Heating resistance cable from TASH in single-core and two-core version:
1 — shell;
2 — copper braid;
3 — insulation;
4 — wires
Option when the cable is passed in a loop inside the downpipe
Copper mounting tape for cable
Winter in our area is rarely equally cold or, conversely, warm. More often than not, thaws are replaced by frosts, frosts- thaw. ATIn such a situation, most owners of country houses have a difficult problem- icy cornices and icicles on gutters. You can fight ice with the help of an anti-icing system.
Why ice- this is bad
Under certain weather conditions, the weight of an icicle in just one day can increase by several tens of kilograms. Thus, a picturesque ice cone will pose a very real threat to all residents of the house. So what, you think, the probability of an icicle falling is not too great, but on occasion it can be knocked down by any means at hand. Why waste money installing some kind of anti-icing system?
In fact, the problem of roof icing is much broader than the question of whether an icicle will fall or not. Not only that, the failure of sufficiently massive ice masses creates a real danger to people’s lives and can damage not only vehicles, but also the architectural elements of the house. Due to the accumulation of ice, the mechanical load on the roof elements, the brackets for fastening downpipes and gutters increases, which inevitably leads to a reduction in their service life, which means an increase in your costs for the corresponding repairs. Since drains and gutters are clogged with ice, water in the autumn-spring period and in winter during thaws either flows onto the facade or lingers on the roof surface. ATin the latter case, leaks are possible. And then the upper floors of the house and parts of the facade near the drains and valleys (that is, the lines of joints of the roof planes) suffer. ATAs a result, you are faced with the problem of mechanical cleaning of the roof. This work is very time-consuming, and the roof itself can suffer considerable damage, because most roofing materials (metal tiles, galvanized steel, copper) are very sensitive to mechanical stress.
It turns out that it is necessary to deal with ice. And here the electric heating system of those sections of the roof, where the probability of its formation is most likely, can come to the rescue. ATin systems of this kind, special cables are used as a heated element, laid in gutters and gutters. Thanks to this, the melted snow does not turn into ice, but flows down to the ground in the form of melt water.
All on ice!
What can be opposed to the onslaught of nature? Perhaps only modern technology. When creating anti-icing systems, engineers proceeded from considerations that it is more profitable to heat melt water without letting it freeze than to melt the already formed ice. ATIn this case, much less power will be needed, which means that energy consumption will become more economical. So the main task of the system- during the winter and off-season, to accompany the water formed on the roof to ground level, simply preventing it from freezing on the roof elements and in the gutters, and at the same time to exclude leaks, damage to the facade finish and downpipe fasteners. This idea, quite simple in its essence, is implemented in the form of a complex engineering complex. The principle of its operation is summarized as follows.
In the most “unfavorable” places of the roof (gutters, gutters, valleys andt.where ice is most often formed, and along the entire route of the melt water, a heating cable is laid with power supply from the mains with a voltage of 230B. Heating is controlled by a special automatic thermostat that receives commands from one or more sensors installed on the roof. These can be sensors for temperature, humidity and precipitation, a sensor for the presence of water. As soon as they signal that conditions are developing in the atmosphere conducive to the formation of ice (and this usually happens during precipitation during the cold season or drip melting of snow cover on the main part of the roof during a thaw), a thermostat (or a programmable thermostat, a kind of home weather station) “activates” the power supply, and the heating cable begins to generate heat. The resulting water flows freely and without hindrance along the gutters, trays and gutters.
Why do icicles appear
By itself, snow falling on the roof does not pose any danger. The trouble is that the snow mass begins to turn into ice under the influence of two factors.- technogenic and natural. Daily air temperatures fluctuate with an amplitude reaching 15
The main reason for the appearance of ice- temperature difference between the central part of the roof and the edge where the drains are located. It may occur for several reasons. The most common- this is heat removal through the upper floors and the roof, due to which the temperature of the central part of the roof is higher than the temperature of the outside air. The temperature difference increases if there are no ventilated attic spaces in the house, if the under-roof space is rebuilt for living quarters, or heat-generating equipment is placed there, for example, expansion tanks, heating collectors, etc. The lower layer of snow cover on a relatively warm roof is heated up, turns into melt water , which flows into cold gutters and freezes there, blocking further water drainage. Mansards, turrets, all kinds of superstructures, complex roofs with internal corners, horizontal platforms and protruding “collars” of roof windows do not go out of fashion. And, alas, contribute to the formation of snow cover. By the way, from this point of view, experts consider the most effective in the conditions of central Europe a pitched roof of the simplest form with an angle of inclination of at least 30
Due to solar radiation at the boundaries of the snow cover, melting is activated. According to meteorologists, on average, about 70 temperature transitions through the 0 mark are recorded during the winter.
Usually, the system of anti-icing and heating of the roof and gutters consists of several functional subsystems. Firstly, this is the so-called “heating part”- the actual heating cables, which must be electrically safe, mechanically strong, resistant to sunlight and precipitation. An important component of the “heating” subsystem are all kinds of fasteners. They fix the heating cables in a given place on the roof and in the gutter structures. And secondly, the distribution network- a set of power and signal (information) cables and junction boxes for switching wires. This subsystem is responsible for providing power to all elements of the heating part and to conduct information signals from sensors to the control panel. The “heart” of the anti-icing complex is an automatic control system, which involves special temperature controllers, temperature and humidity sensors, ballasts and protective equipment.
Heat runs through the wires
Now is the time to talk about the most important components of the system. Let’s start with the most important- from heating elements. The role of the heater in anti-icing complexes is played by special cables. Their purpose- convert the electric current flowing through them into heat. Therefore, power per unit length (specific heat release)- their most important technical parameter. The cable is laid and fixed in places of expected icing- along the edge of the roof and drip, in valleys, around protruding structures (lanterns, pipes, skylights andt.as well as along the entire drainage system. On flat roofs and low slope roofs (up to 30
Resistive cables have a constant constant resistance along their entire length and consist of a heat-generating metal core, insulation, copper braid and an outer sheath. Today on the European market there are resistive cables manufactured by such companies as SPECIAL SYSTEMS AND TECHNOLOGIES, or CCT (Europe), THERMO, KIMA Heating Cable (Sweden), CEILHIT (Spain), ENSTO, TASH (Finland), NEXANS Norway AS (ALCATEL, Norway/France), DEVI (Denmark).
As a rule, either cable sections or cable supplied in coils (drums) are used for laying. Sections- these are ready-made products in which a piece of cable of a fixed length is docked at the factory with the help of a special sleeve with the so-called “cold end”- a supply wire designed to connect the heating (“hot”) cable to the electrical network. The length of the “cold ends” is also fixed and is 0.75–3m. The ends of the supply wires are brought into the distribution terminal box, where they are joined with other electrical wires, through which power is supplied from the power shield. So basically the heating section- the main element of the anti-icing system, and the couplings connecting the cold wires to the constantly heating and cooling heating cable,- the most critical element of the whole structure. The durability of the system depends on the reliability of the couplings, so manufacturers usually test the heating section under very harsh conditions. Many firms connect the heating conductors of the cable to the “cold” wires using mechanically crimped bushings. Those are placed in a plastic box and then filled with special mastic. This ensures the reliability and tightness of the connection. Sections cannot be cut.
Another variant- laying the heating cable from the coils. Such a cable is cut directly at the installation site, and heat-shrinkable couplings are used to connect power wires or other heating sections.
Most companies produce both ready-made heating sections and coiled cables. Thus, cables of the DSIG series from DEVI, Thermocable SVK from THERMO, Tassu from ENSTO are supplied in sections with a fixed length of heating and power wires. Cables in reels are offered by CEILHIT, NEXANS, DEVI, TASH, etc. But you cannot make cuts of any length: the length of the cable is determined by such characteristics as resistance, power density and the voltage used. The power of heat release depends on the size of the segment. Tofor example, to obtain the required power of 30W/rmm for a cable with a resistance of 70ohm/rmm need length 15.5m. If it is less, the cable will overheat, if more- will not reach the rated linear power.
The problem of ice formation is most relevant not in cold winters, but during periods of thaws, when the air temperature passes through zero and the water from the melted snow freezes almost immediately. Sometimes at +3…+4
Operation of anti-icing systems at temperatures below ‑15
It is not scary if the snow falls in frosty weather. To melt it, you will, in theory, have to put 3 or 4 strands of cable. But this is an increase in the cost of the system by 2 or 3 times. Therefore, it makes sense to wait until it gets warmer and the snow begins to melt. That is why the operating mode of the systems is limited from below by a temperature of ‑6 … ‑15
To date, manufacturers produce resistive cables of either single-core (with one heating core) or two-core design (one core- heating, second- connecting). A section with a single-core heating wire is connected to the mains at both ends, and a two-core cable- only from one end (on the opposite end there is a plug, inside which the heating and connecting cores are connected). Using two-core heating cables is somewhat easier to install, but they are slightly more expensive than single-core ones. The heating conductors are protected by high molecular weight polyethylene insulation, on top of which another layer of insulation is applied, and then a copper shielding braid. Outside, the cable is protected by a high-strength sheath made of polyvinyl chloride (PVC) or fluoropolymer compositions.
Of course, each manufacturer makes sure that its cable lasts as long as possible and is as reliable as possible. For example, in THERMO’s Thermocable SVK resistive cables, the current-carrying cores are protected by a tinned copper shield braid. The internal insulation of the cores is made of silicone rubber, resistant to temperature extremes. AThigh-strength polyester film acts as additional insulation. The cable itself is reinforced with fiberglass, and the outer sheath is made of PVC. CEILHIT cables with Teflon-coated cores appeared on the European market, which allows not only to increase the maximum operating temperature of the heating element (up to 50–60
As a separate variation in the class of resistive “heater wires”, the so-called zone cables can be mentioned. They are represented, for example, by the products of HEATTRACE (Great Britain) and CCT. The heat-generating element here is a piece of high-resistance alloy wire, superimposed in a spiral on two insulated conductive wires. Moreover, the step of connecting the “spiral” with these cores- no more than 1m. Thus, heat release zones connected in parallel are formed. The cable has many heating zones and can be used in pieces. By cutting them, you do not risk disrupting the operation of the entire chain. Zonal cables are sometimes referred to as “quasi-self-adjusting”, since during installation they can be cut “in place” into pieces that are multiples of the length of the heating zone, directly on the object. This reduces cable wastage.
Zone wires have a specific heat release from 15 to 200W / m (depending on the section of the spiral) and are powered from one end. They are recommended to be laid on roofs, in long and extra long drains (40m and more), as well as in systems where the absolute absence of ice is necessary. ATAs a result, it turns out that in this case, the rigid characteristic of the zonal cable develops from a disadvantage into an advantage.
A separate type of resistive cables can be considered their armored versions with an additional single or double braid of galvanized steel wires.- for reliable protection against mechanical damage. The main scope of such cables- laying in a concrete screed when arranging heating systems for open areas, ramps, steps, as well as concrete drainage trays.
|Power range, W/m
|Applicability on roofs
|Heating of pipelines, trays, drains
|5–30; fixed power
|Fixed, 10–200 m
|Heating of pipelines, trays, drains
|5–60; variable power
|Any up to 150 m, cutting on site
|Heating of pipelines, trays
|10–80; fixed power with the possibility of slight correction
|Any up to 150 m, cutting on site
|Heating of long drains
|Heating of open areas, drains
|20–60; fixed power
|Fixed, with the possibility of cutting in place 1–2 m
|Heating of drains, droppers, concrete trays
In EU, resistive cables with “armor” are mainly represented by products of the SST company. It produces, in particular, a resistive two-core cable TSB of increased power (up to 30W/m) for heating roofs, gutters and outdoor areas. The product has high mechanical strength and resistance to short-term overloads. If necessary, you can choose a cable with a high specific heat, for example, an armored EM2-XR from RAYCHEM with a power of up to 130W/m ToAmong the “lightly armored” cables are PSV cables (two-core, with a coaxial copper-steel metal braid) from CEILHIT, Kima Armor D from KIMA, as well as the lightweight armored cable MBk manufactured by SST in a polymer sheath.
European resistive cables are the cheapest. As for imported products, 1linearm of cable of any brand costs $1.5–5. Two-core options are more expensive than single-core ones by about $0.05–0.1. At the same time, the quality of products from different manufacturers is at the same fairly high level. A domestically produced resistive cable for the Teploskat anti-icing system from SST costs about $2.5–3 for 1linearm.
Unlike resistive cables, self-regulating cables automatically change their heat dissipation depending on the ambient temperature. Moreover, the amount of heat generated varies, so to speak, locally: each section of the cable “adapts” to the conditions surrounding it. How does this happen? The heating element in self-regulating cables is the so-called matrix, made of a polymer with the addition of a conductive carbon material and located between two current-carrying cores. When the cable section is exposed to low ambient temperatures, the material of the heating element contracts, the resistance decreases, the current passes through the matrix, and it intensely releases thermal energy. That is, on a cold piece of cable, the current does not flow along the wires, but across, from one wire to another. As the temperature rises, the electrical resistance of the matrix becomes very high, which leads to a sharp decrease in the heat dissipation power. The heat dissipation power of cables also varies depending on the physical environment in which the cable is located, say, in melt water or in air. For efficient operation of systems in European climatic conditions, according to experts, a cable with specific heat release at 0
In our market, self-regulating cables are represented by modifications of various power (from 13 to 66W/m). Suffice it to say D3 from RAYCHEM-ISOPAD (Germany),
At first glance, it seems that you can save money by looking for cheaper goods in the store. In fact, the actual cable system without project development and installation work is meaningless. As a rule, large installers work with certain suppliers of materials and equipment. ATthis makes sense, because the company is gaining experience in designing and optimally adapting the system to European conditions. For example, the KPD group of companies installs anti-icing systems based on cables from DEVI, SEMRIS uses self-regulating cables from RAYCHEM and ISOPAD, as well as resistive ones from TASH, SIM-ROSS uses products from NEXANS, CCT- “Teploskat” system based on cables of own production.
What type of cable is better to choose? Resistive cables provide increased power per unit length and, if necessary, can be laid in several strands (for example, cables from TASH with a unit capacity of 25–30W / m is usually mounted in drains and gutters in two or three threads). The use of increased power per unit length reduces the required cable length and reduces the number of fasteners. BUTa large line of cable resistances per unit length provides the possibility of heating almost any roofing element. Resistive cables- the most elastic, have a small allowable bending radius (about 100mm) and fit well in place on roofs of almost any complexity.
Of course, this type of cable is cheaper, but they have several serious drawbacks. One of them- the need for constant care and maintenance. ATin particular, the periodic removal of debris from the roof, at least before the onset of the winter season, which is not easy if it is a roof with a soft roof or with steep slopes. Big disadvantage of resistive cables- fixed resistance along the entire length of the section. That is, under different operating conditions of individual sections of the cable, the heat release remains the same. Imagine: one section of the section lies on a clean roof, the second- under a pile of fallen leaves, and the third- under a thick layer of snow. Sensors, reacting to moisture under the snow cover, turn on the system, but only the segment that is under the snow works effectively, while the rest simply heat the air, wasting electricity. BUTunder a pile of foliage, the cable can even burn out.
Self-regulating cables change their heat dissipation depending on ambient conditions and temperature. Tofor example, models
Self-regulating cable is expensive, but it can be cut into pieces of almost any length (from 20cm). The resistive one is laid in sections of a fixed length, usually not coinciding with the length of the gutters. You have to “round” up to the nearest section, which means that the cable consumption increases. The more cable is laid, the greater the amount of work, that is, the cost of installation increases. FROMon the other hand, a resistive cable is more suitable when you have to deal with a lot of the same type of nodes (for example, 10 downpipes 10 meters high).m). By choosing a section of the desired length, cable overrun can be reduced to a reasonable minimum.
According to the weather service…
There are limits on the installed capacities of the heating part of the systems, determined on the basis of practice. Failure to comply with them leads to the inoperability of the system in the specified temperature range, and a significant excess- to excessive consumption of electrical power without any improvement in performance.
On the horizontal sections of the roof, the total specific power per unit area of the surface of the heated part (tray, gutter andt.n.) must be at least 180–250W/m2. Linear power of heating cables in gutters should be at least 20–30W per 1m of length and grow as the length of the drain increases to 60–70W/m The estimated power of the entire system for a country house depends not so much on the area of the roof, but on its configuration, the length of the drainpipes and trays, the height (number of storeys) of the building. ATaverage is 3–4kW. A simple gable roof needs 2 times less power than a complex one.- with turrets, attics, valleys, junctions andt.e. Tellingly, the type of cable does not affect the design power included in the project. After all, the main task- so that it is sufficient for the effective functioning of the entire system.
Heating cables- although the main, but not the only component of the anti-icing system. Many believe that the system should be turned on when it snows, someone else- that she must act all winter. Last thing- it’s like drowning banknotes. In fact, the anti-icing complex works according to a given algorithm, either activating the heating or turning it off and transferring the system to standby mode.
The control function is assigned to special temperature controllers manufactured by DEVI, ENSTO, RAYCHEM, Danish OJ ELEKTRONIK, German EBERLE. For small, simple roofs, the simplest option is suitable- based on a temperature sensor and a thermostat that turns on the system only in a given temperature range (usually from ‑10 to +3–4
The temperature range at which there is a risk of ice formation and, therefore, it is necessary to use cable heating is “set” on the thermostat panel. The system works according to a more complex algorithm than a simple thermostat. If the outdoor temperature is within the specified range and the sensors have detected the appearance of moisture or precipitation, the thermostat automatically turns on the system. As soon as it gets warmer, and the sensors “report” that there is no precipitation and ice, the system will go into “standby mode”.
For example, in the Teploskat system from CCT, the PT200E controller ($186, together with automatics- $230) to which a digital temperature sensor, a water sensor and a precipitation sensor are connected. The controller monitors not only the specified temperature range, but also the presence of precipitation in the form of snow. The precipitation sensor, made in the form of a “cup” with heating and two contacts that close when snow gets on them, gives a signal to turn on the system during a snowfall. The cables heat up, the snow and ice in the gutters and trays begin to melt, the melt water flows down. If the snow has stopped, the precipitation sensor transmits a corresponding signal to the control cabinet. But at the same time, the system still acts on the water sensor, which is installed in the lowest place (somewhere near the drainpipe) to control whether all the moisture is on the glass. After all, it may happen that heavy snow will fall for a short time. It will stop going, but it will still take some time for the melt water to go down freely along all inclined planes. It turns out that the main work is performed on three sensors. A situation may arise when there is no snow, but at 0
The temperature sensor is installed in the shade, in a ventilated place, away from heat sources, air conditioners, chimneys, so that the measurements are the most objective. The precipitation sensor is best placed in an open area so that nothing hangs from above. It is advisable to choose a place of installation so that in case of strong wind the fallen snow does not blow off the sensor. Finally, the water sensor is placed at the lowest point in the drainage system. You should not discount the “orientation” of devices to the cardinal points. It is advisable to put the water sensor on the south side, because it is there that the water begins to melt during the thaw. As a rule, one set of automation is mounted on a country house.
Installation and cost
You can order the design and installation of a cable system in a specialized company. In principle, there are not so many of them. If you decide to deal with icicles, it is better to call a specialist on the spot. Departure, measurements and calculation, as a rule, are free (but a number of companies charge $fifty). In order to find out the approximate cost of the system by phone, you need to know at least the total length of the trays and downpipes and tell in a nutshell what kind of roof you have. If the roof is simple (two or four slopes), the length of the trays and pipes is known, you will most likely be told quite accurately how much the work, materials and equipment will cost. If the roof is complex, it is difficult to talk about anything without going to the site and taking measurements.
But the specialist will measure individual heated sections of the roof, try to identify areas that are dangerous in terms of snow accumulation and ice formation. The height of the building is also determined; length, height and width of the roof; roof pitch; length and diameter of drainpipes; length and dimensions of trays, gutters. FROMyou will discuss the location of the heated areas of the roof, evaluate the specific heating power for all nodes of the system, the number of threads and type of heating cable, and, if necessary, discuss the algorithm of the system.
The issue of fixing the heating cable in the drain channels is very important, since it is not enough just to throw the cable into the tray- it should lie exactly in the place where the water flows. Some installers offer “proprietary” plastic fasteners from cable manufacturers. Installation in this case is quick, and you will be charged less money for the work. But if the plastic fasteners are of unknown origin, they will last one, maximum two seasons. Other companies use strips of galvanized sheet, from which special clamps are bent. They are attached in such a way that they do not leave any damage in the trays (at the top of the pipe).
The higher the skill level of installers, the fewer holes in the roof. ATtrays and pipes do not make holes, the wires are fixed with fasteners in the upper part. BUTif the cable is laid on the roof, it makes sense to install snow retention (the latter is “attracted” to the roof sheathing using self-tapping screws or anchor bolts).
Installation technology depends on the material of the roof. For example, cables are usually not laid out on natural tiles, since almost no ice forms on its surface. Due to the fragility of the material, walking on the roof and drilling holes in it is quite difficult, so only trays and pipes are heated.
If the roof is covered with metal tiles, make sure that the number of holes in the roof is minimal. Many companies (SEMRIS, KPD, CEILHIT) in this case, first stick a rubberized fabric on the roof, to which the heating cables are attached. Soft roofs are good with a thick roofing cake, the role of additional protection here is played by a continuous layer of moisture-resistant plywood. If, as an addition to the heating of gutters, snow retention devices are to be fixed on such a roof, a conscientious installer will ensure that all openings are carefully sealed with sealant.
When it comes to the comparative cost of anti-icing systems for roofs based on resistive and self-regulating cables, a fourfold difference in price does not mean that the total cost of the systems will also differ several times. After all, many components (control cabinet, power supply system, fasteners) are the same for all types of heating elements. So the difference is not so big: a system with self-regulating cables is 30–40% more expensive.
Control gear from different installers is represented by different brands, but in any case, these are products of reputable manufacturers: ABB, LEGRAND,
How much does it all cost together? For example, the snow melting and anti-icing system from SIM-ROSS based on NEXANS cables (Norway) provides for laying cables with a capacity of 35–40 mm in standard gutters and gutters.W / m, and along the edge of the roof (band 50–60 widecm) cable power density 300–350W/m2. Thus, say, for a roof with a perimeter of 60m (the area of one floor is 200m2) height 12m with four drains you will need a system with an installation capacity of 12.2kW. Considering that there are approximately 35–40 days in a year when weather conditions contribute to the formation of ice and snow, it is possible to determine the electricity consumption for the season. When used as a “weather station” control system, this indicator will not exceed 6–10thousandkW
The basic cost of installation for different installers ranges from 30–35 to 50% of the cost of materials and equipment (for a one- and two-story country house). If high-altitude work is required related to the construction of scaffolding, the installation of towers or aerial platforms, then these services are paid separately.
Service maintenance costs about $100–250 per year. During routine maintenance, a company specialist inspects the external condition of the heating sections, tightens the contacts in the terminal boxes, tests the control cabinet and the operation of all automation. ATMost of the work is carried out in the summer or in the off-season, before bringing the system into “combat readiness”.
But be sure that with the advent of cold weather, you will not have to independently wage a hopeless battle with ice on the roof. Modern technology has achieved much greater success in this matter.
The editors would like to thank the representative offices of RAYCHEM, DEVI, CEILHIT, as well as SAMRIS, SPECIAL SYSTEMS AND TECHNOLOGIES, KPD for their help in preparing the material