Many manufacturers of boiler equipment require that at the inlet to the boiler there be water not lower than a certain temperature, since the cold return has a bad effect on the boiler:

• the efficiency of the boiler is reduced,
• condensation on the heat exchanger increases, which leads to boiler corrosion,
• due to big difference temperatures at the inlet and outlet of the heat exchanger, its metal expands in different ways - hence the stress and possible cracking of the boiler body.

Below we will look at how to protect the boiler from a cold return.

The first method is ideal, but expensive. Esbe offers a ready-made module for adding to the boiler return and controlling the load of the heat accumulator (relevant for solid fuel boilers) - the LTC 100 device is an analogue of the popular Laddomat unit (Laddomat).

Phase 1. The beginning of the combustion process. The mixing device allows you to quickly increase the temperature of the boiler, thus starting the circulation of water only in the boiler circuit.

Phase 2: Start loading the storage tank. The thermostat, opening the connection from the storage tank, sets the temperature, which depends on the version of the product. High, guaranteed return temperature to the boiler, maintained through the entire combustion cycle

Phase 3: The storage tank is in the process of being loaded. Good management ensures efficient loading of the storage tank and proper stratification in it.

Phase 4: The storage tank is fully loaded. Even at the end of the combustion cycle, the high quality of the regulation ensures good control of the return temperature to the boiler while simultaneously fully loading the storage tank

Phase 5: End of the combustion process. By completely closing the top opening, the flow is directed directly into storage tank using the heat in the boiler

The second method is simpler, using a high quality three-way thermal mixing valve.

For example valves from ESBE or or VTC300. These valves differ depending on the capacity of the boiler used. VTC300 is used for boiler power up to 30kW, VTC511 and VTC531 - for more powerful boilers from 30 to 150 kW

The valve is mounted on the bypass line between the boiler supply and return.

The built-in thermostat opens input "A" when the temperature at the outlet "AB" is equal to the thermostat setting (50, 55, 60, 65, 70 or 75°C). Inlet "B" closes completely when the temperature at inlet "A" exceeds the nominal opening temperature by 10°C.

A similar valve releasesHerz Armaturen- three-way thermostatic mixing valve Anti-condensate. Two types of Heiz Anticondensate valves are available- with switchable and fixed bypass.

Heiz Three-Way Mixing Valve Application Diagram Anti-Condensation

When the coolant temperature at the outlet of valve "AB" is less than 61°C, inlet "A" is closed, through inlet "B" hot water from the boiler return. When the temperature of the coolant at the outlet "AB" exceeds 63°C, the bypass inlet "B" is blocked and the coolant from the return of the system through the inlet "A" enters the return of the boiler. Bypass outlet "B" reopens when the temperature at outlet "AB" drops to 55°C

When the coolant passes through the outlet "AB" with a temperature of less than 61°C, the inlet "A" from the return of the system is closed, the hot coolant is supplied to the outlet "AB" from the bypass "B". When the outlet "AB" reaches a temperature of more than 63°C, the inlet "A" opens, and the water from the return is mixed with the water from the bypass "B". To equalize the bypass (so that the boiler does not work constantly on a small circle of circulation), a balancing valve must be installed in front of the input "B" on the bypass.

When buying and installing a solid fuel boiler, it is imperative to take into account the features of its operation, namely, the high probability of overheating in emergency situations, which can result in a serious accident and even destruction of the water jacket of the unit (explosion). Also, considerable harm can be caused by the formation of condensate on the walls of the combustion chamber, which happens under certain operating modes. To eliminate such troubles, protection of the solid fuel boiler from overheating and condensate should be provided, which will be discussed in our article.

How to get rid of condensate in the boiler furnace?

In solid fuel boilers, moisture can form on inner walls combustion chambers. This happens when the firewood has already flared up and the blower fan (if any) is running at full speed, and the water in the heating system is still cold.

From the temperature difference, condensate occurs, which, mixing with combustion products, settles on the walls of the chamber. This plaque causes corrosion of the metal, as a result of which the life of the boiler is significantly reduced.

Note. Boilers with a cast-iron heat exchanger are not afraid of corrosion, but, in turn, are sensitive to sudden changes in the temperature of the coolant.

Decide this problem it’s not difficult, you just need to include a three-way thermostatic valve in the piping circuit, set to a coolant temperature of 55-60 ºС, as shown in the figure below. The protection of a solid fuel boiler against condensate operates as follows: until the water in the boiler is heated to a predetermined temperature, it circulates through a small circuit. After sufficient heating, the three-way valve gradually mixes water from the system. Thus, there is no temperature difference and condensate in the furnace.

The introduction of a mixing unit into the circuit also protects the cast-iron heat exchanger from the heat carrier temperature drop, since the valve will not allow cold water to get inside the heat generator.

Ways to protect the boiler from overheating

Excessive heating and boiling of the coolant in solid fuel units can occur during operation for the following reasons:

• power outage;
• the electronics or temperature sensor is out of order, then the blower fan may not turn off or the ash pan door may not close;
• air damper controlled mechanical thermostat with a chain drive, did not close completely.

The most popular method of protecting the boiler from overheating during sudden and frequent power outages is the use of uninterruptible power supplies or electric generators. In general, a prudent owner who lives in an area with frequent power outages should think about this in advance and take all measures to ensure the energy independence of his heating system.

Advice. In order for the system to be non-volatile, it must be calculated and made gravitational with natural circulation of the coolant. Heating equipment should be selected as simply as possible, where there is no electronic control unit and a blower fan for the boiler.

Since, in addition to an emergency with a power outage, there are other malfunctions that lead to overheating, the presence of independent sources of electricity is not a panacea, more universal solutions are needed. Here they are:

• installation of a two-way safety valve;
• introduction to the piping circuit of a bypass for natural circulation, which removes heat to a buffer tank or heat accumulator.

Note. In some models of solid fuel units, overheating protection is implemented using a built-in or remote heat exchanger. In the event of an accident, cold water from the water supply network is passed through it. This solution can also be used by those who undertook to make a solid fuel boiler with their own hands.

Use of the safety valve

This is not the same as a safety valve. The latter simply relieves pressure in the system, but does not cool it. Another thing is the boiler overheating protection valve, which takes hot water from the system, and instead supplies cold water from the water supply. The device is non-volatile, connected to the supply and return lines, water supply and sewerage.

At a coolant temperature above 105 ºС, the valve opens and, due to the pressure in the water supply system of 2-5 bar, hot water is forced out of the heat generator jacket and cold pipelines, after which it goes into the sewer. How the solid fuel boiler protection valve is connected is shown in the diagram:

The disadvantage of this method of protection is that it is unsuitable for systems filled with antifreeze liquid. In addition, the scheme is not applicable in conditions where there is no centralized water supply, because along with a power outage, the water supply from a well or pool will also stop.

Circuit with emergency bypass

The following scheme for protecting a solid fuel boiler from overheating has practically no drawbacks:

Stops when power goes out circulation pump, which during operation presses the petal check valve which prevents water from flowing through the bypass. But after stopping, the valve will open and the coolant will continue to circulate naturally. Even if at this time some kind of accident occurs with the solid fuel boiler and the water heating does not stop, the heat will be removed to the buffer tank until the firewood in the furnace burns out.

True, several conditions must be met here:

• the presence of a heat accumulator or a buffer tank of sufficient volume;
• pipes of the boiler circuit to the tank must be steel, with increased diameters and slopes suitable for natural circulation;
• non-return valve - only petal type, mounted in a horizontal position.

Conclusion

It is better to select the scheme and method of protection in accordance with the operating conditions. In one case, an electric generator will suffice, in the other, a bypass and a buffer tank are indispensable. But the use of the latter is considered preferable, in some countries Western Europe the operation of solid fuel heat generators without a buffer tank is generally prohibited.

A solid fuel boiler, unlike gas, electric or liquid fuel boilers, does not work constantly, but periodically, especially if it is intended for heating country house or cottages.

Why is condensate dangerous for the boiler?

When kindling a solid fuel boiler, one has to deal with the fact that the cold coolant washes the walls of the already heated combustion chamber, cools them, which leads to the condensation of water vapor, which is invariably present in the flue gases. Water particles, interacting with flue gases, form acids, which leads to the destruction of the inner surface of the combustion chamber and chimney.

But the negative effect of condensate is not limited to this: particles of soot that settle on the walls dissolve in drops of water. Under the influence of high temperatures, this mixture is sintered, forming a dense and durable crust on the inner surface of the combustion chamber, the presence of which sharply reduces the intensity of heat exchange between the flue gases and the coolant. The efficiency of the boiler drops.

It is not easy to remove the crust, especially if the combustion chamber of the boiler has a complex heat exchange surface.

It is impossible to completely eliminate the formation of condensate in a solid fuel boiler, but the duration of this process can be significantly reduced.

The basic principle of boiler protection against condensate

To protect the solid fuel boiler from the formation of condensate, it is necessary to exclude the situation in which this process is possible. To do this, do not allow cold coolant to enter the boiler. The return temperature must be 20 degrees less than the supply temperature. In this case, the supply temperature must be at least 60 C.

The easiest way is to heat a small amount of coolant in the boiler to the nominal temperature, create a small heating circuit for its movement and gradually mix the rest of the cold coolant with hot water.

The idea is simple, but it can be implemented different ways. For example, some manufacturers offer to purchase ready-made mixing unit, the cost of which can be 25 000 and more rubles. For example, FAR (Italy) offers similar equipment for 28500 rubles, and the company Laddomat sells a mixing unit for 25500 rubles.

More economical, but no less effective method to protect a solid fuel boiler from condensate is to regulate the temperature of the heat carrier entering the boiler using a thermostatic valve with a thermal head.

Kau stroen thermostatic valve

Thermostatic valves are of two types:

• mixing- flow A entering the valve is distributed to flow B and flow AB
• distributive- flow A entering the valve is divided into 2 flows

The mixing valve is installed on the return pipeline and the diverting valve is installed on the supply pipeline. The valve is controlled by a thermal head with a thermoflask.

The thermoflask with the help of a special sleeve is attached to the surface of the return pipeline in close proximity to the heating boiler. Inside the flask is a working fluid, the temperature of which is equal to the temperature of the coolant before entering the boiler. If the temperature of the coolant rises, the working fluid increases in volume, and, conversely, when the temperature of the coolant decreases, the volume of the working fluid decreases. Expanding or contracting, the working fluid presses on the stem, closing or opening the thermostatic valve.

Using the thermal head, you can set a certain temperature, above (below) which the heating medium will not be heated. How to set the temperature by choosing the operating modes of the thermal head is described in detail in the instructions for it.

Another feature of the thermostatic valve is that it reduces the flow of coolant to the boiler, but never shuts it off and does not open it completely, protecting the boiler from overheating and boiling. The valve is fully closed only when the boiler is started.

How does a thermostatic control valve work?

The thermostatic valve is installed on the supply in front of the bypass section (section of the pipeline) connecting the supply and return of the boiler in close proximity to the boiler. In this case, a small coolant circulation circuit is formed. The thermoflask, as mentioned above, is installed on the return pipeline in close proximity to the boiler.

At the time of boiler start-up, the coolant has a minimum temperature, the working fluid in the thermoflask occupies a minimum volume, there is no pressure on the thermal head rod, and the valve passes the coolant only in one direction of circulation in a small circle.

As the coolant heats up, the volume of the working fluid in the thermoflask increases, the thermal head begins to put pressure on the valve stem, passing the cold coolant to the boiler, and the heated coolant into the common circulation circuit.

As a result of mixing cold water, the return temperature decreases, which means that the volume of the working fluid in the thermoflask decreases, which leads to a decrease in the pressure of the thermal head on the valve stem. This, in turn, leads to the cessation of the supply of cold water to the small circulation circuit.

The process continues until the entire coolant is heated to the required temperature. After that, the valve blocks the movement of the coolant along the small circulation circuit, and the entire coolant begins to move along the large heating circle.

The mixing thermostatic valve works in the same way as a control valve, but it is not installed on the supply pipe, but on the return pipe. A valve is located in front of the bypass, which connects the supply and return and forms a small circle of coolant circulation. The thermostatic bulb is attached to the same place - on site return pipeline in close proximity to the heating boiler.

While the coolant is cold, the valve passes it only in a small circle. As the coolant heats up, the thermal head begins to put pressure on the valve stem, passing part of the heated coolant into the common circulation circuit of the boiler.

As you can see, the scheme is extremely simple, but at the same time effective and reliable.

The operation of the thermostatic valve and thermal head does not require electrical energy, both devices are non-volatile. No additional devices or controllers are needed either. It takes 15 minutes to heat the coolant circulating in a small circle, while heating the entire coolant in the boiler can take several hours.

This means that using a thermostatic valve, the duration of condensate formation in a solid fuel boiler is reduced by several times, and with it, the time for the destructive effect of acids on the boiler is reduced.

It remains to be added that the thermostatic valve costs about 6,000 rubles.

To protect the solid fuel boiler from condensate, it is necessary to correctly piping it using a thermostatic valve and creating a small coolant circulation circuit.

RUSSIAN JOINT STOCK COMPANY ENERGY
AND ELECTRIFICATION "UES OF RUSSIA"

STANDARD INSTRUCTIONS
ON LAUNCH
FROM VARIOUS THERMAL STATES
AND I WILL STOP THE BOILER
THERMAL POWER PLANTS
CROSS-LINKED

RD 34.26.514-94

SERVICE OF EXCELLENCE ORGRES

Moscow 1995

DEVELOPED BY ORGRES Firm JSC

CONTRACTOR V.V. KHOLSHCHEV

APPROVED by RAO "UES of Russia" on September 14, 1994.

First Vice President V.V. CURLY

The Instruction takes into account the comments and suggestions of research and design institutes, energy enterprises and adjustment organizations.

RD 34.26.514-94

Expiry date set

from 01.01.1995

until 01.01.2000

The standard instruction is intended for engineering and technical personnel of thermal power plants. This Manual is being reissued. From similar works, the “Collection of instructions for servicing power plant boilers” (M.-L .: Gosenergoizdat, 1960), “Temporary instruction for servicing a TGM-84 type boiler when burning natural gas and fuel oil” (M .: BTI ORGRES, 1966).

When operating the boiler, you should be guided by the requirements:

existing PTE, PTB, PPB, "Rules for the device and safe operation steam and hot water boilers”, “Explosion safety rules when using fuel oil and natural gas in boiler plants”;

factory operating instructions for the boiler;

local instructions for maintenance and operation of the boiler and auxiliary equipment;

local job descriptions;

. GENERAL PROVISIONS

The procedure for switching on automatic regulators when starting the boiler is given in the appendix.

The basic principles of organizing the modes of starting and stopping the boiler are set out in the appendix.

The scope of temperature control is given in the appendix.

In the process of filling, turn on the dosing pumps of the conservation plant to supply the hydrazine-ammonia solution (Fig. ) to one of the possible points on the boiler (drum, lower points, power unit). When full, turn off the dosing pumps and connect the boiler to the hot (or cold) feed water assembly; make a pressing.

During pressure testing, take a sample and determine the quality of water in the boiler, including visually. If necessary, flush the screen system through the lower points until the boiler water is clarified. The concentration of hydrazine in the boiler water should be 2.5 - 3.0 mg/kg, pH > 9.

steam valves PP-1, PP-2 for blowing the boiler into the atmosphere;

steam valves PP-3, PP-4 from the section of the superheater into the atmosphere;

turn on the dosing pumps at the request of the chemical workshop and, in the absence of phosphates in the boiler water, organize the phosphating mode, maintaining the pH value of the clean compartment boiler water at least 9.3;

install cover control valve continuous purge the required flow rate of boiler water from remote cyclones, making sure that the quality indicators of feed water and steam are stabilized at the standard level.

. START-UP OF THE BOILER FROM THE UNCOOLED STATE

. BOILER START FROM HOT STATE

. STOP THE BOILER TO STANDBY

Turn on moment

Lowering the water level in the boiler drum

When the pressure in the drum reaches 13.0 - 14.0 MPa and the readings of the level gauges are compared with the readings of direct-acting water-indicating instruments

Increasing the water level in the boiler drum (limit II)

Extinction of the torch in the furnace

At a load of 30% of the rated

Decrease in gas pressure after the control valve

With the opening of the gas valve to any burner

Reducing the oil pressure after the control valve

With the opening of the oil valve to any burner

Reduction of oil pressure in the lubrication system of mills with direct injection with its centralized supply

Switching off all primary air fans

Shutdown of all mill fans when transporting dust with a drying agent from these fans

Tarnishing of the pulverized coal torch in the furnace

Shutdown of all smoke exhausters

With the opening of the fuel stop valves for any pilot burner

Shutdown of all blowers

Disabling all RWPs

Failure to ignite or extinguish the flame of any pilot burner

Function at start

Turn on moment

Kindling water level regulator in the drum

Maintaining a constant level

After switching to the control valve on the bypass with a diameter of 100 mm of the power unit

Drum water level regulator

After switching to the main PKK

fuel regulator

Maintaining fuel consumption in accordance with the task

According to local regulations

Live steam temperature controller downstream of the boiler

Maintenance of the nominal temperature of live steam by means of injection

When the nominal temperature of live steam is reached

Continuous purge controller

Maintaining a predetermined flow rate of continuous purge

After turning on the boiler in the main

General air regulator

Maintaining a given excess of air in the furnace

Primary air flow regulator

Maintaining a predetermined primary air flow

After switching to dust incineration

Vacuum regulator in the furnace

Maintaining vacuum in the furnace

With boiler ignition

Appendix 3

BASIC PRINCIPLES OF THE ORGANIZATION OF START AND STOP MODES OF THE BOILER

Earlier, as is known, it was proposed to control the temperature of the water in front of the drum when filling the hot boiler, which should not differ by more than 40 ° C from the temperature of the metal at the bottom of the drum. However, this requirement can be met only if the first portion of water is sent in addition to the drum. Existing schemes for supplying water to the boiler drum usually do not provide for such a possibility. Nevertheless, when developing a scheme for monitoring the temperature state of the drum, it was decided to keep the measurement of the water temperature in front of the drum; the saturation temperature control is also retained.

Filling the drum for hydropressing is prohibited if the temperature of the metal of the top of the empty drum exceeds 140 °C.

The graphs given in the tasks for firing up the boiler from various thermal states are of a specific nature: the testing of starting modes was carried out on the TPE-430 boiler of the TPP with cross connections; The graphs also apply to boilers of other types.

Rice. nine . Temperature distribution along the superheater path:

Depending on the technology used, boiler shutdowns are divided into the following groups:

shutdown of the boiler in reserve;

shutdown of the boiler for a long-term reserve or repair (with conservation);

shutdown of the boiler with cooldown;

Emergency Stop.

Boiler standby shutdown refers to a short shutdown while keeping the water level in the drum, mainly due to downtime of non-repairable equipment over the weekend. During a shutdown lasting more than 1 day, the pressure in the boiler, as a rule, decreases to atmospheric pressure. When stopping for more than 3 days, it is recommended to put the boiler under excess pressure from a deaerator or other source for conservation purposes.

The boiler shutdown technology is adopted as simplified as possible and provides for unloading the boiler up to 20 - 30% at nominal parameters, followed by its redemption and disconnection from the main steam pipeline.

To maintain steam pressure during shutdown, the boiler purge valves to atmosphere are not opened. The requirement contained in the "Scope and technical conditions for the implementation of technological protection of thermal power equipment of power plants with cross connections and hot water boilers" (Moscow: SPO Soyuztekhenergo, 1987), on the opening of purge valves during boiler shutdowns, was revised and when listing the actions performed by technological protection, this operation is not mentioned (Circular No. Ts-01-91 / T / “On Amending the Technological Protection Schemes of Thermal Power Equipment of Operating TPPs” - M .: SPO ORGRES, 1991).

Enough to confine remote control purge valve.

When equipment is put into long-term reserve or repair, this Standard Instruction provides for its conservation with hydrazine with ammonia in the boiler shutdown mode. Other preservation methods are also possible.

Shutdown with cooldown of the boiler and steam pipelines is used if it is necessary to repair the heating surfaces in the furnace, gas ducts, warm box. When the boiler is extinguished, the draft machines remain in operation for the entire cooldown period. The drum is cooled down by steam from a neighboring boiler (through jumpers) both without maintaining the water level in the drum (such a mode is given as an example in this Standard Instruction) and with maintaining the level. In the latter case, the supply of steam for cooling down is carried out only in the upper collectors of the drum. With the help of RRDU, the rate of reduction of steam pressure, which is first discharged into the auxiliary collector, then into the atmosphere, is regulated.

The steam pressure reduction rate must be maintained in such a way as not to exceed the allowable rate of temperature decrease in the lower generatrix of the drum, which at shutdown is [↓Vt] = 20 °C/10 min. The temperature difference between the upper and lower generatrices of the drum should not exceed [ Dt] = 80 °C.

Appendix 4

SCOPE OF TEMPERATURE CONTROL

Control for temperature regime of the superheater during boiler start-ups, it is advisable to use standard thermoelectric thermometers installed at the outlet of individual stages, refusing to measure using coil thermoelectric thermometers. In start-up modes, first of all, it is necessary to ensure control over the steam temperature in the first stages of the superheater as the most heat-stressed heating surfaces in such modes, as well as over the steam temperatures at the boiler outlet in both flows. It is recommended to bring these measurements to automatic registration along with the existing drum metal temperature registration. The latter must be brought into line with the requirements of the application of Sec. 1.6 "Collection of administrative documents for the operation of power systems (Heat engineering part). Part 1." M.: SPO ORGRES, 1991:

the number of temperature measurements along the top-bottom drum was reduced to six: in the center and in the extreme sections;

measurement of saturation temperatures is provided by installing sleeve or surface thermocouples on the steam outlet and drain pipes of the drum;

it is provided to measure the temperature of the feed water behind the economizer (for control when filling the drum).

The massive use of solid fuel boiler equipment poses special requirements for the owners of private houses. Despite the technical progress that has made it possible to bring modern solid fuel heaters to perfection, the operation of such equipment carries a certain danger. Failures in operation, violations of the operating conditions of heating equipment can cause equipment to fail at the height of the heating season. In the worst case, the occurrence of emergency situations with a running unit can result in serious injuries for the inhabitants of the house, damage to residential buildings.

In this aspect, one of the most important conditions for safe operation will be the protection of the solid fuel boiler from overheating. Accurate compliance with the safety rules for the operation of heating equipment, the availability of capable automation and control devices, will provide you with the necessary protection against unforeseen situations.

Let us consider in more detail what the protection of boiler equipment against overheating is based on. What could be the reason for the boiling of the coolant in the heated circuit and what are the consequences of such a state of emergency.

Reasons for overheating of a solid fuel boiler

Even at the stage of selection and purchase, it is important to consider the performance characteristics of the heater. Many models that are on sale today have a built-in overheating protection system. Whether it works or not is another question. However, it is necessary to adhere to certain knowledge and skills, hoping to create an effective and safe autonomous heating system at home.

The reliable operation of the heating unit depends on the operating conditions. In case of obvious violations of technological parameters heating equipment and abuse of standard safety rules, a high probability of an emergency.

For reference: If the temperature in the combustion chamber exceeds the permissible parameters, it can cause the boiler water to boil. The result of an uncontrolled process is the depressurization of the heating circuit, the destruction of the heat exchanger housing. In case of hot water boilers overheating may cause an explosion.

Warn possible Negative consequences it is possible even at the stage of installation of a solid fuel boiler. Correct strapping heating apparatus will guarantee your safety and reliable operation of the unit in the future.

Speaking in detail, in each case, the protection system of a solid fuel boiler has its own specifics and features. Each heating system has its pros and cons. For example:

• When we are talking about solid fuel boilers with natural circulation of the coolant, it is necessary to take care of the safety and performance of the heating equipment even during installation. The pipes in the system are metal. Moreover, the diameter of such pipes must exceed the diameter of the pipes used for laying the circuit with forced circulation of the coolant. Sensors installed on the water circuit will signal a possible overheating of the coolant. Safety valve and the expansion tank play the role of a compensator, reducing excess pressure in the system.

A significant disadvantage gravity system heating is the lack of an effective mechanism for adjusting the operating modes of solid fuel boilers.

• Great technological opportunities for consumers are provided by those working with forced circulation of the coolant in the system. Already only the presence of the second circuit significantly increases the ability to regulate the heating temperature of the boiler water. The only negative in the operation of such a system is a working pump, which can make it difficult to operate the heating system with its work.

This is due to the fact that when the electricity is turned off, the pump ceases to perform its functions. Stopping the circulation process and the inertia of solid fuel heating boilers can lead to overheating of the heating unit. If the boiler equipment is not equipped, the situation with a power outage is fraught with extremely unpleasant consequences.

Effective protection against overheating of a working solid fuel boiler should be based on the mechanism for removing excess heat generated by the heating device.

What are the ways to protect heating equipment from overheating

Manufacturing companies are trying, in order to increase the consumer attractiveness of their products, to include any guarantees of its safety in the technical passport of boiler equipment. The uninitiated consumer has no idea about the means of protecting the heating boiler from boiling.

There are currently the following ways to ensure the protection of solid fuel units used for autonomous heating systems. The effectiveness of each method is explained by the operating conditions of boiler equipment, and the design features of the units.

In most cases, in the data sheet for the heater, manufacturers recommend using tap water for cooling. In some cases heating boilers on solid fuel are equipped with built-in additional heat exchangers. There are models of boilers with remote heat exchangers. A safety valve is used to prevent overheating. The safety valve is designed only to relieve excessive pressure in the system, while the safety valve opens the access of tap water when the boiler overheats.

Important! In the presence of cast-iron heating devices, such a measure is fundamentally wrong. Cast iron heat exchangers afraid of a sudden change in temperature. Supplying cold water to the circuit can lead to loss of integrity of the heat exchanger housing. (heated to high temperature cast iron will simply burst on contact with cold water).

Exceeding the coolant temperature of 100 0C creates an overpressure that opens the valve. Under the action of tap water, which is supplied under a pressure of 2-5 bar, hot water is forced out of the circuit by cold water.

The first aspect that causes controversy about cooling tap water– lack of electricity to ensure the operation of the pump. The expansion tank does not have enough water to cool the boiler.

The second aspect that this method of cooling dismisses is associated with the use of antifreeze as a coolant. In the event of an emergency, up to 150 liters of antifreeze will go down the drain along with the incoming cold water. Is this protection worth it?

The presence of a UPS will make it possible to maintain the operation of a circulating pump in a critical situation, with the help of which the coolant will evenly diverge through the pipeline without having time to overheat. As long as the battery capacity is sufficient, the uninterruptible power supply guarantees the operation of the pump. During this time, the boiler should not have time to heat up to critical parameters, the automation will work, starting the water through the spare, emergency circuit.

Another way out of a critical situation would be to install an emergency circuit in the piping of a solid fuel unit. The shutdown of the pump can be duplicated by the operation of a spare circuit with natural circulation of the coolant. The role of the emergency circuit is not to provide heating for residential premises, but only to be able to remove excess thermal energy in an emergency.

On a note: the installation of an emergency circuit can be replaced by the installation of a bypass, which will, in extreme cases, divert superheated boiler water to an expansion tank or heat accumulator.

Such a scheme for organizing the protection of the heating unit from overheating is reliable, simple and convenient in operation. You will not need any special funds for its equipment and installation. The only conditions for such protection to work are:

• Availability expansion tank or storage capacity in system;
• the use of a check valve only petal type;
• the pipes of the second circuit must be of a larger diameter than the conventional heating circuit.

Conclusion

Assessing the technological capabilities of modern solid fuel boilers, one should think not only about its operating power, but also foresee the installation of protection elements for the entire system. Overheating of the boiler is a frequent and well-known phenomenon for the inhabitants of private houses. Using the available means to ensure protection will not only avoid emergency situations, but also extend the operation of the heating units. Everyone is free to choose the means and method of protection. It will be enough for one to install an electric generator, which, together with the UPS, will not allow the circulation of water in the system to stop. Other owners of a private house, on the contrary, will need to install a bypass or equip a spare, emergency circuit for safety reasons.

According to experts, the installation of a buffer tank or the installation of a bypass are the most effective ways protection of the heating system from overheating.

Note: in the USA and in European countries, the operation of solid propellant devices without a buffer tank is prohibited.