- How snow melting systems work
- Cable or tape
- Standard and typical systems
- Roof and gutter installation
- Electrical connection and control
Too much snow may fall. In such cases, it is no longer necessary to talk about additional insulation of the roof with a snow cap, the main thing is to prevent overloading on the rafter system. One of the best ways is to melt snow using special heating systems, which we will talk about in this review..
How snow melting systems work
Some types of roofs with solid thermal insulation practically do not receive heat from the inner layers, and a lot of snow accumulates on them. This can be a serious problem, especially if your region is prone to heavy rainfall. If in winter the air temperature constantly changes from positive to negative, then the danger can also come from icing. Snow definitely requires removal on roofs with a slope of less than 6 ° and with a rough surface.
Where manual snow removal is impossible, previously it was necessary to knowingly allow heat leakage through the ceiling and roof, which led to its useless waste in the absence of precipitation. You can use energy more productively with roof heating systems.
Their organization is extremely simple: a heating element is laid under or on the roof covering. Power is supplied only when excess snow accumulates on the roof. Using different temperature regimes, it is possible to cause partial melting and flow of melted snow into the drain, or local controlled snow removal from the roof. Mainly heating as anti-icing is organized by:
- along the cornice;
- on the drain;
- along the valley;
- around the perimeter of skylights.
Cable or tape
The design of snow melting systems is identical in design to an electric underfloor heating. Heating can be carried out both with a resistive cable with high resistivity and with a film with graphite conductive tracks. Cables are classified into:
- passive with constant power;
- self-regulating, changing its resistivity depending on temperature.
Not to say that any of the systems has pronounced advantages, it’s just that they are convenient under different conditions of implementation..
The obvious advantage of a resistive cable is its relative ease of installation. In this case, the risk of damage to the conductor by the fastening material is minimal. However, the connecting elements of the system, and there are much more of them than on a warm floor, can heat up too much due to the increased resistance at the point of contact.
Roof heating cable system diagram: 1 – drainpipe; 2 – gutter; 3 – cable fastening clips; 4 – valley; 5 – heating cable
It is optimal to use cables on roofs with a metal support system and non-combustible insulation. When used on wooden roofs, additional protection measures and the use of a containment cable will be required.
In self-regulating cables, the active heating element is a semiconductor polymer matrix located between two conductive wires. Its efficiency is higher, and the cost of electricity for heating the roof is less, due to the variable power consumption depending on the ambient temperature. However, its cost is much higher than a conventional resistive element..
Self-regulating cable: 1 – conductive conductors; 2 – self-regulating conductive matrix; 3 – thermoplastic insulation; 4 – metal braid; 5 – external insulation
The film provides uniform heating, which leads to the simultaneous melting of the snow layer and its descent. This allows you to turn on the heating less often, saving energy, moreover, for the film, the power limit per square meter is higher – up to 100 watts. Nevertheless, the film is not always suitable due to its high cost, the likelihood of breakdown when fixing the coating, and also due to the insufficient widespread use. It can only be fixed under roofing material.
Standard and typical systems
Conventionally, snow melting systems are divided into open and hidden installation complexes. The first type is popular due to its ease of installation and almost complete independence from the roof structure. However, it is impossible to break the roofing, therefore the fixing of the heating element is often very arbitrary..
For surface mounting, only a heating cable is used, usually paired with a system of snow retainers, so that the avalanche-like icing does not harm the system. As a rule, in open systems, only an area 1–1.5 m from the eaves overhang is heated; on long slopes, heaters are installed just above each line of snow holders.
Concealed systems are often film-based. The exception is projects in which the cable is laid in the gaps between the sheathing boards. The heating elements of such systems are completely isolated from the external environment, they are more durable and do not spoil the appearance of the roof..
For flat operated roofs, this is the only option. But for a flexible roof, this approach is completely inapplicable: even if the installation is carried out under a layer of solid crate, there is a high probability of damage to the elements by fasteners.
Heating systems for overflows, gutters and hidden rainwater systems are performed with an exposed heating cable. The system is laid through all downpipes and excludes re-freezing of snow and ice that melted on the roof.
Roof and gutter installation
It is recommended to use heating systems, fasteners for which are installed in the course of the installation of piece roofing elements. Long plates or knitting needles can securely attach to the sheathing and support the cable without breaking the cover.
There are other ways to secure the heating cord:
- on stretch marks;
- using a mounting plate;
- by chemical fixing of brackets to the surface.
The choice between installation methods depends on the type of roofing, the slope of the slope and a number of other conditions.
To mount the cable in the gutter of the drainage system, use arches-clips attached to the wall of the drain by means of rivets. In vertical pipes and blind ducts, the heating cable is folded in half and mounted together with a stainless or anodized chain, to which it is connected with plastic clips. To support the cable, a suspension on a steel spoke is used, the opposite end is looped 10-15 cm from the bottom mouth of the drain and is attached to it.
Electrical connection and control
The greatest difficulty in the installation of anti-icing systems is the assembly of switching and automation devices, as well as the distribution of power cables. There are two parts of the contour. Warm is a heating cable or film, and cold is a copper wire supplying it with stranded cores with foamed vinyl insulation.
Cold wires should be wrapped in PVC corrugation, resistant to ultraviolet radiation and temperature extremes. At the junction of the two zones, insulating plates are installed with subsequent sealing. Cold wiring runs along the wall of the building or eaves to the junction boxes, which are connected by thicker conductors to the output terminals of the control unit.
To operate the system in automatic mode, two sensors are used – precipitation (humidity) and temperature. The temperature sensor is mounted on the north side of the house and connected by a signal wire to the control unit. It is also possible to install a second temperature sensor directly under the roof at the location of the heater. This allows you to limit the maximum heating temperature and save a significant part of electricity..
Automatic roof heating control system: 1 – humidity sensor; 2 – temperature sensor; 3 – controller (control unit); 4 – heating cable
The humidity sensor can be integrated into the temperature sensor, sometimes it is also placed in a blind section of the drain. The principle of operation is to turn on the heating of the roof when precipitation appears and turn it off when they are gone. Temperature monitoring is not performed for active cables.
The control unit can consist of a complete device including a controller and a relay group, or it can be recruited from modular devices. In the latter case, a DIN 35mm rail mounting technique is used. The assembly includes a timer, multi-pole contactor, thermostat and protective automatics, and when operating at low voltage, also a power source.