DHW pump UP20–15 (GRUNDFOS)
UPS heating pump32–120F (GRUNDFOS) flanged
RL pump30/70 (WILO)
To select a pump, first determine the parameters of the operating point of the system, which is plotted on the Q, H graph. The pump characteristic curve must not be lower than the operating point of the system
The speed switch is located on the pump terminal box
Three-speed pump UPS25–60 (GRUNDFOS) with a wet rotor and a cast iron body for heating systems, the maximum head of which is 6m, and the feed- 3.3m3/h Atof this pump, the inlet and outlet pipes are arranged in a line, which makes it easy to mount it. The distance between the nozzles, called the base of the pump, is 180mm
Special taps for pump installation (BUGATTI)
Pumps for the heating system:
a-VA65/130 (DAB) with a maximum head of 6.3m and feed 3m3/h;
b- three-speed pump for Star RS heating system25/6–3P (WILO) has a head of 6m and feed 3.5m3/h
The result of installing a pump with a cast iron casing in a DHW system. After a year of operation, the pump failed due to jamming of the rotor of the electric motor. The initial savings turned into high costs for the purchase and installation of a new device. DHW pump housings are made of corrosion-resistant materials such as stainless steel or bronze
Not so long ago, systems with forced circulation of the coolant were an inaccessible luxury for owners of private houses. Such equipment was used exclusively in municipal and industrial networks. Now, with increased requirements for comfort and energy saving, circulation pumps are widely used in everyday life.
Why do you need a circulation pump
According to the laws of physics, the operation of a water heating system is based on the circulation of a coolant. In order for the heaters to give off the required amount of heat, the coolant flow must be sufficient (this is determined by calculation). The circulation of the coolant can be natural and forced. Natural is achieved due to the difference in the densities of the heated and cooled liquid, forced- using a special circulation pump.
Natural circulation systems require significant fuel consumption due to the need to maintain a high temperature of the water in the supply line. After all, the higher the temperature of the water, the lower its density and, consequently, the higher the speed of movement through the pipes. When operating such a heating system, it is difficult to maintain a comfortable temperature in the premises, since it is problematic to use thermostatic shut-off and control valves in systems with natural circulation. Needless to say, today’s popular underfloor heating without a circulation pump cannot be equipped?
The circulation pump in the hot water supply system (DHW) is needed first of all in order to be able to get hot water immediately by opening the tap at any point of the water intake. Also, heated towel rails can be connected to the DHW system, for the operation of which the circulation of the coolant is necessary.
ATunlike water-lifting ones, which raise water to a certain height, circulation pumps only make it move in a vicious circle. The purpose of such equipment- pump the required volume of coolant, overcoming the hydraulic resistance of pipelines and system elements.
Pump selection and a little theory
The main parameters of the circulation pump are the head (H), measured in meters of water column, and the flow(Q), or productivity measured inm3/h Max head- this is the greatest hydraulic resistance of the system that the pump is able to overcome. In this case, its supply is equal to zero. The maximum flow is the largest amount of coolant that can be pumped in 1h pump when the hydraulic resistance of the system tends to zero. The dependence of pressure on the performance of the system is called the pump characteristic. Atsingle-speed pumps have one characteristic, two- and three-speed pumps- respectively two and three. AtVariable speed pumps have many characteristics.
The selection of the pump is carried out, taking into account, first of all, the required volume of coolant, which will be pumped over the hydraulic resistance of the system. The flow rate of the coolant in the system is calculated based on the heat loss of the heating circuit and the required temperature difference between the direct and return lines. Heat losses, in turn, depend on many factors (thermal conductivity of building envelope materials, ambient temperature, orientation of the building relative to cardinal points andetc.) and are determined by calculation. Knowing the heat loss, calculate the required flow rate of the coolant according to the formula
After determining the required flow rate of the coolant, the hydraulic resistance of the heating circuit is determined. The hydraulic resistance of the elements of the system (boiler, pipelines, shut-off and thermostatic valves) is usually taken from the corresponding tables.
Having calculated the mass flow rate of the coolant and the hydraulic resistance of the system, the parameters of the so-called operating point are obtained. After that, using manufacturers’ catalogs, a pump is found whose operating curve lies not lower than the operating point of the system. For three-speed pumps, the selection is carried out, focusing on the second speed curve, so that there is a margin during operation. To obtain the maximum efficiency of the device, it is necessary that the operating point is in the middle of the pump characteristic. It should be noted that in order to avoid the occurrence of hydraulic noise in pipelines, the coolant flow rate should not exceed 2m/s. When using antifreeze, which has a lower viscosity, as a coolant, a pump is purchased with a power reserve of 20%.
For clarity, consider an example of choosing a pump for a cottage with an area of 200m2where a two-pipe heating system made of polypropylene pipes with a diameter of 32mm and length 50m. Temperature chart of the heating system- 90/70
Pump energy efficiency
Currently, manufacturers of pumping equipment are paying more and more attention to the energy efficiency of their products. According to this indicator, all electrical appliances are divided into classes, denoted by the letters of the Latin alphabet- from A to G. Kclass A includes the most economical devices to date. Conventional one or three speed pumps have class level energy consumptionC. At the same time, the power of the devices is relatively low: in terms of energy consumption, they are comparable to incandescent lamps of 75 or 100Tue Toclass A can only belong to pumps with electronic speed control of the rotor of the electric motor. In addition, the low noise level generated by their electric motors can be noted.
Circulation pumps with frequency regulation at 50–70% is more expensive than usual, so their use should be justified. For example, it does not make sense to use an electronically controlled pump if there is no thermostatic shut-off valve in the heating system, and the temperature of the heating circuit (device) changes not due to a decrease in the mass flow of the coolant, but as a result of a change in the temperature of the water in the supply line (using three- or four-way servo valve).
Circulation pumps are divided into two large groups: with a wet and with a dry rotor. As the name implies, in the devices of the first group, the rotor rotates directly in the coolant, which in this case plays the role of a lubricant. The stator is isolated from the rotor by a sleeve. The advantages of such a pump are simplicity of design, small dimensions and weight, low noise level, and a wide range of manufactured models. Tothe disadvantages include the possibility of rotor jamming due to the accumulation of deposits on its surface, as well as a smaller range of ambient temperatures at which the device can function normally. ATIn private homes, pumps with a wet rotor are mainly used.
Pumps with a dry rotor are distinguished by the fact that the rotor of the electric motor is connected to the impeller shaft of the pump through a mechanical seal and does not come into contact with the coolant. The advantage of this design lies in the possibility of using electric motors of greater power and, as a result,- in greater device performance. A wider range of ambient temperatures should also be noted, since the engine is less susceptible to heating from the coolant. The disadvantages of such pumps are rather impressive dimensions and a higher noise level than devices with a wet rotor.
The standard operating temperature range of those and other circulation pumps- 2–110
Some unscrupulous installation organizations install cast iron pumps in DHW systems, which allows the customer to save a small amount. Paying for these savings- an increase in the iron content in the DHW system and the likelihood of jamming of the pump rotor due to accumulation of deposits, up to the failure of the electric motor.
For ease of installation, the inlet and outlet pipes of the pump are located in one line (the so-called in-line version).
To protect the engine when the rotor is jammed, some models of pumps are equipped with thermal relays that break the power circuit when overheated. There are pumps that are not afraid of jamming,- with the so-called spherical rotor. ATIn these models, the magnetic field is transmitted from the stator to the rotor in the aquatic environment, through the conductive parts of the pump. ATUnlike traditional wet rotor devices, the spherical motor does not have bearings. The chamber with the rotor is hermetically separated from the stator by a stainless steel spherical cup. ATAs a result, this type of pump is less susceptible to the effects of impurities and lime deposits contained in the water. It is very easy to dismantle the device for cleaning without removing the housing from the pipelines. In this case, you just need to disconnect the electric motor from the housing by turning the threaded ring. Note that pumps with a spherical rotor are available only for domestic hot water systems.
ATIn critical cases, so-called twin pumps are used to increase the reliability of the system. ATthey have one impeller driven alternately by one or the other electric motor. The latter are located in a common building. When one of them fails, the other one automatically turns on. ATIn normal mode, for uniform operating time, the engines replace each other at regular intervals. Such a pair is somewhat cheaper than two conventional devices. So, for example, the UPD model32–80 F (GRUNDFOS) offered at a price
Comparative characteristics of circulation pumps for heating systems (voltage- 230AT)
|Power consumption, W
|Star RS 25/6
Comparative characteristics of circulation pumps for hot water systems (voltage- 230AT)
|Power consumption, W
|UP 20–30 N
|Wilo Star‑Z 15 C
|Wilo Star‑Z 20/1
Features of the use of pumps in hot water systems
Usually, a large capacity pump is not required to circulate hot water. But the operating conditions of such a model differ significantly from the conditions of heating systems. The high oxygen content in tap water does not allow the use of devices with a cast iron body in this case.
Poorly treated water (with a high content of hardness salts) leads to the formation of lime deposits on the pump rotor. This occurs most intensively at a water temperature of more than 55–60
If the pump is connected to a modern boiler control panel, this problem is solved at the software level. If the boiler is equipped with a standard control panel or a panel that does not support the connection of a DHW circulation pump, you can purchase a pump with a built-in timer, for example, model BWZ152 (VORTEX, Germany) worth
For the operation of the boiler for the heating system and heating the water in the boiler, GRUNDFOS produces a combined pump UPP15–50. It consists of two pumps in a common housing. One of them is designed to circulate the coolant in the heating system, and the other is the loading pump of the indirect heating boiler. ATdesign includes a diverter valve. Model cost-
Manufacturers and prices
Pumps from such companies as GRUNDFOS (Denmark), VORTEX, KSB, WILO (Germany), DAB, WESTER LINE (Great Britain) andetc. The cost of circulation pumps for heating systems is relatively low:
The pump is installed on the supply pipeline, in a pipe section. To connect, use quick-release connections with a union nut (“American”) or special taps for strapping. Shut-off valves for the installation of pumping equipment are offered by OVENTROP (Germany), GIACOMINI, BUGATTI (Italy) and other manufacturers. The cost of one crane with a diameter of 1inch-
At the end of the installation of the entire system, it is filled. We must not forget that after starting the pump with a wet rotor, it is necessary to remove air from its chamber. To do this, set the maximum engine speed and unscrew the protective cap. Water begins to come out of the hole with air bubbles. When it comes out, the cap is twisted again. By the way, the presence of air in the pump can cause noise.
Rotor jam prevention
Sometimes pumps remain idle for a long time. to prevent jamming of the shaft, they must be periodically turned on for a short time. If you have a modern control panel, such as Loga-matic 4211 (BUDERUS, Germany; cost-
We would like to thank RUSKLIMAT, STK-GROUP and the representative office of GRUNDFOS for their help in preparing the material.