All heating boilers must be equipped with devices to control the operation of the device, to protect it from overheating. A similar element is a thermocouple for a gas boiler. It has a fairly simple design, its action is based on separate laws of physics.
The device and principle of operation of the thermocouple
Due to this mechanism, the safety of the functioning of the heating equipment is ensured.
Device:
- Consists of 2 different types of conductors, which must be in contact in one or two places.
- When heated, a voltage is created between different types of conductors, which is subsequently used in the operation of the heating unit.
- Due to the properties of the conductors, there is no need to use external excitation of the heating device, the elements are powered autonomously.
A thermocouple is a sensor for monitoring the temperature in the heating unit. Its device is quite simple, but when buying, you should definitely check the quality of the connection of the points. Otherwise, an unacceptable error exceeding 1 ° C may occur.
Operating principle:
- The junction points of dissimilar metals are heated to a certain temperature value.
- A measuring device is connected to the cold ends of the conductors on which voltage is generated, the electrical circuit is closed.
- Induction occurs in the valve coil, under the influence of which it opens and remains in this position.
If the gas heating unit is out of order, it is recommended first to check the thermocouple is working properly. It most often becomes the cause of the failure of the entire system.
Control sensors are made from base metals. For the purpose of reliable protection from external influences, they are placed in the pipe, the existing movable flange fixes the structure. The latter consists of the following elements:
- sealed body with a lid;
- porcelain speakers (fastened to the head with screws).
The material for production is determined by the range of temperatures that will be measured by the device.
Basic types
The following types of appliances installed in gas heating boilers are considered the most popular.
Type K
It is the most common. Marking - TXA. The composition contains plates of chromel, aluminum. Operating temperature range - from -200 to + 1350 ° С. The devices are very sensitive to any changes in temperature, but they are highly dependent on the external environment.
Type E
Made from chromel and constant. Has high reliability. Manufacturer's marking - ТХКн. Operating temperature range - 0 - 600 ° С.
Type N
It is a modification of type E, capable of operating at temperatures up to +1200 ° C. Nichrosil and nisil are used for the production of plates. Such models are considered the most accurate devices used in heating equipment.
Advantages and disadvantages
The thermocouple has many advantages:
- Low price due to the lack of expensive parts and materials.
- Long term of use.
- Easy installation and replacement.
- Huge range of measured temperature values.
- Accuracy.
Some cons:
- Disproportionate rise in temperature and potential difference (no linear relationship).
- The limit voltage limit is 50 mV.
If the thermoelectric sensor fails due to a poor-quality junction, it will not be possible to repair it.
Sometimes the thermocouple stops functioning due to poor contact at the junction. To fix this problem, you need to unscrew the nut, remove the conductor, clean its end, and put everything back together.
Thermocouple in the gas control system
Any thermocouples for a gas boiler have the same operating principles:
- The user mechanically opens the valve for gas supply by pressing a button for 15-30 seconds.
- After turning on the piezo ignition, a spark appears, the burner ignites.
- The solenoid valve button is held for another 30-60 s until the thermocouple junction produces the required voltage.
- When the button is canceled, the combustion does not stop, since the heated thermocouple creates the necessary voltage to keep the valve open. The heating unit operates normally.
- When there is no combustion, the flame does not heat up the sensor, resulting in insufficient voltage to keep the valve open. Therefore, it closes, the gas supply stops.
Most models of control sensors are suitable for a wide variety of gas heating units. This is due to the simplicity of their design, versatility.
Installing a thermocouple on a gas boiler
Connection is made only with wires made of thermocouple material or metal with similar parameters. On the eve of connecting the thermocouple, you need to strip the ends of the wires to improve the accuracy of measurements. During installation, ensure that all gas pipes point downward.
When a breakdown occurs, the device cannot be adjusted. Therefore, you need to understand how to check the thermocouple with a multimeter.
To study the performance of the device, it is necessary to connect one end to a multimeter, and heat the other with a lighter. The working thermocouple has an approximate voltage of 50 mV.
DIY repair
Troubleshooting requires:
- Using a wrench, unscrew the clamping nut, remove the elements.
- Clean the ends from dirt.
- Check the thermocouple with a multimeter.
- Compare the required values of the indicators.
- Assemble the thermocouple, turn on the boiler.
Temperature control sensors are actively used in modern automation of gas boilers. If the consumer needs an explanation for the selection of the right device, it is recommended to consult a specialist. He will tell you which model to choose so that it matches the parameters of the gas unit.
The thermocouple is the only precision sensor designed to measure high temperatures. It is widely used in boiler equipment to control and protect against overheating.
