Build Daily


August 12, 2017 18:06

Connecting the RCD without grounding : from theory to practice , advice electrician

Connecting the RCD without grounding

There is a prejudice that for proper operation of the RCD is required three-wire electric network, ie,phase, zero and grounding.Note, however, that the role of the RCD - to disconnect electrical equipment in the event of a leakage current in the body, and thus prevent human electric shock.

Driving RCD connection .The single-phase network.

scheme RCD connection.The single-phase network - Photo 1

purpose of grounding the same: in the case of an electric current of not live on the grounded parts of the equipment to create a short-circuit mode, which will work overcurrent circuit breaker, and the equipment is de-energized.It turns out that the same objectives can be achieved by using two different methods:

  • Connecting the RCD without grounding scheme which will be discussed later, or
  • installation of protective grounding.

These two methods of protection can complement each other, but can also be used separately.How do I connect to a single-phase circuit RCDs?This will be discussed further.

Can I install an RCD on the network without earth?

From the above it can be concluded that the installation of RCDs can be carried out even in a two-wire electrical circuit, which does not provide ground staff.This conclusion is confirmed by the construction of the security apparatus, which has a phase and neutral terminals, but it is not terminal for connection of the grounding conductor.This is important, because the grounding conductor is only used in new buildings.

The block diagram of the electrical wiring in the room

Block wiring diagram of the room - Photo 2

Homes built under the Soviet Union, two-wire system is used without grounding conductor.Especially in this case, the RCD must be installed in the apartment.The difference between the tripping RCDs in the network with a grounding conductor and grounding without RCD tripping point only.

The circuit grounding device works immediately at the time of occurrence of the leakage current and RCD wiring diagram without grounding provides protection tripped only when touching the appliance housing, emergency energized.However, in this and in another case, the RCD provides protection against electric shock due to the instantaneous trip.

operating principle of an RCD (what RCD)

to deal with connectivity features of the RCD in a private home or apartment, you should consider its operating principle.It is based on a simple physical law that states: the current in the circuit with a series connection of consumers, regardless of their power, does not change in all areas of the circuit.

In other words, the current that passes through the phase and neutral conductor to the same branch circuit remains the same.To connect the RCD and the phase and neutral conductor, and this unit compares the value of current flowing through each of these conductors.If the current is the same - the electric circuit is operating normally.If the current strength varies, it means that there was a leakage current, then the RCD instantly activates and deactivates the emergency section of the circuit.

Wiring RCD as an example apartment flap

Wiring RCD on the example of the apartment shield - Photo 3

This is the theory.Now consider its application in the practical example.Assume that the visor is connected to the circuit feeding the electric heater in the bathroom.Of the protective devices in the chain there is only a circuit breaker that protects the circuit from overload and short circuit.

assume that inside the water heater was a violation of the insulation and the conductor touches the metal housing.If no earthing, the circuit breaker will not respond to such emergency operation.But it is dangerous, because the body is under stress, and if you touch it, you can be hit by an electric shock.

situation will change, RCD installed in a private home, apartment or office.After all, the current leaving the housing cylinder, and a leakage current, the appearance of which, in the case of a touch to the body, triggered RCD, emergency de-energizing the controlled portion.If the chain is included RCD without grounding, the circuit is much safer from the point of view of the possibility of electric shock.

How to connect the RCD without grounding

Let us turn to the very important issue of our article: What is the connection scheme of the RCD without grounding?

As for the connection of the RCD, it can be made in two ways.

first wiring diagram of single-phase RCD - set a single high power protection unit for all electrical house or apartment.This method is advantageous because it is most simple.After the account of the electric machine phase conductor is incoming RCD terminals, then onto the terminal wire goes to circuit breakers.From automatic wire goes to the electrical power supply: sockets and lighting.

Such a scheme does not take up much space in the distribution board.The disadvantage of this method of installation of RCDs is that when activated turns off all electrical house or apartment.Also difficult to quickly determine the cause of the shutdown.

second way to connect without the RCD ground - is the installation of a separate device for each dangerous section.In this case, the protection device will be more expensive, and in the control panel will take up more space.On the other hand, if you disable one part of the circuit, while others will remain connected to the electricity, and do not have to face a situation, when the whole house will be de-energized.In this case the wiring diagram of single-phase RCD is this: on the meter phase wire is connected to each of the circuit breaker, and from there to each RCD.

When connected to the RCD network should adhere to the following rules: it is impossible to combine the zero conductors in the assembly after the RCD.This will lead to false positives.In addition, after the installation of a protective circuit should be checked properly assembled wiring diagram RCD without grounding.This can be done as follows: connect to the electrical outlet, which is located in the RCD circuit.If after switching on the RCD is turned off - circuit properly connected.You also need to check on the operation of the RCD as a result of leakage current, by pressing the "Test" button on the RCD.

errors that should not be allowed

It is important to avoid these mistakes.Some in order to improve the safety of the circuit, connect the grounding wires of the conductor outlet to zero or to make their own ground.This is dangerous, because only working correctly configured, grounding can ensure the security of the person.Homemade circuits can cause an electric shock.For the same reason, do not connect the grounding conductor to the water supply outlets and other conductive structures engineering structures.

It is not recommended to connect the neutral wire to the ground in order to supposedly improve system reliability.Finally, at the idle grounding is recommended to disconnect and insulate the earth conductor, coming in from the electrical switch box.If you do not, then all the emergency housing units will be under dangerous voltage.

Installation ground, as well as the installation of RCDs in an apartment or private house it is best to trust the qualified technicians.Remember that the quality of the electrical network installation may depend on the life and health of people.