The massive use of solid fuel boiler equipment poses special requirements to the owners of private houses. Despite the technical progress that has made it possible to bring modern solid fuel heating devices to perfection, the operation of such equipment carries a certain danger. Malfunctions, violations of the operating conditions of heating equipment can become the reasons for equipment failure at the height of the heating season. In the worst case, the occurrence of abnormal situations with a working 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 safe operation will protect the solid fuel boiler from overheating. Accurate observance of the safety rules for the operation of heating equipment, the presence of capable automation and control devices, will provide you necessary protection from unforeseen situations.
Let us consider in more detail what the protection of boiler equipment against overheating is based on. What may be the reason for the boiling of the coolant in the heated circuit and what are the consequences of such an emergency.
Even at the stage of selection and purchase, it is important to consider performance characteristics heating device. Many models that are on sale today have a built-in overheating protection system. Whether it works or not is the second question. However, it is necessary to adhere to certain knowledge and skills, hoping to create an efficient 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 the technological parameters of heating equipment and abuse of standard safety rules, there is 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, destruction of the heat exchanger body. In case of hot water boilers possible explosion if overheated.
Prevent possible Negative consequences it is possible even at the stage of installing a solid fuel boiler. Correct strapping heating apparatus will guarantee your safety and reliable operation of the unit in the future.
In detail, in each case, the solid fuel boiler protection system has its own specifics and features. Each heating system has its own pros and cons. For instance:
A significant disadvantage of the gravitational heating system is the lack of an effective mechanism for adjusting the operating modes of solid fuel boilers.
This is due to the fact that when the electricity is cut off, the pump stops performing its functions. The stoppage of the circulation process and the inertia of solid fuel heating boilers can lead to overheating of the heating unit. If the boiler room 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.
Manufacturing companies are trying to increase the consumer attractiveness of their products, to include in the technical passport of boiler equipment any guarantees of its safety. The uninitiated consumer does not have the slightest 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 systems heating. The effectiveness of each method is explained by the operating conditions of the boiler equipment, and the design features of the units.
In most cases, in the data sheet for heater manufacturers recommend using tap water for cooling. In some cases heating boilers for solid fuels are equipped with built-in additional heat exchangers. There are models of boilers with external heat exchangers. Used by a safety valve to prevent overheating. The safety valve is designed only to relieve excessive pressure in the system, while the safety valve opens access when the boiler overheats tap water.
Important! In the presence of cast iron heating devices, such a measure is fundamentally wrong. Cast iron heat exchangers are afraid of a sudden temperature drop. The supply of cold water to the circuit can lead to the loss of the integrity of the heat exchanger housing. (cast iron heated to a high temperature will simply burst upon contact with cold water).
If the temperature of the coolant exceeds the 100 ° C mark, it creates an excess pressure that opens the valve. Under the influence of tap water, which is supplied under a pressure of 2-5 bar, hot water is displaced from the circuit by the cold one.
The first aspect that raises controversy about cooling tap water- lack of electricity to ensure the operation of the pump. The expansion vessel does not have enough water to cool the boiler.
The second aspect, which sweeps aside this cooling method, is associated with the use of antifreeze as a heat carrier. In the event of an emergency situation, up to 150 liters of antifreeze will go into the sewer along with the incoming cold water. Is this protection method worth it?
The presence of a UPS will allow maintaining the operation of the circulating pump in a critical situation, with the help of which the coolant will evenly disperse through the pipeline, without having time to overheat. As long as there is enough battery capacity, an uninterruptible power supply ensures that the pump is running. During this time, the boiler should not have time to heat up to the critical parameters, the automation will work, starting the water along the spare, emergency circuit.
Another way to get out of a critical situation will be to install an emergency circuit in the piping of a solid fuel unit. Switching off the pump can be duplicated by the operation of the reserve circuit with natural circulation of the coolant. The role of the emergency circuit is not in providing heating of living quarters, but only in the ability to remove excess thermal energy in case of an emergency.
On a note: the installation of the emergency circuit can be replaced by the installation of a bypass, which in extreme cases will divert the overheated boiler water to the 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 special funds for its equipment and installation. The only conditions for such protection to work are:
Evaluating the technological capabilities of modern solid fuel boilers, one should think not only about its operating capacity, but also foresee the installation of protection elements of the entire system in advance. 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 prolong 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 for safety reasons or equip a spare, emergency circuit.
According to experts, installing a buffer tank or installing a bypass is the most effective way to protect the heating system from overheating.
Note: in the USA and in European countries, the operation of solid fuel devices without a buffer tank is 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.
When firing up a solid fuel boiler, one has to face the fact that a cold coolant washes the walls of an already heated combustion chamber, cools them, which leads to condensation of water vapor, which is invariably present in the flue gases. Particles of water 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: soot particles that settle on the walls dissolve in water droplets. Under influence high temperatures this mixture is sintered, forming a dense and strong 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 boiler efficiency drops.
Removing the crust is not easy, especially if the boiler's combustion chamber has a complex heat transfer 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.
To protect the solid fuel boiler from the formation of condensation, it is necessary to exclude a situation in which this process is possible. To do this, do not allow cold heat carrier to enter the boiler. The return temperature should be less than the flow temperature by 20 degrees. 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 a ready-made mixing unit, the cost of which can be 25 000 and more rubles. For example, FAR (Italy) offers similar equipment for 28,500 rubles and the company Laddomat sells a mixing unit for 25,500 rubles.
More economical, but not less effective method to protect a solid fuel boiler from condensation consists in regulating the temperature of the coolant entering the boiler using a thermostatic valve with a thermal head.
There are two types of thermostatic valves:
The mixing valve is installed in the return pipe and the control valve is installed in the supply pipe. The valve is controlled by a thermal head with a thermal bulb.
The thermo bulb with the help of a special sleeve is attached to the surface of the return pipe in close proximity to the heating boiler. Inside the flask there 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 thermostatic valve.
With the help of 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 the coolant to the boiler, but never blocks it or opens it completely, protecting the boiler from overheating and boiling. The valve is fully closed only at the moment of starting the boiler.
The thermostatic valve is installed on the flow in front of the bypass section (pipeline section) connecting the boiler flow and return in the immediate vicinity of the boiler. In this case, a small circulation loop of the coolant is formed. The thermo bulb, as mentioned above, is installed on the return pipeline in close proximity to the boiler.
At the moment of starting the boiler, the coolant has a minimum temperature, the working fluid in the thermowell occupies a minimum volume, there is no pressure on the stem of the thermal head, 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 thermowell increases, the thermal head begins to press on the valve stem, passing the cold coolant to the boiler, and the heated coolant into the general circulation circuit.
As a result of mixing in cold water, the temperature in the return line decreases, which means that the volume of the working fluid in the thermowell decreases, which leads to a decrease in the pressure of the thermal head on the valve stem. This, in turn, leads to the termination of the supply of cold water to the small circulation loop.
The process continues until the entire coolant is heated to the required temperature. After that, the valve closes the movement of the coolant along a small circulation loop, and the entire coolant begins to move along a large heating circle.
The thermostatic mixing valve works in the same way as a control valve, but it is not installed on the flow line, but on the return line. The 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 in the same place - on the section of the return pipeline in the immediate vicinity of the heating boiler.
While the coolant is cold, the valve passes it only in a small circle. As the heat carrier heats up, the thermal head begins to press on the valve stem, passing part of the heated heat carrier into the general circulation circuit of the boiler.
As you can see, the scheme is extremely simple, but at the same time effective and reliable.
The thermostatic valve and thermal head do not need electrical energy to operate, both devices are non-volatile. None additional devices or supervisors are not needed either. To heat the coolant circulating in a small circle, 15 minutes are enough, 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 several times, and with it the time for the destructive effect of acids on the boiler is reduced.
It remains to add that the thermostatic valve costs about 6,000 rubles.
To protect the solid fuel boiler from condensate, it is necessary to correctly pip it using a thermostatic valve and at the same time creating a small coolant circulation circuit.
When buying and installing a solid fuel boiler, it is imperative to take into account the peculiarities of its operation, namely, the high probability of overheating in emergency situations, which can result in a serious accident and even destruction of the unit's water jacket (explosion). Also, considerable harm can be caused by the formation of condensation on the walls of the combustion chamber, which happens under certain operating modes. To eliminate such troubles, the solid fuel boiler must be protected from overheating and condensation, which will be discussed in our article.
In solid fuel boilers, moisture can form on the inner walls of the combustion chamber. This happens when the wood has already burst into flames and the blower fan (if any) is running in full force and the water in the heating system is still cold.
From the temperature drop, condensate arises, which, mixing with the combustion products, settles on the walls of the chamber. This deposit corrodes the metal, as a result of which the service 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.
It is not difficult to solve this problem, you just need to include in the piping circuit a three-way thermostatic valve set for a coolant temperature of 55-60 ºС, as shown in the figure below. The protection of a solid fuel boiler against condensation works as follows: until the water in the boiler heats up to the set temperature, it circulates along a small circuit. After sufficient heating, the three-way valve gradually mixes in water from the system. Thus, there is no temperature drop or condensation in the furnace.
Schema injection mixing unit also protects cast iron heat exchanger from the temperature difference of the coolant, since the valve will not allow cold water to enter the heat generator.
Excessive heating and boiling of the coolant in solid fuel units can occur during operation for the following reasons:
The most popular method of protecting the boiler from overheating during sudden and frequent power outages is the use of blocks uninterruptible power supply or electric generators. In general, a prudent owner living 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. For the system to be non-volatile, it must be calculated and made gravitational with natural circulation of the coolant. heating equipment you need to choose as simple as possible, where there is no electronic control unit and a blower fan for the boiler.
Since, in addition to an emergency situation 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:
Note. In some models of solid fuel units, overheating protection is implemented using a built-in or external heat exchanger. In the event of an accident, cold water is passed through it from the water supply network. This solution can also be used by those who have undertaken to make a solid fuel boiler with their own hands.
It 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, it is connected to the supply and return mains, water supply network and sewerage system.
At a coolant temperature above 105 ºС, the valve opens and, due to a pressure in the water supply system of 2-5 bar, hot water is displaced from the jacket of the heat generator and cold pipelines, after which it goes into the sewage system. How the solid fuel boiler protection valve is connected is shown in the diagram:
The disadvantage of this protection method is that it is not suitable for systems filled with antifreeze liquid. In addition, the scheme is not applicable in conditions where there is no centralized water supply, because together with a power outage, the supply of water from a well or a pool will also stop.
The scheme for protecting a solid fuel boiler from overheating presented below has practically no drawbacks:
When the power goes out, it will stop circulation pump, which, during operation, presses the petal of the check valve, which prevents the movement of water through the bypass. But after stopping, the valve will open and the coolant will continue to circulate in a natural way. Even if at this time some kind of accident occurs with a solid fuel boiler and the heating of the water does not stop, then the heat will be discharged into the buffer tank until the firewood in the firebox burns out.
True, several conditions are required here:
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 one cannot do without a bypass and a buffer tank. But the use of the latter is considered preferable; in some countries of Western Europe, the operation of solid fuel heat generators without a buffer tank is generally prohibited.
RUSSIAN JOINT STOCK SOCIETY OF ENERGY
AND ELECTRIFICATION "UES OF RUSSIA"
TYPICAL INSTRUCTIONS
ON START
FROM DIFFERENT THERMAL STATES
AND STOP THE STEAM BOILER
THERMAL POWER PLANTS
WITH CROSS LINKS
RD 34.26.514-94
ORGRES BEST EXPERIENCE SERVICE
Moscow 1995
DEVELOPED by JSC "Firm ORGRES"
CONTRACTOR V.V. KHOLSCHEV
APPROVED BY RAO "UES of Russia" 09/14/94
First Vice President V.V. CURLY
The Instructions take into account the comments and suggestions of research and design institutes, energy companies and commissioning organizations.
|
RD 34.26.514-94 |
Expiration date set
from 01.01.1995
before 01.01.2000
The standard instruction is intended for the engineering and technical personnel of thermal power plants. This Instruction released again. From similar works, the "Collection of instructions for the maintenance of boilers of power plants" (Moscow-Leningrad: Gosenergoizdat, 1960), "Temporary instructions for the maintenance of a TGM-84 boiler when burning natural gas and fuel oil" (Moscow: BTI ORGRES, 1966).
When operating the boiler, one should be guided by the requirements:
current PTE, PTB, PPB, "Rules for the construction and safe operation of steam and hot water boilers", "Rules of explosion safety when using fuel oil and natural gas in boiler plants";
factory instructions for the operation of the boiler;
local guidelines for maintenance and operation of the boiler and auxiliary equipment;
local job descriptions;
The procedure for turning on the 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 metering pumps of the conservation installation to supply the hydrazine-ammonia solution (Fig.) To one of the possible points on the boiler (drum, lower points, power unit). After filling, turn off the metering pumps and connect the boiler to a hot (or cold) feedwater assembly; make a crimp test.
In the process of pressure testing, take a sample and determine the quality of the water in the boiler, including visually. If necessary, flush the screen system through the lowest 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 cut of the superheater into the atmosphere;
turn on, at the request of the chemical department, metering pumps and organize, in the absence of phosphates in the boiler water, a phosphating mode, maintaining the pH value of the boiler water of the clean compartment at least 9.3;
set the required flow rate of boiler water from remote cyclones by covering the continuous blowdown control valve, making sure that the quality indicators are stable feed water and a couple at the standardized level.
The moment of inclusion
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 verified with the readings of direct-acting water indicating devices
Raising the water level in the boiler drum (II limit)
Extinguishing the torch in the furnace
At a load of 30% of the nominal
Decrease in gas pressure downstream of the control valve
With gas valve opening to any burner
Reduction of fuel oil pressure downstream of the control valve
With oil valve opening to any burner
Reducing oil pressure in the lubrication system of direct injection mills with its centralized supply
Switch off all primary air fans
Shutdown of all mill fans when transporting dust with a drying agent from these fans
Tarnishing of a pulverized coal torch in the firebox
Disabling all smoke exhausters
With the opening of the fuel shut-off valve to any pilot burner
Switch off all blowing fans
Disabling all RVPs
Failure to ignite or extinguish the torch of any pilot burner
Start function
The moment of inclusion
Kiln regulator of the water level in the drum
Maintaining a constant level
After switching to a control valve on a bypass with a diameter of 100 mm of the supply 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 regulator behind the boiler
Maintaining the nominal live steam temperature by injection
Upon reaching the nominal live steam temperature
Continuous blowdown regulator
Maintaining the set flow rate of continuous blowdown
After connecting the boiler to the main
Total air regulator
Maintaining a given excess air in the furnace
Primary air flow regulator
Maintaining a given flow rate of primary air
After switching to dust incineration
Furnace vacuum regulator
Maintaining vacuum in the furnace
With boiler firing
Previously, as you know, it was proposed to control the temperature of the water in front of the drum when filling a non-cooled 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 fulfilled only if the first portion of water is directed outside the drum. The existing schemes for supplying water to the boiler drum usually do not provide for such a possibility. Nevertheless, when developing a circuit for monitoring the temperature state of the drum, it was decided to keep the measurement of the water temperature in front of the drum; control over the saturation temperature is also retained.
Filling the drum for hydraulic pressing is prohibited if the temperature of the metal on the top of the empty drum exceeds 140 ° C.
The graphs given in the tasks for the kindling of the boiler from various thermal states are of a specific nature: the start-up modes were tested on the TPE-430 boiler at the TPP with cross-links; the schedules also apply to other types of boilers.
Rice. nine ... Temperature distribution along the superheater path:
Depending on the technology used, boiler shutdowns are divided into the following groups:
stopping the boiler in reserve;
shutdown of the boiler for a long-term standby or repair (with conservation);
shutdown of the boiler with cooling down;
Emergency Stop.
Boiler shutdown in reserve means a short shutdown with maintenance of the water level in the drum, mainly associated with downtime of equipment that does not require repair on weekends. When stopping for more than 1 day, the pressure in the boiler, as a rule, decreases to atmospheric. When shutting down for more than 3 days, it is recommended to put the boiler under overpressure from a deaerator or other source for conservation purposes.
The boiler shutdown technology is adopted as simplified as possible and provides for the unloading of the boiler up to 20 - 30% at the nominal parameters, followed by its shutdown and disconnection from the main steam pipeline.
To maintain steam pressure during shutdown, the boiler vent valves are not opened. The requirement contained in the "Scope and technical conditions for the performance of technological protection of heat and power equipment of power plants with cross-links 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 / Т / "On amendments to the schemes of technological protection of heat and power equipment of operating TPPs" - M .: SPO ORGRES, 1991).
It is enough to confine ourselves to the remote control of the purge valves.
When putting equipment into a long-term standby or repair, this Standard Instruction provides for its conservation with hydrazine with ammonia in the boiler shutdown mode. Other methods of conservation are also possible.
Shutdown with cooldown of the boiler and steam pipelines is used when it is necessary to repair heating surfaces in the furnace, gas ducts, and a warm box. When the boiler is turned off, the draft machines remain in operation for the entire period of cooldown. Cooling down of the drum with the steam of the neighboring boiler (through the jumpers) is performed both without maintaining the water level in the drum (this mode is shown as an example in this Standard Instruction), and with maintaining the level. In the latter case, steam is supplied for cooldown only to the upper collectors of the drum. With the help of the RROU, the rate of decrease in the pressure of steam is regulated, which is discharged first into the auxiliary collector, then into the atmosphere.
The rate of decrease in steam pressure must be maintained so as not to exceed the permissible rate of decrease in the temperature of the lower drum generatrix, which, when stopped, is [↓ Vt] = 20 ° C / 10 min. The temperature difference between the upper and lower generatrix of the drum should not exceed [ Dt] = 80 ° C.
Control for temperature regime When starting up a steam superheater, it is advisable to carry out standard sleeve thermoelectric thermometers installed at the outlet of separate stages, abandoning measurements using coil thermoelectric thermometers. In start-up modes, it is first of all necessary to ensure control over the temperature of the steam in the first stages of the superheater as the most heat-stressed heating surfaces in such modes, as well as over the temperature of the steam at the outlet of the boiler along both streams. It is recommended to put the indicated measurements on automatic registration along with the existing registration of the temperature of the drum metal. The latter must be brought in accordance with the requirements of the appendix, section. 1.6 "Collection of regulatory 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 has been 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 water lowering pipes of the drum;
provision is made for measuring feed water temperatures downstream of the economizer (for control when filling the drum).
Many manufacturers of boiler equipment require that at the inlet to the boiler there is water not lower than a certain temperature, since a cold return has a bad effect on the boiler:
The first method is ideal, but expensive. Esbe offers a ready-made module for mixing into 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. Commencement of the combustion process. The mixing device allows you to quickly increase the boiler temperature, thus starting the water circulation 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: Storage tank in the process of loading. Good governance ensures efficient loading of the storage tank and correct stratification in it.
Phase 4: The storage tank is fully loaded. Even at the final stage of the combustion cycle, the high quality of regulation ensures good control of the return temperature to the boiler, while the storage tank is full at the same time
Phase 5: End of the combustion process. By completely closing the top opening, the flow is directed directly to the storage tank, using the heat in the boiler
The second method is simpler, using a high quality three-way thermo-mixing valve.
For example valves from ESBE or or VTC300. These valves differ depending on the output of the boiler used. VTC300 is used for boiler power up to 30 kW, VTC511 and VTC531 - for more powerful boilers from 30 to 150 kW
The valve is installed on the bypass line between the boiler flow 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). Input "B" closes completely when when the temperature at input "A" exceeds the rated opening temperature by 10 ° C.
A similar valve releasesHerz armaturen- three-way thermo-mixing valve Anti-condensate... Two types of Heiz anti-condensate valves are available- with disconnectable and fixed bypass.
Application diagram of the Heiz 3-way mixing valve Anti-condensation
When the temperature of the coolant at the outlet of the "AB" valve is less than 61 ° C, the input "A" is closed, through the input "B" hot water flows from the boiler supply to the return. When the temperature of the coolant at the "AB" outlet exceeds 63 ° C, the bypass input "B" is closed and the coolant from the system return through input "A" enters the boiler return. Bypass output "B" opens again when the temperature at outlet "AB" drops to 55 ° C
When a heat carrier with a temperature of less than 61 ° C passes through the "AB" outlet, the "A" input from the system return is closed, the "AB" outlet is supplied with hot heat carrier from the "B" bypass. When the temperature at outlet "AB" reaches more than 63 ° C, inlet "A" opens and the return water mixes with water from bypass "B". To equalize the bypass (so that the boiler does not operate constantly on a small circulation circle), a balancing valve must be installed on the bypass in front of the "B" inlet.
