- How to make an external entry for electrically heated water pipes
- HDPE pipes and their features
- Self-regulating cable – what is it
- The procedure for carrying out work on the arrangement of the insulated input
- Useful Tips
The article is devoted to new opportunities for equipping non-freezing pipelines and the use of self-regulating electric cables for the device of external water inlets in individual houses. The technology of the work and the materials required for this are described in detail.
How to make an external entry for electrically heated water pipes
When arranging a water well outside the boundaries of the house in areas where groundwater comes close to the surface, and there is no way to dig a trench for laying external water mains below the level of soil freezing, the problem of protecting water pipes from frost becomes urgent. In addition, houses in such areas are built on shallow foundations. In fact, such a foundation is nothing more than a sand embankment, limited along the perimeter in one way or another from spreading. Any attempt to bring a pipe into an already built house is fraught with sand sprinkling into the trench and breaking the stable structure of the building. In this case, equipment for external water input into the house is required. Existing methods of passive isolation are effective up to temperatures of the order of -20.
The same problem arises if you need to bring a water supply to a building built on a columnar foundation, the design of which assumes that the structure is located above the ground level and there is a gap between the floor and the ground. An example of such a structure is a log bath, which is usually installed on a columnar foundation. In both of these cases, it makes sense to combine passive pipe insulation with active one. These frost control measures are especially effective in combination with HDPE pipes used for outdoor work everywhere..
HDPE pipes and their features
HDPE is the abbreviated name for the term “low pressure polyethylene”. This plastic has revolutionized, replacing metal in the production of pipes for all kinds of purposes. Important features of the HDPE pipe are:
- Complete absence of corrosion;
- Polyethylene pipes stretch without changing their properties (when water freezes in a PE pipe, it does not fail, these pipes are insensitive to ground movements, for example, during an earthquake);
- The inner walls of the pipe do not retain scale, products from the transported liquids do not settle on them;
- HDPE pipes are very light compared to steel pipes. With the same mass, the length of the HDPE pipe will be 5-7 times longer;
- The working lengths of small-diameter PE pipes significantly exceed the lengths of steel pipes, and butt welding of polyethylene is much easier and cheaper;
- Fittings for HDPE pipes are very easy to install, reliable and do not require auxiliary equipment.
Practical experience shows that PE pipes freeze for a long time. It happens that the frost has already subsided and it seems that you can take a breath, but it was not there – the pipe completely grabbed. They seem to accumulate cold and no insulation can prevent this process..
HDPE pipes thaw for a very long time. And if you do not take action, then under natural conditions, even at positive temperatures, this may take several days. To speed up this process, you can pour boiling water on the pipes, but the easiest way is to prevent them from freezing at all. To do this, equip the external water inlet with a self-regulating electric heating cable..
Self-regulating cable – what is it
The idea of using electricity to prevent frosting of stair steps, eaves and other external structures has been used for a long time – about 15 years. But they decided to use such a cable to protect pipelines from freezing recently – about five years ago..
The photo shows the packaging of such a cable from one of the Russian manufacturers.
The cable itself outwardly differs little from the cable used for floor heating in houses. It also consists of a warm section, end and transition couplings, and a cold section. The difference is that it is flat (this is due to the need to ensure the maximum possible contact area with the pipe), and the insulation is made of a very strong polymer.
There are professional cable options that are capable of keeping volumetric structures under control (large containers of water, industrial pumping equipment, etc.). Their maximum heating temperature reaches + 195! For home use, sections with a maximum operating temperature of 65 degrees are quite suitable. The power consumed by the section is low – about 20 W per meter of cable. Both continuous operation and thermostat control are allowed. The section has three terminals – yellow-green (ground), brown or black (phase) and blue (neutral wire). Operating voltage of sections 230 V.
The procedure for carrying out work on the arrangement of the insulated input
Let us consider the technology of equipment for an insulated external input using the example of a bath installed on a columnar foundation. An ejector pumping station is installed in the bath, which takes water from an artesian well located at a distance of 5 m from the entry point, and feeds it into the pressure water main supplying a residential building located at a distance of 12 m from the bath. All highways are laid in trenches at a depth of 1.3 m, rising almost vertically to the pumping station and passing through an open area between the ground and the floor of the bath. The complexity of the input device is that it is necessary to simultaneously protect three pipes from freezing. All pipes are made of HDPE. One 32mm pipe and two 24mm pipes.
This system was in operation for 4 years and had passive insulation in the form of sealed bags with mineral wool 10 cm thick. The thermal resistance of the insulation, revealed experimentally, was -24 degrees. At temperatures close to -30, all three pipes froze. In order to avoid such problems, it was decided to secure himself and install a self-regulating cable..
The photo shows the beginning of work. All three pipes were dug to the depth of the laying, and the old insulation was removed. It is noticeable that the pipes go under the bathhouse and enter through the ceiling inside.
For passive insulation of all three pipes, it was immediately decided to pass them all through a piece of pipe with a diameter of 150 mm with external insulation made of polyurethane foam (PPU), which is used when laying standard heating mains of central heating systems
The photo shows a piece of such a pipe, already cut to size.
To pass a pipe of this diameter through the ceiling, a 270 mm hole had to be cut in it. All three pipes had to be disconnected from the pumping station without draining the water from them. The view from the bath to the cut-out floor and the disconnected pipes is shown in the photo below..
To improve thermal conductivity, the pipes must be pasted over with aluminum tape. This operation will prevent local overheating. Indeed, one of the disadvantages of HDPE pipes is their low heat resistance. Although practice has shown that they tolerate steep boiling water well. That is, they are not really afraid of temperatures up to 100 degrees. Polyethylene softened only a little, but did not lose its shape.
Now it is time to attach the cable section to the pipes. Considering that the lowest point of all pipes lies below the freezing depth, it was decided to use one cable 4 m long. With a pipe diameter of up to 50 mm, you can fix the cable along the pipe. Otherwise, the cable must be wound in a spiral or even loop. The cable itself is fixed to the pipe with the same tape..
Below and above, the transitions from one pipe to another are made by air. The cable must be distributed in such a way that the cold side of the section starts from the place where the pipe ends.
On top of the self-regulating cable, insulation for pipes must be put. This operation is easy to do. The main thing to remember is that the insulation is already pre-cut along the length and you only need to tear it at this place and put it on the pipes. So that it does not crawl, it must be additionally fixed with tape..
Now all pipes can be passed through the passive insulation section. A piece of PPU pipe must be carefully put on all three pipes without damaging the cable. To limit the course of this massive part, you can screw in several self-tapping screws around its perimeter, which will catch on the floor and prevent it from going further and deform the HDPE pipes below.
It remains to connect to the pumping station, check the heating cable by applying power to it, and wait for winter, which can now be met fully armed. After all, pipelines equipped with a self-regulating cable can easily tolerate frosts down to -60.
If it so happens that the HDPE pipe is frozen, and you have not yet decided to equip it with electric heating, then you can warm it up with boiling water or a technical hair dryer. It is best to pour boiling water inside the pipe, having previously disconnected it from the nearest fitting. The frozen pipe thaws very slowly, and the boiling water cools down quickly. Therefore, the water from the pipe must be pumped out every 3-5 minutes through a hose of a smaller diameter in a chauffeur-driven manner and boiled water must be refilled.
A technical hair dryer must be used carefully, quickly moving a torch of hot air along the pipe so as not to melt it. After all, the temperature at the outlet of the hair dryer can be above 600 degrees!
The electric heating system must be turned on with the onset of stable frosts and must not be turned off again until the arrival of spring. Only, as a last resort, thawing of the frozen pipe is allowed by connecting the cable.
To protect the system from freezing, if it is not equipped with a self-regulating cable, you can open the tap and let water in a very thin stream so that the pumping station turns on no more than once every five minutes. This measure helps well, but the resource of the station is greatly reduced at the same time.
Don’t rely on electricians in winter. You need to have alternative sources of power supply in an individual house – a battery UPS and a small power plant.