Electrical safety requirements, both for a household network and for an apartment or a private house, require the connection and installation of at least two options for basic protection.
The first is automatic switches that protect the electrical network from voltage surges and short circuits.
Second - RCD (residual current device). It protects a person in case of current leakage or when touching live parts. This protection is most relevant in wet areas such as bathrooms.
The difference between an RCD and a circuit breaker
It is a mistake to assume that the RCD and the circuit breaker (automatic) perform the same functions. The machine serves as the main protection of the electrical network. In case of overload or short circuit, it reacts to exceeding the permissible current parameters and turns off the power, thus cutting off the emergency line from the main network.
RCD, unlike the machine, stands guard over human life, not the network, reacting even to the weakest currents.
The principle of operation of the RCD
People constantly use a large number of various household appliances, sometimes quite large power. Electrical wiring has a lifespan and over time there comes a time when the old wires are not able to withstand the voltage. As a result, the insulation layer on the wires is damaged and the wiring comes into contact with the ground. The current changes direction and now part of it goes to the ground. It is deadly dangerous for a person to accidentally get in the way of such leaks.
If a similar situation occurs in the wiring of the water heater, then touching its body is likely to cause serious injury to the consumer, even death. To protect against such influences, RCDs are used. Some manufacturers sometimes release their devices already with built-in RCDs for the water heater. Termex, for example, offers an RCD complete with a cord for connecting the device.
The device will instantly stop supplying current as soon as it detects an earth leakage. The quick reaction of the device is due to the fact that it constantly compares the difference between the current values at the input and output. In a normal situation, it should be equal to zero. If there is a current leakage, then the readings will differ. Since each RCD is designed for a certain trip value, as soon as the difference in readings reaches the passport value, the devicewill disconnect the problem device from the network.
Connecting a protective device
When connecting an RCD, usually there are no problems. First, the circuit breaker is connected to the network, then the RCD for the water heater, and from its output contacts the wires are connected to the socket, to which the water heater or other household appliance is then connected.
In order not to mount two devices, it is convenient to use one, which already contains both an RCD and an automatic device. Such a combined device is called a differential machine and is widely used in a household electrical network.
The only drawback of the differential machine is its high cost. This explains the fact that many still use two devices installed in series (automatic device and RCD).
However, in the case when the consumer has many different household appliances that require protection, it is more rational to use one difavtomat, for example, for a water heater, a washing machine, a boiler, and so on. Such equipment will not overload the electrical panel, and there is enough space for all the necessary machines.
Parameters and characteristics of the RCD
To select the required RCD for a water heater, all the characteristics of this device should be taken into account, namely:
- The value of the rated current - reflects the amount of current that is allowed to pass through the RCD during its operation and is measured in amperes. Standard denominations: 6, 10, 16, 20, 32,40, 50, 63 A.
- Time-current component - reflects the dependence of the speed (time) of RCD operation on the amount of leakage.
- Rated differential current - the value to which the RCD will react and turn off the consumer. Standard range: 10, 30, 100, 300, 500 mA.
- Rated breaking capacity - the maximum short-circuit current that a device can break and still continue to operate.
- Temperature range - typically 20 to 45 degrees.
The indicated parameters are always indicated either on the RCD case or in its passport. Among other things, there is a connection diagram on the case, the type of combined RCD (electromechanical or electronic) and its frequency value, usually 50 Hz. You should definitely familiarize yourself with these data before connecting the RCD to the water heater.
Varieties of RCD
Protection devices are available in three types, differing in the form of current leakage that they are able to stop:
- "A" - sinusoidal and pulsating waveform
- "AC" - variable sinusoidal leakage
- "B" - variable sinusoidal, rectified and constant pulsating leakage
Select protection device
The RCD required to connect the water heater is selected based on all its indicators. In this case, it is imperative to take into account the conditions in which the boiler is located. Easy to use cord with RCD for water heater. Thus, the device is simply connected to the outlet, while the RCD is alreadyembedded in the cable.
It is recommended to use RCD type "A". This is due to the fact that although a sinusoidal current passes through the domestic network, often used household appliances have special electronic components on semiconductors. Due to this, the sinusoidal current is converted into a pulsed one, and a less expensive device of the "AC" type simply cannot cope with it and does not turn off the device in time.
When choosing an RCD for a water heater, you must carefully study the boiler passport. Often, manufacturers indicate which devices are recommended for use with their devices. Type "A" usually appears.
RCD malfunctions
There are times when the RCD, when a water heater is connected through it, turns off. This is due to:
- water heater defective;
- difavtomat or RCD does not match the existing network parameters;
- short circuit in the power cable;
- damaged power supply or heater;
- Installation of the protective device was made with errors;
- There has been a voltage surge or current leakage in the network.
Installing an RCD for a water heater will protect the device from fire and power surges for a long time, as well as protect people nearby from electric shocks.
