- Icing system components
- Choosing a heating cable
- We design the system
- Standard heating zones
- Power calculation
- We carry out commissioning works
The success of self-assembly of an anti-icing system depends on the correct choice of components and proper placement of elements. We figure out which wires to choose, where to lay them, how much power is needed and how to calculate the required amount of materials.
The anti-icing system prevents the accumulation of snow, the formation of ice on the roof and elements of the drainage system, ensures the proper operation of the drainage system in winter and spring seasons.
As long as the snow is clear, it reflects most of the sun’s rays, but as soon as there is a minimal coating of dust, the heat absorption increases significantly. The snow begins to melt from below. The ice crust is irreversibly thickened. The process takes on a serious scale in spring, when the air warms up to +5 during the day and minus 5–10 at night. In winter, warm areas of the roof help the sun – they melt the snow, melt water turns into ice under the influence of low temperatures. It is not as easy to melt ice as snow – the heat generated by the roof is not enough for that. But it is enough to form an even larger crust of ice..
The anti-icing system heats the snow-covered areas. Melt water goes through the drains. The main task of anti-icing is to ensure free drainage of melt water. Cables are laid all the way.
Icing system components
The system consists of a cable, junction boxes, an information and distribution network (sensors and wires that supply power and transmit information to the control unit), a control unit.
Additional parts (for installation):
- construction hair dryer;
- mounting tape;
- set of KTU;
- couplings for installing cables into pipes;
- clamps for fixing cables to pipes;
- clamps for fixing cables in troughs;
- glue (polyurethane) for fastening building materials.
The KTU set includes an end sleeve, tubes connecting the cores and braiding, heat-shrinkable tubes. Whether a kit is needed is decided after the choice of the cable: sometimes it is terminated at the factory, and this part from the kit is no longer required. Tubing and mounting tape sold separately.
Mounting tape can be self-adhesive adhesive, aluminum, copper. Metallic tapes are preferred because they transfer heat from the cable to the heated surface, increasing the efficiency of the system. Aluminum is the best option (copper is several times more expensive).
If the length of the downspout is about 6 m, you will need a steel cable and clamps: the cable must be lowered into a pipe with a cable (to avoid the wire sagging under its own weight).
The heating part of the system is equipped with an RCD. If the system is divided into sections, an RCD is needed for each (10 mA machines can be used).
Choosing a heating cable
For heating roofs and gutters, resistive (Latin: resistere – to resist) cables are used. Heating occurs due to high resistance, which transforms electrical energy into heat. Resistance can be constant or variable, which means that the cable is unregulated or self-regulating. In many stores, it is divided into resistive and self-regulating. In this case, a resistive cable should be understood as a cable of constant resistance..
Unregulated cable is available in single-core and double-core. A single core may not even be considered:
- The need to connect at both ends creates difficulties in both design and installation.
- The cable cannot be cut – if you bought 150 m, you need to lay all 150 m and go back to the connection point.
A two-core cable is easy. Connecting two ends at one point is not required. But this is the only plus, and then relatively single-core. An unregulated cable works at full power no matter how much heat is needed. In the event of a malfunction, the cable cannot be repaired – the entire section will have to be replaced. The anti-icing system will have to be divided into many sections, which will significantly complicate both design and installation.
Self-regulating cable consists of two cores, matrix, insulation, braided shield, outer protective layer. The matrix is fundamental. It reacts to a change in temperature – this is a property of semiconductors: when heated, the resistance increases (the current is less – the heating is less), when it is cooled, it decreases (the current is more – the heating is more).
Do I need to equip a system based on self-regulating cables with thermostats and sensors? Necessary: after reaching the desired temperature, the cable does not disconnect – it continues to maintain this temperature, consuming electricity (albeit with minimal power) when it is not required. To prevent the system from working idle, thermostats and relays are introduced into it, turning on and off the current supply as necessary.
A cable with a constant resistance is significantly cheaper, but much less economical than a self-regulating cable. The cable must be bought once, but the electricity meter ticks permanently.
Manufacturers offer ready-made sections, they just need to be connected. With such sections, you can mount a mixed system: use cables of both types, installing self-regulating ones in difficult areas, and unregulated ones – on simple ones, where crossing wires is technically impossible. But is it necessary? Self-regulating cable was very expensive when it first came out. Now the difference is not so significant.
We design the system
For specialists, the design of the system begins with a study of the drawings provided by the customer, and the heated areas of the roof must be indicated on these drawings. Theoretically, all the schemes should remain in the hands of the owner of the house, after the builders finish their work (or the owner himself, without the drawings, the roof is not built).
At the second stage, it is necessary to form a list of hazardous areas most prone to icing. Then determine the height of the building and the roof, the width and area of the roof, the slope of the roof, the diameter and length of the downspouts, the dimensions of the gutters and trays.
Standard heating zones
- Endows and other joints (windows, attics, etc.).
- Elements of the drainage system: water cannons, gutters, trays, funnels, pipes, bends.
- Elements of the drainage system: drainage and drainage gutters located under the downpipes.
- Gutter and pipe connection areas.
- Heat-generating surface areas.
Around the funnels provide a meter (1 m2) heating zone. Skylights are lined with a cable around the perimeter and along the path of the outflow of water.
The cable is laid over all elements of the drainage system. If there is a storm sewer, they heat the water path to the collector, the cable is lowered below the freezing point of the soil.
Heating tray and downpipe
Having determined the heated area, they draw a layout diagram and use it to calculate the amount of cable, the total power of the system. Here are some figures based on practice. The cable is laid:
- along the gutters – at the rate of 200-300 W / m2;
- into drainpipes (diameter up to 100 mm) – cable at least 28 W / m2;
- into drainpipes (diameter over 100 mm) – cable at least 36 W / m2;
- in valleys (2/3 from the bottom) – 250-300 W / m2;
- in trays (width up to 100 mm) – cable at least 28 W / m2;
- in trays (width over 100 mm) – cable at least 36 W / m2;
- along the edge of the cornices – 1 cable at the rate of 180-250 W / m2;
- on droppers – 1–3 cables at the rate of 180–250 W / m2.
On the eaves, the cable is laid in a zigzag, observing the minimum bend specified in the instructions. The calculation is simple: according to the layout, they determine how much cable is needed, according to its number – the total power of the system.
Cable routing in the valley and on the eaves
The control system is a ready-made module. Wires from temperature and precipitation sensors are connected to it. The precipitation sensor is a heating element with 2 electrodes. Snow, falling on a warm sensor, melts, melt water changes the resistance between the electrodes – a signal about precipitation is sent to the control unit. For greater savings, moisture sensors are used that work as precipitation sensors. They are installed in trays and gutters. When the water leaves these areas, the system will shut off the sections (applicable in a multi-section system).
Connecting sensors to the control unit: 1 – temperature sensor; 2 – control unit; 3 – precipitation sensor; 4 – water sensor; 5 – heating cable
With sectional configuration, it is possible to use independent relays responsible for the operation of a section up to 30 m long.
We carry out commissioning works
Functional tests must be carried out prior to commissioning the anti-icing system. Since the system mainly works in standby mode and turns on when necessary, checking it in the summer is futile. In the warm season, you can only check the control equipment, and even then you will have to simulate precipitation (water is simply dripped onto the sensors).
The tests should be carried out at the beginning of autumn. Verification steps:
- insulation resistance test;
- equipment check;
- trial inclusion;
- setting of thermostats;
- working inclusion.
The resistance of the cable and insulation is checked with a megohmmeter (if it is not there, you need to purchase it: the system must be checked periodically). The RCD is checked by pressing the test button “T”. The minimum and maximum temperatures are set on the thermostat. It makes no sense to operate the system at temperatures below –20 ° C, as there is no precipitation in cold weather.
We recommend checking every year in early autumn: if there are cable faults, it is better to detect them in advance – before the use of the system becomes necessary.
Important! Cable routing on the eaves does not eliminate the need to install snow guards.
Installing the de-icing system yourself is not that difficult. The main difficulty is working on the roof. We recommend that you familiarize yourself with the safety rules and strictly follow them.