Introduction
Heating elements made of high-resistance alloys based on chromium and nickel are used in all modern household devices designed to convert electricity into heat. Nichrome spirals or tapes are highly resistant to oxidation due to the formation of oxide films. For this reason, reliable soldering of nichrome heaters in the absence of special equipment (vacuum chambers, gaseous media) should be carried out after treating the surfaces to be joined with fluxes, which contain acids that can destroy the protective layer of oxides. Nichrome spirals last longer than their analogues made of fechral alloys, however, they are also subject to destruction during long-term use. The likelihood of burnouts and breaks increases in areas of the conductor where there are mechanical damage, nicks, kinks or overlaps with the surface of adjacent heating elements. Repairing a damaged nichrome spiral can be done at home. If simple technologies are followed, the operational characteristics of electrical equipment will be completely restored.
Homemade heater
It is easier and cheaper to make a heater based on nichrome. A meter-long piece of self-regulating cable costs 330 rubles and goes on forever.
Sellers surprisingly consistently forget to indicate the temperature of the system setting, but provide information about power that directly depends on conditions, and the indicator, by definition, in the described case is not constant. If we were talking about a resistive cable, the above would make sense.
For example, a self-regulating one works independently and does not require a thermostat. Has high fault tolerance. This means that the risk of fire is minimal if you happen to make a homemade heater.
Small homemade heater
Heaters and cables
Not everyone has ever encountered a self-regulating cable; let’s tell you a little more about these interesting components for defrosting systems for building gutters. The ohmic wire generates heat according to the Joule-Lenz law.
The effect is directly proportional to the current, inversely proportional to the resistance, and depends on the operating time of the structure. To obtain useful heat in heaters, people were looking for materials with increased resistance. This seems to reduce the Joule-Lenz effect, but the trivial wire cannot be connected to the 230 V network - the core burns out.
There is a short circuit. Try to make a heater with your own hands without danger to others.
For example, to get a 2 kW heater, take a wire with a resistance of 28 Ohms. Try making something out of copper wire. Nichrome is endowed with significant resistivity; 3-5 meters of material will allow you to wind a spiral. If you reduce the cut length, the power will increase, but the situation is unfavorable. The conductor is characterized by a certain maximum power per linear meter that it dissipates. If the value is too high, the coil will burn out. The process will take place quickly in the air.
First tip on how to make a heater:
Research the market for similar factory-made designs. What is the power and internal structure of the heater, what materials is the product made of.
Next we copy the technical specifications. Look in the reference book to see what linear power nichrome dissipates. By the way, the technique uses fechral from Norway, the composition of the material is a secret and cannot be obtained in stores.
What to make from nichrome. Metal factories produce:
Everywhere the ability to provide heat in doses is used (unlike copper, where the released linear power is small, the chance of burning plugs is high). The difference between tubular electric heaters is that the spiral is protected by pressed powder from water and air. The outer copper shell is used to maintain the shape of the dielectric. This will allow electrical isolation of the device. Don't forget, nichrome is metal, it's easy to get an electric shock if you don't take precautions.
The self-regulating cable independently monitors the temperature. We would like to inform the readers that the resistive cable is made of an ohmic conductor. Not nichrome or copper.
Self-regulating cable
The composition of the resistive cable is not important, the main thing is that it generates heat while the supply voltage is applied. New technologies have led to the emergence of a dielectric matrix interspersed with graphite. The concept is the basis for cables that self-regulate and expand as the temperature rises. As a result, graphite inclusions gradually cease to contact each other.
Due to this, the resistance of the area increases. The voltage is constant - 220 V - which means the current drops. Consequently, the Joule-Lenz effect is reduced. When the area cools, the reverse process occurs.
The self-regulating matrix contracts, there are more graphite bridges, the resistance drops, the current increases, and the thermal effect increases. To make a cable, two parallel copper wires are taken to supply potential. A self-regulating matrix with graphite inclusions is laid between them along the length.
The beauty of the design is that the fragments will be heated independently. Temperature plays a decisive role in the magnitude of the thermal effect.
The matrix is configured at the factory. More often we see products with heating temperatures in the region of low positive temperatures, just above zero. The vast majority of cables are used in defrosting branches of structural elements of buildings, so the properties are selected accordingly. It felt a little icy, the temperature dropped to zero, the matrix shrank, and the cable began to heat up. The advantage of the design is that there is no need to monitor the device. At the same time, a resistive cable gives a fixed thermal effect.
Resistive cable
If the process is not controlled, the temperature rises limitlessly until the cable sheath melts and a fire starts. It’s clear that you don’t want to deal with thermostats: it’s complicated and expensive.
A resistive cable costs a penny, but the price of a self-regulating cable has already been indicated. In light of the above, we believe that the first is best used for heated floors (but not ceilings), the second is ideal for atypical structures, such as a heating pad under a seat. Don't forget to insulate properly. For example, place a foil screen between the person and the cable, reliably grounded. In this case, nothing terrible will happen during a breakdown. It is better to turn on such devices through a differential protection device.
Examples of homemade heaters
As already noted, it is easier to make a heater from nichrome. You will need a section with a resistance of 27 - 28 Ohms to get a power of 2 kW. Do not connect such spirals in parallel. In this case, the power is multiplied by the number of heating elements, and the home switchboard in the Khrushchev building draws 5 kW. If you do not take into account modern high-rise buildings. Power is calculated using the formula:
N=U2/R
Do-it-yourself heater-wind blower
With a resistance of 28 Ohms, the result is 1728 W, if the effective voltage value is 220 V. It is unlikely that you will be able to assemble a tubular water heater at home, and there are as many nichrome spirals as you like.
Wind the wire around a ceramic rod, as is done in electric fireplaces, or on plates, as in hair dryers or wind blowers. Where to get heat-resistant material. It costs a penny in the capital market, but it’s expensive to buy online. Disassemble old equipment and borrow what you need.
Do not use steel for winding; this action will cause unpredictable consequences. By the way, the soldering iron has a ceramic insulator inside.
If nothing comes to mind, use a special hammer (for bricks) to chop off a thin plate from the brick and use it. The fragment is heavy, but reliable. If you find a fire brick, it is better to use a heat-resistant one. Ceramic tiles will do.
Don’t forget to make a recess at the ends of the plate for the wire, wind it in one layer, no more. In this case, the heat exchange conditions are violated, and the nichrome can burn. By the way, make holes in the tiles using special drills (for tiles, with a stone at the end).
If forced airflow is expected, for example, with a processor cooler, this will improve heat transfer.
By the way, fans are not used at all to increase power, as it seems. The thermal effect of nichrome depends little on air temperature. The wind just picks up the heat and spreads it around the room faster. The heating is more even. Ceramic tiles can be installed using any method, including heat-resistant adhesive (temperatures of at least 800 degrees). When heated, nichrome glows and works as an infrared heater. If the above is not enough, introduce airflow.
It is better to take 230 V motors. Low power asynchronous motors used in hoods or household fans are suitable. Do not use commutator motors: they are noisy and spark. By the way, you can get asynchronous electric motors in a refrigerator, kitchen hood or air conditioner. Linear compressors should be avoided; there are no rotating parts inside. A homemade heater for an apartment is assembled based on a cassette recorder. There are quiet motors inside; you need to properly adjust the speed for rewinding.
If you need a homemade heater for your summer house, assemble a burner based on an injector. They described a similar design, these are popular in the USA. Do not use gasoline to generate heat; the vapors are explosive.
We do not recommend blowing ionized air through the nozzle in the heater, but it is possible to place a perforated tile into the fire. It will serve as a ceramic grille, battery and heat emitter. It’s easier to make a homemade heater using a collet travel cylinder.
It is necessary to make the attachment correctly, for example, based on a commercial one for cooking.
Source: https://VashTehnik.ru/obogrevateli/samodelnyj-obogrevatel.html
Repair of nichrome spiral
There are 3 ways to restore the integrity of a nichrome conductor:
- Mechanical - twists, couplings, threaded clamps using washers, screws and nuts.
- Soldering.
- Welding.
The latter method is the most reliable in terms of strength and durability. Welded connections do not significantly affect the parameters of electrical circuits, so the technical characteristics of the devices remain the same. Connections in the form of twists, couplings and clamps create conditions for the accumulation of oxidation products, affect the overall resistance of the circuit, and can also create areas of increased heating, which increases the risk of repeated breaks and failure of electrical equipment.
How to weld nichrome
In production, the argon arc method is used for reliable welding of nichrome wire or tape. However, small diameter wires that are used as heating coils in household appliances can be welded using a homemade welding system at home. This will require a 12-24 V power source with a current of 10 amperes or higher. You can use the graphite rod of a salt battery as an electrode. The connecting ends of the heating coil are twisted. The negative wire from the power source is connected to the nichrome wire. A graphite rod is connected to the positive wire through the choke of the fluorescent lamp. When the graphite touches the welding area, a low voltage arc appears, the energy of which will be enough to melt the nichrome.
Copper Welding Machine
Quality welding machines for copper:
- – semi-automatic and automatic machines;
- – TIG – devices;
- – inverters.
Popular models are produced by TESLA, SPETSELECTROMASH, ESAB.
BUDDY TIG 160 from ESAB (pictured on the right) has two and four stroke torch firing modes. It can be used to join stainless steel and most other types of metals. It is compatible with almost any generator.
RENEGADE ES 300i ESAB inverter stores several welding parameters in its memory. Automatically sets the best starting parameters based on the configured current. It is lightweight but has high power.
Inverter machines allow you to weld copper rods; they generate a current of 60-110 amperes. For them you need to buy copper/carbon electrodes. HUNTER company produces semi-professional models, for example, MMA 257D, designed for continuous operation for two hours.
TESLA is known for reliable devices such as MMA 265, 275, 255. They have a non-contact arc excitation function. They connect to a regular household network without any problems. They are convenient for welding copper and its alloys, non-ferrous metals.
For welding with electrodes
Pulse-arc welding of copper plates is possible with tungsten electrodes in an argon atmosphere using an Orion 150s or 250s . They are lightweight and allow you to weld copper efficiently and reliably. The inverter welding device Resanta SAI-220 PN can be connected to a network with a voltage of 140-220 volts. It is easy to move with, it is equipped with a forced cooling system, so it does not overheat.
For wire welding
To perform copper wire welding work, the semi-automatic inverter Energomash SA-97PA20 is used. It has a light weight of 13 kilograms. It allows you to work with wire of different thicknesses 0.6-0.9 mm.
Smooth material feeding is ensured by the Shyuan MIG/MMA-290 model at a speed of 2.5-13 meters per minute. The device makes it possible to use 1-5 kilogram cassettes and allows you to work with electrodes.
The inverter semi-automatic welding machine Soyuz SAS-97PA195 is characterized by the presence of a 60 Volt idle speed function. It has an operating voltage adjustment range of 15-23 volts. A wire of 0.8-1 mm is suitable for it. It has a light weight of 10 kilograms, it is comfortable and reliable.
How to solder nichrome
You can solder a nichrome spiral in the following ways:
- Heating of the winding in the form of thin copper wire.
- Use of lapis (silver nitrogen).
- The use of special solders and acid-containing fluxes.
- A mixture of petroleum jelly, glycerin and zinc chloride.
- Lemon acid.
- Aspirin.
- Factory-made fluxes, type F-38N PET.
- Measurement using instruments.
- Tabular method.
The first method is the simplest and most accessible, but it is only suitable for connecting high-resistance conductors with a thickness of no more than 0.5 mm. It is best to take copper wire for winding with a thickness of 0.1 mm. Heating is done using a gas burner, but you can also use a regular turbo lighter. The copper wire heats up red hot and sticks to the nichrome, creating electrical contact at the atomic level.
The soldering method using lapis is used to strengthen the contact of mechanical twisting if the operating temperature of the heating element in the device does not exceed 200 °C (the fusion limit of silver nitrate). The substance is applied to the twist when it is heated by electric current. The most reliable results are obtained by soldering using special solders and fluxes. The oxide film that forms on the surface of chromium-nickel spirals is the main obstacle to high-quality tinning. In industrial production conditions, to solve this problem, it is advisable to use vacuum chambers or neutral gas environments.
At home, acid-containing fluxes are used: the surfaces to be joined are cleaned of the oxide film, degreased and coated with fluxes using a soldering iron. After this, preliminary tinning and soldering are carried out using POS 40/50/61 solders.
"Little tricks". Part 3.
How to extend the life of a soldering iron
Like an incandescent lamp, soldering irons have a spiral - a heating element. As a rule, it burns out when the soldering iron is turned on, less often - when it is turned off. During long (time-consuming) installation work, it is not advisable to turn off the soldering iron, but sometimes it is enough to just limit the heating.
To do this, a button (with fixation) with contacts for closure is inserted into the break in the electrical circuit “network - heating coil”. And in parallel with this button, a rectifier diode of type D226B - D226Zh, KD213 or similar is turned on.
When the button contacts are open (but the plug is plugged in), limited heating of the soldering iron coil occurs. One has only to close the contacts of the button, and the heating goes “in full force”. At the same time, the soldering iron heats up faster, because it was already ready for use. Using this method, it is possible to significantly extend the “life” of the soldering iron!
How to connect high-resistance nichrome wires
A simple method can be used to ensure reliable electrical contact in wires made of high resistance alloys (nichrome, constantan). To do this, the wires at the junction are stripped and twisted. Then such a current is passed through them that the junction becomes red hot. You need to put a piece of lapis in place of the twist. When heated, it will melt and provide reliable electrical contact at the junction.
How to solder contacts made of stainless steel, chrome and nickel
When the material is difficult to solder, you need to use soldering acid or aspirin. In this case, it is necessary to preheat the soldering area until scale appears.
Another method of soldering such metals is a little simpler. It is necessary to thoroughly clean and degrease the soldering area. Then tin and spread with glue like BF-4 (or similar). After this, use the tip of a heated soldering iron to press the surfaces to be soldered for 5-7 seconds. After cooling, apply a drop of instant glue to the soldering area to completely harden the contact.
How to solder aluminum parts
It is not difficult to solder the leads of radio components or the ends of conductors to a copper, brass or steel surface. But try to do this on an aluminum chassis and you will see that the solder will not even stick to its surface. The reason is an oxide film - the result of the combination of aluminum with oxygen in the air. This film prevents the solder from joining the metal.
The oxide film can be removed electrochemically. Stock up on saturated copper sulfate, a 3336 battery (or power supply) and copper wire without enamel insulation. Thoroughly clean the area of the intended soldering of parts or conductors on the aluminum surface and carefully apply 2-3 drops of copper sulfate. Connect a conductor from the negative terminal of the battery (power supply) to the chassis, and connect a piece of copper wire to the positive terminal. Dip the end of the wire into a drop of vitriol on the chassis (the wire should not touch the aluminum). After some time, a layer of red copper will settle on the chassis, to which, after drying, you can solder the leads of the parts.
How to prepare conductive glue
Tsaponlak and graphite from any battery (central rod) are mixed until sour cream is thick, a thin layer is applied. Can be used to restore graphite tracks on remote controls and other similar devices.
How to connect a burnt out nichrome spiral
The method of repairing a burnt-out nichrome spiral is selected depending on the thickness of the wire, as well as the characteristics of the device in which the failed heating element is used. If the operating temperature exceeds 150-200 °C, welding should be used. Mechanical connections in the form of twists, couplings and clamps will give only temporary results, and soldering using thin copper wire and a gas torch will be a reliable solution for low-power electric heaters that use thin wire spirals. Soldering with solders creates excellent contact, but quickly breaks down if the temperature exceeds 300 °C.
How to solder or weld nichrome at home
In the absence of special equipment, reliable repair of a nichrome spiral is best carried out using the contact welding method with a low-voltage arc created by a graphite electrode. This requires a special power source, but if you don’t have one at hand, you can use the soldering method using thin copper wire. The connection is strong and relatively durable, and if repeated burnout occurs, the rupture can be easily repaired using this method in a few minutes. To carry out high-quality soldering, the ends of the wire need to be stripped, immersed in citric acid powder and heated with a soldering iron. The substance will melt and cover the metal surface with a thin layer. The oxide film will be destroyed. Before tinning, the connecting ends can be additionally treated with rosin.
How to check the resistance of nichrome
The electrical resistance of nichrome wire is easily measured using household multimeters. The operation is carried out for the purpose of calculating resistivity. One contact is attached to the end of the conductor. The second contact is connected at different distances from the place where the first contact was created. The obtained readings are entered into a table. The dependence of resistance growth on length is linear. To obtain data on the resistivity of a wire 1 m long, you need to measure this characteristic with a conductor of the appropriate size, or derive this parameter by calculation if the wire is of insufficient size. Before taking readings, the device is calibrated, or the own resistance of the device’s wires is measured in order to determine the correction by which the data obtained when measuring the resistance of nichrome should be reduced.
How to calculate the resistance of a nichrome spiral
Calculation of the resistance of a chromium-nickel alloy spiral is carried out using the following methods:
If you have a ready-made spiral, then calculating its resistance using the device will not be difficult. However, if it is necessary to perform a preliminary calculation of the parameters of the spiral before its manufacture, then the tabular method is used. Tables of resistivity of various nickel and chromium alloys can be found on the Internet or in specialized literature. The tables provide data for each alloy for both wire and strip.
Data on wire conductors are given taking into account the diameter (from 0.1 mm). Indicators for tapes are given taking into account cross-sectional areas. To calculate the resistance of the spiral, you need to multiply the total length of the wire by the resistivity of 1 m of conductor with the appropriate cross-section. If information about the alloy grade is not available, the resistivity is calculated experimentally using instruments.
The production facility produces spirals with predetermined characteristics from various grades of nichrome alloys. We will efficiently and quickly produce a product from wire of the required thickness, with a certain number and diameter of turns, as well as with specific characteristics of resistance, power, energy release and energy consumption!
Features of the material
Welding nickel alloys is difficult due to their sensitivity to impurities, and they are also prone to the formation of pores, since nitrogen, hydrogen and oxygen dissolve well in the molten metal. Different alloying elements have different effects on the formation of pores in the weld: titanium, chromium, vanadium reduce the formation of pores, and manganese, carbon, silicon, iron, on the contrary, increase pore formation.
An important feature is that when heated, the base metal does not undergo structural transformations and is not hardened; accordingly, parts of small thickness are not heated before welding.
In most cases, it is necessary to introduce additional alloying elements contained in the filler wire or electrodes into the weld. In this regard, the chemical composition of the weld and the base metal will be different. Nichromes are prone to intergranular corrosion due to chromium alloying. To avoid this, the finished product is annealed after welding.
