Build Daily

Furnaces And Heating Systems

August 12, 2017 18:06

The heating cable is a warm floor

heating system « warm floor" has long proved its efficiency and comfort, so it is widely used in all world.The fundamental question is, what kind of energy source used to generate heat?While there is a difference in modern energy, a person burn less solid fuel or hydrocarbons, heat production of heat water prices, and then pump it on pipes warm floor.But it is much more convenient to use as a heating cable warm floor rather than a complex piping system, the collector units and pumps.The domination of hydrocarbons in the energy market will not last forever, and more convenient for the transfer and use of electrical energy will inevitably be used increasingly for heating.

The heating cable is a warm floor

heating cable as a warm floor

theoretical educational program heating cable

Article Contents

  • 1 theoretical educational program heating cable
  • 2 Classification heating cables
    • 2.1 resistive heatingcable
    • 2.2 resistive zone (sectional) cable
    • 2.3 heating mats
    • 2.4 Self-regulating heating cable
  • 3 heating cable as a warm floor
    • 3.1 heating cable for underfloor directactions
    • 3.2 heating cable for thermal storage underfloor
    • 3.3 General requirements for the heating cables, floor heating
  • 4 Conclusion
    • 4.1 Video: Crash test floor heating cable
    • 4.2 Video: Installation of floor heating cables Devi
    • 4.3 Video: Installation of heating mats

as we know from school physics course, the electric current - is not nothing but a directed movement of charged particles under the influence of an electric field. If a substance has the free charged particles that can move, it is called a conductor and if not, then the dielectric.Those substances which can change the amount of particles depending on certain external factors called semiconductors.In conventional metals, the charge carried by electrons, in electrolytes - cations and anions, and electrons in gases and s and ones.

any conductor does not pass a stream of charged particles smoothly and has him certain resistance which is physically due to the fact, that particles collide with the conductor atoms, "undermine" them, losing their energy , and as a result energy electric current is partially converted into internal energy conductor, that is expressed in its heating.

ability to resist the flow of electrical conductor current is quite logical named resistance.

At the heart of the heating cable is property of conductors having a resistance to heat during the flow of electric current

At the heart of the heating cable is property of conductors having a resistance to heat during the flow of electric current

As can be seen from the formula, the resistance depends on the resistivity, which relates to the reference data (it is always for a specific material), conductor length andits cross section.The resistivity of different conductors can be found in the table.

The resistivity of the main conductors

resistivity of the main conductors

Obviously, for the transmission of electric energy should be used materials having the lowest resistivity - then the percentage of loss is low.It's aluminum, copper and steel for the manufacture of large cross-section cables, wires, power lines.The electronics used: silver, gold, tin, platinum.

If wires will be used for heating, is detrimental to the energy transmission loss properties are very useful to provide heat, so choose materials with high resistivity: tungsten, nichrome, galvanized steel, various alloys, which the manufacturer of heaters can keep a secret.

To assess the amount of thermal energy that can release the conductor during the flow of electric current through it, the law Joule - Lenz, outdoor even in the XIX century.

Joule - Lenz

Joule - Lenz

According to this law, the amount of heat Q equal to the work A, and it depends on the square of the current strength - I of, resistance - the R, and the period of time Δt.

From given scheme shows, that in a closed circuit flows current measured by the ammeter, and it will be the same on each of its site.The water tank heating element is R, the resistance of which is greater than other conductors so that they can simply be ignored.According Joule law - Lenz, the resistance R, would be allocated certain amount of heat, it begin to heat water in the reservoir, while other sections of the heat circuit is highlighted.Rheostat you can change the current in the circuit, the amount of heat generated will vary accordingly.

The experimental setup , confirming the law Joule - Lenz

Driving experience, confirming the effect of Joule's Law - Lenz

That this law we see in the example electric kettles, irons, boilers, where the resistance of the thermoelectric heaters - TEN , far more than the wiring.Therefore, the heat they emit more.The heating cable is the same heater, only having a longer length, so heat generation occurs locally, and the entire length of the cable.Dedicated cable heat is transferred on building structures, including flooring.The heating cable can be laid in screed material in the tiled glue, special assemblies of metal.The supply power cable having low resistance, referred to as "cold" or mounting ends.

Classification heating cables

It would seem that what could be simpler?It is necessary to take a material having a high resistivity, make it a cable, calculate the heat generated them and you're done.But in fact, it's far from it, the heating cable must meet certain set of requirements, which will be discussed below.

The heating cable systems (CSR) can be used completely different in design, materials used, the specific power cable, depending on the destination:

  • Heating facilities.First of all, the system is used « warm floor", but still used and warm walls and even warm ceiling.Typically, electrical warm floors make for comfort or additional heating in the appendage main system.As the main source of heat can not be predicted due to unprofitability and in most cases is unacceptable, since there is no electricity supply company will not give permission to the selected power.
On the floor comfortably warm is not only ride, but also to sit on it

On warm floor comfortable not only walk, but also to sit on it

  • heating of the roof and gutters most effectively by means of heating cables, as they save on costly repairs of the roof as well as the rule reflux traffic injuriesfalling icicles.
Heated of roof prolongs its service life

heating roof prolongs its service life

  • heating steps, stairs, ramps, entrance to the garage, the space under the gate of entry into the territory of the house.In the winter, benefit from the comfort and safety while at Menen CSR in these places felt.
In a heated porch will never be slippery

on the heated porch never be slippery

  • heating pipes in private homes.The pipes must always be laid below the depth of soil freezing, but it happens that in the exit areas, passing through the foundation, even the insulation does not help protect pipes from freezing.Heating cables - a better salvation.
Heating pipes

heating pipes

resistive heating cable

In the name of this type of cable, it is understood that it is a resistive load - kind of elongated conductor having a fixed resistance that is greaterthan the resistance "cold cables": power and installation.Heating occurs conductive copper or special alloy, heating conductors, prisoners in isolation.On top of isolation necessarily applied screen copper braid or foil envelope with residential drainage.

screen performs a very important function:

  • screen reduces the electromagnetic radiation, which is characteristic of any current-carrying conductor, especially variable.
  • screen connected to ground (conductor PE), which is part of the potential equalization system (EMS).If happen insulation breakdown, that the ki leak closed on the screen, and go to the land that will protect a person from electric shock.In addition, it will trigger the circuit breakers and residual current devices (RCD).

Resistive cable in its execution are:

The structure of the resistive heating cables

structure resistive heating cables

  • Solid resistive cable - one conductor is used to heat the vein.It is the most inexpensive form of heating cables the required reflux Carefully laying, as the beginning and end of the cable must converge at one point and connect to special regulatory devices - thermostats.
  • twin-core heating cable in the central part has two cores, prisoners at the screen.At the same time, or both strands may be heating or heating one core and the other feeding or its called - return.At the end of section two-conductor cable has a special end structure that connects the two heating wires and cable insulation.The advantages are obvious two-wire cable - for his laying it is just necessary to put the snake on the scheme, without the need to return back to the thermostat.The level of electromagnetic radiation in a two-conductor cable is much less than a single-core , as in the veins of the heating currents flow counter.Obviously, such cables are expensive.

resistive cables are sold ready-sections having a fixed length, which are categorically not be changed.Why?The fact that the most important characteristic of any heating cable is a specific power released one chase meter cable.It should be in the range of 10-20 W / m and in any case no longer, as it lead to overheating of the cable and its failure.For example, when shortening the resistive cable doubled, the resistance is reduced by half, that law Joule leads to a twofold increase in the amount of heat, but it is not designed cable material.

Set the length of the resistor cable fixed with the mounting kit

komlekte resistive cable of fixed length with mounting kit

long sections are selected on the basis of calculations .Manufacturers produce kits with section lengths of 10 to 110 meters, so choose the required cable with the required power density is always possible.There resistive cables on reels from which can be cut any length, but it is the prerogative of specialists capable of doing the necessary calculations .

advantages of resistive heating cable:

  • reasonable cost.
  • constancy of performance.
  • absence of inrush current does not require the use of special circuit breakers C.

disadvantages of the resistive cable are:

  • When illiterate installation there is the danger of local overheating that lead to failure of the cable.
  • Inability to reduce the length of the heating cable without changing the characteristics.
  • cables do I need to provide the desired heat settings.

resistive zone (sectional) cable

the evolution of resistive heating cables was invention zone (sectional) of the cable in which the center are two low resistance conductor, prisoners in isolation.Pove p pr ovodnikov wound coil of wire with a high resistance.After certain interval (typically 1 meter) this wire is connected alternately to one and then to the other center conductor.Obviously, in this case, each portion (zone) will be independent of the other heating element, similar to the parallel connection of resistors.

scheme zoned resistive heating cable

Benefits zonal cable:

  • Same specific power cable along the entire length.
  • stability characteristics.
  • not consume large currents at startup.

Disadvantages zone resistive cable:

  • danger of local overheating.
  • Necessity ensure heat.
  • higher price as compared to conventional resistive cables.

heating mats

To facilitate the process of laying warm floor manufacturer make special heating mats, where the cable with the required step attached to the polymer network.These mats are very comfortable to lay on a flat surface before laying ceramic tiles.They can be mounted directly in the tile adhesive layer, this is their main advantage.However, it is necessary to watch closely, not to leave air pockets that cause local overheating.

Heating mats on the polymer network facilitate the process of laying

heating mats on the polymer network facilitate the process of laying

In areas with complex geometry can be difficult when laying the mats.That is their main disadvantage.

Self-regulating heating cable

flagship among all the heating cable is self-regulating heating cable that can change the heating temperature, and, hence, the heat depending on the ambient temperature.

between two conductors pressed into a special polymer matrix with semiconductor properties.By lowering the temperature of the matrix is ​​compressed, but it's a lot of heat-conducting paths with a high resistance to it.Current flow causes heating of the matrix and the cable.With increasing temperature causes the polymer to expand and reduce the amount of current flow paths and, in the end, there comes a time when the currents are negligible, resulting in the termination of the heating cable.Each cable section works independently.

Саморегулирующийся кабель сам "выбирает" где и как нагревать

Self-regulating cable itself "chooses" where and how the heat

top of a semiconducting polymer layer there is a heat-resistant insulation, then a copper or steel screen and even a single layer of insulation.Each cable has its own dependence sweatshop (specific) power on the temperature and is selected based on the operating conditions and purpose.

The dependence of the linear power cables of various self-regulating temperature

dependence of the linear power is different from the self-regulating cables

temperature Advantages of self-regulating cables:

  • energy savings, which occurs at the expense of heating just enough warm areas.
  • specific power regardless of cable length.
  • This cable is "forgiving" installation error.Even overlap cable not lead to overheating and failure.

Disadvantages of self-regulating cables:

  • These cables have high starting currents, especially if there are long cold spots.This obliges put breakers Class C, allowing the current ten-fold jump compared to the nominal.
  • semiconductor polymer matrix has a limited life.
  • High tse on on such cables often makes their use of dubious benefit.