What is a gas boiler draught sensor and where it is used

Having a solid understanding of the technology underlying our heating systems is essential to maintaining a warm and comfortable home. The gas boiler draught sensor is one important part that is sometimes disregarded. What precisely is it, then, and why is it significant?

A tiny but essential component installed in a gas boiler system is the draught sensor. Its main job is to keep an eye on the airflow or draught inside the boiler’s combustion chamber. Although it may sound complicated, this basically makes sure that the boiler receives the proper amount of air for safe and effective combustion.

Consider your gas boiler as a ravenous animal that requires precisely the correct amount of oxygen to efficiently burn fuel. As its guardian, the draught sensor continuously checks and modifies the airflow to preserve ideal circumstances. Without it, the boiler could overheat and waste energy, or suffocate from a shortage of air.

So where is this little smart sensor used specifically? It is, however, firmly installed in contemporary gas boilers, both residential and commercial. It’s likely that a draught sensor is silently keeping your boiler system operating smoothly, whether it’s a more sophisticated condensing boiler or a more conventional boiler system.

Gas heating boiler automation

Specific guidelines govern how gas equipment is to be operated. This document mandates that safety automatics be installed on any gas-fired unit. Among its responsibilities are:

• detection of characteristics that deviated from the normative;
• Processing of the received data and transfer of the signal to the executive mechanism, which turns off the fuel supply;
• switching on the alarm (light or sound), which will notify about the shutdown of the gas boiler.

Apart from the draught sensor, the safety system for gas boilers consists of:

1. Temperature sensor for the coolant. It controls the temperature of the water inside the heating system. If the latter rises, the gas supply is cut off.
2. Heat carrier pressure sensor. Its task is to control the operation of the circulation pump.
3. The flame sensor of the furnace. It is responsible for the presence of a flare. That is, if the last one goes out, the boiler is switched off completely, because it is impossible to allow gas leakage into the room.
4. Sensor of the temperature of the air surrounding the boiler.

Boiler unit’s temperature and draught sensor

Gas boiler draught sensor: principle of operation

One crucial aspect of the gas boiler’s operation is traction. As a result, the furnace chamber’s air exchange is arranged correctly, influencing the fuel’s combustion coefficient. and consequently, the apparatus’s own efficiency.

Here, the extraction of carbon monoxide gases is formed by the draught. For instance, carbon monoxide gases start to seep into the boiler room when the chimney’s interior temperature is low. And this has an impact on people’s health.

The place where the controlling device is usually installed:

• in the space between the boiler drum and the chimney;
• inside the smoke hood.

Prior to providing a response to the question of how a gas boiler’s draught sensor operates, it is important to note that its primary function is to track the rate at which carbon monoxide is escaping the chimney.

A high value for this characteristic indicates a high likelihood of the fire inside the furnace chamber going out. It’ll appear to be removed from the burner. Conversely, if the speed is low, part of the carbon monoxide will enter the boiler room because it won’t have time to escape the furnace.

For this reason, the draught indicator has a standard. It falls between 20 and 30 Pa. In this case, the unit of measurement for the change in rarefaction of the air masses inside the furnace chamber of a gas boiler is the Pascal, which is the unit of pressure measurement.

Every manufacturer independently modifies the attribute under factory settings. As such, it is not required to tamper with the sensor’s operation. The boiler will simply shut off if the setting becomes confused or if the rate changes for any reason.

The two types of gas boilers that manufacturers offer are distinguished from one another by the kind of draught that is produced in the chimney. The first had a forced draught, while the second had a natural one.

The temperature sensor, which tracks the temperature range of carbon monoxide gases, is added in the first instance in addition to the draught sensor. In the second, a pressure switch, as the boiler’s fan or smoke evacuator is the forced method of removing waste combustion fuel.

Both a turbine boiler with a forced draughtand an atmospheric boiler with a natural draught

Although the devices installed in various boiler units have different structural characteristics, the gas boiler’s draught sensor functions the same in both versions.

Turbine boilers

This gas boiler’s sensor is a device with a sensitive diaphragm that is based on a pneumatic relay. It responds quickly to variations in the airflow velocity containing carbon monoxide gases.

• As soon as the gas boiler is turned on, the fan or smoke pump is also turned on;
• The pressure inside the flue increases due to the increase in air velocity;
• The diaphragm bends in the direction of the air mass movement and closes the sensor contacts (this position is called the working or "closed" position);
• if the pressure in the pipe decreases, the diaphragm opens the contacts, which leads to disconnection of the gas boiler unit from the power supply through the control unit.

This kind of boiler has a sealed combustion chamber. In order to keep the gas burning, outside air is supplied to the chimney. This is the most effective option because of its higher efficiency, but it requires electricity to power the smoke pump or fan.

Boilers with natural draught

Atmospheric boilers are another name for these gas boilers. Since they are not designed with air blowers, their high temperature is what removes carbon monoxide. In other words, the laws of physics govern how gases move. So, the chimney’s stringent requirements are as follows:

• maximum verticality;
• horizontal and sloping sections are possible, but the length of no more than 2 meters;
• No more than three diverters along its entire length;
• lead the chimney out of the roof of the house.

An open combustion chamber is a feature of atmospheric boilers. Thus, the draught sensor’s design features, which need to keep an eye on the flue gases’ temperature, were created. The apparatus is actually a thermostat, with a bimetallic thin plate serving as its primary component that responds to variations in the ambient temperature.

• when the temperature of carbon monoxide gases increases, there is a bending of the plate, which closes the contacts of the device;
• when the draught decreases, the gases overheat, which accumulate in the chimney or in the boiler hood;
• increased temperature makes the plate bend even more, causing the contacts to open;
• The signal is transmitted to the control unit, and from there to the solenoid valve, which cuts off the fuel supply.

Only once the furnace’s temperature drops to the required levels will it be feasible to turn on the gas boiler. The latter range from 70 to 100 °C. They also claim that the sensor is adjusted.

Design and working principle of the plate-type device

Causes of gas boiler draught sensor activation

The sensor shouldn’t go off if the gas boiler was installed correctly and in accordance with the manufacturer’s instructions. However, under certain circumstances, the boiler unit may shut down due to a draught sensor malfunction. The principal ones are:

1. A strong gust of wind has driven a large amount of air into the chimney by counterflow. The draught will go to zero, and the sensor will be triggered necessarily. The problem is solved simply – it is necessary to install a special device in the chimney pipe, which is called a stabilizer.
2. The pipe is clogged, e.g. birds have made a nest. The problem is solved with the help of a protective cap, which is mounted on the end of the chimney.
3. The controller is triggered by contamination of contacts. Therefore, the device needs to be cleaned periodically.
4. The settings of the safety system are out of order.
5. During installation of the gas boiler the requirements of its installation were violated. This is especially true for the assembly and laying of the chimney.

How to check the draught sensor

Gas boilers nowadays that come with extra features are pricey. However, they operate in a convenient manner. When the sensor operates incorrectly, the panel instantly displays the error. Usually, a yellow-colored indicator will illuminate, signifying that the unit has shut down due to a weak draft.

Not every customer purchases one of these boilers. The majority of people strive to save costs, so the heating equipment is not designed with a screen. However, it is possible to comprehend that the boiler unit’s frequent turning on and off triggers the sensor. It is essential to inspect the control unit if this occurs. Three techniques are available:

1. Before checking the draught sensor of the gas boiler, it is necessary to install an ordinary mirror near it. If the device is switched off, and the mirror surface does not mist up, it means that the shutdown occurred in the normal mode. If fogged, then the shutdown was due to the error of the sensor itself. It will have to be replaced with a new one.
2. Close the chimney cross-section by half. The draught decreases, the temperature inside the pipe increases, the velocity of carbon monoxide movement decreases, which should lead to the triggering of the device. If it doesn"t, then the sensor is not working correctly.
3. Two-circuit boiler is checked according to a different scheme. To do this, it is transferred to the "DHW" mode (hot water supply), disconnecting the heating system. Then open all the hot water taps in the house. If the boiler has switched off due to the fault of the sensor, it means that the latter is not working properly.

These three techniques to check the draught sensor’s performance are not always reliable. Interfere occasionally with supply network voltage surges, misconfigured control unit settings, debris-clogged chimneys, etc. Thus, it’s essential to identify the precise reason behind the device’s malfunction before swapping it out for a new one.

Is it possible to disable the draught sensor in a gas boiler?

You can’t in terms of operation. This apparatus serves as a safeguard. Tragedy can result from its absence. However, a lot of people want to unplug the draught sensor when their gas boiler suddenly stops working for no apparent reason. Avoid doing this; it is preferable to call a master and find out why the boiler unit is operating in this way.

In the event that gas equipment requires repair or preventive maintenance, the draught controller can be disconnected. Since the boiler unit in this instance is totally cut off from the gas and electrical supplies, the draught sensor will likewise stop working.

Video: draught sensors of mounted gas boilers

Watch the video below to find out more about the draught sensors that are used in mounted boilers.

A gas boiler draught sensor is a tiny but essential part of a heating system that contributes to efficiency and safety. It performs the vital job of identifying any air or gas flow within the combustion chamber of the boiler. The sensor prevents problems like incomplete combustion or the release of hazardous gases into the house by alerting the boiler to change its operation when it senses insufficient draught.

These sensors are commonly found in contemporary gas boilers, where they are essential for maximizing efficiency and cutting down on energy waste. They aid in preserving the ideal ratio of fuel to air, which promotes more effective combustion and less fuel consumption, by keeping an eye on the draught. By lowering carbon emissions, this helps homeowners save money while also promoting environmental sustainability.

Domestic heating systems are one of the main uses for gas boiler draught sensors. These sensors make sure that the combustion process is operating safely and smoothly in homes that have gas boilers. Homeowners can rest easy knowing that their heating system is running effectively and posing no risks to their safety or possessions.

Additionally, commercial and industrial settings that use large-scale heating systems use gas boiler draught sensors. These sensors are essential to preserving peak performance and regulatory compliance in these settings, where efficiency and safety are of the utmost importance. They assist in averting potentially dangerous scenarios, like carbon monoxide leaks, which can have detrimental effects in small areas.

To sum up, the gas boiler draught sensor is an essential part of heating systems that guarantee both safe and effective operation in commercial and residential settings. Through the monitoring of airflow within the combustion chamber of the boiler, these sensors contribute to improved safety, energy conservation, and performance optimization. These sensors are essential for preserving user comfort, dependability, and peace of mind in residences, workplaces, and industrial facilities.

Draught sensors for gas boilers are vital parts of contemporary heating systems, built to guarantee safe and effective operation. By controlling the airflow, these sensors help to maintain ideal combustion conditions by detecting the flow of air within the boiler’s flue. They keep an eye on the draught to keep dangerous gases like carbon monoxide from accumulating and to make sure the boiler runs as efficiently as possible. In residential, commercial, and industrial settings where gas boilers are utilized for heating, draught sensors are frequently utilized. They are essential to any heating system because of their role in preserving efficiency and safety, giving building managers and homeowners alike peace of mind.

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