Modern distribution cabinets can not be compared with those that were mounted in Soviet times. Shields in old-built houses are generally a problem area for electricians of service companies. There is no question of any protection for home networks, rather the opposite. The condition of most of them is truly dangerous. And the point here is not even the lack of automation, but in the methods of wiring. The absence of grounding and zero tires in the shields leads to fires and other emergency situations. It is worthwhile to understand why this happens.
What is a zero bus and why is it needed
So called brass plate with terminals, which is mounted inside the switch cabinet. It serves to distribute zero across apartment lighting groups and power lines. At present, the rules of the installation of electrical installations (PUE) provide for the mandatory installation of a zero bus in the shield in order to ensure the absence of its gaps throughout. With good contact on the bar, protection against reverse heating is achieved.
Everyone who once disassembled an old outlet, noticed a burning of insulation on one wire in the absence of such signs on the other. Any experienced electrician, barely looking at something like this, will say that the blackened contact is zero, and he will be absolutely right. It is he who accounts for the main load, which is much higher in the power cabinet. It is to prevent such situations that the zero bus in the shield is required.
Rules for installing and connecting the contact strip
A similar terminal block can be installed in any easily accessible place of the power cabinet. The connection of the zero bus in the shield is as follows. An input zero is supplied to the fixed bar. The contact is tightly fixed. After that, all zero wires going to the apartment groups are clamped to the terminals. From the zero bus, they go directly to the premises or to residual current circuit breakers (RCD) or residual current circuit breakers (AEDT).
It is important that the strap is firmly fixed. Otherwise, it will not work to stretch the zero contacts, which will lead to an increase in temperature at the junction. Moreover, only one loosely fixed contact will lead to heating of the entire strip, which will lead to weakening of the remaining connections.
The procedure for installing the zero bus in the flap
If you are installing a new switch cabinet, this work is easier to do. It is more difficult if you have to upgrade the old assembly. In this case, the fitter often encounters aluminum wires, which are strongly oxidized, which leads to a weakening of the contacts.
The zero bus is mounted in the shield at the stage of the location of protective automation even before it starts connecting. Switching is performed simultaneously with AB, RCD, AVDT and an electricity meter. For this, an input zero is pulled from the input two-pole circuit breaker, after which the bus starts to make wiring in groups.
What is the difference between a ground bus and a ground bus
RCD or AVDT for protection today are widely used. It is for their correct operation that grounding is required, which must be distributed as well as zero. It is for this that the same bracket with terminals is used. If there is no circuit, you can proceed as follows. The zero bus in the shield is combined with a ground bus, after which separate wires come from each of them.
The main thing is that after RCD or AVDT they do not touch. Otherwise, there can be no question of correct operation. Such an action is called protective grounding. This is not a full-fledged grounding, but it copes with its task.
Advantages of installing a zero bracket in a control cabinet
Not everyone understands the importance of such an installation, believing that if it is necessary to combine only 3-4 cores in the shield, this can be done using ordinary twisting. It can be answered that such switching is enough to be under a good load, and after 20-30 minutes the insulation will start to warm up, after which it will flash. It is worthwhile to understand what advantages the installation of a zero bus in the shield gives:
- The presence of many points to which you can connect the neutral wires.
- Providing easy access for serviceability when auditing electrical power cabinets.
- Improving the efficiency of protective automation elements due to the lack of heating.
A few zero tire maintenance tips
Like any other power cabinet equipment, such a bar requires constant attention. After putting the switchboard into operation, after 1-2 weeks, the connections should be extended again. The fact is that the oxide film formed on the surface of the core will burn by this time, which will lead to a weakening of the connection.
At least 2 times a year, this procedure should be repeated, as is the case with protective automation. It must be ensured that dust does not accumulate on the zero tire. Ideally, if it is closed with a plastic transparent cover. You should sometimes check the bar visually - a bad contact will reveal itself by darkening the bus or the insulation of the wire near the connection.
To summarize the above
Do not underestimate the importance of installing a zero tire, content with twists or bolts. Such a bar is a security element that complements automation, allowing it to work correctly and to do what it is mounted for, namely to ensure the safety of electrical wiring.