Relay Wiring Diagram: Device, Application, Rules For Selecting And Connecting The Relay

Unstable mains voltage leads to the breakdown of household appliances. If you manage to prove someone else's fault for such damage to property, you will receive compensation. But, agree, it is much easier to prevent this situation than to go to courts and experts.

We will tell you how to avoid voltage surges - why it happens, what devices to use and how the voltage relay connection scheme looks working.

Content of Article:

  • Why do voltage surges happen?
  • Can you stabilize voltage yourself?
    • The principle of voltage relays
    • How to choose a voltage relay?
    • Voltage relay settings
  • The principle of connecting a voltage control relay
  • Conclusions and a useful video on the subject

Why do voltage surges occur?

The various appliances that are powered have voltage limitations. This is true even for incandescent light bulbs, but it takes a big overvoltage to cause them to burn out.

Relay wiring diagram: device, application, rules for selecting and connecting the relay

Low line voltage affecting for example a refrigerator threatens the compressor with short circuits and breakdowns. A too high voltage affects the compressor as well as the electronic parts, causing damage and costing a lot of money to repair

And again, even a wide range of voltages does not mean that it will run in voltages ranging from 100 to 240 for example. This means its viability within a given interval, provided the mains is stable.

Generating electric installations are designed with an automatic voltage regulator. In this case, the deviation from the norm, according to GOST 721 and GOST 21128, should not be more than 10% in short-term mains failure and more than 5% in long-term.

At least 7 main causes of natural, emergency, man-made nature can provoke them:

  1. Worn-out electrical wiring in the house.
  2. Lack of stabilizers at the transformer substation.
  3. Use power overload on the line.
  4. Transmission line failure.
  5. Break in the neutral line.
  6. Breaking of meters by unscrupulous consumers.
  7. Natural factors.

The consumer is responsible for the operation of electrical appliances, competent load distribution on the internal wiring and the condition of these networks. If a fault or an emergency is detected, the Electricity Authority must be called immediately.

Relay wiring diagram: device, application, rules for selecting and connecting the relay

The voltage can be measured with a special device, a multimeter (tester). If you find a deviation of more than 10%, it is advisable to immediately contact the emergency services of the local electricity network to determine the cause of the voltage surges

The mains electricity supply is entirely in the care of the electricity suppliers. One of their tasks is just to monitor voltage;deviations from the norm on& the assigned area.

But in spite of the separation of duties, even with strict control, voltage fluctuations are quite common.

If the person responsible for the voltage surges on the line is identified, it is possible to obtain justice and full compensation for ruined property or poor quality service.

Can one stabilize the voltage himself?

Even if you believe that justice will be done and the guilty party will compensate you, accidents of this kind can lead to stalemate, and litigation is not pleasant.

In order to prevent the consequences of voltage deviations, it is possible to buy and install special devices - voltage control relays and/or a stabilizer.

Relay wiring diagram: device, application, rules for selecting and connecting the relay

To equalize the optimum voltage parameters in the network, stabilizers - local or stationary - are usually used. But this is not always a good choice, because the devices do not respond quickly and it can take too long before they are up to rated voltage. For surge-sensitive electronic equipment, this is usually not a good option

Control relays are one of the most budgetary, reliable and easy to use options. It will not be able to stabilize the voltage, but the equipment will be reliably protected.

The principle of operation of the voltage relay

It is recommended to buy and install it when the voltage surges are not too frequent.

The device uses a microcontroller to record the electric current and it opens the power supply if it exceeds the range set by the operator, up or down. When the relay has stabilized the line, it will automatically resume power.

Relay wiring diagram: device, application, rules for selecting and connecting the relay

The voltage relay can look different and also have different functions. Some devices can even be controlled remotely through a contactor

Also, on many relay models, you can set an on/off delay time. The timer is necessary to monitor short-term voltage spikes, for example, it will not open the circuit immediately when out of range, but if deviations are observed for 5-10 seconds.

With regard to the delay on, manufacturers specify a time for their devices to wait before restarting in order to prevent them from burning out.

The relay has its disadvantages, it cannot smooth out fluctuations, but in complex with this device you can use voltage stabilizers.

It has many more advantages than disadvantages:

  • saving the purchase price (lower than the other protection devices);
  • reliable to use;
  • visual control of the voltage parameters via the digital display;
  • quick response.

It is easy to use and operate. It is also very easy to choose and install.

How to choose a voltage relay?

The relay is available in 4 types: DIN-rail module (block), single appliance protection (plug/socket), multi appliance protection (extension cord with several sockets), three phase device (for equipment using 3 phases).

There is also an intermediate relay, designed to monitor independent circuits, delay the tripping of protection when high loads are required and to monitor appliances requiring high voltage values.

Relay wiring diagram: device, application, rules for selecting and connecting the relay

The transfer voltage relay is designed, depending on the model, for a current of 6 to 16 Amperes. To connect consumers with larger appetites, either install multiple units or DIN-rail models

When selecting the current rating, focus either on the circuit breaker rating of the relay on the DIN-rail or on the power consumption of the electrical appliances.

Buy with 20-30% margin.The choice should also include:

  • switching speed;
  • phase (single phase or three phase units);
  • voltage range and operating limit adjustable;
  • range of display;
  • time control option;
  • relay overheating protection function.

Which type of relay to choose depends on the amount of expensive and sensitive equipment.

If you choose a din-rail device, you will protect all consumers, but with a long-term surge, de-energizing the whole house is not always suitable for the owners, in which case local relays are appropriate.

Setting the voltage relay

Most often the relays already have factory working settings, optimal for almost any case. But if you want to adjust the device to your needs, it is quite realistic, if the functionality allows.

There is nothing complicated, basically only 3 functions:

  1. Umaxthe option to set the maximum voltage value for the relay to operate. Most often set from 210 to 270 volts.
  2. Umin is the minimum threshold voltage. Usually from 120 to 200 volts.
  3. Setting the switching timer after normalizing the line parameters. It is possible to set from 5 to 600 seconds.

Set the desired parameters either digitally on the LED screen or electromechanically by means of a variable resistor.

Check the factory settings if you want to keep them whether they are suitable for your operating conditions.

Relay wiring diagram: device, application, rules for selecting and connecting the relay

Some voltage relays do not have the ability to individually set the high and low trigger thresholds. They usually cost less, but are less convenient to use

If you are not happy with the standard setting for all appliances, you can make a separate mains line for them with an extra RNC. The manufacturer will usually give you the instructions to set up your appliances.

Power Control Relay Wiring Principle

If you have at least some electrical experience, it shouldn't take more than 20 minutes to wire up. The set of tools is very simple: a screwdriver, a screwdriver and a knife. In general, the wiring diagrams differ from model to model, but the manufacturers put them on the case or in the data sheet. Therefore, once you understand the general installation steps, you can easily handle most types of devices.

Relay wiring diagram: device, application, rules for selecting and connecting the relay

The single-phase voltage control relay is usually installed between the UPS and a group of circuit breakers. The input of the device is phase and zero and only the phase goes to the load

Let's look at the simple step by step instructions for connecting a single phase voltage relay:

  1. Unplug the electrical appliances.
  2. Make sure you de-energize the mains with a circuit breaker.
  3. Use an indicator screwdriver to check that the area prepared for installation is de-energized.
  4. Insert the RCC on the pre-fixed DIN rail according to the manufacturer's instructions, checking the quality of the fixing.
  5. Clean the wires from the meter to the consumers.
  6. Locate the input and output (often signed on the instrument), connect the wires, from the meter to the input and the output to the consumers.
  7. Wire the circuit breaker. Check, using a screwdriver, whether there is voltage at the relay input.
  8. Activate the relay, set voltage thresholds and delay timer.

Wiring a three phase voltage control relay is more complicated. If you don't know how to do it and you can't install it with a diagram, call in an expert.

Commentary and Helpful Videos

Video #1. How to wire a voltage control relay yourself:

Video #2. How to install a three-phase voltage monitor relay:

Video #3. 3 voltage monitoring relay wiring diagrams:

Voltage monitoring relay will help keep the electrical appliances in your home or apartment intact. In fact, it's the easiest and least expensive way to prevent surges from negatively affecting your home's electrical system. Despite the different models, even non-professional electricians can connect the device.

Have you ever installed a voltage monitor in your home? What difficulties have you encountered and what tips can you give our readers? Share your experiences and ask questions about the subject in the comments.


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