Cooking on a gas hob or gas hob is as easy as cooking on a conventional electric hob. Even the use of a gas oven rarely causes any problems. But many people immediately have a question about the safety of such equipment, because "blue fuel" is explosive.
Hardly anyone wants to see their home destroyed as a result of an explosion of gaseous fuel. To prevent such a tragedy, a device such as a thermocouple in a gas stove is used. It is the main element of the health monitoring system of the most popular gas appliance.
Agree that in the case of natural gas, special attention should be paid to the topic of reducing the risks of fires and explosions. In the article presented by us, the rules for the operation of household equipment that process gas are given and described in detail. We have added useful information with valuable recommendations.
The content of the article:
- Why does a gas stove need a thermocouple?
- Device and principle of operation
- Varieties of temperature sensors for gas
-
Gas control repair manual
- How to check before replacement?
- How do I change the device?
- Conclusions and useful video on the topic
Why does a gas stove need a thermocouple?
The gas in the stove burner is ignited with matches, a manual piezo lighter or a built-in electric ignition. Then the flame should burn itself without human intervention, until the fuel is shut off by a valve.
However, it is not uncommon for a fire on a gas hob or oven to go out as a result of a gust of wind or a splash of water from a boiling pot. And then, if there is no one nearby in the kitchen, methane (or propane) begins to flow into the room. As a result, when a certain gas concentration is reached, there is a pop with fire and destruction.
The thermocouple monitors the presence of an open flame in the burner, and if it is absent for half a minute or a minute, it cuts off the gas supply to prevent a tragedy
The working function of the thermocouple is to control the presence of a flame. While the gas is burning, the temperature at the tip of the control device reaches 800-1000 0C, and often even higher. The result is an EMF that keeps the gas solenoid valve open on the burner pipe. The hotplate is working.
However, when the open fire disappears, the thermocouple stops emitting EMF to the electromagnet. The valve and the fuel supply are shut off. As a result, gas does not enter the kitchen without accumulating in it, which excludes the occurrence of a fire from such an abnormal situation.
A thermocouple is the simplest temperature sensor with no electronics inside. There is nothing to break in it. It can only burn out from prolonged use.
With a full set of sensors designed to monitor and safe the operation of the gas water heater next articlecompletely devoted to this interesting question.
Burnout of a thermocouple usually occurs only in gas boilers and boilers that operate constantly. In gas stoves, the considered gas control temperature sensors serve until replacement for 20-30 years
Among the advantages of thermocouples:
- simplicity of the device and the absence of breaking mechanical or burning out electrical elements;
- the low cost of the device is about 800-1500 rubles, depending on the model of the gas stove;
- long service life;
- high efficiency of flame temperature control;
- fast gas shut-off;
- ease of replacement, which you can do yourself.
The thermocouple has only one significant drawback - the complexity of repairing the device. If the thermocouple sensor is defective, it is easier to replace it with a new one.
To repair such a device, it is necessary to weld or solder at a high temperature (about 1300 0C) two different metals. It is extremely difficult to achieve such conditions in everyday life at home. It is much easier to buy a new control block for a gas stove for replacement.
Device and principle of operation
The thermocouple is based on the Seebeck thermoelectric effect. According to it, at the ends of sequentially connected conductors made of different metals, provided that their contacts are at different temperatures, a thermo-EMF (TEMF) arises.
That is, it is necessary to have two conductors of different composition, which are able to withstand a strong heating, and high-temperature heat (in the case under consideration, from combustible natural gas) at their point connections.
In most steam, the electromotive force arising between cold and hot contacts is very small and hardly applicable. But there are metals and alloys, the combination of which gives up to 4-5 mV / 100 0WITH. And this is already quite enough to control an electromagnet that controls a particular shutter.
Thermo-EMF in most types of thermocouples for gas stoves reaches 15-30 mV, and 5-10 mV is usually enough to keep the solenoid valve open
The principle of operation of thermocouples mounted in gas stoves is extremely simple:
- There is a flame - a TEMF arises between the contacts, the valve on the gas supply to the burner is open.
- No fire - TEDS disappears, the valve closes under spring pressure and shuts off the gas.
The thermocouple consists of two thermostable conductors up to one and a half meters long, which are connected at one end by soldering or welding.
It is this tip that is directly in the fire and is heated by the burning gas. The other end of the device is a pair of pins or a connector for connecting to a solenoid valve.
Varieties of temperature sensors for gas
Gas stove thermocouples differ in the alloy of the conductors and the type of connection to the valve. And the main thing here is that each manufacturer of gas equipment uses its own versions of electromagnets with different connection connectors.
In most cases, it is not possible to move the thermocouple gas control sensor from one tile to another.
The thermocouple must correspond to the model of the gas stove, it is forbidden to install the "left" control device for safety reasons
The following alloys and metals are used to create thermocouples:
- constantan + chromel;
- copper + constantan;
- copper + copel;
- nisil + nichrosil;
- alumel + chromel;
- constantan + iron;
- chromel + copel;
- platinum rhodium + platinum;
- tungsten + rhenium.
The accuracy of the device and its operating temperature range depend on the alloys used. For example, a chromel-alumel thermocouple is rated for 0-1100 0С, iron-constant at 0-700 0C, and platinum-platinum-rhodium can withstand heating up to +1700 0WITH.
In household gas stoves, thermocouple sensors made of alumel and chromel or constantan and iron are usually used. They are inexpensive and are quite suitable for the temperature conditions of the gas hob.
Gas control repair manual
If the gas on the stove goes out, then the problem may lie not only in the thermocouple. However, more often than not, it is in her.
The main symptom of problems with gas control is that after lighting the burner and releasing the handle or button for opening the "blue fuel", the flame immediately goes out. This is due to the overlap of the valve, since the thermo-EMF is absent or insufficient to keep it open.
Causes of noise gas stove burners are detailed in the article, with useful information worth reading.
Before purchasing a new thermocouple, you need to determine the reason for the poor performance of the existing device - perhaps the problem is in the loose contacts on the valve, then you just need to tighten them
You should independently check, repair and replace the thermocouple in the gas stove with your own hands only when the gas is completely shut off. First you need to close the valve on gas cylinder or a pipe with methane, and only then start any work. Also, do not forget about turning off the power supply if there are volatile devices in the design.
The tip of the thermocouple is located directly next to the burner and gas fire. And in the oven, you can find it near the flame divider at the top of the oven. This tip must be free of carbon deposits, mineral deposits and any damage.
If the working tip of the thermocouple sensor is covered with scale, then it must be cleaned off with sandpaper. The more carbon deposits, the less heat reaches the thermocouple, and the less it creates EMF, respectively. The received millivolts may simply not be enough to open the solenoid valve.
How to check before replacement?
A thermocouple usually has one tip for installation near a fire. But there are also options with two or three temperature control tips. They are usually used in ovens, but it all depends on the specific stove model.
Thermocouples with several working tips have a peculiarity - if only one of them is not hot or out of order, then the solenoid valve will be closed. Therefore, in order to accurately find the cause of the problems, such thermocouple devices will have to be checked especially carefully. Only one of the sensors can be faulty.
A working thermocouple for a gas stove, when heated above a candle, gives an EMF of the order of 15-20 mV after 20-30 seconds - if it is less, then the sensor must be changed
One more point - the thermocouple conductors in the area up to the valve must be stretched or dangling in the stove body. At the same time, their connection to the electromagnet must be rigid, the connector hanging "on parole" is unacceptable here.
The devices under consideration are available in lengths from 40 to 130 cm. A thermocouple gas control device should be chosen very carefully for this indicator. On the one hand, the wire of the conductors must not be overstretched, and on the other, it must not lie on heated surfaces or dangle freely.
How do I change the device?
Before replacing a damaged thermocouple in a gas stove, you should inspect the device for:
- the presence of carbon deposits on the working tip (if there is, it must be cleaned with sandpaper);
- no burnout of this tip (in this case, only a complete replacement);
- the rigidity of the connection between the contacts of the thermocouple sensor and the valve (tighten if necessary);
- serviceability of the thermocouple itself with EMF heating at a level of at least 15 mV.
The device in question should be changed only when it is definitely faulty. In many cases, to get the gas stove working again, you can do with cleaning the tip of carbon deposits and checking the contacts.
To replace the thermocouple, you will have to remove the front panel from the gas stove, and also lift the top cover with the burners on it
The working tip of the thermocouple is rigidly fixed near the burner or burner with a nut. If it cannot be unscrewed due to scale, then you should not press on the key unnecessarily. This can only break the mount. Better to use a solvent first.
The other end of the thermocouple is attached to the solenoid valve using a threaded connector or two crimp contacts. Removing them is not difficult. The new thermocouple sensor is installed in a similar sequence - with one end it is attached near the burner, and the other to the electromagnet.
Conclusions and useful video on the topic
How to replace a thermocouple with your own hands:
How the gas control works in the hob and oven:
Thermocouple device for gas stoves:
A gas stove without a properly functioning thermocouple is a source of danger. If the gas control has ceased to function, it is quite permissible to replace the sensor with your own hands. There is nothing difficult in dismantling the old one and installing a new control device. You just need to purchase a device that matches the existing tile model, and work a little with a gas wrench and a screwdriver.
If you have any comments on the topic or your comments on the above information, write them in the block below. Your stories about the nuances of replacing a thermocouple that you produced yourself will be of interest to us, as well as to other readers. Do not hesitate to write.
