How to turn off the draft sensor of a gas boiler

Troubleshooting of Lemax boilers

They are assembled from parts made by recognized leaders in the production of heating equipment. Vaillant, Sit and other well-known manufacturers.

With excellent quality, the cost of Lemax boilers is two or more times lower than that of the “Europeans.

Basically, this is achieved by removing all additional devices and assemblies from the construction, leaving only the most necessary elements.

This has a positive effect on the performance of units, reduces the frequency of breakdowns or failures, but some malfunctions still occur.

How to disable the draught sensor in a gas boiler

Changing the draught sensor floor and wall gas boiler produce in stages. Stop the heating system, remove the housing, remove the relay. The thermostat is analyzed and if defective, a new thermostat is installed.

Defective draught sensor can cause an air lock and reverse draught

Disabling the thermostat entails great danger to human life. In the event of an emergency situation, the inclusion of the protective function of the boiler is impossible. Therefore, experts recommend in case of breakage of the thermostat to immediately replace it.

Types of draught sensors

Relay device is distinguished by the principle of functioning of the combustion chamber. There are 2 types of construction: open and closed. In a gas boiler with an open type of combustion chamber the draught sensor works. It is installed in the smoke filter. The gas supply is stopped if the bimetal has exceeded its expansion rate, breaking the contact in the circuit. The valve reacts to the signal and blocks the movement to the igniter.

Boilers with an open combustion chamber present a risk of reverse draught. It occurs if:

In this case, carbon monoxide smoke is drawn from the chimney into the room. The draught sensor is not designed for such cases, so experts advise installing a gas sensor in addition. This will prevent accidents from occurring.

In gas boilers with a closed combustion chamber type the pneumorelay is installed. Its work consists in controlling the fan, which creates a forced draught and contributes to the drawing of combustion products into the chimney and bringing them outdoors.

There are wired and wireless sensors. The first alarms require additional installation to the wired connections. Wireless relays work on a radio signal. Such sensors are installed in cases where the device is controlled from another room.

The wireless annunciator consists of 2 units. The first one is installed near the boiler and connected to its terminals, and the second one is installed in the room where the equipment is controlled. These units are connected by a radio signal. The controller is equipped with a keyboard and a display for convenient operation.

Thermostats are divided into simple and programmable according to the functions. The first relay performs only one task: to monitor the set temperature. Programmable annunciators can perform the functions required to analyze the boiler remotely:

  • setting the temperature mode for day and night;
  • programming the device by days of the week;
  • tracking humidity in the room (in this case, the device is additionally equipped with a hydrostat);
  • Maintaining the humidity set point.

The type of draught sensor depends on the operating principle of the gas boiler

Incorrectly positioned chimneys contribute to wind blowing and blowing out of the burner. To avoid such cases, experts recommend installing an additional stabilizer.

The main causes in the emergency operation of the boiler:

  • Draught or resolution does not correspond to the admissible parameters, set by the boiler operation card. This is the main reason for the triggering of the traction sensor. This problem can occur due to incorrectly installed blowing air systems and gas ducts. The problem may also be associated with a violation of the integrity of the chimney ducts, in case the individual parts of the pipes are poorly connected to each other. After the work on sealing. the draught or vacuum is restored.
  • Reverse draught. a dangerous kind of low-quality rarefaction. This situation also occurs when there is an air lock in the chimney system, preventing removal of exhaust gases into the atmosphere. This problem is quite often caused by poor insulation of the chimney system.
  • Chimney blockage. Such a malfunction occurs when its outlet has no barriers and protection against external clogging. In this case various atmospheric and natural debris, such as leaves, can fall into it. Protection against this defect. mandatory annual cleaning of chimney ducts, before the heating period.
  • High wind pressure. If the draught controller will not work in this case, the gas will flow into the boiler without control, but the combustion will not occur, and thus an explosive gas mixture may form in the room. In order to prevent this development of the accident, you must buy a stabilizer and install it in the system at the point of pipe outlet to the atmosphere.
  • If any of the above mentioned draught sensors in the gas boiler did not work. it is necessary to replace it.

Indicators of the need to change the DT:

  • The controller is non-stop shutting down in the absence of breakdowns in the gas draught system of the boiler.
  • The gas boiler unit does not operate for more than 30 minutes, after which it shuts down and can only restart after the heating surfaces and furnace chamber are completely cooled.

In the case when one of these signs is detected, it is better to invite a service technician, especially if the boiler is under warranty service.

Thus, we can summarize that the principle of operation of the draught sensor of gas-fired boiler, working on gaseous fuel, is to give a signal when the parameters in the flue system are too high, set by the manufacturer of equipment. A signal will come on the gas shutoff valve of electromagnetic type, which will instantly cut off the gas supply and the boiler will stop. In cases where the unit is under warranty service, or the user can not own to conduct repairs on the draught sensor, it is better to apply to the service center.

Traction sensor for gas boilers

The draught sensor of the gas boiler is designed to ensure safety. This device is an automatic device that protects against excessive accumulation of harmful gas in the room and is responsible for trouble-free operation.

Types of gas boiler draught detector

There are two varieties of gas boilers. The first is boilers with natural draught, and the second is equipment with forced draught. Each type needs its own type of device.

An open combustion chamber in combination with a correctly selected flue ensures a normal natural draught. The sensors for these boilers contain a bimetallic plate connected to an electric contact. The principle of operation is quite simple.

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If the draft is good, the temperature inside the boiler is normal and the plate closes the contact, but if it decreases, the temperature in the boiler begins to rise, leading to an expansion of the metal plate and at some point it deforms, opening the contact and closing the gas valve. When the problem is corrected, the plate returns to its original position and gas continues to flow into the burner.

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Closed combustion chamber by means of blowing devices defines the equipment with forced draught, which contains a sensor, the so-called pneumatic relay. The device controls the operation of the fan and the flue gas exhaust velocity. Structurally, the device consists of a diaphragm that flexes during normal draught under the pressure of flue gases. As soon as the pressure of gases becomes lower than normal, the membrane reduces the deflection and the contacts open with the closure of gas valve. Sensors guarantee the normal operation of the heater. Device is a fundamental element of the boilers protection, because at low draft the process of flue gas backflow and combustion products leave the boiler not towards the street, but into the room is possible.

How it works

The main task of device is an instantaneous signal to gas valve, cutting off fuel supply to burner. If there is an interruption in the normal flow of flue gases from the boiler to the outside, the sensor is triggered. In the absence of such a device, or if it does not work, carbon dioxide and carbon monoxide will penetrate into the living space, which may cause serious harm to human health.

The principle of operation of the gas boiler draught sensor is to change the position of the metal plate depending on the temperature. The device is adjusted to the required temperature according to the fuel used. When using natural gas temperature range will be from 75 to 950 ° C, with liquefied. from 75 to 1500 ° C.

In case of draught deterioration, the flue gases heat up, which is registered by the device and the gas supply is cut off. In boilers with an open combustion chamber, the device detects the speed and temperature of the flow, while in boilers with forced combustion chamber, it monitors the air pressure from the turbine.

Functional check

If there are problems in the boiler operation, it may be necessary to replace the sensor. For example, if the burner switches off regularly, but there are no problems in the combustion gas exhaust system. It is also necessary to check the operation of the device when it switches off periodically in 20-30 minutes.

To check the efficiency of the boiler sensor you need to consider 3 ways:

  • Attach an ordinary mirror near the device. If the sensor works properly, then the surface of the mirror should not be covered with condensate.
  • A simple way to check by partially closing the chimney. Operating sensor will promptly give a signal and the equipment will turn off.
  • If a two-circuit boiler is used as a heating equipment, then to check the device can be switched to DHW mode, without heat supply. Then open the faucet to a powerful jet of water. Here the situation is reversed. disconnection of the sensor will be a sign of its problematic work.

There are many manufacturers of sensors draught. Among them are such market leaders as Junkers, KAPE, Sitgroup, Eurosit. Some manufacturers of boilers (Baxi, Danko) produce devices for their heating equipment. It is necessary to select the right sensors for the equipment used (gas heaters, wall or floor standing boilers). It is important to periodically check the efficiency of the boiler draught sensor.

Traction sensor installation

Installation of the device is performed individually, depending on the equipment used, the choice of a convenient location. First, it is important to buy the right appliance for this type of boilers. Detailed information about proper installation can be found in the technical documentation of heating equipment.

Installation of the device should be entrusted to a specialist, as incorrectly installed sensor will malfunction and, as a consequence, pose a threat to human health from gas poisoning. A specialist also helps to adjust the appliance correctly.

What to do if there is no draft

There are several reasons for the triggering of the safety devices of gas boiler equipment: improperly installed flue gas extraction system or sensor failures. So, why there is no draft in the chimney? To avoid the failure or malfunction of the device and ensure that there is a normal draw from the boiler to the outside it is necessary to perform a proper installation of the smoke exhaust system, guided by important criteria:

  • Calculate the height of the chimney should be based on the distance from the ridge of the roof to the chimney;
  • To place the chimney preferably in the center of the roof to the top of the pipe elevated above the ridge of more than 0,5 meters;
  • Install the boiler draught regulator in the vicinity of the outlet to prevent the flame from blowing out in strong winds.

If the draft is insufficient, this will cause an increase in the gas temperature in the boiler and shut off the gas valve. During regular servicing of the boiler, it is mandatory to check the system of gas removal: the condition of the pipes, tightness, cleaning, operation of the turbine of the boiler.

How to check the draft in the chimney of gas boiler? You can use an anemometer. a device that measures the velocity of the gases, by applying a sheet of thin paper or by using the smoke from a cigarette. It is also necessary to visually inspect the chimney for mechanical blockages. If there is a need to increase the temperature threshold for triggering the draught sensor, the expert can adjust the necessary gap in the device. The device must be periodically cleaned of soot produced during the combustion of fuel or the incorrect mode of gas and air supply to the burner.

How it looks and where it is located

According to the safety rules of gas industry PB 12-368-00, household heating boilers must be equipped with a draught sensor. Installation place is usually the smokebox (located in the smoke extender) or the free space between the ventilation duct and the boiler drum.

In atmospheric boilers, the draught sensor looks somewhat different.

It is worth noting that it can not be attached to the surface of the flue. Paronite gaskets are used as a “separator”: such a measure reduces the probability of contact heating, as well as to allocate a gap that will provide technical access to the flue opening and to the draught sensor.

How to increase the draught in the water heater?

One of the main reasons for the lack of draft is a clog in the chimney. Often such a problem is found in older apartment buildings.

In the so-called khrushchevkas are laid 2 shafts. for the column and ventilation. The first thing to do is to call in professionals to do the cleaning.

In a private home, improving the draft should begin with an inspection of the chimney and an assessment of the fouling of the clogged pipe. After removing the clog, a mirror is placed inside the duct. At the top of the chimney should be light. It is recommended that this procedure be done at least once every three years.

Bad draft can also be caused by improper installation of the chimney hood or a large number of unnecessary turns, sharp angles and bends in the pipe. If correcting mistakes made during installation did not help, you can strengthen the draft in the chimney with the help of chimney pumps and fans.

How to turn it off

The manual does not tell you how to turn off the draft sensor in the gas boiler. It does not recommend deactivating this safety system on your own. This may have negative consequences for both the appliance and human health, as the activation of the sensor is a clear sign of danger.

Disabling the draft sensor is a direct violation of the safety rules established by the heating equipment manufacturer!

Carbon monoxide poisoning has the following signs:

  • mild. headache, dizziness, chest pain, pounding temples cough, lacrimation, nausea, vomiting, possible hallucinations, redness of the skin and mucous surfaces, palpitations, hypertension;
  • Medium. tinnitus, drowsiness, paralysis;
  • Severe. loss of consciousness, seizures, involuntary defecation or urine diversion, respiratory failure, blue skin, fatal.

The consequences of carbon monoxide poisoning can adversely affect further human life.

In this case, the design of the boiler allows the possibility of turning off this system. To do this, disconnect the thermocouple breaker and traction sensor wiring from the electromagnetic valve, as well as from the electronic control unit of the boiler.

turn, draft, sensor, boiler

Thus, the control unit will continue autonomous control of the boiler, without regard to the temperature readings of the burned gas and the force of its emission into the atmosphere.


Autonomous operation of the gas boiler is achieved by an electronic control system. It provides control through sensors, collecting technical data from various parts of the construction. In the event of a deviation from the norm, the control system changes the boiler operating mode or stops it.

Gas boiler draught sensor is a control device that determines the presence and degree of draught in the chimney, as well as transmits the appropriate signals to the electronic control system of the boiler.

It is the main device that protects the health and lives of people from the accumulation of carbon dioxide in the room.

Purpose and construction

Gas solenoid valve is designed to control the flow of gas in the pipes

The gas valve of this type can be a regulating or shut-off valve and it can be controlled manually or by an automatic system. The design and purpose of this element resembles its standard analogue, the difference being that the shut-off part is actuated by an electromagnet combined with a moving core. When voltage is applied to the coil, it starts pushing or retracting the core which is connected to the plunger. This part is designed for use in industrial installations, domestic heating systems and water supply. The valve design has a standard design:

turn, draft, sensor, boiler
  • body with two nozzles;
  • the chamber with the seat;
  • shut-off part of a poppet, lobe or ball type;
  • spring with return;
  • stem to connect the shut-off part and the core;
  • solenoid.
turn, draft, sensor, boiler

Housing for the installation is made of metal alloys of nonmagnetic type or durable plastic. Its optimum tightness allows the valve to be used in various environments. The process of controlling the part is carried out by wires that are connected to the electric contacts of the sensor, located on the outside of the housing.

The valve must be able to withstand noise, vibrations and electromagnetic fields.

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