A home electrician is a rather complex and diverse topic, and it is advisable for every homeowner to know the basic details, since not only money costs, but also the security of your home depend on it. In this article, we will try to find out what is better - difavtomat or RCD.
Introduction to the topic, or what is difavtomat?
To deal with this issue, first we’ll try to decide on the basic concepts. So, difavtomat.
The device, called a differential circuit breaker , successfully combines the functions of both an RCD and a conventional circuit breaker. This machine protects a person in case of touching bare sections of the conductive part of the wire or those parts of the electrical networks that are energized due to damage to the wiring or other similar factors. Today, there are a huge number of such devices that are designed for different operating currents as well as for different leakage currents.
Its main distinguishing feature is that it consists of two well-separated functional parts: a circuit breaker (two or four poles), as well as an electric shock protection module. The installation of the difavtomat should be done exclusively on the mounting DIN rail, and this design takes up much less space than the combination of an RCD and a circuit breaker.
Given the speed of operation, which is only 0.04 seconds, differential machines provide the most adequate protection against electrical shock in a person in almost any operating condition. It is also important that the differential machine qualitatively protects the devices in the network from overloads that inevitably arise during various types of emergency. And further. Its design provides the fastest possible power off in conditions when voltage surges over 250 V are observed on any part of the network.
Given the unenviable characteristics of domestic electrical networks, as well as the degree of their deterioration, the latter characteristic is especially important.
The main advantages of difavtomat
• Very high response speed.
• Protection of equipment from power surges and operating overloads.
• Ability to operate in conditions of -25 to +50 degrees Celsius.
• Huge threshold of wear resistance.
What is an RCD?
You can not ignore the second "opponent" in the dispute on the topic "difavtomat or RCD." What is an RCD?
This abbreviation stands for "residual current device". The operation is carried out when detecting the presence of leakage currents. Simply put, how much current came to the device through one wire, the same amount should go to another section of the wiring. If the current begins to go to ground or through the ground wire, the protection instantly trips, immediately disconnecting the network from the power source.
Such a system must (!) Be placed on outlet groups, as well as on boilers, washing machines and electric stoves. Such devices do not protect (!) Your equipment and wiring from system overloads or short circuits.
The latter circumstance very often is not taken into account by unfortunate electricians, who often use only one RCD for the sake of cheaper circuits. In addition, there is a selfish interest when it is given out as a differential automaton, the cost of which is higher.
Basic information about the RCD device
What is the principle of operation of the RCD? His work is based on the reaction of the current sensor to a change in the differential value of the current in the conductors.
What is a current sensor? This is the most common transformer, but made like a toroidal core. The response threshold is set using a magnetoelectric relay, which has an extremely high sensitivity.
It is important to note that all RCDs made according to this classical scheme are extremely reliable and simple devices that have very high reliability and reliability.
It is necessary to warn that today there are electronic RCDs, which are based on a special electronic circuit. A relay or circuit acts on a mechanism that opens the electrical circuit if necessary. Here is what the RCD device includes.
What parts does the actuator consist of ?
- From the direct contact group set to the maximum current value.
- A spring that directly opens the circuit if there are any problems in its operation.
If you want to independently test the device for operability, it will be enough to click on the "Test" button. In this case, a current is artificially supplied to the secondary winding, and the relay is triggered (it should, in any case). So, if necessary, you can easily and without any costs be able to check the health of all your equipment.
The principle of operation of the RCD
If we talk about the normal mode of operation, then the current (I1 = I2) flows in the opposite direction, inducing magnetic currents in the secondary winding of the transformer (F1 = F2). They have exactly the same value, due to which they mutually cancel each other. Since the current in the secondary winding is practically zero in this case, the relay cannot operate.
RCD operation in case of leakage
In contact with conductive parts, a leakage current occurs. In this case, the current I1 is not equal to I2, and therefore, a current appears in the secondary winding, the value of which is sufficient for the protective relay to trip. It provokes a spring switch, the RCD is turned off.
Differences between the two protection systems
To continue our story further, we also have to find out what is the difference between RCD from difavtomat. This is not to say that the differences are so dramatic, but they still exist.
It should be noted that the coverage of this issue is extremely important, since even some electricians are sometimes unable to distinguish these devices. However, there is nothing to be surprised at: they are extremely similar even in photographs.
The main difference between the differential machine and the RCD is that they are intended for several different purposes. We have already said this above, but we will repeat it again: RCDs cannot be used to protect equipment and wiring from overload or short circuit! Moreover, before the RCD, it is necessary to mount a circuit breaker, which will save the device itself from this kind of trouble. That's the difference between an RCD from a difavtomat.
Be sure to consider this when buying or consulting with especially “thoughtful” electricians who will be happy to save on your own equipment.
Difavtomat in this regard is much better, because it combines in one case both an RCD and a circuit breaker. Accordingly, this kind of device not only protects a person from electric shock, but also saves your wiring and equipment from burnout in the event of a short circuit. Thus, UZO and difavtomat, the difference between which we have just disclosed, are somewhat diverse mechanisms.
We recall once again that a differential circuit breaker can be used as a fuse in those houses where there is a constant danger of chronic overloads in the network.
This is a detailed difference between the RCD and the difavtomat. But how to make the right choice in the store? After all, we have already said that these devices are extremely similar to each other even in photographs.
We buy correctly!
First, pay attention to the direct name of the device itself. Today, almost all manufacturers have finally met the consumers, deigning to indicate on the case of the device itself information about the difavtomat or RCD in front of you. Therefore, we would not recommend buying a similar Chinese-made equipment. Sneaky Asians either do not indicate anything at all, or do it using only some clear notation.
Approximately the same category includes advice on carefully familiarizing yourself with the marking, which should always be indicated all on the same device case or on its packaging (less reliable option).
So, if you see on the case only the value of the rated current (16, for example), and there is no letter before this designation, then you are holding an RCD. Note that “16” in this case means “ampere”. If there are letters B, C or D in front of the numbers, then you have a difavtomat in your hands. The letters indicate typical characteristics of thermal and electromagnetic releases, but at the household level, paying special attention to them is not necessary.
In addition, it does not hurt to look at the connection diagram as well. This method is somewhat more complicated, but it gives a 100% guarantee of differentiation. This information should also be displayed on the case. So, if the scheme indicates only the presence of a difavtomat with the designation “Test”, then an UZO is in front of you (do not confuse!). Accordingly, if there is a “Test” and the windings of the releases are indicated, then you are holding a differential automatic device.
Finally, it makes some sense to pay attention to overall dimensions. If we talk about old models of difavtomatov, then they are an order of magnitude wider than RCDs. In those days, they simply did not know how to produce sufficiently compact trip units, and therefore larger enclosures were required. Attention! All modern differential automata just take up less space!
However, it is important to warn you that paying any serious attention to the last item is not worth it, since at present there are a huge number of completely identical devices in size.
We pass to the main
So, difavtomat or RCD? What conclusion can be made based on the foregoing? What is better to choose, which is more reliable and suitable for operation in domestic realities? To answer this question, we will conduct a comparison of devices on six indicators at once. After comparing all the pros and cons, we will try to come to a consensus.
Volume occupied by the device in the shield
Of course, in this aspect, only those people who have very little space in the apartment can see any important differences, which does not allow us to mark a normal electrical panel in the hallway. However, given the universal desire for compactness and beauty, there are most of those in our country. In addition, it is better to place everything in advance as small as possible, since subsequently the shield will not have to be expanded if it becomes necessary to install more powerful electrical equipment in the apartment.
So, at the present time the RCD (three-phase - including) takes up much more space in the shield than a differential automaton. What is the reason for this? The most attentive readers themselves could already find the answer to this question in the article.
We have already talked about the need to install circuit breakers in front of an RCD, so because of this, the entire structure in the shield begins to take up more space. If you mount a differential machine there, you can save some amount of space. For example: in the standard case, RCDs with circuit breakers occupy three modules at once, while a differential circuit breaker only takes two.
Thus, in this “round” the difavtomat won, allowing to leave a place for expansion of the structure.
Easy installation
As in other cases, for many electricians it is the speed and ease of installation of the entire structure that is important. If you are interested in installing an RCD, the phase is led to the switch, and from its output a jumper is mounted to the input of the trip device. Zero is also connected to the input. It should be noted that there are several connection schemes that are studied by professional electricians. As a rule, they are not needed in everyday life.
How to mount a differential machine?
But what about connecting a difavtomat? If we talk about a differential automaton, then the phase and zero immediately clings to the input terminals of the device, so that in the general circuit there are much fewer jumpers and transitions. Accordingly, the internal structure of the flaps is also greatly simplified.
Thus, connecting a difavtomat is much easier and faster, so in this case too, we are confidently awarding the victory to him.
Operation benefits
Theoretically, we can assume that once on the line of outlets in the bathroom, an RCD worked. You can immediately assume that somewhere on the line there was a current leak. Of course, the troubleshooting algorithm is somewhat more complicated, but the main conclusions can be drawn immediately.
If the circuit breaker has tripped, then the reason is obvious: overload or short circuit. You only have to find out the cause and eliminate it. Given that the reason for turning off the machine is more or less clear, it will not be so difficult to do this.
Now let's look at the same thing, but with reference to a differential automaton. But when you turn it off, the reason is not immediately clear, so you have to check all known causes. Accordingly, it will take much more time. That is the difference between RCDs from the difavtomat in this regard.
Thus, at this stage, we would prefer an RCD.
Cost issue
Since today there are a huge number of the most varied manufacturers on the market, consider the cost of the products of EKF, which is quite popular among professional electricians. So, a standard 16 A EKF-difavtomat costs about 600 rubles, an RCD for the same current strength costs the same 600 rubles, and a circuit breaker is sold at a cost of about 40 rubles. By purchasing the same thing on specialized sites, you can even count on automatic shutdowns, which in such cases are sold almost by weight.
Before connecting the difavtomat, make sure that there are no frequent and sudden voltage drops. Why are we talking about this? This will become clear after considering the features of the replacement of this equipment.
Given the fluctuations in cost depending on the supplier, it is difficult to talk about the benefits of a particular option.
Life and replacement cost
As can be assumed, the characteristics of this criterion automatically follow from the previous one. Everyone knows that any electrical equipment has a certain service life, after which it becomes unsafe to operate. Let's assume that for one reason or another, an RCD or an automatic shutdown machine failed. What to do next? Change a failed part, after which the system will continue to work as before.
But with the difavtomat, the situation is not so clear. Suppose that the winding of any of the releases has failed, while the built-in RCD during testing has shown its full performance. Alas, this does not matter, since in any case you have to replace the entire difavtomat, the price of which makes this event extremely unprofitable. It is much easier to replace a penny machine, which often fails.
Thus, in this round the victory is again for the RCD.
Reliable operation
Among experts, it is widely believed that devices that combine several functions at once are less reliable compared to machines that are designed for only one thing. So an RCD or a difavtomat? What to choose for the highest reliability?
You can argue about this for a long time, but practice has unequivocally shown that in fact the failure rate is almost the same. It is possible that this option is solely vendor specific. So in this case it is extremely difficult to draw a conclusion about the unequivocal advantage of a particular device.
We can only say that the RCD, the connection diagram of which we examined above, assumes greater reliability in the conditions of domestic voltage drops. Naturally, if you do not forget to connect an automatic shut-off machine in front of it, as we have repeatedly mentioned above.
Thus, in most cases, it is still an RCD that will be the best choice. However, it all depends on the characteristics of your network, as well as the size of the electrical panel.