Thermal automation saves us money. Single-stage, two-stage and modulating burners for heating boilers. Overview Two-stage burner control

After familiarizing yourself with various types gas burners, you can confidently make a decision about choosing exactly the burner that is suitable for your purposes.

Manufacturers of modern boilers, constantly improving their products, endow them with new functions and at the same time complicate the choice the required boiler and its setup. This is no wonder, because the heating system of a modern country house consists not only of a boiler, pipes, radiators under the windows, but it also includes many heating circuits, the management of which should be entrusted to automatic controllers.

Otherwise, homeowners will have to constantly adjust individual elements manually to ensure a sufficient level of comfort. However, more a complex system management is always more high price. “Do I need this?” — the buyer asks a rhetorical question.

In this short article we will try to convey to readers the physics of processes in working system heating, which is inherent in all heating systems, including complex ones. Having an idea of ​​what you have or are planning to buy is very important when choosing a heating system, its operation or modification. To the structure modern systems heating system already has functions that require its modification and improvement.

So, boiler automation is assigned two important functions: a security system and thermal comfort. Of course, ensuring safety has the highest priority among other tasks. For example, the upper limit for boiler water regulation is set in such a way that due to temperature overrun it never exceeds the limit level. The magnitude of the possible temperature rise depends on the design and material of the boiler and is taken into account by the automation manufacturer when installing upper limit regulation of temperature in the boiler.

In our article we focus on the operation of automation to ensure a comfortable temperature in heated rooms.

The feeling of thermal comfort is largely subjective. In this regard, experts in the field of climate systems use the concept of the Fagner comfort index. It provides seven positions corresponding to subjective sensations

• -3 “cold”
• -3 “cool”
• -1 “slight coolness”
• 0 "neutral"
• 1 "light heat"
• 2 "warmth"
• 3 "hot"

A particular temperature in the room is established when a balance is reached between heat losses and heat transfer from devices. At the same time, in order to maintain the set temperature value, any change in heat loss caused by weather changes must be compensated by appropriate correction of the coolant temperature or its volumetric flow through the heating devices.

Let us first consider the second case, namely the regulation of room temperature by changing the volume flow through heating devices.

This problem is easily solved using thermostatic valves installed on radiators or convectors. In this case, the task of the boiler automation is to maintain the temperature of the coolant at a given level (simply turn the potentiometer knob on the boiler remote control, setting the desired temperature). In most boilers this is what happens and does not imply anything more. The boiler operation algorithm differs depending on the burner: modulating, one or two-stage.

When working with single stage burner The temperature controller works as a threshold switch that turns the burner on and off when it reaches temperature supply threshold values. There is a certain difference between the on and off thresholds - “on hysteresis”. As a rule, the on and off thresholds are located symmetrically with respect to the set supply temperature, so that the average temperature value over a long period coincides with the set one.

Problem occurs when the volume of coolant is small and the heat consumption is significantly less than the burner power, the burner temperature will rise too quickly. Occurs danger of turning on the burner too frequently, which may affect its resource. The problem is being overcome different ways. For example, using a time-varying hysteresis value.

At low thermal loads and, accordingly, short periods heating of the boiler, the increased hysteresis value applies. If the switch-off threshold has not been reached within the specified hysteresis time, the hysteresis value is automatically linearly reduced to the standard 5 g. Celsius. Buderus uses a different algorithm called “dynamic switching” - when the supply temperature, increasing or decreasing, is compared with the set temperature and the system begins to calculate the integral of the function of changing the mismatch over time.

The burner is switched on and off when the integral reaches the set value, such that when the boiler heats up quickly, the switching temperature is higher than when the boiler heats up slowly. Thus, the switching threshold is automatically adjusted to the characteristics of the heating system and the amount of heat consumption

For two-stage burner the process is not fundamentally different from what was discussed above - only there are twice as many switching thresholds.

Modulating burner makes it possible to constantly proportionally control the supply temperature, when the burner power value linearly depends on the temperature mismatch value. However, such regulation is not always possible, since for many modulating burners the power smoothly changes not from zero, but from 30-40% of the maximum value. If the heat consumption in the heating circuit is below this limit, then we are again faced with threshold regulation. Until now, we have considered processes when the set boiler temperature was set manually using a potentiometer on the boiler remote control, and the task of the boiler automation was to maintain this temperature.

Maintaining a comfortable room temperature by regulating the boiler water temperature. This happens by introducing a room thermostat into the automation system.

notice, that room thermostat usually not included standard equipment boiler Control of the boiler operation in order to maintain the set temperature in the room can be carried out by one of two types of regulation: two-position (on/off) or continuous. In the first case, the control algorithm is the same as for a boiler with a single-stage burner. However, compared to the boiler water temperature, the room temperature changes much more slowly and this can lead to large overruns beyond the threshold values. Therefore, on-off control is usually not recommended for heating systems with boilers larger than 25-30 kW.

With continuous regulation The control action is the supply temperature, which changes depending on the temperature deviation in the room. The temperature sensor must be located in a specific room (let's call it a reference room) and the temperature in other rooms is set relative to the temperature of this reference room. Comfortable temperature in different rooms different from each other. In the bedroom, for example, it is lower. During the day the premises are usually empty and maintained comfortable temperature- pointless, a waste of money.

The function of setting and executing a daily temperature schedule in the premises naturally suggests itself. Daily temperature programming is often possible for different days weeks (weekdays, holidays, parties, vacations). Big problem with this control method, the temperature in the rooms is regulated relative to the reference one, by linking it into a single circuit.

In addition, by increasing comfort in the reference room, we risk reducing it in other rooms connected to the same control loop. In addition, thermostats cannot be used in the reference room. heating devices, since they represent independent systems control with the same input parameters as boiler automation.

To control a boiler that heats water for several heating circuits at once with different characteristics, a certain input parameter common to these circuits is required. Simple and effective solution was found.

Using air temperature outside the building as an input parameter

Indeed, the supply temperature of any heating circuit, necessary to compensate for heat loss in premises, is related to the outside air temperature by well-known relationships, which in graphical representation are usually called heating schedules or heating curves. All that remains is to include these relationships for each specific circuit in the operating algorithm of the boiler room control system. In the automation of most manufacturers, for this you need to select one of the proposed curves. There are other approaches to this problem, for example, it is enough for a Buderus boiler adjuster to set two points from which the automation itself will construct the entire curve. Note that it is extremely important to place the temperature sensor on north side home away from heat sources such as windows and chimneys. In this case, the weather-compensated automation works as correctly as possible.

What happens if you open the window? System that controls the boiler and heating circuits according to external temperature, can respond to unexpected changes heat balance in heated rooms. In most cases, this possibility is provided in the form of automatic adjustment (most often parallel transfer) of the heating curve of the corresponding circuit based on readings room sensor temperature.

Moreover, many manufacturers offer, in addition to weather-compensated automation, a room thermostat. When external and room sensors are used together, the thermal regime can be adjusted taking into account additional heat sources in the room. Simply put, if the stove is on in the kitchen, and due to this it has become warmer there, the controller will “take into account” this fact and adjust the indicators external sensors or is the room located on sunny side and requires heating only when the sun “goes away”.

As automation becomes more expensive, its capabilities are enhanced by the ability to control more complex burners (with step, step-progressive and modulation control), cooking unit hot water, one or more (the number of radiator circuits is growing), low-temperature (warm floor) circuits, implement various other programs (connection solar water heaters) etc.

Let's summarize: why all these difficulties with weather-dependent control? How is it better than the simple “permanent boiler” scheme plus thermostats on all batteries?

Proponents of weather-sensitive management they say that in the main part heating season the heat demand is much less than the calculated one, so constantly heat the coolant until maximum temperature- a waste of money. It works especially effectively during periods of frost and thaw, thereby achieving the most comfortable room temperature and significant savings in resources, since the inertia of the system is reduced and the boiler does not have to make extra work, burning fuel. In addition, in the case of working with a constant temperature of the coolant, and it is almost always high, heat loss increases, which is greater, the more higher temperature coolant. In general, boiler efficiency decreases with increasing average temperature boiler water.

Most Western manufacturers ( « Buderus» , "Viessmann") bet onproduction of low-temperature boilers.

Opponents of weather-independent control argue that the price of such automation is too high. And the price of fuel so far fully compensates for the costs.

Let's turn to the specialists. on the forum, the site clearly says that weather-proof automation saves money, and this is not counting the comfort that it brings to the house and ensures longer trouble-free operation.

The Time company offers a programmable controller as weather-compensating automation calorMATIC 430 West. In fact it works like remote from the boiler. The homeowner does not have to run to the boiler room to turn it warmer or cooler if he installs the display panel in a convenient location.