Recirculation pump for hot water. Choosing a DHW circulation pump - expert advice How to choose a DHW circulation pump
DHW pumps are equipment that circulates and recirculates water in a heating system. They fully distribute cold and hot liquid flow. When the unit is installed in the house, high-quality heating is provided, since it constantly moves water in the system with its help.
The circulation pump for domestic hot water ensures the stability of the pressure in the system. For this purpose, water is drained into a reservoir, from which it is supplied to water intake points. Circulation pumps for hot water systems provide their high-quality water supply. They can be used for arranging a closed system. It should contain:
- storage tank;
- locking devices;
- Regulating elements.
After water enters the storage tank, the Grundfos pump provides pressure, which guarantees the continuity of water circulation in the system.
Offers to buy DHW pumps. We have a low price for equipment. If necessary, you can contact the experts who will make the selection of equipment. They make a choice according to the volumes of water in the system. Employees know that they need to select pumps based on their capacity.
Advantages
Our store sells units that have a low level of electricity consumption. We sell equipment in the cities of Moscow and St. Petersburg. Immediately after ordering the unit, it is carried out. Our company provides quality assurance for pumping equipment, which guarantees its excellent performance and long-term operation.
In what cases should a circulation pump be installed on the water supply? What functions does it perform? What kind of devices can be used on the water and how are they selected according to the parameters? Today we have to answer these questions.
Why is it needed
First and foremost: circulation pumps for water supply systems are used only on hot water.
The essence of the problem
The fact is that the cold water circuits are usually made dead-end. Water in them moves through pipes only when drawing water.
Let's clarify: the exception is utility and fire water pipelines of public and industrial buildings, for which SNiP 2.04.02-84 recommends designing ring circuits to ensure peak water consumption in case of fire. However, they also lack continuous circulation.
For a long time, hot water supply systems for residential buildings were also designed as dead ends. This is how hot water supply is arranged in the vast majority of buildings built before the end of the 70s of the last century.
In the late 70s, compact and low Khrushchevs in large cities began to be replaced by high-rise buildings. Engineering systems of buildings with 10 or more floors, for obvious reasons, are characterized by a large extent.
In particular, it became a serious problem in them to ensure the fast supply of hot water to the consumer: after a long absence of water intake (primarily in the mornings), the homeowner had to (and still has to this day, since the old houses have not disappeared anywhere in the province) to drain the water before it heating.
Please note: in the presence of a water meter, a dead-end hot water supply scheme is doubly unprofitable. The homeowner drains cold water for a long time, but pays for it at much higher DHW rates.
Dead-end hot water supply creates two more problems:
- The drop in its temperature due to heat loss on long bottlings and risers. Owners of apartments far from the heating point receive noticeably cooled water, which often does not fit into the requirements of regulatory documents (according to the current SP 31.13330.2012, the temperature of hot water at the consumer should be in the range of 60-75 ° C);
- The actual lack of heating in bathrooms and toilets. In Khrushchevs, heated towel rails are responsible for heating them, opening the hot water supply. As you might guess, they heat up only when hot water is drawn from one of the faucets in the apartment and keep the temperature high for no more than an hour or two a day.
The consequences of the combination of dampness characteristic of a bathroom with a low temperature are well known: stale air, flaking wall coverings and the appearance of fungus.
Solution
That is why, from the beginning of the 80s, new buildings began to be designed mainly with hot water circulation systems, which was enshrined in the same SNiP 2.04.02-84.
In an open heat supply scheme, circulation is realized due to the pressure difference between the heating mains:
- DHW cuts into the supply and return to the water jet elevator, at two points on each thread;
- Retaining washers are installed between the tie-ins - steel pancakes with holes a millimeter larger than the diameter of the elevator nozzle;
Captain Evidence suggests: in this case, the washer creates a pressure drop when water flows through the hole in it, but does not interfere with the normal operation of the elevator.
- Two DHW bottlings are bred around the house. The risers are connected to them in turn, and connected by jumpers on the top floor, forming a closed loop;
- Hot water, depending on the season (and, accordingly, the supply temperature), is switched on according to the “supply-supply”, “return-return” or (outside the heating season) “supply-return” schemes.
Hot water circulation pumps perform the same function: they provide round-the-clock circulation of hot water in a closed circuit.
Circulating pumps for water supply systems are used:
- In a closed heat supply scheme, with the preparation of hot water in heat exchangers using the energy of the heat carrier. Such a system is fed from a dead-end cold water supply, therefore, by definition, it does not have the pressure drops necessary for circulation in the absence of water intake;
- On intra-apartment bottling and DHW connections (with a significant distance from the riser to the points of water intake and heated towel rails);
- In private houses with autonomous hot water preparation (again, at a considerable distance from the boiler, hot water column or double-circuit boiler (see) to mixers or when using bathroom heated towel rails for heating).
Wiring diagrams
How can it look like with a circulation pump? Let's get acquainted with it using the example of an autonomous hot water supply with water preparation in a boiler (electric or indirect heating).
The video in this article will help you learn more about hot water systems with recirculation.
Boiler with three outlets
Before us is the simplest scheme: the DHW supply forms a closed circuit with continuous circulation. Make-up, compensating for water consumption, is provided by connecting the cold water system directly to the boiler.
Captain Evidence suggests: in this case, the boiler must have an outlet for connecting the circulation circuit, which is not available for all water heaters.
Boiler with two outlets
Circulation pump for hot water supply - from an indirect heating boiler without outlet for recirculation
To obtain a stable temperature in the DHW circulation circuit, a three-way thermostatic mixer is used here. To lower the temperature of the water from the primary circuit (at the outlet of the boiler), he mixes water from the cold water supply into it; it also feeds the boiler, compensating for the consumption of hot water.
Curious: the high temperature in the boiler tank is useful in that it disinfects it, preventing the growth of bacteria and the appearance of a specific unpleasant odor in the water.
Pump selection
How to choose the device we are interested in?
To answer this question, you first need to understand how the circulation pump works in the water supply system.
It has two functions to perform:
- To force the water to move, overcoming the hydraulic resistance of a closed circuit. This resistance linearly depends on the length of the circuit and vice versa - on its diameter (the smaller the pipe section, the more it slows down the water). In addition, the hydraulic resistance is strongly affected by the roughness coefficient of the pipes: the smoother the walls of the filling or supply line, the less resistance it has to the movement of water;
Reference: for all types of polymer and metal-polymer pipes, the roughness coefficient is minimal and does not change throughout the entire period of their operation. For steel pipes, it is not only high initially, but also grows over time due to corrosion of the walls and their overgrowth with lime deposits.
- In addition, the hot water circulation pump must provide a certain speed of water movement and, accordingly, a minimum temperature difference between the beginning and end of the DHW circuit.
Hint: from the technical characteristics of the device, pressure is responsible for the first function, and performance is responsible for the second.
In general, when installing hot water in a private house with your own hands, you can do without complex calculations for two reasons:
- The pressure that drives hot water in the DHW circulation system or the coolant in the heating system of an apartment building is only 1-2 meters. The most low-power circulation pumps for water supply have a pressure of 1.2 meters - with a deliberately lower hydraulic resistance of the circuit;
- The volume of the water supply is small, and, therefore, the required productivity is also small. For example, a pipe with an internal diameter of 15 mm typical for a cottage water supply with a length of 100 meters will have an internal volume of only 3.14 (pi) * 0.0075 2 (radius of the internal section of the pipe in meters squared) * 100 (pipe length in meters) \u003d 0.0176625 m 3, or 17 liters.
The minimum capacity of circulation pumps for hot water is calculated in cubic meters per hour and will be obviously excessive.
Practical conclusion: for the hot water circuit of a private house, you can safely buy the youngest circulation pump in the model range of your chosen manufacturer.
Nuance: for hot water, a pump with a brass rather than a cast-iron body is preferable. The instruction is connected with a much larger amount of oxygen in the water of the DHW system compared to heating: the corrosion resistance of cast iron is not absolute, and prolonged contact with oxygen-saturated hot water significantly reduces the life of the device.
Calculation scheme
How to calculate the hot water circulation pump if you want to make sure that its parameters meet your needs?
Here is a relatively simple pump flow calculation scheme, suitable for pipelines up to 20 mm (3/4 in) in diameter:
- We calculate the heat loss in the pipeline. In heated rooms with the indicated diameter, they can be taken equal to 7 watts per meter, in unheated rooms (subject to thermal insulation of the pipe) - 11 W / m. For our example with a 100-meter hot water pipe running through an unheated basement, the total loss is 1100 watts;
- The norm for the temperature difference for the beginning and end of a circuit up to 200 meters long is 2 degrees, over 200 meters - 5-7 degrees;
- Consumption with known heat losses and allowable temperature difference is calculated by the formula V=Q/(p*c*Dt).
- Q - heat loss,
- p is the density of water (1 kg/l);
- c - specific heat capacity of water (1.2 W * h / (kg * K);
- Dt - allowable temperature difference.
For our case, the calculated flow rate in liters per hour is 1100/(1*1.2*2)=458.
Conclusion
We hope that our material will help you select and install a circulation pump for hot water supply. Good luck!
Every home owner wants their home to be comfortable. To do this, it is necessary to take into account every little thing. Many are annoyed by the inability to get hot water right away. This requires the installation of a circulation pump. It will solve this problem, and the residents will not have to waste time waiting for the cold water to finally stop flowing from the tap.
Therefore, this unit also allows you to save consumable resources. It allows you to increase the pressure in the system to the desired value, which guarantees a constant movement of water through the pipes.
Devices of this kind divided into two groups:
- with a wet rotor;
- dry rotor.
Mostly the device of circulation pumps for water supply looks like this:
wet rotor
The devices belonging to the first group differ in that their rotor rotates in the coolant itself. In this case, water acts as a lubricant. The stator is isolated from the rotor by means of a sleeve.
These pumps have their advantages.:
- simplicity of design;
- small dimensions;
- small mass;
- reduced noise level;
- large selection of models.
The disadvantages of such devices include:
- the likelihood of the rotor jamming due to the fact that lime deposits accumulate on its surface over time;
- small range of ambient temperatures in which the pump can be used.
Wet rotor fixtures are usually used in small private homes.
Dry Rotor
Pumps equipped with a dry rotor have their own characteristics. The rotor in this case connected through a mechanical seal to the impeller shaft. It does not come into contact with the coolant in any way.
The advantages of such devices include:
- the possibility of using electric motors of greater power, which directly affects performance;
- wider range of ambient temperatures.
These units also have disadvantages.:
- rather large dimensions;
- higher noise level.
Standard the temperature range at which both types of pumps can operate is 2-110°C.
If the owners of the house leave for a long time in cold weather, turning off the heating, they will need equipment that can work with a coolant that has low temperature. In this case, a non-freezing coolant must be poured into the system.
Run similar device at a temperature in the dwelling -10-15 ° С can be done without hassle, and a pump operating with a normal temperature range may break down in this case.
When selecting a circulation pump for hot water supply, it should be borne in mind that the housings of devices for DHW systems must be made exclusively bronze or stainless steel. The impeller is usually made of heat-resistant plastic.
If you install a unit with a cast-iron body in the DHW system, then, of course, you can save a little. But you don't have to do it, the iron content in the DHW system will increase, and the likelihood that the rotor will quickly seize due to a large accumulation of deposits will increase dramatically. This may damage the electric motor.
To protect the motor from failure when the rotor is jammed, some devices provide a thermal relay. When overheated, they break the power circuit.
On sale there are units that are not afraid of jamming. They are equipped spherical rotor. The magnetic field in this case is transmitted through the conductive parts of the pump in the aquatic environment.
The spherical electric motor, unlike the traditional one, does not have bearings. The chamber in which the rotor is located is separated by a spherical cup made of stainless steel from the stator. That's why such pumps are less susceptible to impurities contained in water, and lime deposits.
To clean the device, you need to disassemble it. In this case, the body does not have to be removed from the pipeline. He will only need disconnect the motor by turning the threaded ring.
To improve system reliability, double pump can be used. It has one impeller, which moves thanks to two electric motors that turn on alternately. Both motors are in the same housing. If one of them breaks, the second will turn on automatically. In the normal state, they replace each other after the same time intervals.
Connecting equipment
Install such equipment not too hard. It must be embedded in any section of the pipeline and connected to the electrical network.
You can embed the unit on the return or direct supply pipe. For example, if the apartment is equipped with a system, it is advisable to connect the pump to the return pipes. This will stimulate the movement of water.
When it comes to long-term DHW pipeline, it is desirable to mount on a direct supply pipe. Then the people living in the house will receive hot water in the amount they need.
Installation of the circulation pump in the water supply system is carried out in several stages:
- Assembly of the pump in accordance with the instructions attached to the device.
- Choice of mounting location.
- Shutdown of water supply.
- Cutting or removing a section of pipe.
- Connecting the unit using flanged or threaded connections.
- Sealing all joints.
- Connecting the device to the electrical network.
- Testing and setting up the device.
It is advisable to mount the pump in your pocket. This is the name of a short pipe outlet cut off by shutoff valves. Then the system will turn out to be the most functional, because it can be turned off and dismantled, if necessary, by reorienting the coolant to the central branch.
When installing the pump, remember that:
- it is undesirable to mount the device before air is removed from the system and it will fill with water. When running dry, the unit may deteriorate;
- when installing equipment with a wet rotor, care must be taken to ensure that shaft is horizontal;
- pump must not be installed. more performance than needed, since this will introduce noise into the system;
- before starting the unit, it is required to properly flush the system;
- need to make sure that the possibility of removing air from the pump and pipes exists. If this is not possible, you will need to purchase a device with an air vent;
- equipment supplied thermostat, it is forbidden to mount next to heating tanks that will overheat the device;
- if the system is closed, the unit must be installed on the return pipeline, since it is there that the lowest temperature is observed.
Launch Rules
After installing the pump, it will need to be started. When doing this, you should follow the steps:
- dry running- the device should not work when there is no coolant in it. This is fraught with overheating of the device;
- water hammer- to avoid it, you must manually fill the pump with liquid before starting. Otherwise, water will flow into an empty vessel, which will damage the blades;
- freezing of water in the equipment case- when not in use, liquid must not be left in it, and it is also forbidden to turn on the device at a temperature not specified in the operating instructions.
If the pump is selected correctly and correctly installed, used in accordance with the instructions given by the manufacturer, then it will serve properly for a long time.
Before the purchase to calculate the necessary parameters of the equipment, it is advisable to contact specialists because it is quite difficult to do it yourself. Then the device will provide the house with hot water and will supply it uninterruptedly.
Circulation pumps can be of two types:
- with a wet rotor of the engine;
- with a dry motor rotor.
If the engine belongs to the first option, then its parts are wetted with a certain liquid during operation, which eliminates regular maintenance. If the instruments have a dry type engine, then there is a need for regular cleaning and lubrication of its parts. At the same time, this engine has the advantage that its working parts wear out less often.
As a rule, the devices are very economical, and therefore beneficial to use. You can switch them only with the help of a conveniently located button, which is located on the terminal box. Circulation pumps are good in underfloor heating systems and for quick space heating, if you urgently need to increase the air temperature. Among other things, it is worth noting that the designers have tried on the external design, making this thing not only functional, but also spectacular.
The price of circulation pumps usually depends on manufacturers, but now you can purchase this product at a bargain price. You can buy such a device in Moscow in our online store, where managers are ready to offer you the most profitable options.
We are all accustomed to the fact that in the hot water supply system, water moves solely due to the main pressure. On the one hand, this is not bad, but such a plumbing scheme has one significant drawback - by opening the tap, we wait until the cold liquid drains, and only after that we enjoy the blessing of civilization called “hot water”. Agree, a little wrong. It is this problem that the DHW circulation pump is designed to solve, which we will talk about in detail in this article - together with the website, we will talk about how the correct hot water supply system works in a private house.
Circulating pump for hot water photo
DHW circulation pump: what it is used for and how it works
The fact that by installing a pump for hot water, you will not wait until cold liquid flows from the tap, you already understood. The principle of operation of this pump remains not entirely clear. It is simple and consists in the device of a closed circuit, through which hot water constantly circulates. That is, a ring along which water makes an endless movement and is periodically heated to a predetermined temperature. A faucet or a mixer can be connected anywhere in this ring.
Anticipating your next question, I will say that hot water does not enter this circuit through a heating device that uses fuel to heat water. This circuit is powered from the heating boiler through a special heat exchanger, called - the water here is heated by. In fact, a battery (coil) is mounted inside such a boiler, upon contact with which water is heated. This is not a flowing water heater - it is a storage boiler that has at least five connection pipes. Two of them are used for connecting to heating, two for hot water circulation (supply and return, so to speak) and one for cold water inflow into the tank.
Recirculation pump for hot water photo
If you describe the cycle of operation of such a unit, then it looks like this. When the tap on the mixer is closed, the water, thanks to the circulation pump, moves in a circle and is heated by the coil to the maximum temperature limit. As soon as you open the mixer, water is consumed - at the same time, fresh cold water enters the indirect heating tank from the water supply, which is immediately heated from the coil. In general, the same thing happens here as in a conventional electric one, only instead of a heating element, it uses a coil.
When and how it is advisable to use a circulation pump for hot water
Such a hot water supply scheme in a house is not always advisable - in short, in small houses with 3-5 rooms it is unjustified. For such cases, the usual double-circuit is suitable - the short length of the hot water supply lines will not make you wait long for the heated water to flow from the tap. Another thing is large houses with several bathrooms and a complex heating system. Here it shows itself one hundred percent with a circulation pump. What tasks are solved in this way?
- First of all, the presence of hot water in the tap is constant - not a second of waiting until you get heated water.
- The second point is the increase in pressure in the system. In large houses, as a rule, pipes stretch for a long distance - the result of a long pipe length is a weakening of the pressure in the system, which compensates for the hot water recirculation pump.
These are the main tasks of the hot water ring circuit. As a bonus, it provides a couple more benefits.
Among other things, the pump itself allows you to save resources. He can do this solely due to the possibility of programming the on-time. Let's just say that hot water is not used at night, which means that there is no need for a circulation pump for hot water supply. Therefore, you need to program it so that it turns on half an hour before you go to the bathroom. What is the savings here? In the termination of circulation - the water in the circuit heats up quickly, and the heat exchanger stops taking heat from the heating circuit. In turn, the coolant in it cools less, as a result of which less fuel will be needed to heat it up to a given temperature.
How to choose a hot water pump
First you need to understand the difference between a heating circulation pump and a DHW pump. It consists of three points. First of all, it is the ability to withstand a certain temperature of the coolant. If heating circulation pumps are able to work with a coolant heated to almost 100 degrees, then DHW pumps can only withstand heating up to 65 degrees. Secondly, pumps for heating are made of cast iron, and pumps for hot water are made of brass. And, thirdly, pumps for hot water supply at home have a smaller power reserve.
At first glance, it may seem that you can install an ordinary one in a hot water supply system - unfortunately, this is not the case. These two types of pumps are not interchangeable, which must be taken into account first of all when approaching the issue of choosing a circulation pump for a hot water supply system.
In addition, when choosing this equipment, it is necessary to take into account the following points.
Also, approaching the issue of choosing a circulation pump for hot water, one should also mention double pumps for hot water - they simultaneously supply the coolant to the indirect heating boiler, and push the hot water heated by it through pipelines. The thing is good, but expensive - separately, these two pumps will cost less.
And finally, I will say a few words about modern pump manufacturers who have already managed to establish themselves exclusively on the positive side. The undisputed leader in this industry today is Grundfos - it supplies the market with economical pumps equipped with several protections. Pumps of this brand are protected against dry running and, as a rule, have built-in pressure sensors. The second manufacturer of pumping equipment worth paying attention to is Wilo. German by origin, which offers circulation pumps for domestic hot water, as they say, for every taste and color - in the range of these products you can find pumps with a mechanical timer, and with electronic control. As they say, for all occasions and for any budget. And an economy option called DAB - despite the low cost, the company produces very high-quality equipment with a rather long warranty period.