Heating cable for sewer pipes: self-regulating for insulation and heating sewerage

The problem of freezing external sewage sewer communications are best addressed at the design stage by using insulation and having major portion thereof below the depth of soil freezing. But because of the great depth (greater than 1m) or presence, additional communications it becomes impossible. Risk of freezing is also subject of the water pipes and drains in places out of their home and the direct contact with the ground. Consequently, all these communications need to be protected from possible frost is not only the thermal insulation layer, but also the heating elements.

There are several ways of thermal insulation constructions for sewage systems with heating, without him, with their hands or without the help of professionals. One of the most popular and effective heating sewerage systems is heating using the heating cable.

Heating cables (types)

resistive

Produced in single- and two-wire performance. The basis of the product of this type is conductive (heating) wire, which during the passage of electric current generates heat by Joule-Lenz. The heating conductor is insulated, typically heat-resistant material (e.g., Teflon). In some types of double insulation. Next is the metal shielding braid in the form of a thin wire mesh or a foil. This shell protects it from mechanical damage, as well as a screen. The surface of the wire is covered with a heat-resistant coating.

It works like the cable way. If it is solid, then the power supply must be carried out with two sides (as shown in the figure below left), and a wire loop is uniformly distributed over the entire length, which is very inconvenient. bilateral power supply problem is solved in two-wire products, although the principle of action is similar, but perform the installation and connection is more convenient (below right). In addition to the two types must use the temperature control surface by means of thermostats.

Zonal

He is a kind of resistive, but rather a modified version of a two-wire. The modification consists in the fact that it added short segments of the heating spiral wires arranged with a certain pitch. Now, in contrast to its predecessor, it can be cut into desired lengths with a certain step.

self-contained

Is a wire with two parallel arranged, copper conductors, between which is a semiconductor. This construction is covered with a protective, electrically insulating and shielding. The resistivity of the electric current of the semiconductor is directly proportional to its temperature. That is, the higher the heating temperature, the resistance between the two conductors increases, and vice versa. As in previous articles, the heat is released by the same law (Joule) but not in the current-carrying veins, and share their semiconductor. Because the conductivity depends on temperature, then the current value will also change, and therefore the capacity. In fact, this lead to himself heater and thermostat on any portion thereof along the entire length. Accordingly, the amount of heat at each site will be allocated in different ways, so that irrespective of the external conditions the surface temperature will be substantially identical at each point.

Inductive

Such a heating cable comprises insulated electrical conductor wound around a ferromagnetic core, which is a pipe. The alternating current creates an alternating magnetic flux that induces eddy currents in it and it and they are heated.

This heating is considered obsolete and is now used very rarely. This is connected not only with low efficiency, but also to the fact that it can be applied only for the pipes made of metal.

Which to choose the heating cable for heating of sewer pipes

To address this question we compare advantages and disadvantages of the above-mentioned wire for heating. Resistive one-, two-wire zone and can be generalized because of their similarity.

Resistive and zoned heating cables

Advantages of resistance (including zone) heating cables:

• Easy device;
• Relatively low cost;
• With prolonged use, the stability of the resistivity;
• With proper installation long life.

Disadvantages:

• The inability to change the length (in the zone, this problem is partially solved, but the length is changed in steps);
• The need for thermal control device;
• In close proximity of the heating wires, as they weave and even if contaminated surface insulation overheats significantly. Overheating of the insulation leading to premature aging and the possible closure;
• Demands for installation.

Self-regulating cable

Advantages of self-regulating cable:

• It does not require a separate thermostat;
• Ability to cut any yardage long (not less than 1.5 m and no more of the passport);
• When mounting and allowed approximation crossing wires, which considerably simplifies the gasket;
• The temperature control takes place independently at each point along its length. This completely eliminates it from overheating;
• The surface temperature over the entire length almost identical.

Disadvantages:

• Compared with resistive, this product high cost.

After analyzing the advantages and disadvantages of different types of cables can be concluded that the self-regulating will be much more effective. In heating sewers and gutters with him except for the above-mentioned advantages can be achieved significant energy savings. This requires additional thermostat to control the temperature of the external environment.

Cable selection for sewer system

The required heating capacity is directly related to the heat loss of the heated tube. It is very important to make the right choice of capacity for the sewer system of the desired diameter and the conditions of its heat.

Important! The wrong choice can result in power:

1. When excessive power to overheating, due to which reduce the life of the heating system service. In the worst cases, drainage of plastic can melt. (When applying self-regulating heating cable is overheated completely excluded).
2. At low power - the system will not be able to withstand low temperatures, resulting in freezing drains.
3. To reduce the economic efficiency of heating.
4. Increased probability of hitting a human or animal electrocution.
5. Reduced service life of both the heating system and that most sewage.

When you are building your own hands sewer, designing its heating and insulation, you can be guided by the table below. It shows the average heat losses depending on the pipe diameter, the insulation layer and the temperature difference.

Power to the unit length taken equal to or slightly larger than the number which is found at the intersection of the desired thickness and temperature difference. Further, length of the pipeline multiplied by the number and the safety factor of 1.3, and then divide by the power cable on the passport - this will be a necessary length.

The reliability of the heating cable

The reliability of self-regulating cable is directly dependent on the quality of the heating array (semiconductor material between the current-carrying conductors). The lower the quality, the faster it gets old - as a consequence of reduced heat resistivity and self-regulation. The service life of such an array of low quality 3-4 years.

Proven manufacturers who care about their reputation, such as Fujikura, Pentair, Devi, Hemstedt use quality materials for production. This of course is reflected in a higher price, but his work throughout the service life (15... 20 years) is worth it.

The main stages of laying the heating cable

In private homes and in the production of the heating installation is carried out at the stage of warming sewer pipes. It is necessary to seal the joints to prevent seepage of moisture. The cable can be routed around the outside of the pipeline (for insulation) or inside it.

internal installation

Such a method of heating the sewage system has far more disadvantages:

• Increases the risk of clogging;
• The heating cable is constantly exposed to aggressive environments sewage (or need to shell out for the purchase of a more stable outer shell);
• To apply this method to the extended communication is extremely difficult;
• You must have an additional tee.

However, the way the gasket inside the pipe can sometimes be the only possible solution. Advantages:

• It is possible to heat the low thermal conductive pipe or the old system with considerable deposits on the walls;
• Conveniently heat in places partially sewage passing through the foundation;
• It is convenient to heat water and drains without thermal insulation.

Basic installation steps:

1. In order to introduce the cable into the sewer establish a special coupling nipple.
2. If no tee or holes for the audit, you can cut a small area, and then mount adapter required diameter.
3. Enter the desired depth of the cable.
4. The sewer pipe must be sealed. It is necessary to tighten the nut from the nipple and check for leaks.
5. Connect the cable to the mains. To do this in advance is necessary to provide a power socket nearby or circuit breaker.

External mounting

For outdoor installation of the heating cable has two ways - a stacking "wave" ( "helix") or along the pipe. Regardless of the method it is laid over the entire length. Higher concentrations stacking locations must comply with high risk of frost. Further, he appears in a warm place, and only then produces an electrical connection.

stacking spiral

This is the most versatile and probably the most effective way. Of course for this it is necessary to spend time and left to have the relevant experience. But this method allows for heating the water drain with the possibility in the future to modify it at a low cost.

Mounting principle:

1. For small length of cable is laid a spiral winding around the pipe. (Estimated length is distributed throughout the pipeline).

1. For large extents. Divide by the number of track sections to two times (approximately).
2. With the stock along the length of cable pre-fastened article.
3. The resulting loops wrapped around the pipe in the opposite direction from one another.
4. Conducting coil winding with a pitch of 30-50 cm.

By tube it is attached with adhesive or aluminum tape with step 0,5-1m or along the cable over the entire length. Aluminum tape is sealed to ensure complete sealing of the cable.

Laying along the pipe

This is a simple installation method, but the heating efficiency is slightly worse. The principle is laying you can see in the picture below. On one (left) and two (right) heating elements. Attaching the cable to the tube through the product 0,5-1m through or over the entire length as in the previous method.

When laying a system of sewer pipes in the ground must be the same insulation and additional heating. Furthermore it is recommended to use an external protective sheath. Self-regulating heating cable is recommended not to stick foil strip, and completely wrap it around the pipe as shown below.

Recommendations installation wizards

1. To improve the economy for heating pipes self-regulating cable sewer system must use an additional thermostat to control the temperature of the external environment.
2. It is necessary to ensure a reliable connection sewage junctions, to prevent the passage of moisture.
3. It is strictly prohibited to install an internal way cable products with conventional insulation.
4. Allowable temperature of the tube material and its insulation should be above the temperature to which the cable is heated.
5. The angles of rotation of the heating cable must comply spelled out in his passport.
6. During installation, the temperature at which the gasket is executed, must be higher than permissible.
7. At the time of the first inclusion of self-regulating cables in the electric power consumption it will exceed the passport several times. After that, a few minutes rate returns to normal.

At first glance, the installation of the heating cable is self-regulating to protect the pipe sewage system is very simple, but it requires knowledge of the relevant rules and regulations. By following them, you will be able to mount an effective and reliable heating system.