How to make grounding in an apartment
A special wiring that connects electrical equipment to grounding devices is vital in modern apartments. Grounding is the main guarantee of electrical safety. It eliminates the possibility of electric shock to a person who inadvertently touches the body of an electrical device in the event of a phase conductor breakdown or insulation failure. Moreover, all instructions for household appliances indicate that these devices cannot be used without grounding. If it is absent, the manufacturers will not be held liable for equipment breakdowns. They do not bear responsibility for any consequences associated with its improper connection. But how to ground in the apartment? What is the technology? And is it feasible in all apartments? The answers to these questions are presented in this article..
- Grounding for a new building
- How to ground in an old house?
- Reasons that preclude grounding
Grounding for a new building
Different houses use different grounding systems. Before starting grounding, you need to find out which of the systems is used in your home. In general, according to the rules that were adopted back in 2003, each building should be equipped with a riser of five wires, in which the 5th wire is just the grounding conductor. If everything is exactly so in your house, then you just have to separate the grounding wire around the apartment (the third wire in the cable), then put special ones everywhere ground outlets, and make a bathtub in the bathroom.
1. So, in new homes, this is, as a rule, a modern TN-С-S system (it has zero working and protective conductors, which are usually connected in the main panel of the building; then they are disconnected everywhere). In this system, 3 phases L are suitable for the access risers, as well as divided N (working zero) and PE (protective conductor). In this case, the connection process is much simpler, since the busbar already has separate buses designed to connect zero, phase and ground. And the ground bus has a metal connection with the body of the electrical panel.
Finding your home connected to this system (TN – C – S) is easy. Just look at the cable that fits the riser (introductory). It should have 5 wires:
- 3 phases, such as L1, L2, L3;
- protective zero PE;
- work zero N.
Connection is carried out as follows:
- the phase wire from the apartment is connected to the same bus where the previous old wire was;
- working zero N wire is connected to the bus with neutral wires;
- grounding PE wire (zero protective) is connected to the shield body.
Important! It is impossible to connect all grounding wires (which are in the shield) to 1 bolt (clamp)! It is necessary to use different bolted connections. It is better to use a bus: screw it to the shield, then connect PE.
It is also important to consider the following:
- with 3-phase input, absolutely all conductors must have the same cross-section (copper up to 16 mm2);
- up to 2 conductors of the 1st section can be clamped under a 1 terminal of the machine
- in order to obtain a uniform load, a 3-phase connection to the hob is preferred;
- all metal parts in the bathroom (pipes, floor heating screen, bathtub, etc.) and the grounding conductor of the outlet (of course, if there is one in the bathroom) must be connected to the DCS bus (or PMC), which should be located there. In this case, the outlet is powered by a 3-wire circuit;
- all PE conductors in the presence of mechanical protection should be 2.5 mm2 in cross-section, if not, 4 mm2. The conductor from the bus control system to the tire of the shield RE (better than the floor) – should be a cross-section of 6 mm2;
- it is preferable to separate the lighting circuits from the power (socket) circuits. However, mixed power is allowed. And the lines for all power plants (stove, oven, SM) should be separate.
2. In some new-type apartment buildings (since 1997), the TN-S system is used (neutral conductors (working and protective) are disconnected throughout). Such grounding is the most reliable. When connecting the house, the ground wire is laid separately, together with the phase, zero wires from the substation to the electrical panels of the house. Therefore, all the conditions in order to connect the ground to the apartment are already there. It is carried out in the same way as in TN – C – S.
How to ground in an old house?
In old houses, the TN-C system is usually found, in which along its entire length the neutral conductors (working and protective) are combined into one neutral conductor (PEN). The electrical equipment case (electrical appliance, shield housing or assembly) is connected to the PEN conductor. Such protection is called grounding. The grounding circuit is installed at the substation that supplies the house. 3 phases L are suitable for access risers, as well as a combined PEN conductor. All floor guards in such a system are nullified, and grounding is not provided for in them..
The electrical wiring in the case of single-phase power supply of the living space is carried out by 2-core cables (phase, PEN). Or 4-core cables (A, B, C, PEN) with 3-phase power supply of the apartment. There are no protective earth contacts in outlets.
This is the oldest and most common grounding system. It existed for a very long time in the USSR and, unfortunately, still continues to exist in many houses. Why “Unfortunately? But because with its use there is a serious threat of electric shock. Circuit breakers (protective switching devices) installed with the TN-C system protect e-mail. circuits (groups, lines) only from short circuit currents. But protection against electric shock is completely absent.
Important! If an electrical specialist recommends wiring using the TN-C grounding system, do not hesitate to refuse! She is completely unable to protect against electric shock! The operation of electrical appliances with such a system poses a potential threat to life! In addition, the PUE (paragraph 1.7.80) prohibits putting RCDs in this grounding system as the main protection.
According to the new standards adopted in 2003, in all old houses, the TN-C system should be converted to either TN-C-S or TN-S through modernization of power supply circuits (installation of a potential equation system). However, poor financing does not yet allow this in all homes. In most cases, energy supplying organizations act as follows: at the entrance to an apartment building, re-grounding the neutral wire is mounted. The PEN conductor is then divided into 2 separate wires:
- zero (N) working conductor;
- protective (PE) conductor.
Important! If you have a TN-C system, you can’t do anything yourself with respect to grounding, unfortunately! You can not build your own personal memory! Since it will be located outside the control room at home and may cause the appearance of stray currents. Therefore, you can only use the existing common house grounding system.
In other words, you must either completely re-equip all the house wiring to new standards, or use electrical appliances with a body made of non-conductive material. It is also recommended to install an RCD on the circuit that feeds the household appliances. Especially important – in the bathroom. UZO is not able to protect against electric shock, but it will save them from a fatal defeat.
Reasons that preclude grounding
- If grounding is not connected to water pipes, batteries, fittings and other conductive parts of the apartment, then dangerous voltage will appear between the equipment connected to such wiring and these parts. But even if you connect and grounding turns out to be good, then from these structures the equalizing current through the grounding will go through the entire apartment. Such currents can be very large, so if PEN (main earthing switch) is violated, there will be a danger of fire due to over currents. But that is not all. In the event of a voltage appearing on the housing of electrical appliances, grounded by means of a battery or a water pipe, all pipes and batteries will come under voltage, including in neighboring apartments. As a result, the neighbor who decided to pour water from the tap can die with electric shock! On the prohibition of the use of pipes is written in PUE 1.7.110.
- Also, it is impossible to simulate the “grounding” circuit by connecting the “zero working” to the “zero protective” conductor in the Euro socket. This is extremely dangerous. There are frequent cases of combustion of the “zero working” conductor in the shield. And this leads to the fact that on the computer case, refrigerator, etc. placed 220 V. Naturally, the consequences will be the most sad.
- The only exception is grounding “to zero”, which is done in houses specially equipped for electric stoves. However, this should be done only after carefully studying the zero conductor per section (at least 16 quadr. For aluminum), as well as continuity (according to PUE 7, paragraph 1.7.131). A qualified electrician must do this..
Thus, we see that in some cases it is not easy to ground the apartment. Everything will depend on the system that is applicable throughout the house. And if it is a TN – C – S system or TN – S, then you can ground yourself yourself (that is, conduct wires through the apartment). If this is an outdated TN – C, then in the case of a single apartment, even an experienced electrician will not help. It needs to be changed throughout the house..