The principle of operation of a gas heating boiler is simple: with the help of fire, a metal heat exchanger is heated, transferring energy to water. At the same time, the unit and all connected elements represent the most complex engineering system. Therefore, in addition to the main components, it provides for many additional ones, such as sensors, fuses and other things. The fact is that the main side of the activity of such equipment is safety. That is what is provided with the help of additional elements.

Draft in a gas boiler — what is it?

During the operation of a conventional or condensing gas boiler, carbon monoxide is released. It can threaten human health in case of its excessive accumulation. That is why it is necessary to remove it from the premises. A special passage is connected to the boiler, whether it is standard or condensing. It must have the required intensity of traction. The process itself is a rarefaction of air, due to which the removal of gas occurs.

Thrust sensor

In most cases, a gas-fired boiler is automatic. It is in connection with this that he must have a special device that will monitor a sufficient level of traction. It just also is the corresponding sensor. The main function is to send a signal in the event of a change in carbon monoxide removal rates. It is he who is responsible for the fact that the gas boiler stops working.

Important! Insufficient draft intensity can lead to the accumulation of flue gases inside the room. In addition, because of this, the flame burns unstable. In the case of poor «sucking out» of combustion products, the likelihood of «reverse thrust» increases.

Main article: what to do if the gas boiler does not work?

The principle of operation of the thrust sensor

Each individual installation has its own sensor, which has an individual principle of operation. Condensing gas boilers, endowed with natural draft, have an open firebox and a chimney of the required diameter — this is what allows you to create the necessary intensity of gas emission. For this kind of installations, a special sensor is used — a thermocouple. It is a bimetallic plate, which is endowed with a moving contact.

The principle of operation of a standard gas boiler draft sensor is based on the physical phenomenon of body expansion when heated. The traction is good — the temperature is within the normal range. When gases are not emitted as they should be, due to the large amount of heat, the plate expands in volume. When the temperature reaches the extreme point, the contact is interrupted and the operation of the igniter stops. As a result, the equipment turns off. That’s the whole principle of operation of an ordinary gas boiler thermocouple.

Important! Propane-butane has an increased calorific value compared to natural gas. Therefore, the temperature of the release of gases is higher. Despite the fact that the principle of operation of a thermocouple is always the same, the device is configured differently for different types of mixtures.

Each individual gas boiler has the same operating principle. In this case, the temperature settings at which the shutdown mechanism is triggered are set at the factory. On natural raw materials, the takeoff can start from 75 degrees and end at 950. But in a gas boiler running on propane-butane, the maximum mark is 1500 degrees.

Equipment that has forced draft is equipped with a closed combustion chamber and a fan. It is the latter that is responsible for the removal of gases. Therefore, in this case, the operation of the draft sensor is to monitor the fan. It is a pneumatic relay. Gases under pressure act on the membrane due to which the contacts are closed. As soon as the pressure drops, the gas valve closes and the boiler stops burning.

Boilers of increased power

Separately, it is worth talking about what a condensing boiler is. In fact, this is the same device, only it has an additional heat intake system. The principle of operation of the condensing equipment is simple. During the combustion of gas, the products are not immediately thrown out, but fill a special chamber. It cools down to 55 degrees and water appears. That is why such a boiler is called a condensing boiler.

The energy that results from this process is sent to the heating system. But at the same time, she does this through the operation of a three-way valve. This mechanism is simple. It is not used often. The element resembles a tee, but it performs completely different functions. The principle of operation of the three-way valve is simple: it mixes water from the system and the chamber. As a result, much less energy is spent to create the desired temperature in the room.

Due to all this, the assembled device makes it possible to save up to 35% of the energy carrier. And this is a significant indicator today.

It should be noted that the condensing boiler is equipped with its own sensor, which is configured in a special way. The fact is that the temperature at the outlet is lower, which means that the thermocouple will react differently.

Types of thermocouple

By itself, the device can not be called complex. A thermocouple is a piece of equipment that you can even make yourself. The main thing is to choose the right components. This device has several main varieties:

  1. Type E. The device, like the others, is made of two metal plates: constantan and chromel. This combination allows you to measure temperatures in the range from -50 to 740 degrees Celsius.
  2. Type J. This thermocouple has an iron plate instead of chromel. The combination allows measurements from -40. But at the same time, the device became more sensitive to changes.
  3. Type K. This thermocouple is considered the most common, as the components are made of aluminum and chromel. This makes it possible to significantly expand the temperature range: from -200 to 1350. At the same time, the device has maximum sensitivity. It should be noted that the duration of operation directly depends on the conditions of use. So, for example, chromel, in constant contact with carbon dioxide, becomes covered with green rust, which quickly disables it.


The installation of such sensors is carried out exclusively on an individual basis. First you need to buy the right component. For this, the description of the boiler and its technical documentation will help. After acquiring a suitable one, the location is calculated. Before the installation itself, you can even familiarize yourself with the video, so that everything fits exactly. In any case, it is advisable to entrust this procedure to a specialist. In addition to the installation itself, it is also necessary to configure it. Only then can the system be started.

A draft sensor on a gas boiler is a mandatory element. Without it, the system can quickly fail or even harm people’s health. It plays an important role, like a flame sensor or a thermostat. This equipment is of several types. The choice depends directly on the conditions of use.


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