Question about installing a voltage relay in an apartment
Please tell me how to properly connect the voltage relay to the apartment. I want to install the relay in the shield in the entrance. An RCD of 40A is in front of the counter, and after the phase it diverges into three machines, one 25A and two 16A each. As far as I understand, the relay needs to be placed after the counter in front of the machines, that is, we take the phase after the counter, and where to get zero, as I understand it, it serves only to control the relay itself. Some say that you need to take zero before the RCD, so that the RCD works correctly, while others say that you can take from the bar where all my zeros go. How right? And yet, will a 40A relay be enough, or should I take it with a margin?
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The voltage relay is connected after the counter and it is connected by the phase and neutral wires that go after the counter. If you take zero to the counter, you will be fined for energy sales. You take for your needs zero and the phase after the counter, connect what you want and how you want, and you should not interfere in the circuit to the meter. If you take the phase after the counter, it means that somewhere there should be a zero that goes to your apartment.
In a voltage relay, zero and phase are used for the relay itself. RCD has nothing to do with it, the voltage relay should not have any effect. The voltage relay uses zero and phase to control the voltage value and to operate the device itself. The modular voltage relay, which you put in the shield, works the same way as the voltage relay, which is connected to the outlet. When you turn on the voltage relay to the outlet, you do not take zero to the RCD - the phase and zero comes from the outlet and the output goes to the included electrical appliance. The same is the case when a voltage relay is installed in the apartment panel - the phase and zero that go to your apartment from the meter are suitable for it.
As for the rating, if you have an RCD, there must be a circuit breaker that will limit the current and protect the RCD, since the rated current of the outgoing machines in total exceeds 40 A. You must choose a voltage relay for the rated current, which must be one step higher than the rating of the introductory machine, which is installed up to the counter. For example, the rated current of the machine is 40 A, then the relay must be rated at 50 A, since the machine can work for a long time in overload mode. Voltage relays are usually not produced with such switched current, and you will have to put a contactor (magnetic starter) in addition to the relay for switching the circuit. But, in any case, you need to clarify - perhaps you will find a voltage relay for the required rated current. It is the switching current that must be looked at in the characteristics of the relay, the current for which the relay itself is designed.
tell me clearly how to connect the contactor correctly so that it switches one phase to another when one phase is switched off ???? Thank.
To do this, you need two contactors or a changeover contactor (It’s not uncommon, but not as easy to find as a normal contactor), but in general there are such things as “phase selection relays” they can be called differently, here is an example of such a device “ELECTRONIC PHASE SELECTOR PEF SELECTOR -319 "