The optimal mode of operation of a wall-mounted gas boiler. The optimum water temperature in a gas boiler At what temperature should a gas boiler be set

A heating boiler is a device that, by means of the combustion of fuel (or electricity), heats the coolant.

The device (design) of the heating boiler: heat exchanger, thermally insulated housing, hydraulic unit, as well as safety elements and automation for control and monitoring. For gas and diesel boilers, a burner is provided in the design, for solid fuel boilers - a firebox for firewood or coal. Such boilers require a chimney connection to remove combustion products. Electric boilers are equipped with heating elements, do not have burners and a chimney. Many modern boilers are equipped with built-in pumps for forced circulation of water.

The principle of operation of the heating boiler- the heat carrier, passing through the heat exchanger, heats up and then circulates through the heating system, giving off the received thermal energy through radiators, underfloor heating, heated towel rails, and also providing water heating in the indirect heating boiler (if it is connected to the boiler).

Heat exchanger - a metal container in which the coolant (water or antifreeze) is heated - can be made of steel, cast iron, copper, etc. Cast iron heat exchangers are resistant to corrosion and quite durable, but are sensitive to sudden temperature changes and have big weight. Steel can suffer from rust, so their internal surfaces are protected by various anti-corrosion coatings to increase their service life. Such heat exchangers are the most common in the manufacture of boilers. Corrosion is not terrible for copper heat exchangers, and due to the high heat transfer coefficient, low weight and dimensions, such heat exchangers are popular, often used in wall boilers, but usually more expensive than steel.
In addition to the heat exchanger, an important part of gas or liquid fuel boilers is a burner, which can be various kinds: atmospheric or fan, single-stage or two-stage, with smooth modulation, double. ( Detailed description burners are presented in articles about gas and liquid fuel boilers).

To control the boiler, automation is used with various settings and functions (for example, a weather-dependent control system), as well as devices for remote control of the boiler - a GSM module (controlling the operation of the device via SMS messages).

Main technical specifications heating boilers are: boiler power, type of energy carrier, number of heating circuits, type of combustion chamber, type of burner, type of installation, pump availability, expansion tank, boiler automation, etc.

To determine required power heating boiler for a house or apartment, a simple formula is used - 1 kW of boiler power for heating 10 m 2 of a well-insulated room with a ceiling height of up to 3 m. Accordingly, if heating is required basement, glazed winter garden, rooms with non-standard ceilings etc. boiler output must be increased. It is also necessary to increase the power (about 20-50%) while providing the boiler with hot water (especially if heating the water in the pool is necessary).

We note the feature of calculating the power of gas boilers: the nominal gas pressure at which the boiler operates at 100% of the power declared by the manufacturer for most boilers is from 13 to 20 mbar, and the actual pressure in gas networks in Russia can be 10 mbar, and sometimes below. Accordingly, a gas boiler often works only at 2/3 of its capacity, and this must be taken into account when calculating. When choosing the power of the boiler, be sure to note all the features of the thermal insulation of the house and premises. In more detail with a table for calculating the power of a heating boiler, you can

So which boiler is better to choose? Consider the types of boilers:

"Middle class"- average price, not so prestigious, but quite reliable, standard standard solutions. These are Italian boilers Ariston, Hermann and Baxi, Swedish Electrolux, German Unitherm and boilers from Slovakia Protherm.

"Economy class" - budget options, simple models, the service life is shorter than that of boilers of a higher category. Some manufacturers have budget models of boilers, for example,

Tell me about boilers and timing. When the predetermined coolant temperature is reached, should the boiler reduce gas consumption and reach the minimum (or so) power? As a result, there should be no clocking. Unless the minimum power turns out to be more than necessary to maintain the set coolant temperature.

Then the question is: how to find out the power range of the boiler (or, equivalently, the gas flow range). With the maximum it is clear - it is indicated everywhere.

Click to reveal...

In one room? As if in each separate room the temperature can change (by + - 1 gr. at least) for reasons independent of the weather and the boiler (they opened the door to the next room, where the temperature is different, opened the window, people came in, turned on the powerful device , the wind direction changed to the opposite - as a result, the temperature difference in the rooms was 1g: at one end of the house + 0.5g, at the other -0.5, total 1g, and so on). 1 degree is enough. For the whole house, 1 degree is very, very decent. You need to spend a lot of cubic meters of gas to raise the temperature in the house by 1 degree (especially if the house is > 200 square meters). And it turns out that for one sensor in one room, the boiler will have to scald at full power for a long time. And then the conditions in a particular room where the sensor will change, and the boiler will have to turn off abruptly. And heating is a very inertial thing. There is a decent amount of water (hundreds of liters, if the house is not small), in order to raise the temperature in the premises by 1g, you must first heat all this water and only then will it give off heat to the premises of the house. As a result, the coolant will heat up, and in the room where the sensor is located, the conditions have already changed (the device was turned off, a lot of people left, the door to the next room was closed). That is, it seems like a signal to the boiler to lower the temperature IN THE WHOLE HOUSE, and the coolant is already heated, and there is nowhere to go, it will give off its heat to the house when, judging by the sensor in one room, it needs to be reduced .....

In general, the point is that it is probably not very correct to determine the operation of the boiler for the whole house from one temperature measurement point in the house, because. if the room is "usual", then the temperature fluctuations independent of the weather and the operation of the boiler are too large (more precisely, sufficient to change the operating mode of the boiler THEN, when the change in the integral temperature throughout the house is NOT ENOUGH to change the operating modes of the boiler), and will lead to a change in the operating mode of the boiler when it is not really necessary.

You need to know the integral temperature around the house - then, based on this temperature, you can determine the operating mode of the boiler. Because integral temperature around the house (especially in big house) changes very, VERY slowly (if you turn off the heating completely, then it will take more than 4 hours for it to fall by 1 gr.) - and this temperature changes by at least 0.5 gr. - this is already a sufficient signal to increase the gas flow to the boiler. From the simple opening of the door, from the fact that the house has become strong more people, etc. - from all this, the integral heat in the house will not change even by 0.1g. Bottom line - you need a bunch of sensors for different rooms and then reduce all readings into one average (at the same time, for good, take not just the average, but the integral average, i.e. take into account not only the temperature of each specific sensor, but also the volume of the room in which this sensor is located).

P.S. For relatively small houses (probably 100m or less), probably, all of the above is not critical.

P.P.S. All of the above - imho

2.KIT of the boiler at different temperatures of the incoming

The lower the temperature enters the boiler, the greater the temperature difference by different sides baffles of the boiler heat exchanger, and the more efficiently the heat passes from the exhaust gases (combustion products) to through the wall of the heat exchanger. I will give an example with two identical kettles placed on the same burners. gas stove. One burner is set to high flame and the other to medium. The kettle with the highest flame will boil faster. And why? Because the temperature difference between the combustion products under these kettles and the water temperature for these kettles will be different. Accordingly, the rate of heat transfer at a larger temperature difference will be greater.

With regard to the heating boiler, we cannot increase the combustion temperature, as this will lead to the fact that most of our heat (gas combustion products) will fly out through the exhaust pipe into the atmosphere. But we can design our heating system (hereinafter referred to as CO) in such a way as to lower the temperature entering into, and consequently, lower the average temperature circulating through. The average temperature at the return (inlet) to and supply (outlet) from the boiler will be called the temperature of "boiler water".

As a rule, the 75/60 ​​mode is considered the most economical thermal mode of operation of a non-condensing boiler. Those. with a temperature at the supply (outlet from the boiler) +75 degrees, and at the return (inlet to the boiler) +60 degrees Celsius. A reference to this thermal regime is in the boiler passport, when indicating its efficiency (usually indicate the mode 80/60). Those. in another thermal mode, the efficiency of the boiler will be lower than stated in the passport.

That's why modern system heating must operate in the design (for example, 75/60) thermal mode for the entire heating period, regardless of the outside temperature, except when using outdoor sensor temperature (see below). The regulation of the heat transfer of heating devices (radiators) during the heating period should be carried out not by changing the temperature, but by changing the amount of flow through the heating devices (the use of thermostatic valves and thermoelements, i.e. "thermal heads").

In order to avoid the formation of acid condensate on the boiler heat exchanger, for a non-condensing boiler, the temperature in its return (inlet) should not be lower than +58 degrees Celsius (usually taken with a margin of +60 degrees).

I will make a reservation that the ratio of air and gas entering the combustion chamber is also of great importance for the formation of acid condensate. The more excess air entering the combustion chamber, the less acidic condensate. But you should not rejoice at this, since excess air leads to a large overspending of gas fuel, which ultimately "beats us in the pocket."

For example, I will give a photo showing how acid condensate destroys the boiler heat exchanger. The photo shows the heat exchanger of the Vaillant wall-mounted boiler, which worked for only one season in an incorrectly designed heating system. Seen pretty severe corrosion from the return (inlet) side of the boiler.

For condensation, acid condensate is not terrible. Since the heat exchanger of the condensing boiler is made of special quality alloyed of stainless steel, which is "not afraid" of acid condensate. Also, the design of the condensing boiler is designed so that acidic condensate flows through a tube into a special container for collecting condensate, but does not fall on any electronic components and components of the boiler, where it could damage these components.

Some condensing boilers are able to change the temperature on their return (inlet) by themselves due to the smooth change in the power of the circulation pump by the boiler processor. Thereby increasing the efficiency of gas combustion.

For additional gas savings, use the connection of the outdoor temperature sensor to the boiler. Most wall-mounted ones have the ability to automatically change the temperature depending on the outside temperature. This is done so that at outdoor temperatures that are warmer than the temperature of the cold five-day period (the most severe frosts), the temperature of the boiler water is automatically lowered. As mentioned above, this reduces gas consumption. But when using a non-condensing boiler, it is important not to forget that when the temperature of the boiler water changes, the temperature at the return (inlet) of the boiler should not fall below +58 degrees, otherwise acid condensate will form on the boiler heat exchanger and destroy. To do this, when commissioning the boiler, in the boiler programming mode, such a curve of temperature dependence on the outside temperature is selected, at which the temperature in the boiler return would not lead to the formation of acid condensate.

I want to immediately warn you that when using a non-condensing boiler and plastic pipes in the heating system, installing a street temperature sensor is almost pointless. Since we can design for the long-term service of plastic pipes, the temperature at the boiler supply is not higher than +70 degrees (+74 during the cold five-day period), and in order to avoid the formation of acid condensate, design the temperature at the boiler return is not lower than +60 degrees. These narrow "frames" make the use of weather-dependent automation useless. Since such frames require temperatures in the range of +70/+60. Already when using copper or steel pipes in the heating system, it already makes sense to use weather-compensated automation in heating systems, even when using a non-condensing boiler. Since it is possible to design the thermal mode of the boiler 85/65, which mode can be changed under the control of weather-dependent automation, for example, up to 74/58 and save on gas consumption.

I will give an example of an algorithm for changing the temperature at the boiler supply depending on the outside temperature using the Baxi Luna 3 Komfort boiler as an example (below). Also, some boilers, for example, Vaillant, can maintain the set temperature not on their supply, but on their return. And if you set the return temperature maintenance mode to +60, then you can not be afraid of the appearance of acid condensate. If at the same time the temperature at the boiler supply changes up to +85 degrees inclusive, but if you use copper or steel pipes, then such a temperature in the pipes does not reduce their service life.

From the graph, we see that, for example, when choosing a curve with a coefficient of 1.5, it will automatically change the temperature at its supply from +80 at a street temperature of -20 degrees and below, to a supply temperature of +30 at a street temperature of +10 (in the middle section flow temperature curve +.

But how much the supply temperature of +80 will reduce the service life of plastic pipes (Reference: according to manufacturers, the warranty service life plastic pipe at a temperature of +80, it is only 7 months, so do not hope for 50 years), or a return temperature below +58 will reduce the life of the boiler, unfortunately, there is no exact data announced by the manufacturers.

And it turns out that when using weather-dependent automation with non-condensing gas, you can save something, but it is impossible to predict how much the service life of the pipes and the boiler will decrease. Those. in the above case, the use of weather-compensated automation will be at your own peril and risk.

Thus, it makes the most sense to use weather-compensated automation when using a condensing boiler and copper (or steel) pipes in the heating system. Since weather-dependent automation will be able to automatically (and without harm to the boiler) change the thermal regime of the boiler from, for example, 75/60 ​​for a cold five-day period (for example, -30 degrees outside) to the 50/30 mode (for example, +10 degrees outside) street). Those. you can painlessly choose the dependence curve, for example, with a coefficient of 1.5, without fear of a high boiler supply temperature in frost, at the same time without fear of the appearance of acid condensate during thaws (for condensation, the formula is valid that the more acid condensate is formed in them, the more they save gas). For interest, I will lay out a graph of the dependence of the KIT of a condensing boiler, depending on the temperature in the return of the boiler.

3.KIT of the boiler depending on the ratio of the mass of gas to the mass of air for combustion.

The more completely the gas fuel burns in the combustion chamber of the boiler, the more heat we can get from burning a kilogram of gas. The completeness of gas combustion depends on the ratio of the mass of gas to the mass of combustion air entering the combustion chamber. This can be compared to the tuning of a carburetor in a car's internal combustion engine. The better the carburetor is tuned, the less for the same engine power.

To adjust the ratio of the mass of gas to the mass of air in modern boilers, a special device is used that doses the amount of gas supplied to the combustion chamber of the boiler. It is called a gas fitting or an electronic power modulator. The main purpose of this device is automatic modulation of the boiler power. Also, the adjustment of the optimal ratio of gas to air is carried out on it, but already manually, once during commissioning of the boiler.

To do this, when commissioning the boiler, you must manually adjust the gas pressure using a differential pressure gauge on special control fittings of the gas modulator. Two pressure levels are adjustable. For maximum power mode, and for minimum power mode. The methodology and instructions for setting up are usually set out in the boiler's passport. You can not buy a differential pressure gauge, but make it from a school ruler and a transparent tube from a hydraulic level or a blood transfusion system. The gas pressure in the gas line is very low (15-25 mbar), less than when a person exhales, therefore, in the absence of a nearby open fire it is safe to make this adjustment. Unfortunately, not all service workers, when commissioning the boiler, perform the procedure for adjusting the gas pressure on the modulator (out of laziness). But if you need to get the most economical operation of your heating system in terms of gas consumption, then you must definitely perform such a procedure.

Also, when commissioning the boiler, it is necessary, according to the method and table (provided in the boiler passport), to adjust the diaphragm cross section in the boiler air pipes, depending on the boiler power and the configuration (and length) of the exhaust pipes and combustion air intake. The correctness of the ratio of the volume of air supplied to the combustion chamber to the volume of supplied gas also depends on the correct choice of this section of the diaphragm. Correct this ratio ensures the most complete combustion of gas in the combustion chamber of the boiler. And, consequently, it reduces gas consumption to the necessary minimum. I will give (for an example of a technique correct installation aperture) scan from the passport of the boiler Baxi Nuvola 3 Comfort -

4. KIT of the boiler, depending on the temperature of the air entering it for combustion.

Also, the economy of gas consumption depends on the temperature of the air entering the combustion chamber of the boiler. The efficiency of the boiler given in the passport is valid for the temperature of the air entering the combustion chamber of the boiler +20 degrees Celsius. This is due to the fact that when colder air enters the combustion chamber, part of the heat is spent on heating this air.

Boilers are "atmospheric", which take air for combustion from the surrounding space (from the room in which they are installed) and "turbo boilers" with a closed combustion chamber, into which air is forcibly supplied by a turbocharger located in. Ceteris paribus, a "turbo boiler" will have greater gas consumption efficiency than an "atmospheric" one.

If everything is clear with the “atmospheric” one, then with the “turbo boiler” questions arise from where it is better to take air into the combustion chamber. The "Turboboiler" is designed so that the air flow into its combustion chamber can be arranged from the room in which it is installed, or directly from the street (via a coaxial chimney, i.e. a "pipe in a pipe" chimney). Unfortunately, both of these methods have their pros and cons. When air enters from interior spaces at home, the temperature of the air for combustion is higher than when taken from the street, but all the dust generated in the house is pumped through the combustion chamber of the boiler, clogging it. The combustion chamber of the boiler is especially clogged with dust and dirt during finishing works in the House.

Don't forget that for safe work"atmospheric" or "turbo boiler" with air intake from the premises of the house, it is necessary to organize the correct operation of the supply part of the ventilation. For example, supply valves on the windows of the house must be installed and opened.

Also, when removing the products of combustion of the boiler up through the roof, it is worth considering the cost of manufacturing an insulated chimney with a steam trap.

Therefore, the most popular (including for financial reasons) are the coaxial chimney systems “through the wall to the street”. Where exhaust gases are emitted through the inner pipe, and outer pipe air for combustion is pumped in from the street. In this case, the exhaust gases heat up the air drawn in for combustion, since the coaxial pipe acts as a heat exchanger.

5.KIT of the boiler depending on the time of continuous operation of the boiler (lack of “clocking” of the boiler).

Modern boilers themselves adjust their output. thermal power, under the thermal power consumed by the heating system. But the limits of auto-tuning power are limited. Most non-condensing units can modulate their power from about 45% to 100% of rated power. Condensing modulate power in a ratio of 1 to 7 and even 1 to 9. Ie. a non-condensing boiler with a rated power of 24 kW will be able to produce at least, for example, 10.5 kW in continuous operation. And condensing, for example, 3.5 kW.

If, at the same time, the temperature outside is much warmer than in a cold five-day period, then there may be a situation where the heat loss of the house is less than the minimum possible generated power. For example, the heat loss of a house is 5 kW, and the minimum modulated power is 10 kW. This will lead to periodic shutdown of the boiler when the set temperature at its supply (output) is exceeded. It may happen that the boiler will turn on and off every 5 minutes. Frequent switching on / off of the boiler is called “clocking” of the boiler. Clocking, in addition to reducing the life of the boiler, also significantly increases gas consumption. I will compare the gas consumption in the clocking mode with the gasoline consumption of the car. Consider that the gas consumption during clocking is driving in city traffic jams in terms of fuel consumption. And the continuous operation of the boiler is driving along a free highway in terms of fuel consumption.

The fact is that the boiler processor contains a program that allows the boiler, using the sensors built into it, to indirectly measure the thermal power consumed by the heating system. And adjust the generated power to this need. But this boiler takes from 15 to 40 minutes, depending on the capacity of the system. And in the process of adjusting its power, it does not work in the optimal mode in terms of gas consumption. Immediately after switching on, the boiler modulates the maximum power and only over time, gradually, by approximation, reaches the optimal gas flow. It turns out that when the boiler cycles more than 30-40 minutes, it does not have enough time to reach the optimal mode and gas flow. Indeed, with the beginning of a new cycle, the boiler begins the selection of power and mode again.

To eliminate the clocking of the boiler, a room thermostat is installed. It is better to install it on the ground floor in the middle of the house, and if there is a heater in the room where it is installed, then the IR radiation of this heater should reach the room thermostat at a minimum. Also on this heater, a thermoelement (thermal head) on a thermostatic valve should not be installed.

Many boilers are already equipped with a remote control panel. Inside this control panel is the room thermostat. Moreover, it is electronic and programmable according to the time zones of the day and the days of the week. Programming the temperature in the house by time of day, by day of the week, and when you leave for a few days, also allows you to save a lot on gas consumption. Instead of a removable control panel, a decorative cap is installed on the boiler. For example, I will give a photo of the Baxi Luna 3 Komfort removable control panel installed in the hall of the first floor of the house, and a photo of the same boiler installed in the boiler room attached to the house with a decorative plug installed instead of the control panel.

6. Use of a greater share of radiant heat in heating devices.

You can also save any fuel, not just gas, by using heaters with a greater proportion of radiant heat.

This is explained by the fact that a person does not have the ability to feel exactly the temperature. environment. A person can only feel the balance between the amount of heat received and given off, but not the temperature. Example. If we take an aluminum blank with a temperature of +30 degrees, it will seem cold to us. If we pick up a piece of foam plastic with a temperature of -20 degrees, then it will seem warm to us.

With regard to the environment in which a person is, in the absence of drafts, a person does not feel the temperature of the surrounding air. But only the temperature of the surrounding surfaces. Walls, floors, ceilings, furniture. I will give examples.

Example 1. When you go down to the cellar, after a few seconds you become chilly. But this is not because the air temperature in the cellar, for example, is +5 degrees (after all, air in a stationary state is the best heat insulator, and you could not freeze from heat exchange with air). And from the fact that the balance of the interchange of radiant heat with the surrounding surfaces has changed (your body has an average surface temperature of +36 degrees, and the cellar has an average surface temperature of +5 degrees). You begin to give off much more radiant heat than you receive. That's why you get cold.

Example 2. When you are in a foundry or steel shop (or just near a large fire), you get hot. But this is not because the air temperature is high. In winter, with partially broken windows in the foundry, the air temperature in the shop can be -10 degrees. But you are still very hot. Why? Of course, the air temperature has nothing to do with it. The high temperature of the surfaces, not the air, changes the balance of radiant heat transfer between your body and the environment. You begin to receive much more heat than you radiate. Therefore, people working in foundries and steel-smelting shops are forced to put on cotton trousers, padded jackets and hats with earflaps. To protect not from the cold, but from too much radiant heat. To avoid heatstroke.

From this we draw a conclusion that many do not realize modern specialists for heating. That it is necessary to heat the surfaces surrounding a person, but not the air. When we heat only the air, first the air rises to the ceiling, and only then, descending, the air heats the walls and the floor due to the convective circulation of air in the room. Those. at first warm air rises to the ceiling, heating it, then descends to the floor along the far side of the room (and only then does the floor surface begin to heat up) and further in a circle. With this purely convective method of space heating, there is an uncomfortable temperature distribution throughout the room. When the room temperature is highest at head level, average at waist level, and lowest at foot level. But you probably remember the proverb: "Keep your head cold and your feet warm!".

It is no coincidence that the SNIP states that in a comfortable home, the temperature of the surfaces of the outer walls and floor should not be lower than average temperature indoors by more than 4 degrees. Otherwise, there is an effect that is both hot and stuffy, but at the same time chilly (including on the legs). It turns out that in such a house you need to live "in shorts and felt boots."

So, from afar, I was forced to lead you to the realization of which heating devices are best used in the house, not only for comfort, but also for fuel economy. Of course, heaters, as you may have guessed, must be used with the greatest proportion of radiant heat. Let's see which heating appliances give us the largest share of radiant heat.

Perhaps, such heating devices include the so-called "warm floors", as well as "warm walls" (which are gaining more and more popularity). But even among the usually most common heating devices, steel panel radiators, tubular radiators and cast iron radiators. I have to assume that steel panel radiators provide the largest share of radiant heat, since manufacturers of such radiators indicate the share of radiant heat, while manufacturers of tubular and cast-iron radiators keep this secret. I also want to say that aluminum and bimetallic "radiators" that have recently received aluminum and bimetallic "radiators" do not have the right to be called radiators at all. They are called so only because they are the same sectional as cast-iron radiators. That is, they are called "radiators" simply "by inertia." But according to the principle of their action, aluminum and bimetal radiators should be classified as convectors, not radiators. Since the share of radiant heat they have is less than 4-5%.

For panel steel radiators, the proportion of radiant heat varies from 50% to 15%, depending on the type. The largest share of radiant heat is in type 10 panel radiators, in which the share of radiant heat is 50%. Type 11 has 30% radiant heat. Type 22 has 20% radiant heat. Type 33 has 15% radiant heat. There are also steel panel radiators produced using the so-called X2 technology, for example, from Kermi. It represents type 22 radiators, in which it passes first along the front plane of the radiator, and only then along the rear plane. Due to this, the temperature of the front plane of the radiator increases relative to the rear plane, and, consequently, the share of radiant heat, since only IR radiation from the front plane enters the room.

The respected firm Kermi claims that when using radiators made using X2 technology, fuel consumption is reduced by at least 6%. Of course, he personally did not have the opportunity to confirm or refute these figures in laboratory conditions, but based on the laws of thermal physics, the use of such technology really saves fuel.

Conclusions. I advise you to use steel panel radiators in the entire width of the window opening in a private house or cottage, in descending order of preference by type: 10, 11, 21, 22, 33. When the amount of heat loss in the room, as well as the width of the window opening and the height of the window sill do not allow using types 10 and 11 (not enough power) and the use of types 21 and 22 is required, then if there is a financial opportunity, I will advise you to use not the usual types 21 and 22, but using X2 technology. Unless, of course, the use of X2 technology pays off in your case.

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I have a BAXI 24Fi boiler, it started just the other day and I immediately did not like its cyclical mode. Very often it ignites the burner (3 minutes, after the pump runs out). But the burner burns a little, literally 20-40 seconds and that's it. Perhaps the boiler power is too big for my heating system

I have a BAXI Eco3 Compact 240FI, an apartment of 85 sq.m. The first heating season, last year worked only on hot water. Before connection room thermostat clocked at a similar interval. At a higher water temperature (60-70 degrees), the burner operates from 40 seconds to 1.5 minutes, then there is a set burner turn-on delay of 30 or 150 seconds, depending on the T-off switch on the board. All this time the pump is running, since the board has a wired overrun time when working for heating - 3 minutes (it’s a pity that you can’t change it). During this time, t of water decreases by 10 degrees from the set value and the cycle repeats. By setting the t of water below (40 degrees), I reduced the burner's operating time to 30-50 seconds.
I experimented with adjusting the maximum power of the heating circuit - I did not notice significant deviations in the burner operation time. Water temperature has a greater effect.

Yes, it's already set up. The jumper on terminals 1 and 2 is, as it were, a "perpetual request for inclusion" from the thermostat. By replacing it with a smart box with a relay, you can limit the burner operation periods by the schedule during the day and week (electronic programmable thermostats) and the air temperature in the room (electronic and mechanical thermostats). The temperature of the coolant is recommended to choose higher (70-75 degrees).

When working without a thermostat, I had to monitor the temperature outside
Now +10 +15 overboard and even setting t=40 you can get heat in the rooms, plus clocking and excessive gas consumption.
With a thermostat, 75 degrees is recommended. Then, during the heating period, which allows raising the air temperature in the room by the “delta of the thermostat”, the water temperature does not have time to reach 75 degrees and the boiler has been operating continuously all this time. So far, at a positive temperature outside, I have this time of 15-20 minutes, when the water heats up to 60-65 degrees with a subsequent downtime of 1.5-2 hours.
Even if it heats the water to 75 before the air warms up, the boiler will turn off and turn on again after the required 150 seconds. just me. Here already the periods of heating will be short, but not numerous. Since the pump is running all this time, the radiators are hot and the air temperature will quickly reach the value set in the thermostat. After that, again idle at 1.5-2 hours.
Immediately set the maximum possible temperature (85 degrees), I think it is not necessary - there is still winter ahead.
And such a remark. After turning off by the thermostat, during the run-out time of the pump, the air in the room still heats up (I have +0.1 to the set one)
With more hot water there will be some "overcomfort" and overspending
So the temperature of the coolant in the presence of a room thermostat mainly determines the rate of heating to a given air temperature.

If about the air temperature delta in the characteristics of thermostats, then 0.5 is quite enough. In more expensive brands, it is also adjustable from 0.1 degrees. So far, I have not noticed the need for such precise temperature maintenance.
Much more interesting moment selection of comfortable and economical temperatures (in terms of some brands of thermostats with two levels of set temperature, these can be "day" and "night").
Usually the factory settings provide for a difference of 2-3 degrees.
But then in the morning before waking up, it will take much more time to raise the temperature to a comfortable temperature than for a heating cycle while maintaining a temperature with a delta of 0.5. Hence the increase in costs. The situation is the same if heating is set before returning from work, and during the day, in the absence of people, the apartment is heated in an economical mode.
Here, of course, you need experience and statistics in monitoring consumption.

If the thermostat holds the permission to operate the boiler (the temperature is below the set temperature), then the burner in the boiler burns constantly until the thermostat removes the permission (when the setpoint is reached) or what? Couldn't he just overheat at this time?

Will not overheat. The thermostat just allows, but does not oblige the boiler to work. When the set coolant temperature is reached, the burner will turn off regardless of the mode on the thermostat.