Precipitation in the form of snow, while on the roof, do not represent any particular risk. However, if the conditions for melting snow under the influence of a heat source, it is converted into water. If the resulting meltwater no way for the rapid withdrawal from the roof, then upon the occurrence of a negative temperature it freezes, turning into ice. Since the necessary conditions for the melting (melting and speed) of ice and snow are quite different, the next short-term and widespread action not heat source may not melt, but rather increase the ice plugs. Such ice formation mechanism may lead to the formation of ice jams, congestion long icicles and tens of meters and weighing hundreds of kilograms.

The sources of heat are:

1. The atmospheric heat. Diurnal temperature range with an amplitude reaching 15 ° C, and fluctuations in the range of + 3 – + 5 ° C during the day to -6 – 10 ° C at night are the most favorable conditions for ice formation. In the spring added to them radiation from the sun. Although the surface of ice and snow reflect most of the radiation incident on them, even a small plaque dirt absorption coefficient increases sharply. In addition, rapidly heated to bare areas roof, and melting is the inside of the layer. Therefore, the formation of ice in spring is more intense.
2. Proper heat of the roof. Heat occurs on any roof. The minimum extent it is observed on the roofs with ventilated attic ( cold roof ). However, common in recent years the use of attic space to living (the attic) or technical floor equipment (which is set a large number of powerful equipment for heating, ventilation and air conditioning) dramatically changes the requirements for the traditional design of the roof, which is not always taken into account by designers and architects. The lack of effective thermal insulation and no air holes lead to the fact that under the surface lying on the roof snow (which is a good thermal insulator) is constantly slowly melting it, and this process takes place at all but the most roof surfaces of its edges. Such a roof can be called warm . They are characterized by the formation of ice in a wider temperature range, which can actually mean danger sosulkoobrazovaniya almost the entire cold season (for Moscow).

deicing systems work at temperatures below -15 – 20 ° C, usually not needed

First, at these temperatures is not icing mechanism according to the first and dramatically decreases the amount of moisture in the second. Secondly, under these conditions, the amount of precipitation in the form of snow is also decreased. Thirdly, for melting snow and moisture by diverting the path of sufficient length need greater electrical powers.

In the development and installation of de-icing system must be borne in mind that the designer must ensure that the water, which appeared as a result of the system, a clear line pending complete withdrawal from the roof and gutters of .

There are also borders of installed capacity heating part of the system, defined on the basis of practice, failure of which leads a non-working system in this temperature range, a significant excess only leads to overspending electrical power without any improvement of the system.

On the horizontal parts of the roof total power density per unit surface area of the heated part (tray, trough, etc.) must be at least 180 – 250 W/sq.m.

The linear power heating cables in gutters must be at least 20 – 30 watts per 1 meter length of drain and increases with the length of the gutter up to 60 – 70 W/m

All of this allows you to make a few general conclusions:

1. De-icing systems work mainly in spring and autumn periods, as well as during thaws. The system is in a cold period (-15 – 20 ° C) not only unnecessary, but can be harmful
.
2. The system should be equipped with temperature sensors, precipitation and water and the specialized thermostat, which can be called rather minimeteostantsiey. He must manage the operation of the system and prevent the possibility of adjusting the parameters of temperature taking into account the specific characteristics of the climatic zone, the location and number of storeys of the building.
3. The heating cables should be installed on all the way thawed Water from the horizontal gutters and with trays, and ending with output of gutters and in the presence of the entrances to the storm sewers & mdash; up to the entrance the collector below the freezing depth.

See. image

standards installed capacity of heating cables for various parts of the system — must be fulfilled; horizontal troughs and gutters and vertical gutters.

The components of the system

Deicing system includes:

1. heating part, consisting of heating cables and accessories for mounting them on the roof and directly performs the task of translating snow precipitation or frost in the water up to their complete removal. The structure of the heating part may comprise a funnel with built-in heating elements snow guard interacting with the heating elements.
2. distribution and information network, providing food for all elements of the heating and holding data signals from the sensor to shield the control system. The system includes power and data cables that meet the criteria Work on the roof, junction boxes and mounting elements.
3. control system comprising a control cabinet, a mini-weather station RT200E, temperature sensors, precipitation and water, starting and protective equipment, corresponding system power and performance of the class of the control cabinet.

Model Heated area

Typical heated areas of the system are:

1. Downpipes the entire length.
2. gutters and trays.
3. Gutters funnel and areas around them of about 1 m ² .
4. input nodes gutters in drainpipes.
5. Roof valleys (the junction line of the roof planes), other contiguity to the roofing plane — roof windows, lights, Attica.
6. water cannons and water-jet window parapets.
7. eaves.
8. Drip.
9. The surfaces of flat roofs and concrete drain tray.
10. Drainage and drainage trays in the ground under the gutters.

In picture an example of a typical heated areas.

The stages of design

design cabling « Teploskat » consists of several stages:

1. Getting the customer's drawings buildings and structures with the designation of the heated parts of the roof and gutters, with a specific purpose designed system of heating.
2. Photography and measurement of individual fragments of the heated sections of the roof.
3. The classification of these sites, followed by separation of characteristic zones, and dangerous (from the point of view of snow accumulation and ice formation) places.
   Hazardous locations are:
   • gutters.
   • Funnels and noted drainpipes.
   • gutters and trays, especially in areas adjoining to gutters funnels.
   • Roof valleys (the joints of planes of different parts of the roof), roof windows, lights.
   • Water Gun.
   • eaves.
   • Drip.
4. Defines the height of the building length, height and width of the roof, roof pitch, length and diameter of the drain pipes, the length and size of bins, chutes.
5. The technical project for the design, in which, based on existing experience and recommendations are determined heated roof area, set specific heating power for all system components; the number and type of thread heating cable, if necessary, refined algorithm of the system.
6. Calculate the required amount of heating cable, heated hoppers and the total electrical power system.
7. The possibility of disruption from the surface roof blocks of ice and icicles, slipping into snowdrifts, outlines solutions to prevent them, to the installation of snow retention, working in concert with de-icing system.
8. determines the type, quantity and parameters of heating sections and preliminary schemes of their layouts. Clarifies the power parameters of the heating system as a whole. Selects the fixings of a standard set. See. image .
9. Draws circuit heating sections layout.
10. Designs were developed power supply network and management system, taking into account the phasing requirements.
11. Available in a full package of project documentation, which includes drawings Layout of cable heating sections, drawings laying power and data cabling, sections wiring diagrams and craters, automation systems, passport on the system cable heating roof « Teploskat »
12. Developed a set budget documentation, if required by the contract with the customer.

System Management — bases and instruments

de-icing systems control algorithm must match the physical processes of ice formation on the roof.

The set to мини-метеостанции RT200E attached датчик outdoor temperature and датчик precipitation. Precipitation sensor is an element with two electrodes, equipped with preheater very small (5 watts) of power. When the snow gets on the surface of the sensor, it is melted and formed water from the snow changes the resistance between the electrodes and the system receives a signal of the presence of precipitation.

In some cases, are used датчики presence of moisture or water trays, based on the same principle. Their use allows to determine the time of leaving the water with horizontal roof pieces (trays and troughs), then you can disable them. This makes the system very economical to operate.

Security Requirements

The basic requirements are in terms of fire and electrical safety.

To meet them fulfilled several requirements:

1. The system comprises only heating cables have the appropriate certificates , including fire safety certificate.
2. The heating part of the system equipped with a differential or RCD machine with leakage current less than 30 mA (for the full requirements of electrical safety & mdash; 10 mA)
.
3. Complex de-icing system is divided into separate parts with leakage currents in each part does not exceed a certain value.

System Testing and evaluation of the effectiveness

The test de-icing system can be divided into two groups. Acceptance and periodicals

Acceptance tests, starting with the insulation resistance test heating and distribution cables. Tests the RCD (or differential automata). Are the appropriate protocols, with specific values. The most informative are tested on the operation, during which test the efficiency of the system. It should be noted that the anti-icing system are not instantaneous systems. They are designed to operate in standby mode, and includes just the appearance of precipitation. If the system was not included early in the season and were on the top layer of snow has accumulated, then it will take time from 6 hours to one day to remove it.

There are difficulties with the delivery of the system in the warm season. At this time, it checks that the operation of the control apparatus, simulated signals from the sensors is checked sistedy shift in load switching mode, turn off the trays, and then drains off.

The periodic tests are carried out, usually in early autumn to check the technical condition of the system and prepare it for operation. First of all, the insulation resistance is tested to identify the damaged areas, then checked the state of the equipment, held its trial inclusion. After checking thermostats settings including the operating system produced, and it remains a work in the & laquo; standby & raquo; mode.