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What is better for a private house - single-phase or three-phase input?
Electricity consumption in residential buildings is constantly growing. Each inhabitant of our country, in terms of per capita, consumes a daily amount of energy many times greater than the data, for example, fifty years ago.
In the middle of the twentieth century, in every private house there were just electrical appliances, an electric stove, several light bulbs, and, at best, a TV or radio. Today, household electrical consumers are simply dark in any residential building, and in private homes three-phase cable entries have become increasingly common. Many refuse a traditional single-phase network.
But in what three phase network advantages? And is it worth it to definitely give her preference?
Many believe that three phase network will allow you to consume more power, that is, turn on more devices. This is not entirely true. The maximum permitted power is indicated in the technical specifications for the connection. As a rule, for a three-phase network this is 15 kW per household, and for a single-phase network it is 10 or the same 15 kW. Obviously, the power gain is small, and may be completely absent.
However, one should not forget that at the same power for a three-phase network, an input cable of a significantly smaller cross section can be used. The reason is literally on the surface: power, and, consequently, the current is distributed in three phases, loading the phase wire separately to a lesser extent. Input Rating circuit breaker in a three-phase network, respectively, will also be smaller.
But these benefits are not significant. Is it really so important, what is the cross section of the input cable and the rating of the input machine? Much more important is the fact that the input switchboard for a three-phase network will have large dimensions.
The latter is due to the fact that three phase meter obviously more than any single-phase. In addition, the opening circuit breaker will occupy three or four modules (if the neutral conductor is also broken). Three phase RCD also differ in increased dimensions, so that the introductory distribution panel for several tiers for the "three-phase" is a common picture.
This is a flaw three-phase input into a private house. But the ability to directly connect three-phase power consumers to the network - electric boilersAsynchronous electric drives - this is a definite advantage. Any happy owner of a private house with three-phase input willingly uses this “handicap”. Indeed, asynchronous motors included in a three-phase network operate with the best energy and mechanical parameters. And powerful electric receivers - boilers, electric stoves, heaters - do not cause phase imbalance.
The “imbalance of phases” in this matter is a very sensitive topic. Since the mains network is always three-phase, and it is almost impossible to ensure the same load in all three phases, the phase voltage will never be the same. Performing a three-phase input will not help change the situation for the better - after all, besides you, there are a lot of different consumers in this network. But in your network, after the metering device, you need to distribute the load as evenly as possible. This places an additional responsibility on the electrician performing the installation.
In a single-phase electrical network, “phase imbalance” often causes consumers connected to an unsuccessful phase to put up with too low a supply voltage. The owners of three-phase input are not aware of such problems, since they can connect important, critical single-phase power receivers to the phase that did not undergo a drawdown due to a “skew”.
The operating voltage of the three-phase network is 380 volts.This is significantly higher than the usual 220 volts. Therefore, when working and operating a three-phase network, more attention needs to be paid electrical safety.
From the standpoint of fire safety standards, a three-phase input is also more dangerous, since the short-circuit current at a voltage of 380 volts will be much higher.
Thus, the disadvantages of three-phase input into a private house include:
1. The need to obtain permission and technical conditions for connection from a local energy retail company. This business is quite troublesome and can ruffle nerves, or even completely fail.
2. Increased risk of electric shock and fire hazard due to higher voltage. This increase in danger is not very large and noticeable. However, it will not be superfluous to install an additional three-pole high-rated circuit breaker immediately before entering the building, especially if the house is wooden. This will save from short circuit at the input.
3. Large dimensions distribution input board. For owners of large country residences, this drawback is not critical - they always have enough space. The rest should take this factor into account.
4. The need for installation modular surge arresters in the opening shield. In fact, such a measure for single-phase input will not be superfluous, but in the "three-phase" it is even more relevant. After all, your individual working zero is likely to break, and this will be fraught with overvoltage in at least one, the least loaded phase.
The advantages of three-phase input are:
1. The ability to redistribute the load between the phases, avoiding the effect of "phase imbalance".
2. The possibility of direct connection to the network of three-phase powerful power consumers. This is the most important advantage of three-phase input.
3. Reducing the current ratings of the input protective equipment and the cross section of the input cable.
4. In some cases, with a loyal attitude on the part of the energy sales company, an opportunity to increase the maximum permitted power consumption of electricity.
Thus, in practice, the implementation of three-phase input becomes appropriate for private houses with a living area of 100 square meters. meters and more. Then there are a lot of single-phase power consumers, and the load can be distributed as symmetrically as possible. Also, a three-phase input is suitable for those who plan to include powerful three-phase power consumers in the network.
For the rest, the transition to the “three-phase” is not a mandatory measure at all, it can only become the cause of an extra headache.
Alexander Molokov
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