Pump heating system with natural circulation. Schemes of a heating system with pump circulation
Such a pump is used as part of a heating system to provide forced circulation of the coolant. The device runs on electricity and consumes little energy - from 60 to 100 watts, which is comparable to an ordinary household light bulb.
Unfortunately, if the power supply to a private house is interrupted from time to time, then the operation of the pump will be intermittent, which will lead to disruption of the movement of fluid through the pipes. Before installing the pump, it is recommended to think in advance how to make the circulation of water in the circuit constant.
Applications
A heating system equipped with a pump for forced pumping of the coolant is appropriate in cases where the liquid cannot overcome hydraulic resistance and therefore does not rise up the pipes. In heating systems with natural water circulation, the slope and diameter of the pipes must be strictly observed, and the slightest mistake will disable the entire complex.
This limits the use of the system to compact rooms: after all, the larger the heated area, the longer the circuit, and, accordingly, the weaker the water flow. Even when using a powerful boiler, the coolant pressure rarely exceeds 0.6 MPa. And changing the piping layout to improve fluid flow will be expensive.
Advantages
A system equipped with a circulation pump is free from these disadvantages. It is excellent for heating rooms ranging from 200 to 800 m2. Its benefits include:
- no requirements for the configuration of the heating circuit - for the circulation of the coolant, it is not necessary to create narrowed places in the pipeline, install pipes at an angle and use other techniques;
- rapid acceleration of the liquid - the circulation of heated water in the circuit begins immediately after the pump is turned on. As a result, the rooms of a private house warm up to the desired temperature in just a few minutes;
- high efficiency - due to the rapid circulation of the coolant, heat losses are reduced. The problem is solved when one of the rooms warms up more than the others. Due to this, fuel is consumed more economically;
- reliable operation - the simple design of the pump eliminates the occurrence of accidental breakdowns.
It is worth noting that difficulties can arise only during power outages, but it is not difficult to deal with them: if the house has an electric generator, the heating system can work continuously.
If it is planned to equip a system with natural circulation with a pump, its scheme remains practically unchanged.
It is only required to mount the pump itself, as well as transfer it from the water supply circuit to the circuit through which it returns to the boiler.
Dry and wet pumps
There are two main types of pumps: "dry" and "wet". The first ones are designed so that the rotor does not interact with the coolant. They have a high efficiency - 80%, but are quite noisy and prone to breakdowns. One of the most common malfunctions of "dry" pumps is damage to the sealing rings, after which the tightness of the device is broken.
In systems equipped with a "wet" pump, this problem is excluded. They are easier to operate and require little maintenance. On the other hand, a "wet" pump has an efficiency of less than 50%, and since there must always be water inside it, you have to carefully monitor the horizontal position of the shaft. For use in heating a private house, a “wet” pump is convenient because it is almost silent. The rotor speed switching mechanism is stepless.
Given the low power, "wet" pumps are suitable for short pipeline lengths. "Dry", on the contrary, it is better to use for heating large areas. In addition, the latter are rarely installed in private homes due to noise during operation, and if there are plans to mount them, then this is done in a pre-prepared place with sound insulation.
Determination of power
Factors to consider when choosing a pump include:
- power of heating radiators;
- speed of movement of the coolant;
- total length of the pipeline;
- flow section of pipelines;
- boiler power.
Each of these parameters is easily calculated if at least one of them is known. So, based on the power of the radiators, you can set the boiler power and water flow. Having determined the water flow, it will not be difficult to find the diameter of the pipes. It is necessary to determine in advance the speed of movement of the coolant in the system circuit: optimally - 1.5 m / s. Knowing the required circulation rate, pipe diameter and other parameters, it will be possible to calculate the pressure force and pump power.
Calculations
To more accurately determine the power of the pump, you can use the rule of manufacturers who "tied" 1 kW of power to 1 liter of pumped water. So, a 25 kW pump can circulate a maximum of 25 liters of coolant.
Sometimes a simplified selection scheme is used, based on the area of \u200b\u200bthe heated room:
- for heating a building with an area of up to 250 m2, they buy a pump with a capacity of 3.5 cubic meters of water per hour and a pressure force of 0.4 atmospheres;
- from 250 to 350 m2 - with a capacity of 4.5 cubic meters per hour and a pressure force of 0.6 atmospheres;
- from 350 m2 - with a capacity of 11 cubic meters per hour and a pressure force of 0.8 atmospheres.
Despite the high performance characteristics some models, the pumps are not suitable for running water along the circuit of the system with artificial circulation in buildings with a total area of more than 800 m2.
European calculation method
When choosing equipment, you can use another technique - standard housing projects developed in the European Union. So, per 1 m2 of space there should be a pump power of 97 watts, provided that the air temperature outside is 25C ° (minus), or 101 watts - if the temperature drops to 30C ° (minus).
This standard applies to buildings with a height of three floors or more. When arranging a private house up to two floors high, the pump power per 1 m2 of area should be 173 watts at outdoor temperatures up to 25 ° C and 177 watts - below 25 ° C.
Performing installation work
Heating systems equipped with a pump can be either single-pipe or two-pipe. Any scheme provides for mounting the device on a pipe through which the cooled coolant returns to the boiler. This is due to the fact that the rubber cuffs and seals of the pump, heating up from hot water, change their consumer properties and wear out quickly. In the return circuit, the water is cooled and does not harm the equipment.
If the forced circulation system is being designed from scratch, it is better to immediately buy small diameter pipes to save money. This will not affect the quality of heating in any way, but it will make the operation of the equipment cheaper.
An important element of the scheme -. It connects to the return circuit and acts as a reference point: here the pressure force changes its sign - in the circuit to the tank it is pumped, pushing water through the pipes, and then it is rarefied, so that the pump sucks liquid into itself. You need to remember the rule: when the pump is on, the hydrostatic pressure at any point in the suction zone must remain high - then the water circulation will not be disturbed.
Also expansion tank needed to compensate for the lack of space in closed system when the coolant expands, the water turns into steam and increases its volume. If it were not for the tank, then when the water overheats, it would be ejected. In addition, to avoid overheating and other problems, it is recommended to install only modern automated boilers.
It is better to install the pump at home in a horizontal position: this way the equipment will produce less noise.
The pump is mounted on threaded connections, cut-off valves are inserted into the circuit - one valve on the straight section of the pipe, one on the outlet directly in front of the pump, and one more - on the outlet behind it. This is necessary in order to cut off the pump from the coolant if necessary.
Heating issues are always relevant in our country, because heating period lasts almost half a year, and in the northern regions most of it.The old Soviet centralized heating systems have fallen into disrepair, and fabulous sums of money are required to repair them or create new heating mains. Therefore, the quality of the heat carrier and, in general, the services for obtaining heat by the population are often very low. In this case, the solution to the problem may be the rejection of central heating and the connection of an autonomous one. In the private sector, where there are no heating networks, there is no alternative to autonomous heating.
Autonomous heating systems are quite simple in design. If desired, they can be mounted with your own hands, but put into operation only after verification by specialists. There are such main types of autonomous heating systems:
- Traditional heating system. The water (coolant) heated in the boiler is supplied to pipelines and heating radiators.
- Air heating. The heat carrier is heated air, which enters the room through the duct system.
- Electric heating
. Heat is emitted by electric convectors, appliances infrared radiation and other devices.
Alternative heat pumps can also be classified as autonomous systems, but they are not very common due to the high cost of equipment.
Traditional heating systems have gained the greatest popularity.. As a rule, they consist of a boiler, pipelines, heating radiators, regulating and stop valves. The key link in such a heating system is the boiler, it can work on various types fuel. The boiler heats the coolant, most often water, which flows through pipes to heating radiators. Passing through the radiator, the water gives off part of the heat and returns to the boiler, where it is heated again. With the help of a double-circuit boiler, in addition to heating, hot water supply can also be connected. There are certain restrictions for installing gas boilers. You can install it in an apartment no higher than the 10th floor.
Pipelines of heating systems are widely represented on the market: copper, steel, polymer and metal-plastic. The best choice for the installation of autonomous water heating are metal-plastic pipes. They are durable, corrosion resistant and hygienic. Steel piping is heavy and rusts quickly, while copper piping is very expensive.
Modern radiators are made of steel, aluminum and cast iron, there are also bimetal radiators They are made up of copper and aluminium. Popularity in autonomous systems gained aluminum radiators, they have high heat transfer and affordable price.
If the total heated area of the premises is more than 100 m2., In such a heating system, circulation pump, after all the rate of natural circulation will not be enough for the normal operation of the system.
Do not forget about energy saving measures in a house or apartment with autonomous heating. By properly insulating the outer walls of the house, you can more than halve energy consumption. Installation of thermostatic valves on radiators heating systems will help regulate the heat flow in each individual room.
There are many different schemes of heating systems, new alternatives are constantly appearing. Mankind is in search of new sources of energy. New ways to get heat are still inaccessible to the layman, so the autonomous water heating scheme with gas boiler by far the most popular among the population.
A natural circulation heating system is a system in which the coolant moves under the influence of gravity and due to the expansion of water when its temperature rises. The pump is missing.
The heating system with natural circulation works like this. A certain volume of coolant is heated in the boiler. Heated water expands and rises (because its density is lower than that of cold water) to the highest point of the heating circuit.
It moves by gravity along the contour, gradually giving up its heat to pipes and heaters - while, of course, cooling itself down. Having made a full circle, the water returns back to the boiler. The cycle is repeated.
Such a system is self-regulating, as well as gravity, or gravitational: the speed of the coolant depends on the temperature in the house. The colder it is, the faster it moves. This is because the pressure depends on the difference in the density of the water leaving the boiler and its density in the "return". Density depends on temperature: the water cools down (and the colder it is in the house, the faster it happens), the density increases, the displacement rate of heated water (with a lower density) increases.
In addition, the pressure depends on how far the boiler and the lower radiator are in height: the lower the boiler, the faster water overflows into the heater (according to the principle of communication of vessels).
Pros and cons of gravity systems
Realization of heating with natural circulation
Such systems are very popular for apartments in which autonomous system heating, and one-story country houses small footage ().
A positive factor is the absence of moving elements in the circuit (including the pump) - this, as well as the fact that the circuit is closed (and, therefore, metal salts, suspensions and other undesirable impurities in the coolant are present in a constant amount), increase the service life of the system. Especially if you use polymer, metal-plastic or galvanized pipes and it can last 50 years or more.
They are cheaper than systems with forced circulation (at least by the cost of the pump) in assembly and operation.
The natural circulation of water in the heating system means a relatively small difference. In addition, pipes and heating appliances due to friction, they resist moving water.
Based on this, the heating circuit should have a radius of about 30 meters (or a little more). Various turns and branches increase the resistance and therefore reduce the allowable contour radius.
Such a circuit is highly inertial: a lot of time passes from the moment the boiler is started to the heating of the premises - up to several hours.
In order for the system to function normally, conditionally horizontal sections of pipes must have a slope along the flow of the coolant. Air locks() in such a circuit, everyone gathers at the highest point of the system. A sealed or open expansion tank is mounted there.
Water boils more often in a gravity-flow type heating system. For example, in the case of using an open expansion tank, sometimes there is not enough water in the system, and also if the pipes have too small a diameter or too little slope (due to this, the coolant speed decreases). It can also happen due to airing.
The speed of movement of water in a gravity circuit
The speed of water in the heating system is determined by a number of factors:
- Heat carrier pressure.
- Pipe diameter ().
- The number of turns and their radius, Optimal - the minimum number of turns (best of all in a straight line, and if they do exist, then with a large radius).
- Shut-off valves: its quantity and type.
- The material from which the pipes are made. Steel has the greatest resistance: the more deposits on it, the higher the resistance, galvanized steel - less, polypropylene - even less,.
forced circulation
Schematic diagram explaining the operation of forced circulation
A forced circulation heating system is a system that uses a pump: water moves under the influence of pressure exerted by it.
The forced circulation heating system has the following advantages over gravity:
- The circulation in the heating system occurs at a much higher speed, and, consequently, the heating of the premises is carried out faster.
- If in a gravity system the radiators heat up differently (depending on their distance from the boiler), then in the pump room they heat up the same way.
- You can adjust the heating of each section separately, overlap individual segments.
- The wiring diagram is more easily modified.
- Air does not form.
The disadvantages of such a system are also available:
- It is more expensive to install: unlike the gravity model, you need to add the cost of the pump and the cost of valves to cut it off.
- It is less durable.
- Depends on power supply. If you experience interruptions in its supply, you need to get an uninterruptible power supply.
- It is more expensive to operate, as pumping equipment consumes electricity.
Selection and installation of the pump
There are a number of factors to consider when choosing a pump:
- What kind of coolant will be used, what will be its temperature.
- Line length, pipe material and diameter.
- How many radiators (and which ones - cast iron, aluminum, etc.) will be connected, what will be their size.
- Quantity and types of valves.
- Will there be automatic regulation, and how exactly will it be organized?
When installing the pump on the "return", the service life of all parts of the circuit is extended. It is also desirable to install a filter in front of it to prevent damage to the impeller.
Before installation, the pump is deaerated.
The choice of coolant
Water can be used as a coolant, as well as one of the antifreezes:
- Ethylene glycol. A toxic substance that can be fatal. Since leaks cannot be completely ruled out, it is better not to use it.
- Aqueous solutions of glycerin. Their use requires the use of better sealing elements, non-polar rubber parts, and some types of plastics; Installation may be required additional pump. Causes increased metal corrosion. In places of heating up to high temperatures(in the area of the boiler burner) the formation of a toxic substance - acrolein is possible.
- propylene glycol. This substance is non-toxic, moreover, it is used as food additive. Based on it, eco-antifreezes are made.
Design calculations of all heating circuits based on the use of water. In the case of using antifreeze, all parameters should be recalculated, since antifreeze is 2-3 times more viscous, has much more volumetric expansion, and lower heat capacity. This means that much more powerful (by about 40 % — 50 %) radiators, high boiler power, pump pressure.
When the temperature of antifreeze is exceeded, it decomposes. In this case, acids are formed that cause metal corrosion, and solid deposits are deposited on the walls of pipes and inside radiators and impair the movement of the coolant.
Antifreezes are also prone to leaks and are the scourge of high volume systems. threaded connections. Its use is justified if the heating system can be left unattended for a long time on frosty days.
Ordinary water as a coolant is also not recommended: it is saturated with salts and oxygen, which leads to scale formation and corrosion of pipes and radiators.
Be sure to read more. There are no trifles in this matter, but there are a lot of nuances.
The preparation of water for the heating system consists in softening it ().
It happens like this:
- Boiling: carbon dioxide escapes, some of the salts (but not magnesium and calcium compounds) precipitate;
- Using chemicals, the water softener for the heating system is magnesium orthophosphate, slaked lime, soda ash. All salts become insoluble and precipitate, to remove the residues of which the water must be filtered.
- Distilled water in the heating system is ideal.
We hope that you understand the difference between natural and forced circulation. And you will choose the type of heating system that is best for you.
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