When autumn confidently strides across the country, snow is flying above the Arctic Circle, and in the Urals night temperatures stay below 8 degrees, then the word form “heating season” sounds appropriate. People remember past winters and try to understand the normal temperature of the coolant in the heating system.
Provident owners individual buildings carefully inspect boiler valves and nozzles. Residents apartment building by October 1, they are waiting, like Santa Claus, for a plumber from management company. The Lord of valves and valves brings warmth, and with it joy, fun and confidence in the future.
The Gigacalorie Path
Megacities sparkle high-rise buildings. A cloud of renovation hangs over the capital. The outback prays to five-story buildings. Until demolished, the house operates a calorie supply system.
Heating of an economy class apartment building is carried out through centralized system heat supply. The pipes enter the basement of the building. The supply of coolant is regulated by inlet valves, after which the water enters the mud traps, and from there it is distributed through the risers, and from them it is supplied to the radiators and radiators that heat the home.
The number of valves correlates with the number of risers. By doing repair work in a separate apartment, it is possible to turn off one vertical, and not the entire house.
The waste liquid is partially discharged through the return pipe, and partially supplied to the hot water supply network.
Degrees here and there
Water for the heating configuration is prepared at a thermal power plant or in a boiler room. The norms for water temperature in the heating system are specified in building regulations ah: the component must be heated to 130-150 °C.
The supply is calculated taking into account the parameters of the outside air. Thus, for the Southern Urals region, minus 32 degrees is taken into account.
To prevent the liquid from boiling, it must be supplied to the network under a pressure of 6-10 kgf. But this is a theory. In fact, most networks operate at 95-110 °C, since most network pipes settlements worn out and high pressure will tear them apart like a hot water bottle.
An elastic concept is a norm. The temperature in the apartment is never equal to the primary indicator of the coolant. Executes here energy saving function elevator unit - jumper between straight line and return pipe. The temperature standards for the coolant in the return heating system in winter allow heat to be maintained at a level of 60 °C.
Liquid from the direct pipe enters the elevator nozzle, mixes with return water and again goes into home network for heating. The temperature of the carrier is reduced by mixing the return fluid. What affects the calculation of the amount of heat consumed by residential and utility rooms.
The hot one went
Hot water temperature sanitary rules at analysis points should be in the range of 60-75 °C.
In the network, the coolant is supplied from the pipe:
- in winter - with reverse, so as not to scald users with boiling water;
- in summer - from a straight line, since in summer time The carrier is heated no higher than 75 °C.
A temperature chart is drawn up. Average daily temperature return water should not exceed the schedule by more than 5% at night and 3% during the day.
Parameters of distributing elements
One of the details of warming a home is the riser through which the coolant enters the battery or radiator from the Coolant temperature standards in the heating system require heating in the riser at winter time in the range of 70-90 °C. In fact, the degrees depend on the output parameters of the thermal power plant or boiler house. In the summer, when hot water is needed only for washing and showering, the range moves to 40-60 °C.
Observant people may notice that the heating elements in the neighboring apartment are hotter or colder than in his own.
The reason for the temperature difference in the heating riser lies in the method of hot water distribution.
In a single-pipe design, the coolant can be distributed:
- above; then the temperature on the upper floors is higher than on the lower ones;
- from below, then the picture changes to the opposite - it is hotter from below.
IN two-pipe system the degree is the same throughout, theoretically 90 °C in the forward direction and 70 °C in the reverse direction.
Warm like a battery
Let’s assume that the central network structures are reliably insulated along the entire route, the wind does not blow through attics, staircases and basements, and conscientious owners have insulated the doors and windows in the apartments.
Let's assume that the coolant in the riser complies with building code standards. It remains to find out what the normal temperature of the heating radiators in the apartment is. The indicator takes into account:
- outdoor air parameters and time of day;
- location of the apartment in the house plan;
- residential or utility room in the apartment.
Therefore, attention: it is important not what the temperature of the heater is, but what the temperature of the air in the room is.
During the day in corner rooms the thermometer must show at least 20 °C, and in centrally located rooms 18 °C is allowed.
At night, air in the home is allowed to be 17 °C and 15 °C, respectively.
Theory of linguistics
The name “battery” is a common one, meaning a number of identical objects. In relation to home heating, this is a series of heating sections.
Temperature standards for heating radiators allow heating no higher than 90 °C. According to the rules, parts heated above 75 °C are protected. This does not mean that they need to be covered with plywood or bricked. Usually a lattice fence is installed that does not impede air circulation.
Cast iron, aluminum and bimetallic devices are common.
Consumer choice: cast iron or aluminum
Aesthetics cast iron radiators- the talk of the town. They require periodic painting, since the rules stipulate that the working surface must have smooth surface and made it easy to remove dust and dirt.
A dirty coating forms on the rough inner surface of the sections, which reduces the heat transfer of the device. But technical specifications cast iron products on high:
- are slightly susceptible to water corrosion and can be used for more than 45 years;
- have high thermal power per section, therefore they are compact;
- are inert in heat transfer, so they smooth out temperature changes in the room well.
Another type of radiator is made of aluminum. Lightweight design, factory painted, does not require painting, easy to maintain.
But there is a drawback that overshadows the advantages - corrosion in an aquatic environment. Certainly, inner surface The heater is insulated with plastic to avoid contact of aluminum with water. But the film may be damaged, then it will start chemical reaction with the release of hydrogen, when creating excess gas pressure aluminum device may burst.
The temperature standards for heating radiators are subject to the same rules as radiators: it is not so much the heating of a metal object that is important, but the heating of the air in the room.
In order for the air to warm up well, there must be sufficient heat removal from work surface heating structure. Therefore, it is strictly not recommended to increase the aesthetics of the room with shields in front of the heating device.
Stairwell heating
Since we are talking about an apartment building, we should mention staircases. The coolant temperature standards in the heating system are as follows: degree measure on sites should not fall below 12 °C.
Of course, the residents' discipline requires closing the doors tightly entrance group, do not leave the transoms of the staircase windows open, keep the glass intact and promptly report any problems to the management company. If the management company does not take timely measures to insulate points of probable heat loss and maintain temperature conditions in the house, an application for recalculation of the cost of services will help.
Changes in heating design
Replacement of existing heating devices in the apartment is carried out with the obligatory approval of the management company. Unauthorized changes in the elements of warming radiation can disrupt the thermal and hydraulic balance of the structure.
When the heating season begins, changes in temperature conditions in other apartments and areas will be recorded. Technical inspection premises will reveal unauthorized changes in the types of heating devices, their quantity and size. The chain is inevitable: conflict - court - fine.
Therefore, the situation is resolved like this:
- if non-old ones are replaced with new radiators of the same size, then this is done without additional approvals; the only thing you need to contact the management company for is to turn off the riser during repairs;
- if new products differ significantly from those installed during construction, then it is useful to interact with the management company.
Heat meters
Let us remember once again that the heat supply network of an apartment building is equipped with thermal energy metering units, which record both the gigacalories consumed and the cubic capacity of water passed through the intra-house line.
In order not to be surprised by bills containing unrealistic amounts for heat when the degrees in the apartment are below normal, before heating season Check with the management company whether the metering device is in working condition and whether the verification schedule has been violated.
In the article we will touch on problems related to pressure and diagnosed with a pressure gauge. We will structure it in the form of answers to frequently asked questions. Not only the difference between the supply and return in the elevator unit will be discussed, but also the pressure drop in the heating system closed type, the principle of operation of the expansion tank and much more.
Pressure - not less important parameter heating than temperature.
Central heating
How does an elevator unit work?
At the elevator entrance there are valves that cut it off from the heating main. Along their flanges closest to the wall of the house, there is a division of areas of responsibility between homeowners and heat suppliers. The second pair of valves cuts off the elevator from the house.
The supply pipe is always at the top, the return pipe is always at the bottom. Heart elevator unit- mixing unit in which the nozzle is located. A stream of hotter water from the supply pipe flows into the water from the return pipe, drawing it into a repeated circulation cycle through the heating circuit.
By adjusting the diameter of the hole in the nozzle, you can change the temperature of the mixture entering the.
Strictly speaking, an elevator is not a room with pipes, but this unit. In it, the supply water is mixed with water return pipeline.
What is the difference between the supply and return pipelines of the route
- In normal operation it is about 2-2.5 atmospheres. Typically, 6-7 kgf/cm2 enters the house on the supply side and 3.5-4.5 on the return side.
Please note: at the exit from the thermal power plant and boiler house the difference is greater. It is reduced as losses due to hydraulic resistance routes and consumers, each of which is, simply put, a jumper between both pipes.
- During density tests, pumps pump at least 10 atmospheres into both pipelines. Tests are being carried out cold water when the input valves of all elevators connected to the route are closed.
What is the difference in the heating system
The difference on the highway and the difference in the heating system are two completely different things. If the return pressure before and after the elevator does not differ, then instead of supply, a mixture is supplied to the house, the pressure of which exceeds the readings of the pressure gauge on the return by only 0.2-0.3 kgf/cm2. This corresponds to a height difference of 2-3 meters.
This difference is spent to overcome the hydraulic resistance of bottlings, risers and heating devices. Resistance is determined by the diameter of the channels through which water moves.
What diameter should be the risers, fillers and connections to radiators in an apartment building?
The exact values are determined by hydraulic calculation.
In the majority modern houses the following sections apply:
- Heating outlets are made from pipes DN50 - DN80.
- For risers, a pipe DN20 - DN25 is used.
- The connection to the radiator is made either equal to the diameter of the riser, or one step thinner.
A caveat: you can only underestimate the diameter of the line relative to the riser when installing heating yourself if you have a jumper in front of the radiator. Moreover, it must be embedded into a thicker pipe.
The photo shows a more sensible solution. The diameter of the liner is not underestimated.
What to do if the return temperature is too low
In such cases:
- The nozzle is reamed. Its new diameter is agreed with the heat supplier. An increased diameter will not only raise the temperature of the mixture, it will also increase the drop. The circulation through the heating circuit will speed up.
- In the event of a catastrophic lack of heat, the elevator is disassembled, the nozzle is removed, and the suction (pipe connecting the supply to the return) is turned off.
The heating system receives water directly from the supply pipe. Temperature and pressure drop increase sharply.
Please note: this is an extreme measure that can only be taken if there is a risk of heating defrosting. For normal operation CHP and boiler houses have a fixed return temperature; By turning off the suction and removing the nozzle, we will raise it by at least 15-20 degrees.
What to do if the return temperature is too high
- The standard measure is to weld the nozzle and re-drill it, with a smaller diameter.
- When an urgent solution is needed without stopping the heating, the difference at the entrance to the elevator is reduced using shut-off valves. This can be done with an inlet valve on the return line, monitoring the process using a pressure gauge.
This solution has three disadvantages:- The pressure in the heating system will increase. After all, we limit the outflow of water; the lower pressure in the system will become closer to the supply pressure.
- The wear of the cheeks and valve stem will accelerate sharply: they will be in a turbulent flow of hot water with suspensions.
- There is always the possibility of worn cheeks falling. If they completely shut off the water, the heating (primarily the access heating) will defrost within two to three hours.
Why do you need high pressure in the line?
Indeed, in private houses with autonomous systems For heating, an excess pressure of only 1.5 atmospheres is used. And, of course, more pressure means much higher costs for stronger pipes and power supply for injection pumps.
The need for more pressure is related to the number of floors apartment buildings. Yes, circulation requires a minimum drop; but the water needs to be raised to the level of the jumper between the risers. Each atmosphere of excess pressure corresponds to a water column of 10 meters.
Knowing the pressure in the line, it is not difficult to calculate the maximum height of a house that can be heated without the use of additional pumps. The calculation instructions are simple: 10 meters multiplied by the return pressure. A return pipeline pressure of 4.5 kgf/cm2 corresponds to a water column of 45 meters, which, with a height of one floor of 3 meters, will give us 15 floors.
By the way, hot water supply is supplied to apartment buildings from the same elevator - from the supply (at a water temperature not exceeding 90 C) or return. In case of insufficient pressure upper floors will be left without water.
Heating system
Why do you need an expansion tank?
Accommodates excess expanded coolant when it is heated. Without an expansion tank, the pressure may exceed the tensile strength of the pipe. The tank consists of a steel barrel and a rubber membrane that separates air from water.
Air, unlike liquids, is highly compressible; with an increase in coolant volume by 5%, the pressure in the circuit due to the air tank will increase slightly.
The volume of the tank is usually taken approximately equal to 10% of the total volume of the heating system. The price of this device is low, so the purchase will not be ruinous.
The correct installation of the tank is with the hose facing up. Then excess air will not get into it.
Why does pressure decrease in a closed circuit?
Why does pressure drop in a closed heating system?
After all, the water has nowhere to go!
- If there are automatic air vents in the system, the air dissolved in the water at the time of filling will escape through them.
Yes, it makes up a small part of the coolant volume; but big change volume and there is no need for the pressure gauge to note changes. - Plastic and metal-plastic pipes may deform slightly under pressure. In combination with high temperature water this process will speed up.
- The pressure in the heating system drops when the temperature of the coolant decreases. Thermal expansion, remember?
- Finally, minor leaks are easy to see only in centralized heating through rust marks. Water in closed loop not so rich in iron, and the pipes in a private house are most often not made of steel; therefore, it is almost impossible to see traces of small leaks if the water has time to evaporate.
Why is a pressure drop in a closed circuit dangerous?
Boiler failure. In older models without thermal control - up to an explosion. Modern older models often have automatic control of not only temperature, but also pressure: when it falls below a threshold value, the boiler reports a problem.
In any case, it is better to maintain the pressure in the circuit at a level of approximately one and a half atmospheres.
How to slow down the pressure drop
In order not to refuel the heating system over and over again every day, it will help simple measure: put the second one expansion tank larger volume.
The internal volumes of several tanks are summed up; the greater the total amount of air in them, the smaller the pressure drop will cause a decrease in the volume of coolant by, say, 10 milliliters per day.
Where to put the expansion tank
In general, there is a big difference for membrane tank no: it can be connected anywhere in the circuit. Manufacturers, however, recommend connecting it where the water flow is as close to laminar as possible. If there is a tank in the system, the tank can be mounted on a straight section of pipe in front of it.
Conclusion
We hope that your question has not been left unanswered. If this is not the case, perhaps you can find the answer you need in the video at the end of the article. Warm winters!
If there is a large temperature difference between the boiler supply and return, the temperature on the walls of the boiler combustion chamber approaches the “dew point” temperature and condensation may form. It is known that during the combustion of fuel various gases are released, including CO 2, if this gas combines with the “dew” that has fallen on the walls of the boiler, an acid is formed that corrodes the “water jacket” of the boiler furnace. As a result, the boiler can quickly fail. To prevent dew, it is necessary to design the heating system so that the temperature difference between the supply and return is not too large. This is usually achieved by heating the return coolant and/or including a hot water supply boiler in the heating system with soft priority.
To heat the coolant between the return and the boiler supply, a bypass is made and a circulation pump is installed on it. The power of the recirculation pump is usually chosen as 1/3 of the power of the main circulation pump (sum of pumps) (Fig. 41). To ensure that the main circulation pump does not “press” the recirculation circuit into reverse side, a check valve is installed behind the recirculation pump.
Rice. 41. Return heating
Another way to heat the return is to install a hot water boiler in close proximity to the boiler. The boiler is “placed” on a short heating ring and positioned in such a way that hot water from the boiler after the main distribution manifold immediately went into the boiler, and from it returned back to the boiler. However, if the need for hot water is small, then both a recirculation ring with a pump and a heating ring with a boiler are installed in the heating system. With proper calculation, the recirculation pump ring can be replaced with a system with three- or four-way mixers (Fig. 42).
Rice. 42. Heating the return using three- or four-way mixers On the pages “Regulation equipment heating systems» almost all technically significant devices and engineering solutions present in classical heating schemes. When designing heating systems on real construction sites, they must be fully or partially included in the design of heating systems, but this does not mean that exactly the heating fittings that are indicated on these pages of the site should be included in a specific project. For example, at the recharge unit you can install shut-off valves with built-in check valves, or you can install these devices separately. Instead of mesh filters, you can install dirt filters. You can install an air separator on the supply pipelines, or you can not install it, but install it instead automatic air vents for everyone problem areas. You can install a deslimer on the return line, or you can simply equip the collectors with drains. Adjusting the coolant temperature for circuits " heated floors» can be done with high-quality adjustment using three- and four-way mixers, or can be produced quantitative regulation by installing a two-way valve with a thermostatic head. Circulation pumps can be installed on common pipe supply or vice versa, on the return. The number of pumps and their location may also vary.
After installing the heating system, you need to configure temperature regime. This procedure must be carried out in accordance with existing standards.
The coolant temperature requirements are set out in regulatory documents, which establish the design, installation and use engineering systems residential and public buildings. They are described in State building codes and rules:
- DBN (V. 2.5-39 Heat networks);
- SNiP 2.04.05 “Heating, ventilation and air conditioning.”
For the calculated supply water temperature, the figure is taken that is equal to the water temperature at the outlet of the boiler, according to its passport data.
For individual heating deciding what the coolant temperature should be should take into account the following factors:
- Start and end of the heating season average daily temperature outside +8 °C for 3 days;
- Average temperature inside heated premises of housing and communal services and public importance should be 20 °C, and for industrial buildings 16°C;
- The average design temperature must comply with the requirements of DBN V.2.2-10, DBN V.2.2.-4, DSanPiN 5.5.2.008, SP No. 3231-85.
According to SNiP 2.04.05 “Heating, ventilation and air conditioning” (clause 3.20), the coolant limit values are as follows:
Depending on the external factors, the water temperature in the heating system can be from 30 to 90 °C. When heated above 90 °C, dust and paintwork. For these reasons, sanitary standards prohibit greater heating.
To calculate optimal indicators, special graphs and tables can be used, which define standards depending on the season:
- With an average reading outside the window of 0 °C, the supply for radiators with different wiring is set at 40 to 45 °C, and the return temperature at 35 to 38 °C;
- At -20 °C, the supply is heated from 67 to 77 °C, and the return rate should be from 53 to 55 °C;
- At -40 °C outside the window, all heating devices are set to maximum valid values. On the supply side it is from 95 to 105 °C, and on the return side it is 70 °C.
Optimal values in an individual heating system
H2_2Heating system helps to avoid many problems that arise with a centralized network, and optimal temperature The coolant can be adjusted according to the season. In the case of individual heating, the concept of standards includes the heat transfer of a heating device per unit area of the room where this device is located. The thermal regime in this situation is ensured design features heating devices.
It is important to ensure that the coolant in the network does not cool below 70 °C. The optimal temperature is considered to be 80 °C. WITH gas boiler It is easier to control heating because manufacturers limit the ability to heat the coolant to 90 °C. Using sensors to regulate the gas supply, the heating of the coolant can be adjusted.
It is a little more difficult with solid fuel devices; they do not regulate the heating of the liquid, and can easily turn it into steam. And it is impossible to reduce the heat from coal or wood by turning the knob in such a situation. Control of heating of the coolant is quite conditional with high errors and is carried out by rotary thermostats and mechanical dampers.
Electric boilers allow you to smoothly regulate the heating of the coolant from 30 to 90 °C. They are equipped with an excellent overheat protection system.
Single-pipe and double-pipe lines
The design features of a single-pipe and two-pipe heating network determine different standards for heating the coolant.
For example, for a single-pipe main the maximum norm is 105 °C, and for a two-pipe main it is 95 °C, while the difference between the return and supply should be respectively: 105 - 70 °C and 95 - 70 °C.
Coordination of coolant and boiler temperatures
Regulators help coordinate the temperature of the coolant and the boiler. These are devices that create automatic control and adjustment of return and supply temperatures.
The return temperature depends on the amount of liquid passing through it. Regulators cover the liquid supply and increase the difference between the return and supply to the level required, and the necessary indicators are installed on the sensor.
If the flow needs to be increased, a boost pump can be added to the network, which is controlled by a regulator. To reduce the heating of the supply, a “cold start” is used: that part of the liquid that has passed through the network is again transported from the return to the inlet.
The regulator redistributes the supply and return flows according to the data collected by the sensor and ensures strict temperature standards heating networks.
Ways to reduce heat loss
The above information will help to be used to correctly calculate the coolant temperature norm and tell you how to determine situations when you need to use a regulator.
But it is important to remember that the temperature in the room is affected not only by the temperature of the coolant, street air and wind strength. The degree of insulation of the facade, doors and windows in the house should also be taken into account.
To reduce heat loss from your home, you need to worry about its maximum thermal insulation. Insulated walls, sealed doors, metal-plastic windows will help reduce heat loss. This will also reduce heating costs.