Automatic temperature control systems. Temperature controllers for heating batteries: selection and installation of temperature controllers

Temperature is an indicator of the thermodynamic state of an object and is used as an output coordinate in the automation of thermal processes. Characteristics of objects in temperature control systems depend on the physical parameters of the process and the design of the apparatus. So general recommendations it is impossible to formulate temperatures for the choice of ACP and a careful analysis of the characteristics of each specific process is required.

Temperature control in engineering systems ah is performed much more often than the regulation of any other parameters. The range of adjustable temperatures is small. lower limit of this range is limited by the minimum value of the outdoor air temperature (-40 ° C), the upper - maximum temperature coolant (+150 °С).

To common features ACP temperature can be attributed to the significant inertia of thermal processes and temperature meters (sensors). Therefore, one of the main tasks in the creation of ACS temperature is to reduce the inertia of the sensors.

Consider, as an example, the characteristics of the most common manometric thermometer in engineering systems in a protective case (Fig. 5.1). The block diagram of such a thermometer can be represented as a series connection of four thermal containers (Fig. 5.2): protective cover /, air gap 2 , walls of the thermometer 3 and working fluid 4. If we neglect the thermal resistance of each layer, then the heat balance equation for each element of this device can be written as

G,Cpit, = a n? sjі ( tj _і - tj) - a i2 S i2 (tj -Сн), (5.1)

where Gj- the mass of the cover, air layer, wall and liquid, respectively; Cpj- specific heat capacity; tj- temperature; a,i, and /2 - heat transfer coefficients; S n , S i2 - heat transfer surfaces.

Rice. 5.1. Schematic diagram of a manometric thermometer:

• 1 - protective cover; 2 - air gap; 3 - thermometer wall;
• 4 - working fluid

Rice. 5.2.

As can be seen from equation (5.1), the main directions for reducing the inertia of temperature sensors are;

• increase in heat transfer coefficients from the medium to the cover as a result right choice sensor installation locations; in this case, the velocity of the medium must be maximum; ceteris paribus, it is more preferable to install thermometers in the liquid phase (compared to gaseous), in condensing vapor (compared to condensate), etc.;
• reduction of thermal resistance and thermal capacity of the protective cover as a result of the choice of its material and thickness;
• reduction of the time constant of the air gap due to the use of fillers (liquid, metal chips); for thermocouples, the working junction is soldered to the body of the protective cover;
• selection of the type of primary converter: for example, when choosing, it must be taken into account that a thermocouple in a fast-response design has the smallest inertia, and a manometric thermometer has the largest.

Each temperature ACP in engineering systems is created for a very specific purpose (controlling the temperature of the air in the premises, heat or coolant) and, therefore, is designed to operate in a very small range. In this regard, the conditions for the use of one or another ACP determine the device and design of both the sensor and the temperature controller. For example, in the automation of engineering systems, direct-acting temperature controllers with manometric measuring devices are widely used. So, to regulate the air temperature in the premises of administrative and public buildings when using ejection and fan coils of a three-pipe heating and cooling circuit, a direct-acting regulator is used direct type RTK (Fig. 5.3), which consists of a thermal system and a control valve. The thermal system, which proportionally moves the control valve stem when the temperature of the recirculation air changes at the inlet to the closer, includes a sensitive element, a setting device and an actuator. These three nodes are connected by a capillary tube and represent a single hermetic volume filled with a temperature-sensitive (working) liquid. A three-way control valve controls the supply of hot or cold water to the ejection heat exchanger.

Rice. 5.3.

a - regulator; b - control valve; c - thermal system;

• 1 - bellows; 2 - setter; 3 - tuning knob; 4 - frame;
• 5, 6 - regulating bodies respectively hot and cold water; 7 - stock; 8 - actuating mechanism; 9 - sensing element

closer and consists of a body and regulatory bodies. With an increase in air temperature, the working fluid of the thermal system increases its volume and the valve bellows moves the stem and the regulating body, closing the passage hot water through the valve. With an increase in temperature by 0.5-1 ° C, the regulatory bodies remain motionless (the passages of hot and cold water are closed), and at a higher temperature only the passage of cold water opens (the passage of hot water remains closed). The set temperature is provided by turning the adjustment knob connected to the bellows, which changes the internal volume of the thermal system. The controller can be set to temperatures ranging from 15 to 30°C.

When controlling the temperature in water and steam heaters and coolers, RT type regulators are used, which differ slightly from RTK type regulators. Their main feature is the combined design of the thermocylinder with the adjuster, as well as the use of a two-seated valve as a regulating body. Such gauge regulators are available in several 40-degree ranges ranging from 20 to 180 °C with nominal diameters from 15 to 80 mm. Due to the presence of a large static error (10 °C) in these controllers, they are not recommended for high-precision temperature control.

Manometric thermosystems are also used in pneumatic P-regulators, which are widely used to control temperature in engineering air conditioning and ventilation systems (Fig. 5.4). Here, when the temperature changes, the pressure in the thermal system changes, which acts through the bellows on the levers that transmit force to the pneumatic relay rod and the membrane. When the current temperature is equal to the set one, the entire system is in equilibrium, both valves of the pneumatic relay, supply and bleed, are closed. When the pressure on the stem increases, the supply valve begins to open. It is supplied with pressure from the mains. compressed air, as a result of which a control pressure is formed in the pneumatic relay, increasing from 0.2 to 1 kgf / cm 2 in proportion to the increase in the temperature of the controlled medium. This pressure activates the actuator.

For automatic regulation room temperature, thermostatic valves from the American company began to be widely used Honeywell and radiator thermostats (thermostats) RTD, issued by the Moscow branch

Rice. 5.4.

with manometric thermosystem:

• 1 - pneumatic relay rod; 2 - node of unevenness; 3, 9 - levers;
• 4, 7 - screws; 5 - scale; 6 - screw; 8 - spring; 10 - bellows;
• 11 - membrane; 12 - pneumatic relay; 13 - thermal bulb; 14 - feeding

valve; 15 - bleed valve

Danish company Danfoss, the required temperature is set by turning the adjusted handle (head) with a pointer from 6 to 26 °C. Lowering the temperature by 1 °C (for example, from 23 to 22 °C) saves 5-7% of the heat consumed for heating. thermostats RTD allow avoiding overheating of the premises during the transitional and other periods of the year and provide a minimum required level heating in rooms with periodic residence of people. In addition, radiator thermostats RTD provide hydraulic stability for two-pipe system heating and the possibility of its adjustment and linkage in case of errors during installation and design without using throttle washers and other constructive solutions.

The temperature regulator consists of a control valve (body) and a thermostatic element with a bellows (head). The body and head are connected with a threaded union nut. For ease of installation on the pipeline and connection of the thermostat to the heater, it is equipped with a union nut with a threaded nipple. The room temperature is maintained by changing the water flow through the heating device (radiator or convector). The change in water flow occurs due to the movement of the valve stem by a bellows filled with a special mixture of gases that change their volume even with a slight change in the temperature of the air surrounding the bellows. The elongation of the bellows with increasing temperature is counteracted by a setting spring, the force of which is adjusted by turning the handle with an indicator of the desired temperature value.

To better suit any heating system, two types of regulator housings are available: RTD-G with low resistance for single pipe systems and RTD-N with increased resistance for two-pipe systems. Bodies are manufactured for straight and angle valves.

Thermostatic elements of regulators are manufactured in five versions: with built-in sensor; with remote sensor (capillary tube length 2 m); with protection against misuse and theft; with setting range limited to 21 °С. In any version, the thermostatic element ensures that the set temperature range is limited or fixed at the required room temperature.

Service life of regulators RTD 20-25 years, although the Rossiya Hotel (Moscow) registered a service life of 2000 regulators for more than 30 years.

Control device (weather compensator) ECL(Fig. 5.5) ensures the maintenance of the temperature of the coolant in the supply and return pipelines of the heating system, depending on the outdoor temperature according to the corresponding specific repair and a specific heating schedule object. The device acts on the motorized control valve (if necessary, also on circulation pump) and allows you to perform the following operations:

• maintenance of the calculated heating schedule;
• night drop temperature graph by weekly (interval 2 h) or 24-hour (interval 15 min) programmable clock (in the case of an electronic clock, the interval is 1 min);
• heating of the room within 1 hour after the night temperature decrease;
• connection via relay outputs of a control valve and a pump (or 2 control valves and 2 pumps);

Rice. 5.5. Weather compensator EC/. with setting,

available to the consumer:

1 - programmable clock with the ability to set operating periods for comfort or reduced temperature on a daily or weekly cycle: 2 - parallel movement of the temperature graph in the heating system depending on the outside temperature (heating graph): 3 - operating mode switch; 4 - a place for the instruction manual: 5 - signaling the inclusion, the current mode of operation,

emergency modes;

O - heating is turned off, the temperature is maintained to prevent freezing of the coolant in the heating system;) - operation with a reduced temperature in the heating system; © - automatic switching from mode comfortable temperature to the low temperature mode and back in accordance with the setting on the programmable clock;

O - work without lowering the temperature on a daily or weekly cycle; - manual control: the regulator is off, the circulation pump is always on, the valve is controlled manually

• automatic transition from summer mode in winter and back according to the set outdoor temperature;
• termination of the night temperature decrease when the outside temperatures fall below the set value;
• protection of the system from freezing;
• correction of the heating schedule according to the air temperature in the room;
• switching to manual control of the valve drive;
• maximum and minimum supply water temperature limits and the possibility of fixed or proportional

temperature limitation return water depending on the outdoor temperature;

• self-testing and digital indication of temperature values ​​of all sensors and states of valves and pumps;
• setting the dead zone, proportional band and accumulation time;
• the ability to work on the accumulated over a given period or current temperature values;
• setting the coefficient of thermal stability of the building and setting the influence of the return water temperature deviation on the supply water temperature;
• protection against scale formation when working with gas boiler. In engineering systems automation schemes,

also bimetallic and dilatometric thermostats, in particular electric on-off and pneumatic proportional.

The electric bimetal sensor is mainly intended for on-off temperature control in rooms. The sensitive element of this device is a bimetallic spiral, one end of which is fixed, and the other is free and satisfies moving contacts, closing or opening with a fixed contact, depending on the current and set temperature values. The desired temperature is set by turning the setting dial. Depending on the setting range, the temperature controllers are available in 16 modifications with a total setting range from -30 to + 35 °C, with each controller having a range of 10, 20 and 30 °C. Operation error ±1 °С at the middle mark and up to ±2.5 °С at the extreme marks of the scale.

The pneumatic bimetallic regulator as a transducer-amplifier has a shutter nozzle, which is acted upon by the force of the bimetallic measuring element. These regulators are available in 8 modifications, direct and reverse action with a total setting range from +5 to +30 °C. The setting range of each modification is 10 °C.

Dilatometric regulators are based on the difference in the coefficients of linear expansion of an invar (iron-nickel alloy) rod and a brass or steel tube. These thermostats do not differ in the principle of operation of control devices from similar regulators using a manometric measuring system.

According to the principle of regulation automatic control systems are divided into four classes.

1. Automatic stabilization system - a system in which the controller maintains a constant set value of the controlled parameter.

2. Program control system - a system that provides a change in the controlled parameter according to a predetermined law (in time).

3. Tracking system - a system that provides a change in the controlled parameter depending on some other value.

4. Extreme control system - a system in which the regulator maintains the value of the controlled variable that is optimal for changing conditions.

To control the temperature regime of electric heating installations, systems of the first two classes are mainly used.

Automatic temperature control systems can be divided into two groups according to the type of action: intermittent and continuous regulation.

Automatic regulators for functional features are divided into five types: positional (relay), proportional (static), integral (astatic), isodromic (proportional-integral), isodromic with advance and with first derivative.

Positional regulators are referred to as intermittent ACS, and other types of regulators are referred to as continuous ACS. Below are the main features of positional, proportional, integral and isodromic controllers, which are most widely used in automatic temperature control systems.

(Fig. 1) consists of a control object 1, a temperature sensor 2, a programming device or a temperature level setter 4, a controller 5 and an actuator 8. In many cases, a primary amplifier 3 is placed between the sensor and the programming device, and between the controller and the actuator - secondary amplifier 6. Additional sensor 7 is used in isodromic control systems.

Rice. one. Functional diagram automatic temperature control

Positional (relay) temperature controllers

Positional regulators are those in which the regulatory body can occupy two or three specific positions. In electric heating installations, two- and three-position regulators are used. They are simple and reliable in operation.

On fig. 2 shown circuit diagram two-position regulation of air temperature.

Rice. Fig. 2. Schematic diagram of on-off air temperature control: 1 - control object, 2 - measuring bridge, 3 - polarized relay, 4 - motor excitation windings, 5 - motor armature, 6 - reducer, 7 - calorifier.

To control the temperature in the regulated object, the thermal resistance TS is used, which is included in one of the arms of the measuring bridge 2. The values ​​​​of the bridge resistance are selected so that at a given temperature the bridge is balanced, that is, the voltage in the diagonal of the bridge is zero. When the temperature rises, the polarized relay 3, included in the diagonal of the measuring bridge, turns on one of the windings 4 of the DC motor, which closes the air valve in front of the heater 7 with the help of a gearbox 6. When the temperature drops, the air valve opens completely.

With two-position temperature control, the amount of heat supplied can be set only at two levels - maximum and minimum. The maximum amount of heat must be greater than necessary to maintain the set adjustable temperature, and the minimum is less. In this case, the air temperature fluctuates around the set value, that is, the so-called self-oscillatory mode(Fig. 3, a).

The lines corresponding to temperatures τ n and τ in define the lower and upper boundaries of the dead zone. When the temperature of the regulated object, decreasing, reaches the value τ n, the amount of heat supplied instantly increases and the temperature of the object begins to increase. Having reached the value τ in, the regulator reduces the heat supply, and the temperature drops.

Rice. 3. Time response of on-off control (a) and static response of on-off controller (b).

The rate of temperature increase and decrease depends on the properties of the regulated object and on its time characteristic (acceleration curve). Temperature fluctuations do not go beyond the deadband if changes in heat supply immediately cause temperature changes, that is, if there is no delay of the controlled object.

With a decrease in the dead zone, the amplitude of temperature fluctuations decreases down to zero at τ n = τ c. However, this requires that the heat supply be varied at an infinitely high frequency, which is extremely difficult to implement in practice. In all real objects of regulation there is a delay. The process of regulation in them proceeds approximately as follows.

When the temperature of the regulated object drops to the value τ n, the heat supply instantly changes, however, due to the delay, the temperature continues to decrease for some time. Then it rises to the value τ at which the heat supply instantly decreases. The temperature continues to rise for some time, then, due to the reduced heat supply, the temperature drops, and the process is repeated again.

On fig. 3, b is shown static characteristic of on/off controller. It follows from it that the regulatory impact on the object can take only two values: maximum and minimum. In the considered example, the maximum corresponds to the position at which the air valve (see Fig. 2) is fully open, the minimum - when the valve is closed.

The sign of the control action is determined by the sign of the deviation of the regulated value (temperature) from its set value. The magnitude of the control action is constant. All two-position controllers have a hysteresis zone α, which occurs due to the difference in the operating and releasing currents of the electromagnetic relay.

Example of using on/off temperature control:

Proportional (static) temperature controllers

In cases where high control accuracy is required or when a self-oscillating process is unacceptable, apply controllers with continuous control process. These include proportional regulators (P-regulators) suitable for controlling a wide variety of technological processes.

In cases where high control accuracy is required or when a self-oscillating process is unacceptable, regulators with a continuous control process are used. These include proportional regulators (P-regulators), suitable for regulating a wide variety of technological processes.

In automatic control systems with P-regulators, the position of the regulatory body (y) is directly proportional to the value of the controlled parameter (x):

y=k1х,

where k1 is the proportionality factor (controller gain).

This proportionality takes place until the regulating body reaches its extreme positions (limit switches).

The speed of movement of the regulating body is directly proportional to the rate of change of the controlled parameter.

On fig. 4 shows a schematic diagram of a system for automatically controlling the room temperature using a proportional controller. The room temperature is measured by a resistance thermometer TC included in the measuring bridge circuit 1.

Rice. 4. Scheme of proportional air temperature control: 1 - measuring bridge, 2 - control object, 3 - heat exchanger, 4 - capacitor motor, 5 - phase-sensitive amplifier.

At a given temperature, the bridge is balanced. When the controlled temperature deviates from the set value, an unbalance voltage appears in the bridge diagonal, the magnitude and sign of which depend on the magnitude and sign of the temperature deviation. This voltage is amplified by a phase-sensitive amplifier 5, at the output of which the winding of a two-phase capacitor motor 4 of the actuator is switched on.

The actuator moves the control element, changing the flow of coolant into the heat exchanger 3. Simultaneously with the movement of the control element, the resistance of one of the arms of the measuring bridge changes, as a result of which the temperature changes, at which the bridge is balanced.

Thus, due to rigid feedback, each position of the regulatory body corresponds to its own equilibrium value of the controlled temperature.

A proportional (static) controller is characterized by residual uneven regulation.

In the case of an abrupt deviation of the load from the set value (at the moment t1), the controlled parameter will come after a certain period of time (the moment t2) to a new steady value (Fig. 4). However, this is possible only with a new position of the regulatory body, that is, with a new value of the controlled parameter, which differs from the set value by δ.

Rice. 5. Time characteristics of proportional control

The disadvantage of proportional controllers is that each parameter value corresponds to only one specific position of the regulator. To maintain the set value of the parameter (temperature) when the load (heat consumption) changes, it is necessary that the regulating body take a different position corresponding to the new load value. This does not happen in a proportional controller, which results in a residual deviation of the controlled variable.

Integral (astatic regulators)

Integral (astatic) such regulators are called in which, when the parameter deviates from the set value, the regulating body moves more or less slowly and all the time in one direction (within the working stroke) until the parameter again takes the set value. The direction of stroke of the regulating body changes only when the parameter passes through the set value.

In integral regulators electric action Usually, a dead zone is artificially created, within which a change in the parameter does not cause movements of the regulatory body.

The speed of movement of the regulating body in the integral regulator can be constant and variable. A feature of the integral regulator is the absence proportional connection between the established values ​​of the controlled parameter and the position of the regulating body.

On fig. 6 shows a schematic diagram of an automatic temperature control system using an integrated controller. In it, unlike the proportional temperature control circuit (see Fig. 4), there is no hard feedback.

Rice. 6. Scheme of integrated air temperature control

In an integral controller, the speed of the regulating body is directly proportional to the deviation of the controlled parameter.

The process of integral temperature control with an abrupt change in load (heat consumption) is shown in fig. 7 with the help of time characteristics. As can be seen from the graph, the controlled variable with integral control slowly returns to the set value.

Rice. 7. Time characteristics of integral regulation

Isodromic (proportional-integral) controllers

Isodromic regulation has the properties of both proportional and integral regulation. The speed of movement of the regulating body depends on the magnitude and speed of the deviation of the controlled parameter.

If the controlled parameter deviates from the set value, the regulation is carried out in the following way. Initially, the regulating body moves depending on the magnitude of the deviation of the controlled parameter, that is, proportional regulation takes place. Then the regulating body makes an additional movement, which is necessary to eliminate the residual non-uniformity (integral regulation).

An isodromic air temperature control system (Fig. 8) can be obtained by replacing the rigid feedback in the proportional control circuit (see Fig. 5) with an elastic feedback (from the regulator to the feedback resistance slider). Electrical feedback in the isodromic system is carried out by a potentiometer and is introduced into the control system through a circuit containing resistance R and capacitance C.

During transient processes, the feedback signal, together with the parameter deviation signal, affects the subsequent elements of the system (amplifier, electric motor). When the regulating body is stationary, in whatever position it is, as the capacitor C is charged, the feedback signal decays (in the steady state it is equal to zero).

Rice. 8. Scheme of isodromic air temperature control

It is typical for isodromic control that the non-uniformity of control ( relative error) decreases with increasing time, approaching zero. In this case, the feedback will not cause residual deviations of the controlled variable.

Thus, isodromic regulation leads to a significant best results than proportional or integral (not to mention positional control). Proportional control due to the presence of rigid feedback occurs almost instantly, isodromic - slowly.

Software systems for automatic temperature control

To implement program control, it is necessary to continuously influence the setting (set point) of the controller so that the controlled value changes according to a predetermined law. For this purpose, the controller tuning unit is supplied with a software element. This device serves to establish the law of change of the given value.

During electric heating, the ACS actuator can act to turn on or off sections of the electric heating elements, thereby changing the temperature of the heated installation in accordance with a given program. Software control of air temperature and humidity is widely used in artificial climate installations.

Temperature controllers are small, but very practical devices for controlling heat transfer in everyday life. Depending on the real need, temperature controllers for radiators increase or decrease the volume of coolant. Agree, this is useful both for the well-being of the owners of the house / apartment, and for their wallets.

For those wishing to purchase thermostats for equipping radiators, we suggest that you familiarize yourself with detailed description types of heat transfer devices. We cited and compared their control methods, principle of operation, cost, installation specifics. Our recommendations will help you choose the best variety.

We supplemented the information presented for consideration, collected and systematized for future buyers of heat regulators, with visual photo collections, diagrams, regulatory tables, and videos.

It is known that the temperature in different rooms houses cannot be the same. It is also not necessary to constantly maintain one or another temperature regime.

For example, in the bedroom at night it is necessary to lower the temperature to 17-18 ° C. This has a positive effect on sleep, and allows you to get rid of headaches.

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The optimum temperature in the kitchen is 19 ° C. This is due to the fact that there are a lot of heating equipment in the room, which generates additional heat. If the temperature in the bathroom is below 24-26 ° C, then dampness will be felt in the room. Therefore, it is important to ensure high temperature.

If the house has a children's room, then its temperature range may vary. For a child up to a year old, a temperature of 23-24 ° C will be required, for older children 21-22 ° C will be enough. In other rooms, the temperature can vary from 18 to 22 ° C.

A comfortable temperature background is selected depending on the purpose of the room and partly on the time of day

At night, you can lower the air temperature in all rooms. It is not necessary to maintain a high temperature in the dwelling if the house is empty for some time, as well as during sunny warm days, when some electrical appliances that generate heat are operating, etc.

In these cases, the installation of a thermostat has a positive effect on the microclimate - the air does not overheat and does not dry out.

It can be seen from the table that in living rooms in the cold season, the temperature should be 18-23 o C. On landing, in the pantry are allowed low temperatures— 12-19 o C

The thermostat solves the following problems:

• allows you to create a certain temperature regime in rooms for various purposes;
• saves the resource of the boiler, reduces the amount of consumables for system maintenance (up to 50%);
• it becomes possible without shutting down the entire riser to produce emergency turn-off batteries.

It should be remembered that with the help of a thermostat it is impossible to increase the efficiency of the battery, to increase its heat transfer. Save on consumables can people with individual system heating. Inhabitants apartment buildings The thermostat can only control the temperature in the room.

Let's figure out which ones exist, and how to make the right choice of equipment.

Types of thermostats and principles of operation

Thermostats are divided into three types:

• mechanical, with manual adjustment of the coolant supply;
• electronic controlled by a remote temperature sensor;
• semi-electronic controlled by a thermal head with a bellows device.

The main advantage of mechanical devices is low cost, ease of operation, clarity and coherence in work. During their operation there is no need to use additional energy sources.

The modification allows you to manually adjust the flow to the radiator, thereby controlling the heat transfer of the batteries. The device differs in high accuracy of regulation of degree of heating.

A significant drawback of the design is that it does not have markings for adjustment, so it will be necessary to configure the unit exclusively by experience. We will get acquainted with one of the balancing methods below.

The main elements of the regulator mechanical type- thermostat and thermostatic valve

The mechanical thermostat consists of the following elements:

• regulator;
• drive;
• bellows filled with gas or liquid;

Electronic thermostats - more complex structures based on a programmable microprocessor. With it, you can set a certain temperature in the room by pressing a few buttons on the controller. Some models are multifunctional, suitable for controlling a boiler, pump, mixer.

Structure, principle of operation electronic device practically does not differ from the mechanical analogue. Here, the thermostatic element (bellows) has the shape of a cylinder, its walls are corrugated. It is filled with a substance that reacts to fluctuations in air temperature in the home.

As the temperature rises, the substance expands, as a result of which pressure is formed on the walls, which contributes to the movement of the stem, which automatically closes the valve. As the stem moves, the conductivity of the valve increases or decreases. If the temperature decreases, then the working substance is compressed, as a result, the bellows is not stretched, and the valve opens, and vice versa.

The bellows have high strength, long working life, withstand hundreds of thousands of compressions over several decades.

The main element of the electronic regulator is a temperature sensor. Its functions include the transmission of information about the temperature environment, resulting in the system generating required amount heat

Electronic thermostats are conditionally divided into:

• Closed thermostats for heating radiators do not have the function of automatic temperature detection, so they are configured in manual mode. It is possible to adjust the temperature that will be maintained in the room and the allowable temperature fluctuations.
• open thermostats can be programmed. For example, if the temperature drops by several degrees, the mode of operation may change. It is also possible to set the response time of a particular mode, adjust the timer. These devices are mainly used in industry.

Electronic controllers are powered by batteries or a special battery that comes with the charger. Semi-electronic regulators are ideal for domestic purposes. They come with a digital display that shows the room temperature.

The principle of operation of semi-electronic devices for adjusting heat transfer by a radiator is borrowed from mechanical models, so its adjustment is carried out manually

Gas-filled and liquid thermostats

When developing a regulator, a substance in gaseous or liquid state(for example, paraffin). Based on this, the devices are divided into gas-filled and liquid.

Paraffin (liquid or gaseous) has the property of expanding with temperature. As a result, the mass presses on the stem to which the valve is connected. The rod partially covers the pipe through which the coolant passes. Everything happens automatically

Gas-filled regulators have a long service life (from 20 years). A gaseous substance allows you to more smoothly and clearly regulate the air temperature in your home. The devices come with a sensor that determines the temperature of the air in the home.

Gas bellows respond faster to fluctuations in room temperature. Liquid ones are distinguished by higher accuracy in transferring internal pressure to the moving mechanism. When choosing a regulator based on liquid or gaseous substance focused on the quality and service life of the unit.

Liquid and gas regulators can be of two types:

• with built-in sensor;
• with remote.

If the radiator is connected to working system heating, then drain the water from it. You can do this with ball valve, a shut-off valve or any other device that blocks the flow of water from a common riser.

After that, the battery valve is opened, located in the area where water enters the system, and all taps are closed.

After water has been removed from the battery, it must be purged to remove air. This can also be done using the Mayevsky crane

The next step is to remove the adapter. Before the procedure, the floor is covered with a material that absorbs moisture well (napkins, towels, soft paper, etc.).

A thermometer is placed in the room, then the valve is turned off until it stops. In this position, the coolant will fill the radiator completely, which means that the heat transfer of the device will be maximum. After some time, it is necessary to fix the temperature obtained.

Next, you need to turn the head until it stops in reverse side. The temperature will start to drop. When the thermometer shows the optimal values ​​\u200b\u200bfor the room, the valve begins to open until the sound of water is heard and a sudden heating occurs. In this case, the rotation of the head is stopped, fixing its position.

Conclusions and useful video on the topic

The video clearly shows how to set up the thermostat and implement it in the heating system. As an example, take the Living Eco automatic electronic regulator from the Danfoss brand:

You can choose a thermostat based on your own wishes and financial capabilities. For domestic purposes, a mechanical and semi-electronic unit is ideal. Fans of smart technology may prefer functional electronic modifications. It is also possible to install devices without the involvement of specialists.

I want to talk about the creation of a simple device that greatly facilitated the life of home inhabitants - automatic regulator gas column temperature. Similar devices have already been created and described here on Habré, I wanted to make a slightly more advanced device and describe in detail the entire creation process from idea and measurement to implementation, without using ready-made modules Arduino type. The device will be assembled breadboard, programming language - C. This is my first development of a complete (and working!) device.

1. Initial data

We live in a rented apartment, which has one very unpleasant property: there is no hot water in the house, cold water is heated on site using a heater (Fluent Gas Water Heater - HSV) located in the kitchen. While taking a shower, if another pressure surge occurs, you have to spank naked to the column or call someone. Integrate a complete smart House» there is no possibility, so it was decided to introduce automatic regulation of the heater. By the way, I quickly found several similar solutions, for example, which means that my problem is known and solved in its own way.

VPG model: Vector lux eco 20-3 (China)
Water pressure: about 1.5 kgf / cm² (pressure is low, the heater operates slightly above the allowable limit)

Solution Requirements

• Simplicity
• PID controller or similar
• Possibility to choose the maintained temperature
• Display of current parameters
• Resolving Device Security Issues

System architecture

After some thought, the architecture of the device was sketched out as follows:

• Servo drive (directly in the body of the HSV)
• Thermal sensor regular HSV
• Thermal sensor signal amplification unit and servo power supply stabilizer (directly in the body of the HSV)
• Control unit (external)

Next, I will describe the development process in chronological order.

2. Servo

Since my profession is software engineering and mechanics has always been the most difficult part, I decided to start with it. I must say that I could not get ready for the first stage for a long time, it was very scary to touch the HSV, but another pressure drop forced me to start.

Having dismantled the column and looked around, I found places to install the TowerPro MG995 servo, somehow ordered “for delivery” on aliexpress a long time ago.

To eliminate the backlash of the drive rods, I made one rod spring-loaded. The backlash was completely eliminated, but another problem turned out - a servo with a torque > 10 kg * cm turned out to be too bold for the HSV. When turned on, the transients in the electronics of the machine cause a jerk to a random position, and after a couple of idle turns, the rod turned out to be bent! Silumin columns will definitely not withstand such treatment. The geometry of the rocker, which was not on the axis of the regulator, also caused criticism, which led to non-linearity of the adjustment. The final view of the throttle drive assembly:

The unit has been redone - springs from the VAZ were used (from the carburetor - bought at an auto parts store) and the rocker is now on the geometric axis of the shaft. This design has a small backlash, but it is linear in adjustment and can dampen the fury of the steering machine. The corners are set to optimal values for adjustment in the most demanded positions of the regulator.

3. HSV sensor unit

The HSV thermistor changes its resistance within 20..50 KΩ, it is problematic to use it directly as a divider - we get low measurement accuracy. But as it turned out in practice - with an increase in the supply voltage to 12V, you can easily get an acceptable output signal range - just use the op-amp in repeater mode (if necessary, you can change the gain) to isolate the divider from the load. Block diagram inside the HSV:

The divider R2 and the column temperature sensor generate a signal with a voltage of 1.4..4.96 V in the full measurement range (in practice - 20..60 degrees Celsius). Initially, he developed a bridge circuit - which can compensate for the loss of the power source, but was discarded due to the fact that the power source had little effect, and the first point of the "TK" was - "simplicity". The operational amplifier provides decoupling of the divider and the load. The zener diode D1 limits the output voltage to 5.1 V in cases where the sensor is disconnected (otherwise the output would be 12V - which is deadly for the controller) - which will be considered an unconditional error by the controller circuit. The integrated stabilizer 7805 feeds the servo - the solution is unsuccessful, when the machine stops, it heats up terribly and I think it can fail if the drive wedges (if the built-in protection does not work). I will not focus on this block anymore.

4. Controller

The controller is assembled on the basis of the Atmega8 IC in a dip-package.

Clocking - internal oscillator at 8 MHz. Power - another 7805 on the board. Indication via standard LCD1602 display. Block diagram:

The power supply of the unit is controlled from the column through a transistor - using a small-sized relay. The temperature sensor signal (Contact No. 4 of the connector) has a pull-up to ground and when the sensor is disconnected during operation, it will show a very high temperature - which will lead to a decrease in the regulator and will not cause dangerous situations. Assembled block:

4. Testing and adjustment

To test the PID controller, a HSV model was written in Qt. It worked out the main points and situations of the heater operation - cold / hot start, pressure drops. To take the characteristics, a UART connector was added to the controller board, where data on indicators were sent once a second - the current temperature, throttle position, etc.

The tests revealed the following:

• Very large HSV inertia from the beginning of exposure to the reaction on the temperature sensor - about 30 seconds
• Rounding to a degree in the controller firmware is a bad idea, the algorithm could work more accurately

The results of measurement and calibration of the temperature sensor, The dependence can be considered conditionally linear:

The first runs in the program for rendering telemetry from the column:

(I forgot to add a legend to the charts. Here and below - red- sensor temperature, green dotted- throttle position, blue- temperature desired by the user)

Almost a successful adjustment

Good odds options

Good start option

The first runs showed the main parameters of the system, then it was not difficult to measure them and adjust according to the accelerated formula, the parameters were selected for a long and painful time. It was not possible to get rid of fluctuations completely, but fluctuations within 1 degree are considered acceptable. Accepted option:

In the process of selection, the integral coefficient had to be completely turned off, I think that this is due to the large inertia of the system. Final odds:

FloatPk = 0.2; float Ik = 0.0; float Dk = 0.2;

5. Enclosure

The device is assembled in a plastic junction box.

And it works like this.

6. Safety of use

An important question that was asked from the very beginning. Let's go through the main points.

Galvanic isolation of column and regulator circuits

What happens if the 12V power supply short-circuits and there is 220 volts on the sensor circuit? This will not cause gas to flow into the column. As it turned out - it will not cause - there are two levels of gas supply in the column - solenoid valve controller and mechanical water valve. It is not enough to open only the solenoid - gas will not flow without water flow.

Disconnection or detachment of the sensor inside the HSV

When the thermistor is disconnected from the block inside the VPG, a 0xFF (5.1V) signal will be generated at the output, which is checked by the program as an error, the controller stops the program execution, the servo drive is set to a minimum.

Disconnection or detachment of the sensor from the controller

In this case, a high temperature is generated (pulling the sensor line to the ground) which will lead to the output of the drive in minimum value which is also safe for the user.

Electronic-mechanical protection of HSV

HSV protection prices remain functional in normal mode, in case of boiling / overheating / column draft sensor, standard systems should turn it off.

In the article we will find out what thermostats can be for home heating. We will analyze the basic principles of work different devices of this type and tell you how to install them correctly. Let's start, however, with a few general concepts.

Why is it needed

But in fact, why do you need a thermostat for heating? Our grandparents did just fine without it and did not suffer at all ...

Saving

Do you remember what the rent was like in the days of grandparents? At the end of the seventies, in two-room apartment on the Far East where the author grew up, it was about 15 rubles. In winter, together with heating and electricity.

For comparison: the salary of a junior researcher at a local institute at that time was about 120 rubles. The average salary in the city, thanks to the northern and regional coefficients, is more than two hundred. It never occurred to anyone to worry about two or three rubles, which were overpaid for excess heat: it was easier to open the window.

However: even at the project level, all radiators were supplied with the great-grandfather of the current thermostats - three-way valve. It made it possible to reduce the flow of coolant through the radiator by completely or partially directing the flow of water into the jumper.

Now most of the state initiatives come down to two main theses:

1. Citizens don't need it.
2. And they have to pay for it themselves.

There are no more subsidies for the maintenance of housing, housing and communal services are in decline, rents are growing, but we ... are adapting as best we can.

Thermostats for heating radiators in conjunction with heat meters are one of the ways to reduce the cost of heating a home. Heat is consumed exactly as much as is necessary to maintain a comfortable temperature at home. Not more.

Convenience

Yes, thermostats aren't the only way to save heat. Heating radiators can also be adjusted manually - with a throttle or a conventional valve.

But, as usual, there are nuances:

• The throttle regulates the patency of the eyeliner. With fluctuations in the temperature of the coolant, the heat transfer of the heater will also change.
• The need for heat varies depending on the temperature outside. Adjusting the patency of the throttle or valve manually several times a day is somewhat tedious.

An alternative to the throttle - the thermostat - is a fully automatic and weather-compensated heating controller. If the room becomes hot due to the increased temperature of the water in the battery, it will reduce the flow of water through it.

If it's cold, it will open up. And all this will happen without your participation.

Principle of operation

There are an infinite number of specific implementations of heating regulators. It is based on only two basic principles of regulation.

Mechanical regulator

Let's see how the Danfoss RAW-K 5030 thermostatic head works.

• The mechanism is based on a container with a liquid or gas with a high coefficient thermal expansion. The container tends to press the valve, blocking the flow of water; it is opposed by a conventional spring.
• Rough adjustment is carried out by the simplest screw mechanism. The closer the initial position of the temperature-sensitive element to the valve, the less stroke it needs to block the flow of water.
• In addition, many thermostats for heating radiators include an additional tuning mechanism - a simple choke. It helps to calibrate the thermostat so that the scale of conventional values ​​​​on it corresponds to real temperatures in the range from 7 to 28 degrees.

However: fine adjustment can also be made with an ordinary throttle mounted on a second, thermostat-free supply to the heater.

The same principle is used, by the way, by an automatic draft regulator for solid fuel boilers. The problem of discrepancy between the damper stroke and changing the dimensions of the temperature-sensitive container is solved extremely simply - using a lever with arms of different lengths.

Electric regulator

All electric heating thermostats use the ability of some materials to change their characteristics when the temperature changes.

Of course, in this case we are talking about electrical characteristics:

• The thermistor changes its resistance as the temperature changes. Accordingly, at a constant voltage, more or less current will flow through it. So, for example, the heater fan speed controller often works. With a small power input, all the current can flow directly through the thermistor.

More complex scheme, however, will allow you to control large currents. So it works room regulator heating VRT 40 from Vaillant: with a current through a thermistor in fractions of an ampere, it can control an electric boiler with a power of tens of kilowatts.

• The thermocouple is an even more curious device. If you solder together two plates of different metals - for example, from nichrome and aluminum-nickel alloy - a potential difference will occur at the junction. Moreover, it will dynamically change with fluctuations in the temperature of the soldering point.

The resulting current will be in millivolts, and by itself is not enough to drive any valve; however, there are transistors for that. The control signal can be arbitrarily small and still control large currents.

The cascade of transistors will theoretically allow an ordinary thermocouple to control the supply of heat not only to a radiator, but even to an entire apartment building.

At general principle operation of electrical thermostats can be analog or digital. The first allow only the simplest setting temperature and are most often equipped with a simple indicator, combined with control - a wheel with a scale. The latter can not only set the current temperature, but also be programmed for a day or a week.

In addition, digital indicators are further divided into two categories:

• Devices with closed logic only allow setting the basic parameters within the factory firmware. They are relatively easy to set up, but have manufacturer-limited capabilities. A typical example is the Calormatic 430 automatic heating controller from Vaillant.

• Open logic devices can be completely reprogrammed. Instead of so-called one-shots - non-erasable chips with firmware - they are equipped with conventional flash memory with an open interface.

These devices are rarely used in heating systems of private houses: the complexity of setting up and high price scare off buyers. But the possibilities that an open logic heating thermostat has are impressive.

Here is a list of functions of the Ukrainian heating regulator Rise RO-2:

• Temperature control taking into account the thermal inertia of the building.
• Calculation of a temperature graph that compensates for sharp fluctuations in temperature outside.
• Protection of the heating network from overloads by rationing the flow of hot water.
• Building a temperature graph for administrative buildings according to their mode of operation.
• Calculation of the heat carrier flow in accordance with the current contract with the heat supplier.

It's easier to say what this thermostat can't do. In addition, if needed additional functions- it can be reflashed.

Installation rules

thermostatic heads

If heating radiators with a thermostat are supplied ready for connection, then the thermostat purchased separately must still be mounted.

How to do it yourself right?

• The installation method itself is no different from the assembly of other threaded connections. Be aware of the brittleness of the brass body: when assembling threaded connections, avoid using too much force. The best thread take-up that is easy to find in any store is sanitary flax; to make it more durable - soak a strand of linen with any paint.
• The thermostat for heating radiators is always located on the supply line. On the reverse thread will great idea insert a valve that allows you to completely cut off the heater. If a throttle for manual calibration is not built into the thermostatic head, the valve can be replaced with a separate throttle.

Attention: the presence of a jumper when installing ANY throttle or thermostat is mandatory. Without it, you will regulate the patency of the riser or the entire heating circuit of a private house.

• In the case of a two-pipe heating system, the use of chokes is mandatory. They are needed to balance the circuit: the batteries closest to the boiler or elevator will have to be pressed, reducing the coolant flow through them. Otherwise, distant radiators simply will not heat up - up to defrosting in extreme cold.

Balancing is carried out with the thermostatic heads fully open (maximum temperature value on the dial). Only after all the heaters start to heat up to approximately the same temperature, you can adjust and calibrate the thermostats.

• If you are installing a heating system in a one-story private house, the best choice Leningradka will become - a single-pipe circuit along the perimeter of the house, parallel to which, without opening it, heating appliances crash.

Connection diagram - bottom or diagonal. A throttle is placed on one of the connections (balancing is not necessary here, but desirable). The second is the thermostat.

• The head is usually placed horizontally. What is the instructions for? The point is that at vertical installation the heat sensing element will often be caught in the hot air rising from the radiator. It is clear that its temperature will have little to do with the AVERAGE temperature in the room.

Electronic regulators

Installation rules depend on where the controller temperature sensor is located.

If it is built into the control panel, it must be mounted according to quite understandable restrictions:

• Height above floor level - not less than 80 centimeters. Close to the floor, the temperature is noticeably lower. Especially with an open window or door to the hallway.
• Out of the updrafts of any heating appliances and generally heated structures. Heat from the back of a refrigerator will affect sensor calibration just as much as a radiator.
• Direct sunlight will also affect the operation of the device. Place the panel with the sensor in the shade.
• Finally, it would be unwise to place the electronic control panel where the wall is often touched by the inhabitants of the house passing nearby.

If the thermostat uses a remote sensor, all items except the last one will refer specifically to the location of the sensor. The panel is mounted where it is convenient for you.

Conclusion

In the video at the end of the article, you can take a closer look at some types of thermostats and the rules for their installation. Different manufacturers may have quite different installation requirements, so be sure to read the instructions.