solutions to the problem is a DHW circulation pump.
Installation of pumping equipment on hot water supply, according to existing building codes, is optional for rooms with a heated area of up to 500 m², in practice, installation may be required even if there are 2-3 separate hot water points.
Why do you need a pump for DHW
The DHW circulation pump is designed to create pressure and constant circulation of water in domestic water supply systems. After opening the tap, you have to wait a long time until the water becomes hot, and the farther from the DHW inlet the taps are located, the longer it takes. The pressure in the system does not always meet even the minimum requirements, preventing normal washing.DHW circulation pumps are installed for the following purposes:
- Ensure stable system pressure- for this, hot water is taken into a special buffer tank, after which it is supplied under pressure to the water supply points.
- Provide instant hot water- the circulation pump for hot water supply is connected to a closed pipeline. The water is constantly in motion. Thanks to circulation, the cooled liquid mixes with the heated one. As a result, immediately after opening the tap, hot water is supplied to the consumer.
What is the difference between circulation pumps for heating and DHW
The use of a circulation pump in a hot water supply system has its own characteristics that differ from the use of stations in water heating circuits. For this reason, the circulation equipment for each system is not interchangeable.The differences between circulation pumps are as follows:
- Performance- heating pumps have a larger power reserve, which is simply meaningless for hot water supply. If necessary, you can put circulation equipment for heating systems on water, but not vice versa. Some manufacturers offer tandem pumps with two electric motors specifically for this purpose. The module is simultaneously connected to DHW and heating.
- Casing - another difference between models for heating, from pumps for domestic hot water, is the material of the casing. In stations for hot water supply, the structure is made of brass, the top is closed with a thermal insulating casing. Cast iron appliances are used for heating.
- Heat carrier temperature. If you pay attention to the technical characteristics of the pumps, you will notice that the equipment for hot water supply can be operated at an operating fluid temperature of no more than 65 ° C. In heating systems, the coolant is heated to 90-95 ° C.
How a circulation pump works in a hot water system
The principle of operation of the DHW circulation pump is almost identical to that used in heating systems. The purpose of the installation is to increase and stabilize the missing water supply pressure.Circulation pumps in domestic hot water systems operate as follows:
- A closed DHW system is installed, consisting of: a storage tank, shut-off and control valves, pumping equipment and a circuit connected to the taps.
- Hot water is drawn into the container. The pump creates the required pressure by forcing a certain amount of water to circulate constantly in the pipeline circuit.
- When the tap is opened, the consumer immediately receives hot water under pressure, sufficient to take a shower, quickly fill a bath, etc.
In addition, there is a risk of dry running. The coolant plays the role of a lubricant. Without lubrication, bearings fail instantly.
Circulation pumps used in hot water supply systems in multi-storey residential buildings are often called booster pumps, since their task is mainly reduced to creating sufficient pressure in the water supply system.
How to choose a pump for a DHW system
Finding a circulating pump for hot water can be difficult, even for a professional. During the selection, several factors are taken into account:- Technical characteristics of pumping equipment.
- Additional functions.
- The company of the manufacturer.
The most convenient to use are models with electronic control. The pump is supplied complete with a thermostat built into the housing. Automation independently examines the intensity of water consumption and, based on the results, selects the required operating mode. The on-off timer allows the module to autonomously switch to "night mode" to save energy.
The average pump life is 7-9 years. In practice, the station, at moderate loads, is guaranteed to work for at least 10 years.
How to calculate the pressure of the DHW pump
An accurate calculation of the pump parameters can be done only after obtaining the following data:- The workload of the water supply system.
- Sufficient flow force.
- The average water consumption for the point taken into account is 150-180 l / h. Accordingly, in a house with two bathrooms and a kitchen, you will need to install a pump with a capacity of at least 0.7 m³ / hour. When calculating, it is necessary to take into account the hydraulic resistance of the DHW system, which for a private house is in the range of 0.1-0.2 atm.
- Head - The height and length of the water pipe also affects the calculation. It is generally accepted that for 0.6 m of the water column, there are 10 running meters of the water circuit. If the technical documentation of the pump gives the parameters of a head of 4 m, this is enough for a water circuit with a length of 60 running meters.
Calculations for the organization of hot water supply with a circulation pump in an apartment building and large cottages should be carried out by the design and installation organization, which will be responsible for the operability of the system.
Which firms produce pumping equipment for hot water supply
There are about a dozen different companies that manufacture pumping equipment specifically for hot water supply. The cost of the pump varies depending on the manufacturer and technical characteristics, from 5 to more than 100 thousand rubles. It is not recommended to purchase cheap modules, since often a low-quality fake is broken due to a low cost.The best manufacturers of pumps for hot water supply are:
Domestic manufacturers focus on the production of equipment for heating systems.
Installing a circulation pump in the DHW system
Installation of the pump in the DHW system must be carried out in accordance with the manufacturer's recommendations and existing building codes. Installation work is carried out as follows:- Place of installation of the DHW circulation pump - the module is mounted on the return line. This arrangement prevents air from entering the station - airing leads to a decrease in the performance of the system. For this reason, the pump should be installed exclusively on the water supply return.
- A check valve is installed immediately after the pump and in front of the storage tank. Shut-off valves are installed in front of and after the station.
- The mains connection is made via a UPS for power supply. After a power outage, the uninterruptible power supply continues to provide autonomous operation of the equipment, for from several hours to a day. (how to choose the right UPS for pumping equipment).
- To evenly distribute the pressure, a complex DHW control system is installed, including several distribution manifolds and special pressure reduction valves.
- Do not start the electric motor at idle speed. After the installation of the pump in the hot water supply system has been made, the water circuit is filled, a test run and a functional check are performed.
- Maintenance - pumps with a wet rotor have a simple design, so they do not need to be inspected and repaired throughout their entire service life. The filter will need to be cleaned and replaced from time to time. Periodicity of maintenance of the pump with a dry rotor, every 2 years. During the work, the lubricant is changed, the body is cleaned.
