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 basic protection options.
The first is circuit breakers that protect the electrical network from voltage surges and short circuits.
The second is an RCD (residual current device). It protects a person in case of current leakage or when touching live parts. Such protection is most relevant in humid rooms, such as a bathroom.
Difference of RCD from 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 during a short circuit, it reacts to exceeding the parameters of the permissible current and turns off the power, thus cutting off the emergency line from the main network.
RCD, unlike the machine, is on guard of human life, not the network, responding to even the weakest currents.
The principle of operation of the RCD
People constantly use a large number of various household appliances, sometimes of rather high power. Electrical wiring has a useful life and over time there comes a time when the old wires are not able to withstand voltage. As a result, the insulation layer on the wires is damaged and the wiring comes into contact with the ground. The current changes the direction of motion and now part of it goes into the ground. It is mortally dangerous for a person to accidentally get in the way of such leaks.
If a similar situation arises in the wiring of the water heater, then touching its housing is likely to cause a serious injury to the consumer, even fatal. To protect against such effects, RCDs are also used. Some manufacturers sometimes release their devices already with built-in RCDs for the water heater. Termex, for example, offers an UZO complete with a cord for connecting the device.
The device will instantly stop supplying current as soon as it detects a leak to ground. The quick response 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 zero. If there is a current leak, then the readings will differ. Since each RCD is designed for a certain operation value, as soon as the difference in readings reaches the passport value, the device will disconnect the problem device from the network.
Protective device connection
When connecting an RCD, usually no problems. First, the circuit breaker is connected to the network, then the RCD for the water heater, and already from its output contacts wires are sent to the outlet, 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 that already contains both an RCD and an automatic machine. Such a combined device is called a differential machine and is widely used in household electrical networks.
The only drawback of a differential automaton is its high cost. This explains the fact that many still use two sequentially delivered devices (automatic and RCD).
However, in the case when the consumer has many different household appliances that require the installation of protection, it is more rational to use one difavtomat, for example, on a water heater, washing machine, boiler, etc. Such equipment will not overload the electrical panel, and there will be enough space in it for all the necessary automatic machines.
Parameters and characteristics of RCD
To select the necessary RCD for the 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 ratings: 6, 10, 16, 20, 32, 40, 50, 63 A.
- Time-current component - reflects the dependence of the speed (time) of the RCD operation on the leakage value.
- The rated differential current is the value by which the RCD will react and disconnect the consumer. Standard range: 10, 30, 100, 300, 500 mA.
- The rated ability to disconnect is the maximum current indicator during a short circuit, which the device is able to disconnect while continuing to work.
- The temperature range is usually from 20 to 45 degrees.
The indicated parameters are always indicated either on the RCD enclosure or in its passport. Among other things, on the case there is a connection diagram, a type of combined RCD (electromechanical or electronic) and its frequency value with a nominal value, usually 50 Hz. You must 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, which they are able to suppress:
- "A" - sinusoidal and pulsating form
- "AC" - variable sine wave leakage
- "B" - a variable sinusoidal, rectified and constant pulsating leak
Protection Device Selection
The RCD required for connecting a water heater is selected based on all its indicators. At the same time, the conditions in which the boiler is located must be taken into account. The cord with an RCD for the water heater is convenient to use. Thus, the device is simply connected to the outlet, while the RCD is already mounted in the cable.
It is recommended to use RCD type "A". This is due to the fact that although a sinusoidal current flows through the domestic network, often used household appliances have special electronic units on semiconductors. Due to this, a sinusoidal current is converted into a pulsed, and a less expensive device such as an AC simply cannot cope with it and will not turn off the device on time.
When choosing an RCD for a water heater, it is necessary to carefully study the boiler passport. Often manufacturers indicate which devices are recommended to be used with their devices. Typically, type "A" appears.
RCD faults
There are cases when the RCD, when a water heater is connected through it, is turned off. This is due to:
- water heater is faulty;
- difavtomat or RCD do not correspond to existing network parameters;
- short circuit in the power cable;
- the power supply is damaged, or the heater;
- installation of the protective device is made with errors;
- There are voltage drops or current leaks in the network.
Installing an RCD for a water heater will protect the device from ignition and power surges for a long time, and also protect nearby people from electric shock.