On the possibility of practical implementation of the regulation of heat consumption of buildings by the method of periodic interruption of the coolant flow. Weather-dependent control of pumping and mixing units in underfloor heating systems

C. Deineko

Weather-dependent regulation for heat points of centralized heating systems centralized systems heating of buildings was carried out at CHPPs, boiler houses and elevator units of central (CTP) and individual (ITP) heating points of buildings. However, due to the large length of the pipelines and the associated inertia of the systems, this did not give a real effect. At the same time, elevator units were installed in the central heating station or ITP, which did not allow quantitative regulation of the coolant. Accordingly, the temperature of the water entering the heating system varied depending on the temperature of the coolant coming from the CHP or boiler house, while the flow rate remained constant. Modern controllers make it possible to carry out qualitative and quantitative regulation of heating systems, and thus save a significant part of energy resources. Consider typical schemes controller applications offered by Honeywell

Modern controllers allow you to control several circuits, each of which can be modified by changing the settings. Consider several schemes for automating the operation of a heat point using weather-dependent regulation.

The scheme of independent connection of the heating system (Fig. 1) allows not only to separate the circuits of the internal heating system from the circuit of the central heating network, to regulate the temperature of the return flow of the primary side (the temperature of the coolant supplied after the heat exchanger to the heat source), but also to carry out weather-dependent temperature control of the internal system heating (secondary side). At the same time, the temperature of the heat carrier in the heating system of the building changes depending on the selected temperature graph and fluctuations in outdoor temperature.

Rice. 1. Scheme of independent connection of the heating system:
SDC7-21N - controller; AF - outdoor air temperature sensor; VFB, WF - coolant temperature sensors; V1 - two-way control valve; DKP- circulation pump heating systems; SDW - indoor temperature sensor or room unit for remote control

The heating medium temperature is controlled by a two-way control valve (V1), (the valve can also be installed on the supply line T1), and circulation is carried out by the operation of the heating system circulation pump (DKP). The valve regulates the amount of heat carrier entering the heat exchanger for heating water circulating in the internal heating system, depending on the readings of the heat carrier temperature sensors (WF and VFB). Depending on the outdoor temperature (AF) and the selected temperature curve, the temperature of the heat carrier circulating in the internal heating system (secondary circuit) changes. Among the possible settings for the individual heating characteristics of the system is the choice of the type of task depending on the enclosing structures, the features of the internal heating system, temporary operating modes depending on the time of day and day of the week, the antifreeze function, and the periodic switching on of the circulation pump in summer.

Air temperature control in heated rooms is carried out by using an indoor air temperature sensor or a room unit (SDW), which can be used as a remote control panel.

Malfunctions in the system are displayed on the controller display. This is, for example, a break in the sensor or a situation where it is impossible to reach the set temperature of the coolant. When using a scheme with one circuit of the heating system and one circuit DHW systems(Fig. 2), it is possible to achieve weather-compensated control of the return flow temperature of the primary side and control of the heating circuit depending on the outdoor temperature, as well as maintaining a fixed temperature value in the DHW system.

Rice. 2. Scheme of independent connection of the heating system and the DHW system:
MVC80 - controller; AF - outdoor air temperature sensor; VFB1, VFB2, VF1, SF - coolant temperature sensors; V1, V2 - two-way control valves; P1 - circulation pumps of the heating system; P2 - circulation pumps of the DHW system; PF - make-up pump of the heating system; SV1 - make-up valve of the heating system; PS1 - pressure switch

The control is carried out by means of control valves (V1 and V2), the operation of the heating and DHW circulation pumps (P1 and P2).

Automatic make-up of the heating system is carried out by the installation, make-up pump (PF) and valve (SV1). If the secondary side minimum pressure switch (PS1) generates a non-critical alarm, the make-up valve SV1 opens and the make-up pump PF starts. Setting custom characteristics carried out similarly to the previous option.

By using a scheme with one heating circuit and a DHW circuit with a two-stage heat exchanger (fig. 3), it is possible to achieve weather-compensated control of the primary side common return temperature and weather-compensated control of the heating circuit, as well as maintaining a fixed temperature in the DHW system. Heat cold water for sanitary needs is carried out by using heat from the coolant after the heat exchanger of the heating system, and heating the water to the required temperature and maintaining it in the DHW system - due to the operation of the second stage of heating and the control valve (V2).

Rice. 3. Control scheme of the heating and hot water system with a two-stage heat exchanger:
MVC80 - controller; AF - outdoor air temperature sensor; VFB1, VF1, SF - coolant temperature sensors; V1, V2 - two-way control valves; P1 - circulation pumps of the heating system; P2 - circulation pumps of the DHW system; PF - make-up pump of the heating system; SV1 - make-up valve of the heating system; PS1 - pressure switch

The scheme of independent connection of two heating circuits is shown in fig. 4. It is used for weather-compensated control of the return flow temperature (VFB) of the primary side via valve V1.

Rice. 4. Scheme of independent serial connection of two heating circuits:
SDC9-21N - controller; AF - outdoor air temperature sensor; VFB, WF, VF1 - coolant temperature sensors; V1 - two-way control valve; MK1 - mixing valve actuator; P1 - circulation pump of the mixing circuit of the heating system; DKP - circulation pump of the direct circuit of the heating system; RLF1 - temperature sensor of the heat carrier from the heating system; SDW - indoor air temperature sensor or room module for remote control, TKM - emergency thermostat to prevent overheating of the coolant

This scheme allows to achieve the control of the mixing circuit of the underfloor heating system and the direct circuit of the radiator heating system with weather compensation or with a constant temperature.

The control is carried out by the operation of the two-way control valve V1), the three-way mixing valve (MK1) as well as the circulation pumps (P1) of the mixing circuit and the direct heating circuit pump (DKP). The return water temperature (VFB) is controlled according to an adjustable temperature curve.

To control the temperature of the heat carrier dependent systems heating (in which network water comes from the heat source and internal system heating) is used three-way mixing valve(MK1) (Fig. 5). Before the control valve, a differential pressure regulator is installed, and in the case when the pressure in the return network pipeline (T2) is not enough for normal hydraulic mode operation of the heating system, a pressure regulator "to itself" can be installed at the outlet of the heating system after the mixing bridge. Also, the circulation pump of the heating system (P1) can be installed not on the supply pipe of the heating system (as shown in Fig. 5), but on the return pipe.

If you turn off the heating system of a non-heat-intensive building at 17:00

at zero outdoor temperature, then the temperature in the premises will drop to + 10 °C only by two in the morning. By this time, the estimated amount of coolant must be supplied to the system for 10 - 15 minutes in order to raise the temperature to 10.5 -11 °C, after which the system must be turned off again for 45 - 55 minutes. In this intermittent heating mode, the system must operate until approximately 6 am, when it must be turned on for continuous operation in order to increase the temperature of the indoor air by the start of the working day. Initially, this temperature will rise rapidly when the calculated amount of coolant is supplied to the system, because the thermal power heating appliances will exceed the calculated value due to the lower air temperature, however, with increasing temperature, the rate of temperature increase will decrease, and up to the calculated (18 °C) value, this temperature will theoretically increase indefinitely, if the heating process is not artificially forced by supplying to the system, starting from 7 hours 30 minutes, the coolant flow rate increased compared to the calculated value. By 9 o'clock in the morning, that is, by the beginning of the working day, the temperature of the internal air will reach 18 °C, and the coolant flow should be lowered again to the calculated value.

The nature of the relative (in fractions of the calculated values) changes in the coolant flow and heat consumption by hours of the day is shown in fig. 6.

It would be wrong to almost completely stop the supply of coolant at night, because in this case the temperature of the water in the return pipe of the heating system would not reflect its actual state in any way, and this would not allow using this important parameter as a signal for controlling the operation of automation. Therefore, the minimum flow rate of the coolant should be at a level of 5 to 10% of the calculated value. Then the short-term maximum, during the period of active flooding, the water consumption will not exceed 140% of the calculated value.

The relative values ​​of the hourly heat consumption will be close to the flow rates, however, they will not be exactly equal to them due to the fact that the temperature of the water in the return pipeline will change along with the change in flow. So, if the minimum heat carrier flow rate is set at 5% of the calculated value, then the minimum heat consumption will be about 8%. Taking this difference into account, the decrease in daily heat consumption at a minimum night temperature of 10 °C is estimated at 18–20%.

Thermal point

The main and indisputable criterion for the quality of a modern heating system is its ability to adequately respond by means of automatic regulation to the changing needs for thermal energy of a heated building, regardless of whether the demand changes as a result of external influences on the building or as a result internal factors. In modern heat points, an adequate response is ensured by means of proportional quality regulation, at which the temperature of the coolant changes smoothly, while the water flow in the heating system remains unchanged.

To implement proportional control in heating point circulating pumps are installed, and the mixing of water from the supply pipeline of the heating network with water from the return pipeline of the heating system is provided by a control valve installed on the supply pipeline, or a three-way control valve installed at the mixing point. When using microprocessor automation, it is possible to provide in this way a fairly effective central control of heating systems, although it should be noted that any central control of a multi-room building is not able to fully solve the problem of economical energy consumption as efficiently as it could be implemented by means of local control.

In Ukraine, silent circulation pumps that could be installed in the heating points of buildings are not produced, and therefore almost all existing buildings attached to systems district heating, are equipped with an elevator thermal input. Unlike an electric circulation pump, a water-jet pump (elevator) is not capable of providing proportional regulation of thermal power, because with a constant nozzle, mixing occurs in it with a constant proportion of mixing media, while the control process implies the possibility of changing this proportion or, as is commonly called , mixing ratio. For this reason, in the West, the elevator is completely rejected as a device for heating points. Perhaps this happened also because there have been no problems with silent pumps for a long time.

Despite the fact that modern silent pumps are now freely offered by foreign companies on the domestic market of Ukraine, we will have many problems with this equipment, if we evaluate these problems, looking from dark basements and impassable technical undergrounds of millions of residential buildings and kindergartens built over the past decade , schools and other buildings. Therefore, it is worth taking a closer look at the elevator, familiar to everyone, to which flaws are sometimes attributed that are not at all characteristic.

They say that the elevator has a low efficiency, and this would be true if it would require energy to operate. In fact, the existing pressure difference in the heat supply pipelines is used for mixing operation. If it were not for the elevator, then the coolant flow would have to be throttled, and throttling, as you know, is a pure loss of energy. Therefore, in relation to thermal inputs, an elevator is not a pump with low efficiency, but a device for the secondary use of energy spent on driving the circulation pumps of a thermal power plant or a district boiler house.

They say that an elevator is a device that is not capable of providing a given mixing ratio, because the nozzle must be designed for the available pressure in the pipelines of the heating network, and the mixing ratio will be the same as it turns out. Unfortunately, in practice this is often done, but this is a wrong practice. The nozzle must not be designed for the available available pressure. Excessive pressure must be eliminated by a differential pressure regulator or a throttle, and the elevator nozzle must be selected in such a way that the specified water flow in the heating system is ensured. It is worse when there is not enough available pressure at the inlet to operate the elevator. This sometimes happens, but then the elevator should not be used.

The inability to provide proportional control is the only drawback of the elevator, a device, in general, very simple, reliable and unpretentious in operation.

Let us now look again at the nature of the change in the flow rate of the coolant with the program control of the thermal power (Fig. 6). There is no need for any proportional change in the flow of network water, that is, there is no need for anything that the elevator could not handle. It immediately opens real opportunities reduce heat consumption in public buildings without resorting to a complete and costly reconstruction of existing heating points, which could be equipped as shown in fig. 7.

A heat meter (pos. 1-3) is installed on the heat input. The nozzle of the existing elevator 4 is calculated to provide design mixing, and throttle washer 5 - for redemption of excess pressure. At the end of the working day, the solenoid valve 6 should close, having a calibrated hole for passing 5% of the coolant when the valve is closed. At the same time, the solenoid valve 7 will close, which disconnects the hot water supply system from the heat source for non-working hours. Solenoid valve 8 opens on a short time before the start of the working day in order to intensively heat the premises,

chilled overnight. The coolant flow through the open valve 8 is limited by a throttle washer installed next to it.

The temperature sensors of the coolant 9 and air 10 provide information for the electronic controller 11, which has a built-in clock (timer). The controller commands the opening and closing of solenoid valves 6, 7 and 8. Commands can be generated based on information received from temperature sensors installed in two control rooms located on different facades of the building, and information about the temperature in the coldest control room should be taken into account. , which is very important for those cases when one of the facades is blown by a strong wind. You can also use information about the temperature of the water in the return pipe in order to calculate the duration of a possible shutdown of the heating system. For example, at outdoor temperatures above +5 °C, the regulator can turn off the heating system for the whole night, and at temperatures of -15 °C and below, the night program control mode can be disabled.

The heat point also includes conventional devices (pos. 12-17) for hot water supply. These devices also include an air collector 15 with a valve 16 for automatic air release.

It is known that in hot water supply systems, oxygen corrosion is a great danger. Many devices are used to suppress this corrosion (eg cathodic protection, silicate water treatment, etc.), but the simplest of these devices is an air collector with a tap installed directly after the water heater. The oxygen liberated from the heated water escapes into the atmosphere before it enters the pipelines.

| free download About features practical implementation regulation of heat consumption of buildings by the method of periodic interruption of the coolant flow (page 2 of 3), Gershkovich V.F,

Equipment additional equipment traditional heating systems can significantly increase their efficiency without radical reconstruction during the modernization of the housing stock.

Potential of heating systems

For a water heating system, an energy-efficient level of heat consumption can be achieved with the following set of functions and capabilities:
- automatic maintenance of the temperature graph at the entrance to the building;
- regulation of heat transfer of the system, including thermo-regulation on heating devices and risers;
- automatic maintenance of the required/calculated distribution of the coolant flow over all parts of the system;
- individual heat metering, motivated by payment according to actual consumption.

According to the design, the following main options for energy-efficient heating systems can be represented:
- a system with horizontal apartment-by-apartment piping with various design options for apartment heating substations or switchboards, including combinations of automatic control, heat exchangers for heating circuits and / or hot water, etc.;
- a traditional heating system with vertical intra-apartment risers - one-pipe and two-pipe, comprehensively equipped with automatic control and heat metering devices.

Others are possible design options systems and their combinations.
For systems with horizontal wiring, the energy efficiency potential and the set of equipment that provides the standard level of heat consumption are obvious and described in the works of many specialists. At the same time, the potential for increasing the energy efficiency of traditional vertical heating systems is not yet obvious to many specialists. However, it is very significant, and the possibility of upgrading such systems should be considered in more detail, because:
- these systems are the most widely used, especially in the existing housing stock;
- the radical constructive transformation of such systems into horizontal ones during the modernization of the building is too costly.

Modernization of the coolant inlet to the building

The most important element of the heating system of any design is the node for entering the coolant into the building. The most energy efficient input solutions are automated node management (AUU, option dependent schema connection of the heating system) or an individual heating point (ITP, option independent scheme connections with heat exchangers of the heating and DHW circuits). These devices ensure compliance with a temperature schedule that is adequate to the outdoor temperature and the current heat consumption of the building, as well as reliable pump circulation coolant in the heating system.

The economic effect from the use of these devices ranges from 10 to 30%, depending on the compliance of the state of the building with design solutions and on the conditions of its operation.

A number of alternative ACs are known technical solutions input node, such as:
- coolant mixing unit with elevators with constant or variable mixing ratio;
- unit without mixing the coolant - used when a coolant is supplied to the building with a temperature equal to the design temperature in the heating system.

In our opinion, the use of these devices and technical solutions in energy-efficient heating systems is unacceptable. Technical argumentation that skillfully substantiates the inadequacy of such solutions for modern systems heating, has long been known. However, for various reasons, criticism is not always taken into account.

A single application of such solutions leads to problems in one particular building. But when the assumption about the use of an elevator is included in the regulations, in particular, in the updated HVAC SNiP, as is done now, this is already a more serious mistake that will lead to massive excesses of the normalized level of energy efficiency in newly erected and modernized buildings.

In confirmation of these words, one can refer to the work of colleagues from VTI, in which a number of possible schemes for automated elevator nodes mixing. The paper considers in detail the main disadvantages of each of the schemes. A common drawback of all schemes is the fact that in order to ensure adequate performance of such devices, it is necessary to maintain a constant and small hydraulic resistance in the heating system. However, these requirements are practically impracticable if there are thermostats and other automatic control valves in the heating system.

It should also be noted the negative operational practice of using such elevators.

Maintaining the design distribution of the coolant flow

This event eliminates overflows or heat shortages on individual risers of traditional vertical heating systems. This possibility is ensured by the installation of automatic balancing valves on the risers, maintaining a constant pressure drop in the risers. two-pipe systems or constancy of flow in the risers of single-pipe heating systems.

For vertical two-pipe heating systems, this event does not raise questions among specialists, however, regarding a single-pipe system, a number of specialists express doubts about its relevance.

These doubts are based on the following:
- a significant number of vertical single-pipe systems, especially in typical housing construction, are calculated using the method of variable (sliding) temperature differences, which theoretically should ensure the hydraulic balance of the risers;
- in single-pipe heating systems, even when thermostats are triggered, a constant coolant flow is maintained, i.e. automated control and adjustment of risers are not required.

For each of these statements there is a fairly simple counterargument. In particular, according to the first statement: the design limitations of this method are known from the literature, which do not allow balancing the risers accurately enough. Also, the statement about the constancy of the flow rate with a leakage coefficient of the order of 0.25 and with a change in the flow rate of the coolant associated with a change in the gravitational pressure in the risers is also incorrect. All this is quite convincingly shown in detailed calculations performed by Ukrainian specialists.

However, all these design effects are offset by the influence of errors and assumptions introduced into the heating system on a massive scale during its design and installation, as well as changes in the design of the system made by residents within the apartment.

The results of a survey of typical sectional buildings showed a spread in the flow rate of the coolant at the control risers within ± 30% relative to the design values. After the balancing valves were installed and adjusted to the design values, the imbalance did not exceed ±3%.

As a result, the heat consumption of buildings decreased by 7-12% due to the reduction of unreasonable ventilation in rooms on "overheated" risers and adjustment of the automation settings of the input unit, which protect "lagging" risers (Fig. 1).

Rice. 1. Differences in the operation of thermostats

Thermal control of risers as a means of high-quality control of heat transfer

The next step in improving the energy efficiency of a traditional single-pipe heating system is to provide quantitative regulation of the heat transfer of the system not only at the level of heaters using thermostats, but also on the risers by installing temperature controllers at the root of the risers, structurally combining them with balancing valves (Fig. 2). The effect is achieved by reducing the coolant flow through a specific riser, the temperature of the coolant in which rises as a result of closing the thermostats with excess heat in individual rooms.

Rice. 2. Thermal control of risers of single-pipe heating systems

The results of the operation of the thermostat on one of the control risers are shown in Figure 3. The graphs show a decrease in the coolant flow in the riser as a result of an increase in the coolant temperature in it as a result of closing thermostats on individual heaters. At the same time, the air temperature in the control room does not change.

Rice. 3. Energy efficiency of automatic balancing risers

The setting values ​​for these devices are determined by surveying the building and identifying the potential sources of excess heat. The most effective are "permanent" thermostats with an electric drive and an automatic control system for the temperature of the coolant in the risers.

The economic effect of the use of thermal control of risers depends on the amount of excess heat entering the building not taken into account in the project, including from the excess heating surface of heating devices. According to the results of the survey of experimental buildings, the effect ranged from 8 to 12%, depending on the condition of the building.

Individual (per apartment) heat metering

Individual (per apartment) heat metering with payment according to its actual consumption is the most important factor motivating residents to save energy. Without this measure, the system of energy saving measures remains "open", based only on administrative levers.

The following main types of systems are known individual accounting heat applied to traditional vertical one-pipe heating systems.
A system with allocators (heatcostallocator - distributor of the cost of consumed heat) on each heater registers the temperature difference (tall) between the surface of the heater and the air in the room. The coolant consumption is recorded on the house meter and is used only in the calculation of the house heat consumption.

The system with coolant temperature sensors installed in the riser on each floor registers the temperature difference (te) of the coolant in the riser within each floor. The coolant flow rate is recorded at each riser and in the house heat meter.

For vertical two-pipe heating systems, only a system with allocators is used.

Both of the above systems are distributive, the principle of their operation is described in detail in the literature.

In this article, only one aspect is considered - the accuracy of the calculation of heat consumption. This information should allow the designer to make a choice between systems that is adequate to the tasks of energy saving and protection of the rights of the tenant to a fair payment for the consumed heat.

The table shows changes in temperature differences tall and test and the corresponding measurement errors in the individual metering systems under consideration, depending on the number of storeys of the building and the temperature of the coolant during heating season. In this case, the error in determining test is calculated taking into account the measurement error of the temperature sensor tdat = 0.05 °C.

Tab. 1. Temperature differences tall and test and the corresponding measurement errors

During the operation of the system, due to a number of reasons, it is possible to reduce the measurement accuracy of the sensor. For illustration, the table in brackets shows the data calculated for tdat = 0.1 °C for the variant with the largest error.

As can be seen from the table, tall >> tet, while the absolute values ​​of tet are very small. Both of these circumstances significantly affect the accuracy of the calculation of payments. So, with an average monthly charge for consumed heat, for example, 2,000 rubles. unreasonable overpayment or underpayment of individual tenants can amount to:
- 450-550 rubles / month - for a system with sensors on risers at tdat = 0.05 °С;
- 650-1,050 rubles/month - for a system with sensors on risers at tdat = 0.1 °С;
- 60-100 rubles/month — for the accounting system with allocators.

As can be seen from the example, the error in calculating payments for a system with sensors on risers is several times higher than the error in a system with allocators. Obviously, the accrual error is possible in both directions - both in favor of the tenant and in favor of the resource provider. In both cases, it is impossible to bring the balance according to the readings of the apartment and house meters, as well as to exclude complaints from the tenants or the heat supplier, up to litigation.

In any case, in the commercial calculation for heat, an individual metering system with the smallest possible error should be recommended for use.

Conclusion

The above measures for the modernization of existing vertical one-pipe and two-pipe heating systems show that in order to significantly increase their energy efficiency, there is no need to radically reconstruct traditional systems in the course of modernization, it is enough just to equip them with appropriate equipment.

Literature
1. Baibakov S. A., Filatov K. V. “On the possibility of regulating the elevator units of heating systems”. // "News of heat supply". No. 7, 2010
2. Bogoslovsky V. N., Skanavi A. N. “Heating”. - M .: Stroyizdat, 1991
3. Mileikovsky V. A. “Mathematical modeling of variable hydraulic and thermal modes of instrument assemblies of single-pipe vertical heating systems”. // Danfoss Info. No. 1-2, 2012
4. ABOK standard “Cost allocators of consumed heat from room heaters”. STO NP "ABOK" 4.3-2007 (EN 834:1994).

Regulation of the heating system implies bringing the process of consumption of thermal energy in line with the real needs for it. A simple example: the colder it is outside, the harder you have to work heating system and, conversely, when the air temperature in the house rises above the limit value, the temperature of the coolant in the heating devices should decrease.

The easiest way to regulate the heating system is to manually control the operation of the boiler and heating devices: it is hot in the house, you can turn off the coolant supply valve to the heating device, as a result of which the return water will return to the boiler hot, which will turn off the boiler or reduce fuel consumption.

An even simpler way to regulate the heating system is to temporarily turn off the boiler and turn it on when the room temperature drops. To date, similar manual control» is outdated and it is possible to talk about it only in relation to heating appliances that do not have automatic control systems, for example, to wood stoves or to some types of wood-burning heating boilers.

Modern heating control systems solve two problems simultaneously:

allow you to create really comfortable conditions in the house, maintaining a predetermined temperature level in it

optimize fuel consumption and, as a result, reduce heating costs

The heating system is adjusted according to one of two parameters

Outdoor temperature

Indoor temperature

It is believed that more comfortable conditions in a private house can be obtained by changing the temperature of the coolant, depending on the conditions inside the room. This is explained simply: heat loss do not always linearly depend on the outside temperature: it is necessary to take into account the wind speed and the location of the building relative to the cardinal points.

For apartment buildings and systems central heating more important is the outdoor air temperature, which makes it possible to obtain averaged results immediately for all consumers of thermal energy.

Methods for regulating heating systems

As mentioned above, the main task of regulating the heating system is to maintain a certain temperature level in the room. You can do this in several ways:

By changing the speed of movement of the coolant through the heating device using stop valves or with a circulation pump. In this case, there is a change in the amount of coolant passing through the heating device per unit of time. This method is called quantitative.

By changing the heating temperature of the coolant (changing its quality). This method is called qualitative.

It should be noted that both methods are inextricably linked with each other and in systems High Quality are used at the same time.

Practical implementation of method No. 1

The easiest way to control heating is to change the operating modes of the circulation pump depending on the temperature in the room: it is cold, the pump operates at maximum speed, which ensures the most intense heat transfer from heating devices. It became hot: the coolant movement speed is minimal. At night or during the day, when all residents of the house are at work or at school, the heat saving mode can also be used, which provides for a minimum flow rate of water in the heating system.

The disadvantage of heating control with a circulation pump is general approach to all rooms in the house, regardless of the actual need for thermal energy.

More accurate, local regulation of the heating system can be obtained by controlling the operation of a single radiator.

How to control the operation of a heating radiator?

In practice, it is possible to change the flow rate of the coolant using automatic heads, the design of which includes a valve and a temperature sensor that responds to changes in the temperature in the room. The principle of operation of the device is quite simple: the head cavity is filled with liquid, the volume of which depends on temperature: when it gets cold, the volume of liquid decreases, the valve opens, while increasing the flow rate of the coolant. When the temperature in the room rises, on the contrary: the volume of liquid increases, the valve closes, blocking the movement of the coolant.

The disadvantage of automatic heads is their low reliability and frequent failure. More perfect and reliable is the method of heating control using a servo driven and blocking the supply of coolant to the radiator, also depending on the temperature in the room.

Both the automatic head and the servo drive are designed to change the temperature of the coolant not in the entire heating system, but only in one individual radiator. If there are several heaters in the room, each of them will have to be equipped with such automatic control systems. Only in this case can you really regulate the heating.

All heating devices in the house can be combined into one automatic heating control system.

Adjustment during operation

There is also another way - operational regulation. As the name implies, the heating system is regulated while it is running. This is necessary to make adjustments as needed. For example, if there is a need to increase or decrease the amount of heat (depending on the air temperature outside and meteorological conditions). The change in the amount of heat generated by the system is provided by adjusting the temperature or by changing the flow rate of the coolant. Thus, it can be conditionally divided into "qualitative" and "quantitative" options for monitoring the system.

Quality regulation carried out directly at the thermal station. There are local and group. Quantitative has three divisions: group, individual and local.

This method of controlling the system is carried out manually using valves and taps, and automatically when the air temperature in the apartment changes. In branched systems, it is necessary to change the coolant flow rate - this should simplify the adjustment task.

In private homes, it requires knowledge about the features of individual water heating. The main task of the system is to provide optimal microclimate for the whole family. Unfortunately, quite often heating gets out of control. Most often, incorrect operation and untimely adjustment of parameters lead to inefficiency of indicators. The reasons may also be errors made in the design of heating, or poor insulation.

As practice shows, during the heating system, people do not ask themselves the question of calculations. Installation specialists prefer to do everything quickly, due to which accuracy suffers. As a result, it can be cool in one room and too hot in another. Comfort in this case can not be expected.

When evaluating the quality of the system and the efficiency of its operation, all parameters and features of your heating should be taken into account. Regardless of the power source (electric boiler or gas), the system must work smoothly, so proper regulation is the key to a warm and comfortable home.

The easiest way to regulate water circulation is to use thermostat located on the boiler. It's kind of lever device, which will allow you to switch heat costs and in this way there will be a decrease in temperature in the house. Also, if necessary, you can increase the level of heating of the liquid and thereby increase the air temperature in the house.

Dear readers! Since the publication of this article in the range of our company, the practice of using equipment, normative documents changes could occur. The information offered to you is useful, but is for informational purposes only.

Advantages of space heating with water warm floors repeatedly considered in numerous publications, and once again it makes no sense to break through the open gate.

However, for some reason, when it comes to the need weather regulation coolant temperature in the circuit floor heating, most of the hosts refer to this event as a fashionable, but completely unnecessary “bells and whistles”. “Why do I need your controller? Ordinary room thermostats will do a great job of controlling the air temperature in the rooms!” - such objections, as a rule, are put forward by the customer when the designer tries to include weather-compensated control of the underfloor heating circuits in the heating project. And it’s not at all about tightness and stinginess - it’s just that people don’t really understand what the controller does, and what is the main difference between its operation and the control of conventional room thermostats. Let's try to understand this issue.

For example, consider an abstract project of a built-in heating system "warm floor". The calculated specific heat loss of heated premises will be taken equal to 80 W / m 2 of the floor area. It should be recalled here that the calculated heat losses are determined by the outdoor temperature for the coldest five-day period heating period. In particular, for St. Petersburg, heat losses will be calculated for an outside air temperature of -26 °C.

We will take the floor design as shown in rice. one: on hollow core slab overlap ( 1 ) with a thickness of 22 cm, a layer of thermal insulation made of expanded polystyrene ( 2 ) 5 cm thick. Underfloor heating pipes are located in the screed ( 3 ) with a total thickness of 70 mm, along which a clean floor of ceramic tiles (4 ) 15 mm thick.

Rice. one. Calculation design underfloor heating

To determine the required coolant temperature, we use the calculation module of the VALTEC.PRG 3.1.0 program ( rice. 2).

Rice. 2. A copy of the screen of the calculation module of the program VALTEC.PRG 3.1.0

On the basis of the performed calculation, we will take the average temperature of the coolant to be 35 °C. With an estimated temperature difference in the underfloor heating circuit of 10 °C mixing unit will be set to a coolant temperature of 40 °C.

At an outdoor air temperature of -26 °C, this setting will provide the required heat input to the room in the amount q calc = 80 W / m 2 and maintaining the air temperature in the room at 20 ° C.

Let's say the outside temperature has risen from -26 to -3°C. The specific heat loss of the room would in this case be 40 W/m 2 . However, this would be true if the internal air temperature was maintained at 20 °C. In fact, taking into account the excess heat gain from the warm floor, the temperature of the indoor air will be much higher. Solving the heat balance equation, it can be determined that in the absence of room thermostats and controllers, the internal air in the room will warm up to 26 °C, and the actual specific heat loss and specific heat flow from the warm floor will be 50 W/m 2 .

Let's see what happens in the off-season, that is, at an outside air temperature of +8 °C. Theoretical specific heat losses will decrease to 21 W/m 2 . The temperature of the internal air will warm up to 28 °C. The actual heat flow from the warm floor will be 35 W / m 2 ( see table.and fig. 3).

Table. Parameters of the underfloor heating system in the absence of automatic control

Rice. 3. Graph of the dependence of the required coolant temperature on the outside air temperature

As you can see, without automatic control of the operation of the underfloor heating loops, talking about some kind of comfort is simply ridiculous.

Let's say we decide to install room thermostats that control electrothermal valve servomotors on the underfloor heating collector ( rice. 4).

Rice. 4. Indoor electronic thermostat VT.AC.701

Thermostats work according to an elementary principle: when the set temperature is exceeded by 1 °C, the thermostat sends a command to the thermoelectric actuator of the thermostatic valve ( rice. 5), stopping the supply of coolant to a specific loop of the warm floor.

Rice. 5. Thermoelectric actuator for thermostatic valve

When the room temperature drops back to the setpoint, the thermostat will command the valve to open. As we found out, in the off-season, the heat flux from the floor should be 21 W / m 2, which is almost four times less than the calculated one. This means that we will be dealing with intermittent heating mode.

When the coolant supply to the underfloor heating loops is stopped, the cooling rate of the room is described by the exponent, from which it follows that the cooling time τ , h, is determined by the expression:

where t x - room temperature after cooling, °С; t c - room temperature before cooling, °C; t n - outdoor air temperature, °C; β - coefficient of heat accumulation by the room (time constant), h. This coefficient is the product of the heat capacity of the calculated layers of enclosing structures With, participating in heat transfer, on their reduced resistance to heat transfer R ex. The accumulation coefficient is numerically equal to the cooling time at which the ratio of temperature differences between the indoor and outdoor temperatures before and after cooling is equal to the number "e" (2.72).

In the proposed example, the room thermostat will give a command to close the valve when the setpoint is exceeded by 1 °C. If the thermostat is set to an internal temperature of 20°C, it will close the hinges at 21°C.

If we accept for the example under consideration that the building is made with brick outer walls 640 mm thick and a glazing factor of 0.2 ( β = 100 h), then you can calculate the time during which the temperature in a given room will decrease by 1 °C at an outside temperature of +8 °C:

At the same time, the air and floor temperatures are almost equalized.

After this time, the thermostat will give a command to open the valve, and the warm floor will begin to heat up again. The time during which the floor heats up again from 20 to 26 ° C can (with certain assumptions) be calculated using the formula:

τ gender = ∆ t· ( with st · S st · δ st · γ st + with P · S P · δ P · γ n+ with t (1/b) v t · γ t)/ q calc =

6 (880 1 0.07 1800 + 840 1 0.015 2000 + 4187 (1/0.15) 0.000113 1000)/80 = 2.9 h.

In the above formula with st, with P, with t is the specific heat capacity of the screed, tile coating and water, J/kg °C; S st, S n - the estimated area of ​​​​the screed and tile coating, m 2; δ st, δ n - estimated thickness of the screed and tiled coating, m; γ st, γ P, γ t - specific gravity screed material, tile coating and water, kg / m 3; v t is the volume of coolant in 1 linear meter. m pipe, m 3; b- pipe pitch, m.

Thus, it is obvious that when using room thermostats, the temperature of the floor surface becomes a markedly changing value and most time will lie outside comfortable limits. That is, having spent funds on creating a warm floor, the user will not receive a full-fledged warm floor in the end ( rice. 6).

Rice. 6. Time course of floor and room temperature with intermittent heating

Permanent alternating loads caused by cyclic temperature deformations piping, reduce the life of the pipes themselves, and can cause pipe connections to loosen. The cyclic mode of heating and cooling gradually reduces the strength cement-sand screed and adversely affects the quality of the final floor coverings.

Besides, significant disadvantage intermittent heating mode is that the circulation pump will drive the coolant in a small circle for the main part of the working time - through the bypass and bypass valve. This will lead to an excessive consumption of electricity, since the bypass valve is adjusted to a pressure drop greater than the pressure loss in the calculated loop, which means that the operating point of the pump will shift towards a higher power consumption. This can be avoided by connecting the thermostats to the manifold valve servomotors via communicators that have the function to turn off the pump when there is no demand for heating. But this is only a half measure.

If the consumer wants to really effective system built-in heating, adequately and promptly responding to changing climatic factors, then in this case you can not do without a controller with weather-dependent automatics.