Owners of country cottages often face the problem of overloading a low-power dacha network that occurs when connecting various powerful equipment. Especially often there is an overload of the network in the cold season, when heating devices are added to the electrical equipment. A frequent problem is the shutdown of the introductory circuit breaker due to overload. You can solve the problem with the help of a special device — a non-priority load disconnect relay.
These relays allow you to increase the number of consumers without exceeding the permitted power, and, consequently, without turning off the input circuit breaker. They are installed in the shield, and electrical circuits are connected to them, to which various consumers are connected, divided into two groups:
- priority (circuit supplying electricity to lighting, refrigerator, etc.), which should not be turned off under any circumstances;
- non-priority (underfloor heating, storage water heater, electric heaters, etc.), which allows short-term interruptions in power supply.
Similar non-priority load disconnect relays are available from a number of large manufacturers, such as Schneider Electric, ABB, Legrand.
How does a non-priority load shedding relay work? Consider the example of the updated line of Legrand non-priority load relays (in the figure). A single-phase relay for currents up to 28 A continuously monitors the current flowing through it (and, accordingly, the power consumed) and turns off a non-priority load, for example, a convector, if both burners of the electric stove are turned on at the same time and the power exceeds the set value of 3.68 kW. As soon as one of the burners turns off, the electric convector turns on, etc. Thus, the relay allows the use of devices with a total power of 5 kW, with a limit of 3.68 kW. The power limit can be changed in the range from 0 to 6.5 kW in steps of 0.01 kW. At the same time, an adjustable time delay from 0 to 999 s is provided. to enable/disable non-priority load. The maximum current of the non-priority load disconnect contact is 16 A (4 kW). The relay is equipped with a unit for measuring power, current and voltage. Information is displayed on the LCD display.
In the case when it is required to control currents of more than 28 A or when a three-phase power supply system is used at home, it is advisable to use a universal relay that can operate in both single-phase and three-phase circuits. In single-phase mode, non-priority loads are divided into three groups. If the total current of the priority and non-priority loads exceeds the set limit, the consumers connected through the relay contacts S1 and S2 are first switched off. If at the same time the total current still exceeds the specified limit, then the consumers connected to the relay contact S3 are switched off. With a decrease in the total load, consumers of the third group will be connected first of all, and then, if there is a power reserve, consumers of the first and second groups.
The maximum load on the contacts of the relay of non-priority loads is 15A.
The principle of operation remains the same, however, it is possible to choose an algorithm for disconnecting non-priority loads. Either all three groups are switched off at the same time, when the threshold value of the total current in one of the phases is exceeded, or each group will be switched off depending on the load in a particular phase.
Benefits provided by non-priority load shedding relays:
- Increase in the number of consumers without changing the allocated power and increasing the cross section of the input cable;
- Prevention of disconnection of the introductory circuit breaker due to overload;
Saving energy by reducing losses in the supply line.
Load Sharing Relay Wiring Diagram