Reading 6 min.
Appliances that provide hot water are called DHW circulation pumps. Prevents stagnation of water in the pipeline. Provide sufficient pressure at the taps (taps, shower).
PURPOSE OF DHW PUMPS
The devices are designed to supply water in water supply systems. The auxiliary function of the aggregates is to prevent diseases of the population. At water temperatures of up to fifty degrees and low circulation, legionella bacteria multiply. At a liquid temperature of sixty degrees and its circulation, bacteria die. The device, accelerating the liquid, prevents the development and reproduction of these microorganisms. The liquid does not cool down and does not stagnate, which means it is safe for use by residents. And residents enjoy sufficient pressure in the taps of their home.
The devices regulate the process of water supply operation, selecting an individual mode for the time of day and year. Thanks to the adjustment function, the devices make water systems energy efficient. maintain a constant temperature of the liquid by mixing cooled water with hot. Water is supplied to the tap immediately and at the required temperature.
TYPES OF PUMPS FOR DHW
By the type of rotor, the devices are divided into dry and wet rotor types.
Sukhoi is distinguished by a high level of efficiency - seventy percent. The noise level is higher than that of a wet type of pump. To increase the comfort of use, it is necessary to place the device in a separate room. Not all users have the ability to host.
The wet rotor runs quietly with an efficiency of forty-five percent. The service life reaches fifteen years. Maintenance free.
Circulation and Recycling Capabilities:
- circulators are distinguished by an increase in the speed of fluid movement. Such devices do not have a filter for cleaning the liquid;
- Hot water recirculation machines are used to increase the speed of the liquid and to reuse it. The hot water recirculation pump is equipped with a cleaning filter. The recirculation pump supplies hot water from the heater to the tap;
- hybrid mechanisms are used for the purpose of circulating and recirculating fluid. Supplied with a cleaning filter.
By location relative to the highway:
- working in a horizontal position;
- working in an upright position.
DIFFERENCES OF DHW DEVICES AND HEATING DEVICES
The design of both types of pumps is similar, but there are differences.
By temperature:
- hot water supply devices are operated at liquid temperatures up to sixty degrees;
- heating devices work with liquid temperatures up to one hundred and forty degrees.
Performance:
Manufacturing material:
- brass body material for hot water stations;
- cast iron material for heating stations.
Types of devices suitable for hot water supply:
- sump pumps are operated when the fluid source is contaminated. Water with a particle size of up to 1 cm is pumped in. The drainage mechanism can be submerged or surface type;
- circulation pumps for increasing the pressure of hot water increase the pressure in the pipeline. The pressure boosting pump is installed without a foundation. Small dimensions, noiselessness and economical power consumption are the advantages of the devices. The pump for increasing the pressure is a centrifugal apparatus with two or three operating speeds. The boost pump is operated in clean water.
RULES FOR SELECTING APPLIANCES FOR DHW
When choosing a pump for hot water supply, take into account the operating conditions, design and requirements for the characteristics of the water supply.
According to their design features, hot water pumps are divided into dry and wet rotor.
Advantages and disadvantages of types of rotors:
- the impeller of wet types is located in a water environment. Hot water is used as a lubricant and cooling agent. The operating period of the devices is fifteen years. The absence of noise effects during operation is another advantage of the mechanisms. Apparatuses of this type are more profitable in terms of price policy than dry ones. They are maintenance-free and rarely fail. The efficiency is lower than that of dry devices and is forty-five percent. The device can only be installed horizontally;
- dry-type devices do not come into contact with liquid during operation. This feature negatively affects the operational ability of mechanisms. Lack of lubrication and cooling causes frequent breakdowns. To prevent breakdowns, the pump undergoes frequent maintenance and the structure is equipped with a fan. The advantage of mechanisms in the efficiency of seventy percent.
Selection by characteristics:
Manufacturer's name:
there are a large number of manufacturers of pumps that provide hot water supply with pressure. But not all manufacturers make high-quality devices.
The main criterion for choosing a device by manufacturer is a name proven over the years.
- Wilo: a manufacturer specializing in the manufacture of pumps. The Star-Z model creates pressure in the tap and shower;
- Grundfos is engaged in the production of pumps of various types and models. The UP model is used for water supply and heating systems (dual model). The device is equipped with a wet rotor. The wet rotor provides a long service life without maintenance. The type of rotor ensures quiet operation of the device, while the efficiency is 45 percent. Liquid circulation reduces temperature losses;
- the German manufacturer Vortex is distinguished by its maintainability and high performance. The BM152 model stands out for its small dimensions, high performance and quiet operation;
- the Espa PA 1C model with a wet rotor is mounted in a vertical position. Pumps cold and hot water. The temperature range of the working fluid is up to one hundred and twenty degrees Celsius.
DHW RECIRCULATION PUMP WILO STAR-Z NOVA (VIDEO)
HOT WATER PUMP INSTALLATION
The installation diagram is shown using a circulation unit as an example.
To ensure the points with sufficient pressure, the apparatus is installed on the direct feed pipe.
Installation steps:
During installation, the following rules are observed:
- wet-look devices are mounted horizontally;
- for comfortable use, the pump power is selected according to the needs of the system;
LAUNCH RULES
- the pipeline is filled with water and pressure is created;
- air from the pump is vented with a screw;
- the boiler or boiler turns on;
- the device turns on. The process is controlled;
- after operation for four to five minutes, the air is released from the disconnected device.
For the productivity of the system and ease of repair and disassembly, the pump is mounted in a branch pipe. During the repair, the water supply system will fully function.
To prevent breakdowns, observe the operating rules:
- do not use the pump dry;
- to prevent deformation of the blades, before starting, the pump is filled with liquid;
- the pump is used in compliance with the temperature regime;
- The centrifugal pump for hot water cannot be used in heating systems due to insufficient power.
Observing the rules of operation, the hot water pump will serve without breakdowns and maintenance for five to ten years.
We are all accustomed to the fact that in the hot water supply system, water moves exclusively due to the main pressure. On the one hand, this is not bad, but such a water supply scheme has one significant drawback - by opening the tap, we wait for the cold liquid to drain, and only after that we enjoy the blessing of civilization called "hot water". Agree, a little bit 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 tell you about how the correct hot water supply system works in a private house.
Circulation 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 a cold liquid flows from the tap, you already understood. Only the principle of operation of this pump remains not entirely clear. It is simple and consists in a closed circuit device through which hot water is constantly circulating. That is, a ring along which water makes an endless movement and is periodically heated to a predetermined temperature. Any place on this ring can be fitted with a tap or connected to a mixer.
Anticipating your next question, I will say that hot water enters this circuit not through a heater that uses fuel to heat water. This circuit is fed from the heating boiler through a special heat exchanger, called - the water is heated here by. In fact, a battery (coil) is mounted inside such a boiler, upon contact with which the water heats up. This is not an instantaneous 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 circulating hot water (so to speak, supply and return) and one for inflowing cold water into the tank.
Recirculation pump for hot water photo
If we describe the cycle of operation of such a unit, it looks like this. With the tap on the mixer closed, the water flows in a circle thanks to the circulation pump and is heated by the coil to the maximum limiting temperature. As soon as you open the mixer, water is consumed - at the same time fresh cold water flows into the indirect heating tank from the water supply system, 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, a coil is used in it.
When and how to use a hot water circulation pump
Such a scheme of hot water supply 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 small length of the hot water supply lines will not make you wait long for the heated water to flow from the tap. Large houses with several bathrooms and a complex heating system are another matter. This is where 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 pressure in the system, which compensates for the recirculation pump for hot water.
These are the main tasks of the circular hot water supply 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 switch-on time. Let's just say - 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 are the savings here? When circulation stops, 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 pump for hot water supply
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 circulating pumps are capable of working with a heat carrier heated to almost 100 degrees, then pumps for hot water supply can only withstand heating up to 65 degrees. Secondly, pumps for heating are made of cast iron, and pumps for hot water supply 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 an ordinary one can be installed in the 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 supply, mention should be made of double pumps for hot water - they simultaneously supply the coolant to the indirect heating boiler, and the hot water heated by it is pushed through the pipelines. Good thing, 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. Grundfos is considered the undoubted leader in this industry today - it supplies the market with economical pumps equipped with multiple protections. Pumps of this brand are protected against dry running and, as a rule, have built-in pressure sensors. The second pumping equipment manufacturer to look out for is Wilo. German by origin, who offers circulation pumps for hot water supply, as they say, for every taste and color - in the range of these products you can find pumps with both mechanical timer and electronic control. As they say, for all occasions and for any budget. And the economy version called DAB - despite the low cost, the company produces very high-quality equipment with a rather large warranty period.
Every home owner wants his home to be comfortable. For 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 residents will not have to waste time waiting for the cold water to finally stop pouring from the tap.
Consequently, this unit also allows you to save consumed resources. It allows you to increase the pressure in the system to the desired value, which guarantees constant movement through the water pipes.
Adaptations of this kind are divided into two groups:
- wet rotor;
- with dry rotor.
Mainly, the device of circulation pumps for water supply looks like this:
Wet rotor
Devices belonging to the first group differ in that their rotor rotates in the coolant itself... In this case, water acts as a lubricant. In this case, the stator is isolated from the rotor by means of a sleeve.
These pumps have their advantages.:
- simplicity of design;
- small dimensions;
- small weight;
- reduced noise level;
- a large selection of models.
The disadvantages of such devices include:
- the probability 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 houses.
Dry rotor
Pumps equipped with a dry rotor have their own characteristics. The rotor in this case connected via 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 higher power, which directly affects performance;
- wider range of ambient temperatures.
Such 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 ° С.
If home owners 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, an anti-freeze coolant must be poured into the system.
Launch a similar device at a temperature in the dwelling of -10-15 ° С can be done without hassle, and the pump operating within the 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 hot water systems must be made exclusively made of bronze or stainless steel... The impeller is usually made of heat-resistant plastic.
If you install a unit with a cast-iron housing in the hot water system, then, of course, you can save a little. But this is not worth doing, because iron content in the hot water system will increase, and the likelihood that the rotor will quickly jam due to a large accumulation of deposits will increase dramatically. This could damage the electric motor.
To protect the motor from damage when the rotor is jammed, some devices are equipped with a thermal relay. When overheated, they break the power circuit.
There are units on sale 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 an aqueous medium.
A spherical electric motor, unlike a traditional one, has no bearings. The rotor chamber is separated from the stator by a spherical stainless steel cup. 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. From him you will only need disconnect the motor by turning the threaded ring.
To improve the reliability of the system, 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.
Equipment connection
Mount such equipment not too difficult... It needs to be cut into the pipeline at some point and connected to the electrical network.
You can embed the unit on return or direct pipe... For example, if the apartment is equipped with a system, it is advisable to connect a pump on the return pipes. This will stimulate the movement of the water.
When it comes to hot water supply pipeline, it is advisable to carry out installation on a direct feed pipe. Then the people living in the house will receive hot water in the amount they need.
The installation of a circulation pump in the water supply system is carried out in several stages:
- Assemble the pump in accordance with the instructions supplied with the device.
- Choice of the place of installation.
- Cutting off the water supply.
- Cut or remove a portion of a 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 a pocket. This is the name of a short pipe bend cut off by shut-off 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, make sure that the shaft was horizontal;
- do not install the pump more performance than needed as this will cause noise in the system;
- before starting the unit, it is required to flush the system;
- you need to make sure that the ability to remove 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 noted.
Launch rules
After installing the pump, you will need to start it. When performing such work, you should follow the steps:
- dry running- the device must not operate when there is no heat carrier in it. This is fraught with overheating of the device;
- water hammer- to avoid it, you need to 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 instruction manual.
If the pump is selected correctly and correctly installed, it is 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 required parameters of the equipment, it is advisable to contact the specialists, since it is rather difficult to do it yourself. Then the appliance will provide the house with hot water and will supply it uninterruptedly.
| Name | vendor code | Power, W | Max. pressure, m. |
Dimensions (HxWxL), cm | price, rub. | |
| Grundfos COMFORT 15-14 B PM (permanent magnet motor rotor) |
99302358 | 7 | 1,2 | 8x8.4x14.4 | ||
 |
Grundfos COMFORT 15-14 BA PM (PM motor rotor; AUTOADAPT function) |
97916757 | 7 | 1,2 | 8x8.4x14.4 | |
 |
Grundfos COMFORT 20-14 BX PM (with shut-off and non-return valve; permanent magnet motor rotor) |
97916772 | 7 | 1,2 | 11x8.4x14.4 | |
 |
Grundfos COMFORT 20-14 BXA PM (with shut-off and non-return valve; PM motor rotor; AUTOADAPT function) |
97916749 | 7 | 1,2 | 11x8.4x15 |
Symbol
Grundfos UP
Design
Grundfos UP pumps are pumps with rotor isolated from the stator by a hermetic sleeve, i.e. pump and motor form a single shaft seal-free unit with only two gaskets.
The bearings are lubricated with the pumped liquid.
Features of these pumps:
- shaft and radial bearings made of ceramic
- graphite thrust bearing
- protective rotor sleeve and bearing plate made of stainless steel
- impeller made of corrosion-resistant material
- pump body made of cast iron, bronze or stainless steel.
Appointment
- For hot water supply systems in single and double-family houses.
- For small heating systems.
- For refrigeration and air conditioning systems.
- Clean, non-viscous, non-corrosive liquids, free from solids or fibers.
- Coolants free from mineral oils.
- Hot water supply systems.
- Softened water.
For example: a concentration of 50% glycol at 20 ° C will increase the viscosity of the aqueous solution to about 10 mm2 / s (10 cSt), which will cause a decrease in pump performance by about 15%.
When choosing a pump, it is necessary to take into account the viscosity of the pumped liquid.
Electric motor
Protection class: IP 42.
Heat resistance class of insulation: F.
Ambient and liquid temperature
Temperature of the pumped-over liquid: from +2 о С to +95 о С.
To avoid the formation of limescale, it is recommended to keep the temperature below 65 ° C.
The ambient temperature must always be lower than the liquid temperature, otherwise condensation can form in the stator housing.
Maximum pressure in the hydraulic system
PN 10: 1.0 MPa (10 bar).
Inlet pressure
To exclude cavitation noise and damage to the pump bearings at high temperatures, the pressure in the pump suction pipe must be higher than the values specified in the following table:
Control devices from GRUNDFOS
Designed to turn on / off pumps for DHW circulation at a specified time. Directly mounted on pumps: UP 20-07N, UP 20-15N, UP 20-30N.
Connected voltage: 1 x 230 V, alternating current, 50 Hz
Switching power: 230 V, 3 A
Internal control voltage: 230 V / 50 Hz
Timer with daily disc: minimum switching interval 15 min
Timer with weekly disc: minimum switching interval 2 h
Power reserve: none
Protection degree: IP 42
Ambient temperature: from -20 o C to +55 o C
Overall dimensions, mm: 76 x 76 x 53 (length x width x height)
Weight: 0.18 kg
Time relay and thermostat for COMFORT pumps
According to the table below, Model B, BT, BX and BXT pump can be retrofitted with a 24-hour time switch.
| Pump type | Equipment | Product number | |||
| Thermal relay | With shut-off and non-return valves | Time relay with a scale for 24 hours | Time relay with 24 hour scale and thermostat | ||
| UP 15-14 B | 96 43 38 91 | ||||
| UP 15-14 BT | + | 96 43 38 92 | |||
| UP 15-14 BUT | + | + | |||
| UP 20-14 BX | + | 96 43 38 91 | |||
| UP 20-14 BXT | + | + | 96 43 38 92 | ||
| UP 20-14 BXUT | + | + | + | ||
ET 2: Temperature relay
Temperature relay ET 2 can be used in conjunction with time relays ST 200, SAT 200 GES 200.
Relay ET 2 is a thermal switch that is triggered depending on the outside temperature, on the room temperature, on the temperature in the flow or return line of the heating network.
Devices for switching on / off pumps based on differential pressure are also available.
The constant circulation of hot water in the house is less than 500 sq. m is not an urgent need. For those who, for the sake of their own comfort, decided to purchase a circulation pump, it will be useful to learn about the criteria for its selection.
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On the picture:
The circulation pump & nbsp is a device that "drives" water through a closed system (DHW circuit).
In order not to wait for hot water to flow from the tap, the DHW system needs a circulation pump. The pump provides the movement of water in a closed circle.
In systems without circulation, the longer the distance from the water heater to the draw-off point, the longer the wait for water is. Arranging a circulating water supply is no more expensive than buying a high-quality boiler of a well-known brand. Let's figure out what the person who chooses the circulation pump needs to know.
- 1 of 3
On the picture:
Examples of circulation pumps.
Pressure& nbsp is the indicator of the circulation pump, which allows you to judge the maximum possible height of the water supply. For a cottage, this is the distance from the lowest point to the highest point of the DHW system, corrected for the total length of the pipeline.
In the photo: DHW circulation diagram.
Circulation pump: parameters
- power pump - an indicator of how much electricity the device will consume. Power determines other characteristics of the device to a large extent;
- performance circulation pump (or volumetric flow, or fluid circulation rate) - it is meant the amount of water that the pump can move through the pipelines per unit of time.
Circulation pump: calculation
Contact the professionals - only they will be able to adequately calculate the characteristics that the circulation pump should have. And then they will be responsible if, due to an error in the calculations, problems arise with the functioning of the system.
It is necessary to take into account many factors that affect the operation of the device: the length and height of the pipeline, its hydraulic resistance, the characteristics of the water points connected to this section of the system, etc.
The estimated head of hot water flowing out of the tap is taken into account. By the way, the maximum allowable value of the last parameter is 4.5 bar, but the minimum is not regulated by any regulatory document, except, possibly, local instructions and recommendations.
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On the picture:
It is necessary to install a non-return valve on the discharge pipe of the circulation pump. Without it, cold water can enter the pipeline and circulate in a closed loop instead of hot water. Which can cause condensation in the pump.
The number of water taps that can be open at the same time is also important. Simple logic dictates that if you create a pressure in the circulation pipeline, for example, 5 bar, then when one valve is opened, the pressure will exceed the permissible value and the jet can damage the plumbing equipment.
However, if water is consumed simultaneously through 4-5 draw-off points, then the pressure in each of them will be relatively low. The term "comparative" in this case means that the amount of water will be enough to rinse your hands, but not enough for a normal shower. A multi-circuit diagram with distribution manifolds, as well as special pressure relief valves, will help prevent this situation.
Interchangeability of circulation pumps
A separate issue when choosing a DHW circulation pump is the interchangeability of the device with a pump for the heating system. Despite the superficial similarity of the devices, interchangeability is limited.
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On the picture:
The principle of interchangeability circulation pumps does not apply to the so-called "twin pumps" & nbsp - devices that back up each other.
The problem lies in the difference in operating temperatures of the pumped liquid: 60-65 ° C for hot water and 90-95 ° C for the heat carrier.
If necessary circulation pump for heating, can be used on DHW pipelines, but not vice versa! Note that neither a solid reserve of power, nor high performance, which distinguish the pumps of the heating system, are simply not needed for hot water supply.
Main conclusions:
- the circulation pump for hot water supply is selected in approximately the same way as for the heating system;
- it makes no sense to use a device whose performance is higher than that of a water heater connected to this circuit;
- the calculation of parameters for a circulation pump is rather complicated, therefore it should be entrusted to specialists: if it is carried out on its own, the savings will be negligible, and the probability of error will be too high.
The article uses images from smedegaard.com, wilo.com, dabpumps.com, grundfos.com, salmson.com
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