Water pump for heating
When deciding on the organization's own heating housing the vast majority of homeowners prefer a water heating system. Methods for the preparation of heat may vary - depending on the availability of energy prevailing in the region fuels efficiency of a particular approach. That is, actually, the boiler can be set depending on circumstances, gas, electric, solid-- long burning or automatic fuel supply, diesel, etc. But the thermal energy distribution on the premises, in most cases carried out by circulating coolant along the tube - water or specially selected technical liquid.
Water pump for heating
When designing a water heating system, either alone or with the assistance of experts, it is necessary to competently approach the choice of units, assemblies and components of the boiler and radiators up to pipes and the last gate - all should fully comply with the planned parameters created by the system. One of the key role played by the water pump for heating, since the system is equipped with a device for forced circulation, always is stable in operation and high efficiency. Accordingly, this publication will be entirely devoted to nuances pump device criteria for their selection and the basic rules of installation.
So I need a circulating pump for heating water?
Certainly, many of the budget hosts will wonder - is it possible to do not "bother" with the pump. After all, in a small house with a slightly branched circuits, it is possible to arrange heating of the natural circulation circuit.
Yes, of course, such a possibility. For this it is necessary to correctly position the expansion tank, pick up tube of appropriate diameter and mount them with a certain bias, optimally arrange the radiators. In a word, when talking about the simplicity of the system with natural circulation, this statement is very doubtful.
The main advantage of natural circulation - not its attachment to the power supply (unless, of course, the boiler itself - a non-volatile). In the rest - it is significantly inferior to the forced circulation.
The simplest heating with natural circulation circuit
Thermal engineering calculations show that even under the most optimal conditions - high efficiency boiler, rational distribution of all components, clean, not overgrown deposits pipes and a minimum of shut-off or other reinforcing elements, the natural increase in pressure due to temperature differences and create a bias is in the range 0, 6 atmospheres. This is obviously not enough to overcome the strong hydraulic resistance in a branched network or even when the case of force majeure &# 8212; blockage occurred in tubes with internal lumen constricted or even stop short of the gas boiler can lead to unbalance of the heating system, and it will have a long "in the sense of lead."
So, let us summarize the advantages and disadvantages of natural and forced circulation:
1. The advantages of natural circulation, as already mentioned, can be attributed only full-volatility and relative simplicity of the boiler piping. But the shortcomings - a list of:
&# 8212; The need to use different tubes, including a sufficiently large diameter, which leads to a rise in the cost of the project and to difficulties in installation. The system requires very careful of thermal calculations, with exact observance of slopes, with the obligatory account elevation location of some elements over others and with different nuances.
&# 8212; The transfer of thermal energy over long distances (heights) is simply impossible. And the height and length of the generated circuit is limited.
&# 8212; The low rate of natural movement of the coolant leads to completely unnecessary energy losses, uneven distribution of heat along the premises, and thus - to reduce the overall efficiency of the system and its cost.
&# 8212; The system with the natural circulation is very difficult to give in to any fine adjustment, optimizing the distribution of heat flows from areas of the house.
2. And now - about forced circulation for heating circuits.
Among its disadvantages attributed dependence on the availability of power - in case of failures in the supply of electricity stops heating.
&# 8212; Well, firstly, there is nothing stopping to organize the whole system in such a way that it can work in both modes &# 8212; sufficient to establish the pump assembly to "return pipe" in front of the boiler. For example, Figure reproduced all the same pattern, but with an indication of the point of connection of the circulation pump. About binding order will be described below.
The same scheme, but with a circulating pump added to it
&# 8212; Secondly, we will agree that now is still not "the dawn of the electrification of the country." And, honestly, give yourself an honest answer to the question - how often, how regularly and for what duration in a particular area (city, town), turn off the electricity. If it is - only annoying episodes associated with some emergency situations, all can be solved installing the UPS system. Power consumption in the circulator pumps are usually very small, and even a small UPS will make it easy to support all operational heating system.
Unless, of course, there are still places where interruptions in electricity supply are systematic and long, in these settlements is definitely better organize heating scheme of natural circulation.
But the installation of pumping equipment at once gives the heating system a lot of advantages:
- consumption of materials produced by the system is sharply reduced - large diameter pipes may not be necessary. And this is - and even facilitate their installation process.
- Subject to the necessary measures of thermal insulation of pipelines, thermal energy can be transmitted over long distances and height, which is very important for the heating system in a large cottage, several storeys or extensions.
- Sharply increases the heating efficiency. The energy consumption for operation of the pump does not go any comparison with the gain, which is achieved by increasing the efficiency of the system.
- There is a possibility "zoning" heating systems using different heat transfer options - conventional radiators or convector water "warm floors".
- heating system turns "flexible" &# 8212; it is easy to adjustments both in general and on some of its sites. In any environment, if desired, can maintain heating of individual level. If necessary, you can quickly organize a redistribution of heat with a focus on a specific area.
- The system with forced circulation is much easier to start up and regular maintenance.
Probably, no longer need to convince: a frame circulating pump water heating system can be considered as an urgent necessity. If it is not worth it, then at the next maintenance of heating with natural circulation or its reconstruction, this question needs to be put into the category of priority.
And now closer to the pump on the device and select the desired models.
How are circulating pumps?
Almost all circulation pumps arranged by centrifugal pattern. In a special chamber (cochlea) rotates the impeller (impeller) which discards the incoming liquid flow from the center to the edges of the chamber. Due to the centrifugal force when the wheel rotates at the center of the inlet 9na) creates a rarefaction region, and output - high blood pressure. This difference is sufficient to create a smooth steady circulating flow in the heating circuit.
The main problem that faced by developers of pumps of this type - to provide a reliable electrical insulation. The first bold attempts were made in the early XX century, when the first circulation pumps with a rotor, completely isolated from the water have been created (dry type). Somewhat later installation with rotors that are in the heat carrier medium (wet-type) have been developed.
Of course, since the design is constantly being improved, but all the same circuit circulation pumps are used to this day - "dry" and "wet."
pumps &# 171; dry&# 187; type is usually sufficient and require massive cantilever Fitting
1. Pumps "dry" type usually massive, with a typical rendered in the engine compartment side elongated. They are quite noisy, and set up in a residential area from this point of view impractical.
Exemplary apparatus dry "pump shown (region filled with coolant, designated green):
Est pump unit circuit &# 171; dry&# 187; type
Electric motor (pos. 2), which during operation of cooling is required, so often it is installed casing (pos. 1), which is hidden under the fan.
rotor shaft ball bearing is dressed on (key 6.), while the inner part of the motor is further protected (7 pos.) O-ring (sometimes - type seal packing).
a motor unit connected with the casing of the pumping part (Pos. 9) through a metal (iron, brass) a support flange (pos. 3) with bolts or screws. Gasket (Pos. 8) ensures the tightness of the coupling.
The actuating shaft sleeve (Pos. 5), a pair of sealing rings (pos. 11) made of special material that ensures the tight fit them to each other due to the difference of the external atmospheric pressure and the pressure created by the pump. The rings are made of special coal agglomerate of ceramic or, more rarely, of stainless steel.
Creating the pressure is provided by rotating the impeller (pos. 12) discards arriving from the entry point into the chamber (pos. 10) to the edges of the liquid "snail".
the air valve (pos. 4) is provided to prevent accumulation of air. Frequently it is possible to set the control pressure gauge at the outlet - the figure shows damped hole for it (13 pos.).
Pumps "dry" type with high productivity, efficiency they reach 80%. But, at the same time, they demand to themselves much more attention - the O-rings to be periodically replaced as quickly wear out. Typically such pumps are installed in separate rooms due to noise and their need for special conditions. The usual field of application - Powerful Heat points, or heating system, where the pumping performance of equipment plays a crucial role. The home systems are used in exceptional cases - there is sufficient pump with "wet rotor".
2. Pumps "wet" type always much smaller (with equal performance metrics). If "dry" pumps usually require a console installation, the "wet" just cut into the pipe.
&# 171; Classic&# 187; type circulation pump &# 171; wet&# 187; rotor
Additional cooling system they do not need - the excess heat is always discharged liquid circulating through them.
Schematically apparatus of "wet" the circulation pump can be represented as follows:
Scheme pump device &# 171; wet&# 187; rotor
motor stator (pos. 4) in this case is located in a sealed metal "cup" (pos. 8). The rotor also has the usual motor-brush collector mechanism Electrotechnical it is organized differently, as rotated in the liquid coolant medium (shown in the same way as in the first scheme greenish background). The rotor shaft (pos. 7) is supported on both sides of the bearing sleeve (Pos. 2), and the heat transfer fluid in the circuit acts as a lubricant never dries. That is why it is important that the air does not accumulate and bearings have always been in the "wet" state inside the pump. To achieve this, the motor shaft for each pump location to be exclusively in the horizontal position, and the air outlet is provided a threaded stopper valve (pos. 6), which sealing gasket is provided in a twisted state (at. 5)
In the rest - the same camera- "snail" iron or brass body (. 1 pos), the impeller (3 pos.), Which creates a centrifugal acceleration of liquid and pressure drop at the inlet and outlet of the pump ..
Dignity - do not need fancy and wearing seals on rotating sites. Conventional gaskets are fixed joints (pos. 10) completely solve the problem of sealing the pump.
Rotation of the rotor occurs in a liquid medium chto¸ course, because of the increased water resistance significantly reduces the efficiency of such a pump (typically this figure is about 50%). Nevertheless, the use of "wet" pump is justified in terms of the individual heating system:
- These pumps operate almost silently - even installed in residential areas (for example, the collector of "warm floor"), they do not bring any discomfort.
- Low efficiency is fully compensated low power consumption. Thus, the initial performance category pumps, which are often used for small heating of homes and cottages have a nameplate power consumption from 25 to 50 watts - compared with a small light bulb.
- Subject to operational requirements, they can last for decades, completely without requiring any intervention - preventive maintenance or repair. The main thing - do not leave a dry rotor. Otherwise, by and large, there is nothing to simply break or abrasions (unlike commutator motors in which brushes wear out, or "dry" pump circuit to gradually abradable seals).
So, no need to split hairs especially - for home autonomous heating systems will be enough pump with "wet" rotor.
They are also convenient in that they have a modular design - can be easily disassembled into its constituent components, each of which, in case of failure, can be replaced by non-defective.
Typically, such pumps have a modular design
In the figure the:
1 - working chamber of the pump housing. Most often made of cast iron, although there are models and copper alloy (brass or bronze).
2 - impeller. It is experiencing a lot of stress on the fluid resistance, therefore made of durable polymer composites reinforced with fiberglass.
3 - the electric pump rotor with permanent magnets.
4 - working axis (shaft) of the rotor. In modern models of pumps are manufactured from high-strength sintered metal. From the side of the impeller is supported by a radial bearing in the bearing cage of stainless steel. On the opposite (motor side) &# 8212; in the support bearing. In both places a strong set bearings of a combination of graphite and ceramic.
5. The next most important value for the correct selection of a pump - it created the water pressure (often referred to as the water column).
The main point here is that the pump is to create a force that will overcome the flow resistance in all parts of the system. In this case, the vertical rise of the coolant in the calculation of themselves, and not accepted, since it is fully compensated by the back direction of the force on the downstream parts of the circuit. But the resistance of pipes, valves, heat exchangers and other elements is very important.
As the reader can see, reading the table above, each heating element gives a certain drop in pressure. The mind, of course, necessary to carry out a detailed calculation of the full - by the way, it is exactly what is done by using special applications. However, experience shows that under conditions of limited systems, the scale of the house or apartment, consider a sufficiently long pipe, and then lead into the formula a correction factor on the "complexity".
The formula is as follows:
H = Σᴸ × R × Zr
H - calculated pump head (the value is obtained in Pascals, Pa)
Σᴸ &# 8212; the total length of the entire heating circuit, including both the supply and the return pipe. If you provide radiant floor heating, make sure you take into account the total length of all circuits, tied to a single pump.
R - resistivity meter pipe portion. Refer to the table - for plastic pipes, the value is 150 Pa / m
zr - factor considering saturation of the system shut-off valves, fittings, temperature regulators, heat exchangers, etc. - all those elements that create a pressure loss. The value of this coefficient is determined to be:
1.3 - if you are using the standard, regular fittings and valves.
1.7 - using a thermostatic system of elements (three&# 8212; or four-way valves, to the desired temperature level).
2.2 - system at highly branched, with many molded and regulatory elements.
Suppose we consider the necessary pressure for the system with a total length of pipes 170 m, and with established thermostats on each radiator. In this case, the coefficient is better to take 2.2
H = 170 × 150 × 2,2 = 56100 Pa
To convert to meters of the water column (about, but with an acceptable level of accuracy) should be divided by 10000. As a result, we get 5.6 meters.
So, in our example, we have determined the choice of the pump - the minimum capacity of 1.23, rounded up to 2 m³ / h with a head of 5.6 generated &# 8212; rounding 6 m.
Calculator for calculating the pressure created by the pump
Overly inflate the parameters of the purchased equipment is pointless. Even in the above formulas have laid a certain margin, which should be enough for all the "force majeure". Excess capacity and pressure simply remain unused and even create a certain imbalance in the heating system, will lead to unnecessary overuse of electricity.
A few tips on installing a circulation pump
Installation of the pump to the heating system usually causes great difficulties, especially when using polypropylene tubes. Instruments and accessories required for this bit.
A typical set of tools and accessories for installation of the circulating pump
Pick up and welded into the path gayki- "American" at a distance corresponding to the length of the mounting device - simple task for an experienced handyman. And then there will be only set the pump itself, to put the gaskets and tighten the American on both sides.
After coupling with collar nuts embedded in the pipe, install the pump itself &# 8212; one minute deal
However, when installing the pump still can not forget about a number of nuances.
- Where the pump would be installed either in front of him along the coolant flow is recommended to mount a mesh ( "skew") filter. Contact with particulates in the "wet" pump bearings may damage them or reduce the effectiveness of the device.
- After the pump is recommended to install a check valve - this measure is aimed at preventing the reverse current is switched off the pump power and protection against possible water hammers
- In conventional radiator or convector heating circulation pump is recommended to set at a very low temperature - the return line in close proximity to the boiler.
Typical installation of the pump in place radiator heating systems
- If organized system "warm floor" the pump, on the contrary, is put only on the pitch. Variations in temperature are small, but the risk of airing loops - quite serious. To avoid the possibility of the flow gap, the pump is placed in front of the feed manifold.
- To be able to switch the system forced to natural circulation of coolant = pump can be mounted then the following scheme:
Recommended circulation pump mounting scheme
&# 8212; The pump itself (pos. 1) is mounted on a regular union gayki- "American" (pos. 5).
&# 8212; As already mentioned, before the pump set mesh strainer (3 pos.) And immediately behind it - the back flow valve (4 pos.).
&# 8212; Management of these units is performed using the three valves (pos. 2). It left open or straight portion - for natural circulation, or vice versa - with the pump portion. By the way, the valve on the straight section may be involved and for the fine balancing of the system while the pump - in this case it plays the role of a bypass.
- About it it has been said, but it is useful to recall - pumps with "wet" the principle of action can be placed in a position allowing a strict rotor horizontally.
- Around the pump installation site power socket must be provided, so that enough length of the cord without tension. In most case, the pump outlet is required to ground the circuit.
When installing the pump, do not forget about the need for its proper connection to the mains
- After installation of the pump in any case it is impossible to include up to complete filling of the coolant system - even a brief idling may damage the appliance.
- Before filling and commissioning the system it is desirable to rinse thoroughly with clean water, so as not to remain solid inclusions in the cavities of pipes.
- Despite the degree of protection IP44, yet to be fully exclude the possibility of contact with the terminal box splash.
- If the pump is equipped with an air valve, then be sure to check before starting the presence of air and release it. The presence of air pockets for pump - is unacceptable.
- If the pump has several operation modes, the selected optimal, the maximum extent appropriate system parameters. Inflate the load should not be - as we have said.
In this regard, particular convenience are modern circulation pumps, which are equipped with electronic control unit produced by pressure control and adjustment of the system, constantly maintaining the necessary parameters depending on the pre-made presets.
EXAMPLE modern circulation pump with electronic control
And finally, the last tip. When selecting the pumps should not take unknown manufacturers. Such a purchase is made for a long time, and it is better to buy really high-quality device that will last for many years without any interference in their work. So, no worries, you can purchase branded products of European companies «Hoffmann», «Grundfos», «Wilo», «Pedrollo» «DAB», «Ebara». Among Russian products can be identified by the pumps' JEELEX "trademark (« Jeelex »).
Video: how to distinguish a real «Grundfos» counterfeiting
The cost of even the most high-quality pumps - not so great resort to totally unjustified "penny savings" in this issue &# 8212; all of which can result in a much more unpleasant consequences.