Installation of electrical wiring in a house or apartment is a laborious and responsible process. However, laying the cables and making the wiring is not the most important thing. The most basic task in this work is the installation of a switchboard, in which, in addition to the electric energy meter, automation is installed to ensure safety for residents. One of the most important elements of the entire system is a residual current device. In today's article, we will discuss in detail how to connect an RCD correctly, the difficulties that a home master may encounter when switching, the most common questions related to such work, and the answers to them.
The principle of operation of the residual current device
The main nodes of the RCD can be called two coils through which the phase and zero flow. With stable operation of the network, there is no potential difference between us. However, everything changes during the breakdown of the phase or neutral conductor to the housing. In this case, part of the current goes along the path of least resistance to ground. As a result, the device picks up an increase in the potential difference, recognizing it as a current leak and works, opening the circuit and removing the voltage from the line. Thus, a properly connected RCD ensures the safety of a person, his protection against electric shock.
The purpose of the residual current device
Many do not fully understand what the RCD is intended for. It makes sense to figure out what its differences are from a conventional circuit breaker (AB). Mainly, the residual current device works for human safety in the event of breakdown of insulation on the housing of a household appliance. After all, almost everyone faced a situation where when you touch the metal parts of a kitchen or other equipment, a slight, but rather unpleasant, electric shock is felt. However, this is not always harmless.
There are times that such situations result in death. The residual current device is just installed to prevent this. However, the correct connection of the RCD in the shield becomes a significant problem for home masters. Even experienced electricians often make mistakes at this stage of installation, which means you should deal with this issue in more detail.
Error No. 1: if there is an RCD, installation of the machine is not required
This misconception is quite dangerous. The problem is that the RCD can detect leakage current, but is completely immune to short circuits and network overloads. In the event of their occurrence, the residual current device will simply fail. At the same time, its contacts “stick”, as a result of which the line on which the short circuit occurred remains energized, the wiring continues to heat up until the insulation ignites. As a result - a fire and loss of all property, possible harm to health or death.
Conclusion: only the correct connection of RCDs and automatic devices in the electrical panel can provide complete protection for the home power network, equipment, life and health of residents.
Mistake number 2: grounding and grounding are one and the same
This issue is worth considering with examples:
- Grounding and neutral wire are in contact on the line after the RCD. With this switching, the residual current circuit breaker will trip for no specific reason, identifying non-existent leaks. This means that using such a line will be extremely problematic.
- Earth is missing. A two-wire system is indispensable here, which means that you will have to mount protective grounding. To do this, an additional bus is installed in the shield, to which zero from the counter is supplied. The main thing is that the neutral output be made before the protective shutdown device, in order to avoid causeless trips.
With the correct connection of RCDs and circuit breakers, the shorting of the grounding and zero contact in the outlet will lead to a cut-off.
We proceed to consider the following error.
Mistake No. 3: to make the correct connection of the RCD, a circuit is not required
Usually, such an error is inherent in experienced craftsmen who rely too much on their memory. However, practice shows that when assembling an electrical panel (regardless of its complexity), even a hand-drawn design accelerates and greatly simplifies installation. In addition, later, when performing a repair of a power home network, this scheme can significantly help.
Joint connection of RCD and additional equipment
In addition to AB, together with a residual current device in the switchboard, other equipment is installed that can ensure the safety of household appliances. For example, connecting an RCD and a voltage relay. How to carry it out correctly, so that, together with the machines, a complex scheme is created that will protect against any force majeure situations that may arise? Of course, here a lot will depend on the availability of free space for the installation of modules and financial capabilities, but the main thing is the exact observance of the manufacturer's instructions and tips, which can be found in the technical documentation.
Also, residual current circuit breakers are compatible with any relays and sensors. The connection diagram of the automation does not change. And in order to make it clearer how such a device is connected, you can see the video below.
How to make the correct connection of RCD without grounding
The answer to this question is not even known to all experienced electricians, which means that it is worthwhile to dwell on it separately. In order to make information easier to perceive, it makes sense to consider the work algorithm step by step:
- First, all protective automation and an electricity meter are located in the switchboard. It is very convenient if 2 DIN rails are provided for this. In this case, the upper one is occupied (from left to right) by the input automaton, counter, RCD. The bottom is for AB in groups.
- Be sure to place two contact bars in the shield - zero and ground. Between themselves, they must be closed.
- From the electric meter, the phase goes directly to the RCD, the neutral wire goes to the bus, and already from it to the residual current device.
- Now the main wiring is done. For lighting groups, an RCD is not required, which means that zero for them will go from the bus. For the rest, the neutral is taken from the output of the RCD. Thus, the correct connection of RCDs and machines without grounding provides a complete three-wire system that uses high-quality protective grounding.
Switching devices in three-phase networks
Some may think that working with a voltage of 380 V is much more complicated and less convenient, but this is a misconception. In fact, three-phase networks are simpler than it seems at first glance. In addition, with 380 V, there are wider possibilities for switching.
The question of the correct connection of a three-phase RCD starts to be solved by drawing up schemes for groups. The main thing here is to distribute the lines so that the load on them is relatively the same. If you connect all household appliances to one phase, there will be a bias that will pull power surges to the other two.
The power input to the RCD is carried out similarly to the previous version with the only difference being that not 2, but 4 wires are used. At the output, we get a total zero and 3 separate lines of 220 V.
Using multiple residual current circuit breakers
If we are talking about a large private house with a lot of household appliances, a separate RCD for a particular line is often required. For example, most often this is necessary when applying power to electric boilers, washing machines and dishwashers. In this case, the wiring diagram in the distribution panel will be slightly different.
The main RCD remains in place, it also feeds on low-power household appliances. However, in addition to them, voltage is supplied to the secondary protective shutdown devices, each of which will have a separate line to this or that device. The main task here is not to confuse the zero conclusions with each other, which often happens when a confident master assembles a distribution board without a circuit. But it turns out this. An electrician takes a phase wire from one RCD, and a zero wire from another. As a result, both residual current circuit breakers start to operate unreasonably. But it’s much more difficult to sort out an already installed switchboard than to do everything according to the rules initially.
The main steps to independently draw up a switchboard layout
The first thing to do is to mark the cables coming to the cabinet from the premises of the apartment or private house. The tags should contain information about the room from which the wire is connected, the number and total power consumption of household appliances that will be powered from it. Next, on a piece of paper in an arbitrary form, the location of the protective automation elements is drawn with notes which cables should be connected to them. In fact, many of this information is enough to correctly connect the RCD and other equipment necessary to protect the network without unnecessary problems.
After placing the elements in the switchboard, it makes sense to duplicate all the information from the circuit onto the box door and number AB, RCD and other automation.
Basic rules for powering the switchboard: tests
Installation and wiring in the cabinet are made from the introductory machine. However, here the main rule should be observed - it should not be powered. Voltage is supplied to it last, after the end of all switching work. By connecting the input cable (the supply is turned off from the feeder or other knife switch), make sure that all the “flags” of the protective equipment are in the “on” position. After that, voltage is applied to the control cabinet. If the RCD connection is correct (the same applies to AB), all the "flags" will remain in their original position. It remains only to press on the RCD the "TEST" button, which simulates the leakage current - a cut-off should occur.
Checking the correct connection of outlets is checked in the simplest way. Using the indicator screwdriver, there is a zero contact, which must be connected to the grounding contact. If everything is mounted correctly, the RCD will work.
Finally
Every home master must know how to properly connect and check the residual current device. This will ensure the safety of people living in the house or apartment. The main thing is to comply with electrical safety rules during all work and not to work with equipment under voltage. After all, electric shock is life threatening.