How does a voltage relay work and what is it used for?

It’s hard to find a person who does not know what is a circuit breakerknown as a vending machine or cork. Everyone knows that this device should be in the electrical panel. And few people know about this type of protective apparatus, such as a voltage control relay, which is also called a volt controller. This device is used not only in industry, but also to protect homes and apartments. Below we consider the device, purpose and principle of operation of the voltage relay RN-104 at 40 A from the company Novatek-Electro.

What is it used for?

This protective device is necessary, as is the circuit breaker. However, this device has a different purpose - to monitor the voltage.

Effective surge protection in the network

Network overvoltage a common reason for expensive equipment to fail, repairs and replacement of which cost a pretty penny, since damage from overvoltage is not a guarantee. And as a rule, such jumps last for several seconds, until the protection works at the substation, this is quite enough for the electronics in the house to fail. Look at how many devices you have plugged in, even if you are not using them at the moment, all of them are in potential danger.

To avoid this, a voltage relay has been created that monitors the state of electric potential in your apartment around the clock and instantly de-energizes the network in case of emergency changes.

Pay attention to the single-phase relay RN-104 volt control from the manufacturer Novatek Electro. Easy to set up and operate, it will guard the electrical network of your house or apartment. Below we will consider the design and principle of operation of the voltage monitoring relay.

Design Features

It is made in a housing with mounting under a DIN rail, for installation in the metering panel next to the circuit breakers, as can be seen in the photo below.

DIN rail mount

On the front panel there is a three segment indicator that shows the current status of the mains. Three regulators and three terminals for connection, everything is extremely simple.

RN-104 photo

The connection diagram is drawn on the right side of the case, 1 phase L input from the circuit breaker, 2 wire N from the zero bus or from the second circuit breaker, depends on your shield, then the zero from this terminal goes to consumers. From the third terminal, the phase goes to consumers or a group of machines, again it depends on your shield, are you installing a new one or upgrading an old one. In detail about how to connect a voltage relay to the network, we told in the corresponding article.

PH connection diagram

Having opened the device, we can carefully look at the device, what it consists of. Accurate soldering indicates that the person did not participate in the assembly of electronic components, this is done on an automatic line. Human participation is minimized only at the stage of assembly into the housing, testing and packaging.

Internal construction

Disassembled voltage monitoring relay

Structurally, the controller is made of two boards, a power unit and a control. Almost the entire surface of the power circuit is occupied by a powerful switching relay of 40 amperes.This allows you to easily turn on the load of a total of 9 kW, which is quite enough for the house and apartment. The conclusions from it are welded to copper leads and are output to screw terminals.


The manufacturers of Novatek-Electro, developing this relay, went to meet people and programmed the basic functions into this device, and left the user a simple choice of several options, such as:

  • automatic restart time (AR) from 5 to 900 seconds (15 minutes);
  • lower cut-off threshold (Umin) from 160 - 210 volts;
  • upper cutoff threshold (Umax) from 230 - 280 volts.

Rotating the potentiometer RN-104 gives a digital representation of the parameter to the indicator, which is undoubtedly convenient and does not need to be guessed.

We recommend that you adjust the characteristics of the voltage relays in this way:

  • AR time 180 seconds;
  • Umin 190;
  • Umax 245.

In practice, there are times when the voltage almost coincides with the set threshold for a rather long time and in order to avoid continuous switching on and off of the relay, a hysteresis of 4-5 volts from the set value is introduced. In this case, the device automatically enters an additional threshold and does not turn on until the voltage drops below the setting by the amount of hysteresis. If this phenomenon is cyclical in nature and periodically repeats, then review the parameter settings and change them.

It is worth saying separately about distinctive features volt control RN-104 Novatek Electro. To avoid false shutdowns during operation, intelligent monitoring of network status is established. If the voltage gradually increased and went beyond the set limits, but not higher than +30 volts from the set threshold, the relay waits 1 second before shutting down. With a sharp jump above the set threshold of more than +60 or above 285 volts, the relay instantly activates in 0.02 seconds.

It is known that when a powerful consumer is turned on, a voltage drop occurs, they can be a refrigerator or air conditioning.With a smooth voltage drop below the set threshold of -60 volts, the device waits 7-12 seconds, which is enough to start the consumer's engine.If the voltage drops below 145 volts, the device trips in 0.12 seconds.

You can clearly see the principle of operation of the voltage relay in the video below:

How RN-104 works at 40 A

By the way, the manufacturer guarantees a relay operating time of 10 years, and warranty support for 5 years.

In general, the device looks powerful and reliable, so when you decide to buy Volt Control, make a choice in favor of the device described in our article, we leave positive feedback about it. This concludes our instruction for describing the device, the purpose and principle of operation of the voltage relay RN-104 40 A.

Useful on the topic:

How RN-104 works at 40 A

(7 votes)


  • Ildar

    Good day! So that I do not understand the relay and the machine is the same thing?
    How does the machine work when the current is exceeded?

    To answer
    • Admin

      Hello! No, a circuit breaker is not the same as a voltage relay. The machine trips when current is exceeded and during a short circuit, and the voltage relay trips when the voltage deviates from the set value. Current strength and voltage are different parameters.

      To answer
  • Sergei

    And this, too, is not a fairly correct answer. The difference is even deeper. In the very concept of "relay" is a "switch".

    To answer
  • Alexei

    RN (voltage relay), looks more like an AVM. (Multiple circuit breaker), but I do not like such a system, for example, when lowering the insulation resistance of the wires, below the norm, when heating the voltage control elements, RN- turn off, when When cooling down, turn on again and so on until the wire insulation’s good if it only seems to me that way, but the thing is good, that’s for sure, I’ll definitely install it too, without any likes, dislikes.

    To answer
    • Admin

      Sorry I do not understand the thought, but where does the decrease in insulation resistance? The pH monitor only changes the level of the mains voltage.

      To answer

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