Rules for connecting the RCD to a single-phase network without grounding: the best scheme + work order
A single-phase electrical network is familiar to every household. Regardless, whether a private house or a municipal apartment is operated, users actively consume electricity in any case.
This kind of energy, meanwhile, cannot be considered completely safe. Therefore, an urgent task is to connect the RCD to a single-phase network without grounding - a special device that significantly increases the degree of safety when using electricity.
A generalized view of the security modules
Despite the construction of electrical wiring diagrams, performed according to the approved rules, the risk of electric shock always remains. Therefore, it is important to take care of safety in a timely manner.
The device of protective shutdown is the way the abbreviation "RCD" is interpreted into a technical language.
From the point of view of construction design, it does not look the most complicated way among modern electrical equipment. Nevertheless, the protection function performs sufficiently high quality and reliable.
It should be noted that there are varieties of RCDs on the basis of which in each particular case a certain protective scheme is being organized:
- guaranteeing the safety of touch;
- proactive technical damage;
- counteracting fire hazard.
Each device with a specific functionality differs from other designs by operating parameters, in particular, by the rated current and cut-off current.
The most sensitive device, of course, is the RCD, which is designed to block the power supply in case of unintentional contact of people with current-carrying circuit parts.The current cutoff range for such devices is in the range of 10-30 mA.
The best schemes for connecting the RCD
For household electrical lines, the introduction of an RCD without a “ground” is characteristic. The main share of circuit design solutions in the residential sector is precisely single-phase wiring, where, in principle, there are only two lines: phase and zero.
Features of circuits without grounding
The circuitry of an electrical circuit without grounding is necessarily carried out taking into account the inclusion of automatic protection for "short circuit" (short circuit) and overload current.
This is an obvious factor, because individual RCD devices are not intended to protect against such phenomena. These devices save only from leakage currents.
The range of cut-off currents and the technical characteristics of the circuit breakers are somewhat different from the operating parameters of the protective RCD.
Meanwhile, there are universal cut-off devices that combine the functions of a circuit breaker and protection against unintended touches to current-carrying electrical buses in one device.
Each protective device constructively involves switching both conductors of the power cable - phase and zero.
At the same time, performing the installation of electrical wiring, you should accurately connect the conductors to the working terminals. Incorrect installation threatens to damage the device protection, which will lead to the inoperability of the protective system as a whole.
Depending on the technical load (the number of household appliances) and the number of premises, a single complete network or a network consisting of several subnets can be operated in an apartment or house.
For the first case, it is usually enough to have a single RCD device for the organization of a protective disconnect. Based on the parameters of the consumed current or the total power consumption, in this case, choose a protective device for the rated current and are determined with the cut-off current.
For the second option, the devices are implemented on each of the existing subnets.In this case, as a rule, all installed RCDs are complemented by automatic switches, designed for the power consumption of an individual subnet.
The classic execution of the schematic of the inclusion of RCD "without land" is traditionally performed as follows:
- The main power cable, consisting of two wires (phase, zero), is supplied to the machine.
- From the circuit breaker both wires lead to the meter.
- Further from the electric meter, two power wires are connected to the input terminals of the RCD.
After the protective device, for the option without subnets, the backup circuit breaker can be omitted, but in some cases, experts recommend it.
If a circuit with subnets is used, then after the RCD, a separate automat must be installed on each branch.
Thus, a phase conductor extending from the protection device feeds the working networks through additional circuit breakers.
The zero conductor, also passing through the cut-off device circuit, is output to a common zero bus, from where it is distributed along zero flow lines to connect the load.
What is the inclusion circuit of the RCD?
The best or worst scheme - these concepts are purely superficial. How effective this or that scheme can be - that is the question.
And here, even to a non-expert, it is clear that the multistage option, where different levels of protection are used, seems to be more effective than any other simplified one.
Therefore, the scheme of the power supply device with subnetworks, when using one common RCD and additional protection devices on each of the branches of the electrical circuit, clearly looks preferable.
The construction of such a scheme, as a rule, involves the installation of the main protective device with a cutoff current of 100-300 mA.And additional devices, distributed on separate branches of the common circuit, have a cut-off current not higher than 30 mA.
In this way, double protection is provided - fire and in case of unintentional contact.
The advantages of building the grid in a similar way are also manifested in the fact that in the event of a response, only a separate section of household electrical wiring is usually turned off, and not a common power zone. Under such conditions, shutting down to detect the place of current leakage is much easier.
On the other hand, the so-called extended circuit for switching on an RCD without earthing is burdensome for the user in terms of increasing the cost of construction.
It is clear that in order to build a multi-stage protection, in this case, more substantial financial investments will be required than under the device of the simplified version.
The scheme of use of RCD in a private house
Municipal buildings usually do not pose any problems with the protection functions, with the exception of frankly old buildings.
Networks of municipal houses, as a rule, are serviced.But in a private house the owners often have to solve such questions on their own.
True, the initiative in such matters is not recommended. And if you want to organize a reliable wiring diagram with the use of RCDs, you should contact the experts-power engineers.
The projects of private housing, especially modern buildings, are characterized by a sufficiently complex scheme of protection solutions for energy supply. Consider one of them for the device in a private house:
- A total of 5 safety devices are used with a variation of cut-off currents from 10 to 300 mA.
- The main protection against "short circuit" and a possible fire is UZO 300 mA.
- Two universal 30 mA devices are used for lighting and a socket panel.
- On the power line of rooms with an aggressive environment and where increased protection is required, highly sensitive devices are installed at 10 mA.
- The overall circuit is divided into subnets, depending on the destination.
The functionality of such a scheme can be described as follows. The first device - RCD 300 mA - performs the functions of fire blocking.
However, this device is characterized by cut-off on the fact of the cumulative leakage current from all subnets, if this value has exceeded the permissible parameter.
Following the fire protection system, a universal one is activated, which guarantees actuation even in case of “short-circuit” detection and current leaks in excess of 30 mA.
The served zone for the RCD of this subnet is the line supplying the lighting devices and the outlet group.
Finally, a kind of third protective stage is formed by highly sensitive devices of 10 mA, which in fact serve the areas where conditions require an extraordinary approach - a bathroom, a children's room.
Protection option for country housekeeping
Modern projects of country farms are increasingly serving as a full-fledged building infrastructure, in no way inferior to the residential sector for living on a permanent basis. It is obvious that the factor of complex protection becomes relevant for country houses.
However, in relation to such farms, the requirements of electrical safety, as a rule, are somewhat underestimated compared to the real residential sector.
Therefore, simplified circuit solutions are traditionally used here using universal RCDs for a cut-off current of 30 mA.
This type of protective device provides quite effective protection in case of unintentional contact with the areas of electricity, where current leakage is possible.
In addition, the same design of the device provides a lock in case of technical damage to equipment or wiring.
In addition to the RCD, the dacha wiring is also equipped with automatic circuit breakers - usually one per line of light and a line of electrical outlets.
If additional equipment operation is required, it is connected to an existing circuit through an additional circuit breaker.
Procedure for connecting
First of all, care should be taken to comply with all required safety measures when performing this type of work.
Disconnect the power supply at the installation site, ensure the process with a serviceable tool. Then you have to follow a number of rules, performing electrical work:
- Installation is carried out strictly according to the previously prepared scheme.
- The device is mounted inside an electrical panel next to the machine.
- The device fastened in the shield is connected to other components through conductors with a cross section of at least 2.5 mm (copper). It is important to use the wiring diagrams printed on the protective device case.
- After completing the installation and wiring of conductors, check the correctness of the connections and apply power to the site.
- Check the operation of the device by activating the button "Test".
As a rule, a correctly selected device successfully passes the test mode.
If this did not happen - the device did not work, then the calculations were performed incorrectly or there are any defects in the device circuit. Then the RCD should be replaced.
Conclusions and useful video on the topic
The video tells about the nuances and shows the details of connecting the protective device in the conditions of operation of electrical wiring, made by the TN-C system. The author’s intelligible explanations about the operation of the RCD in such conditions and practical demonstrations:
Under the completion of the review material of possible circuit configurations with RCDs, it is necessary to note the relevance of using these devices. The introduction of residual current cut-off devices is a significant increase in the level of safety when using electrical networks. The main thing is to choose the right and correctly connect the devices.