RCD for lighting: to install or not according to the PUE

Disputes often arise on thematic forums about whether it is necessary to install an RCD for lighting, and we are sent to the editorial office with related questions on this topic. Therefore, in order not to be repeated several times and to give the most voluminous answer, in this article we talked about when they put an RCD in the light, and when it is not necessary to do it. To make it less controversial, the material is supported by links to regulatory documents.

When you can not install

When installing wiring, one of the main issues is the final cost of work and wiring accessories. Often, in order to save money, they come to simplification. switchboard diagrams and reducing the number of modules in it. At the same time, most people do not ask the question whether it is necessary to install RCD into the light, often sacrificing it to them.

In discussions, opponents of installing RCDs on lighting hide behind

Chapter 7.1. PUE, namely p. 7.1.79, where it is said that the installation of an RCD in the lines that supply stationary equipment and lighting, as a rule, is not required.

What does the postscript “as a rule” tell us? This means that in many cases it is possible not to install differential protection on these devices, and also that there are cases in which protection is mandatory or highly desirable. We will talk about them below.

What do we get if we do not put the RCD in the light?

1. Saving space in the electrical panel.
2. Less cost of work and equipment for the installation of the shield.
3. Less likelihood of false alarms in emergency situations or lamp failure.

In the following cases, you do not need to install a residual current device:

• if the lamps are located at such a height that under no normal situations you will not be able to touch their conductive parts (for example, a metal case);
• if you install a breaker in a phase wire break;
• always turn off the switch when replacing a light bulb, wiping it or repairing a fixture.

In these cases, there is a danger of electric shock if leakage current on the luminaire body is minimal.

When do you need to install

Lighting requirements are outlined in chapter 6.1 of the PUE, and the need to install differential protection is stated in clauses 6.1.14, 6.1.16, 6.4.18, 6.1.49. There is also a recommendation in GOST R 50571.7.714-2014 p. 714.411.3.3.

It says that RCDs for lighting residential and public buildings are installed:

• In rooms with high humidity and fire hazard, as protection against electric shock, a reduced voltage of up to 50V must be used to power stationary lighting.
• When powering light sources in the above premises from 220V, it is imperative to install an RCD or an isolation transformer.
• It must be installed on luminaires, the lowest point of which is located at a height below 2-2.5 meters. These are the lights that you might accidentally hit off the floor. For your information, with a ceiling height in Khrushchev of 2.5-2.7 meters, almost any chandelier will be located below.
• It is necessary to install illumination and illumination of billboards and signboards in the power supply circuit.
• Architectural lighting.
• For outdoor lighting.
• Lighting of public places on the street (telephone booths, bus stops, route signs, etc.).

If you are doing home repairs, then you should know that you definitely need to install an RCD on the lighting groups in the bathroom, in the bathroom, in the bath or sauna and other places with high humidity, like a basement.

Which RCD to choose

When choosing a residual current device for a lighting line, one often wonders which type to choose: A or AC. Type A reacts to alternating and pulsating leakage currents, and type AC only to alternating currents. Then the protection with what parameters must be put into the light in order for the work to be reliable?

In chapter 7.1. PUE p. 7.1.78 says that both types can be used in buildings, and the pulsating current sources are listed below, among which there are "adjustable light sources".

Therefore, it will be more reliable if you install a type A RCD in the light. Its rated current must be equal to or greater than the rated current of the circuit breaker that protects this circuit. Pick-up current as recommended PUE, should be no more than 30 mA.

When installing a protective device on street lighting or advertising illumination, its operating current must be 3 times higher than the line leakage current. Therefore, calculate the leakage current of the line, according to the PUE p. 7.1.83 (10 μA or 0.1 mA per meter of phase conductor length).

You can read about which rated current to choose from the article we referred to below.

Conclusion

When designing electrical switchboard circuits, you need to make a decision in advance about which circuits and by what means will be protected. Based on this decision, you need choose an electrical panel, which will fit more modules than you calculated. In this case, you do not have to sacrifice safety for the sake of economy.

We believe that an RCD should be placed on the light, since current leakage to the luminaire body can occur not only in the case of damage to the insulation of its wires, but it can also save your life if you are electrocuted by accidentally touching the contacts cartridge. This probability increases especially when threaded cartridges (type E27, E14) are connected incorrectly, and the phase is connected not to the central, but to the side contact. In the event of such an accidental touch or damage to the insulation of the wires of the lamp, the RCD knocks out as soon as a leak occurs.

Whether or not to install an RCD on the lighting is of course up to you, but remember the requirements of regulatory documents. If you have any questions regarding the information provided, or you want to express your own opinion - write in the comments, our editorial office is ready for discussion!

Related materials:

• How to make lighting in the house
• How to choose an RCD by power
• What cable is needed for sockets