Electricity Saving Tips For Homes And Offices

Why is RCCB necessary for your house?

By on February 24, 2017

It was in 2013, during the IPL times, if we remember it correctly, when an interesting commercial surfaced for the first time, featuring a patient being taken for a ‘shock therapy’ by the group of doctors in a mental institution. While trying to administer the shock, one of the doctors got a shock himself triggering some kind of a cascading effect wherein the other doctors also received the shock. The patient, in the meanwhile attempted to escape, eventually himself getting the shock when he tries to snatch his toy from one of the doctors. Then there was a dramatic twist in the storyline, when the doctor, as a result of the electric shock, became mentally unstable and hence patients in the same hospital while the patient, got cured by the shock and was now his doctor AND yes, there was a popular song throughout the commercial – shock laga laga shock laga!! The commercial used to end with the voice over saying, “Shock lagega agar Havells MCB aur RCCB nahi lagaya toh”, meaning you will certainly get a shock if you do not use Havells MCBs and RCCBs.

This interesting commercial was directed for Havells by the noted film-maker, Anurag Basu. The electrical goods maker Havells was then creating a campaign to renew its proposition of providing a ‘shock proof’ life. This commercial vastly helped the brand in building a large consumer portfolio for its products such as MCBs and RCCBs, that were erstwhile considered complete B2B categories.

Though, depicted with great comic sense, the commercial was undoubtedly signifying an important message, related to the home safety against the dangers of electrocutions, short circuits and electrical fires, mainly caused due to a faulty wiring or earth faults. Therefore, it is important for every one of us to understand what is RCCB and how will it help in ensuring electrical safety at our houses.

What is a RCCB?

Residual Current Circuit Breaker (RCCB) is a differential current sensing device used to protect a low voltage circuit in case of a leakage fault. It is sometimes also known as Residual Current Device (RCD). It contains a switch device that switches off (in a fraction of a second), whenever  the current leaks out and does not return back through netural. The RCCB provides protection from small current leakage arising due to accidental touch by human being or insulation failure, which is not possible by MCB or fuse alone.

Why RCCB when MCB is already provided?

There are two types of electrical faults that are quite dangerous:

  1. High current fault arising due to short current or low resistance fault and is protected by MCB.
  2. Earth leakage arising due to cable insulation failure, accidental touch by human, etc. Such faults cannot be detected by MCB. It can only be detected by RCCB.

How does it function?

The underlying fundamental principle behind the functioning of RCCBs is that the current flowing in to the equipment shall return back in full. If there is a difference of even few mill-ampere, it will detect and trip the power supply. The current that leaks out of the system is called residual current. The RCCBs are designed in such a way that, they are capable to continuously sense and compare the difference i.e. the residual current values between the live and neutral wires. Any small change in the current value on account of such event would trigger the RCCB to trip off the circuit. Thus, we can say the RCCBs sense the difference between current values in phase and neutral and breaks the circuit in case of an imbalance and hence provides -complete electrical protection along with MCB to human beings and the equipment.

In an RCCB, the ON and OFF Positions are clearly visible with the help of window provided at the top of housing or the chamber. The ‘Green’ colour indicates the ‘OFF’ position, while the ‘Red’ colour indicates the ‘ON’ Position.

With advanced technology, some of the manufacturers have come out with integrated protection for short circuit as well as earth fault, and the device is called RCBO. In such a situation, MCB is not required. This will be discussed in separate post.

Types of RCCBs

As explained above, RCCB is meant for protection from earth faults and associated risk to human life such as electrical shocks. There are 2 types of RCBs available in the market:

  1. The 2 Pole RCCB: It is used in case of a single-phase supply that involves only a live and neutral wire. It contains two ends where the live and neutral wires are connected.
  1. 4 Pole RCCB: It is used in cases of a three-phase supply connection involving three phase wires and a neutral. It consists of two ends where the three phases and neutral wire are connected.

In both these types of RCCBs, a Rotary switch is used to switch the RCCB back to ON or OFF positions. A test button is also provided to periodically test the RCCB functionality.

Different Ratings of RCBs

For your house hold requirement, 32-63A RCCB of 30-100 mA is considered sufficient. 30 mA is very sensitive and you may encounter few tripping without any apparent fault. While selecting the rating, one should consult an electrician and should question his selection criteria based on the understanding given above.


A RCCB is an essential protective device and a necessity in electrical safety for any house. A properly set RCCB will ensure that there is no fatal injury caused to human being in case of an accidental touch to live wires. Therefore, if you are looking for a proper protection for your house, just go to the market in any regular electrical store and ask for RCCB or RCD and they should be able to give you the same. Apart from Havells; ABB, Anchor and Legrand are some other popular RCCB manufacturers.

Never forget that electricity is your friend only with complete protection in place. Never apply any short cuts. And always consult your electrician for issues related to electricity.

Sources of Information:

  1. http://engineering.electrical-equipment.org/electrical-distribution/residual-current-circuit-breaker-rccb.html
  2. https://electricalnotes.wordpress.com/2011/03/20/mcbmccbelcbrccb/

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  • Muhammad Dessouky

    I have a question please. Isn’t the presence of an RCCB cancel out the purpose of the earth wire(earthing)?

    • https://www.bijlibachao.com Abhishek Jain

      You need both RCCB and earth wiring in your house.

      Why is Earthing required: if you have an appliance that has a fault and the appliance is sitting on an insulated base (for e.g. your washing machine may be resting on plastic wheels), and if there is no earthing, then all the current from phase will flow through neutral and RCCB will not be able to detect it. And when you touch your washing machine, there will be shock that you would observe and the RCCB will trip after that. But if there is proper earthing wire (with very less resistance), then the leakage will go through the earthing wire and will not go through your body (which provides higher resistance).

      However, current always follows path of least resistance and there can be situations where your body provides path of least resistance (for e.g. at times a geyser wiring is next to steel pipes and there is leakage and you touch it). And in such situations the current will flow through your body and will provide a shock. These are the cases where RCCB will trip and protect you.

      So Earthing is an absolute must (even as per Indian Standards for Wiring). RCCB provides additional protection and is good to have.

    • Muhammad Dessouky

      Thank you so much!

  • B P Bhat

    Thanks Aswani Srivastava and Abhishek Jain for the beautiful article. I also read the other article “Ways To Setup A Shock Proof House For Kids”. Both are informative and will help people like me to a great extent. May your tribe increase.

    I have many questions and require your help in getting the answers. Let me start with the first few ones.

    I own a 10 year old building, and recently I have constructed a pent house in it. So my penthouse is a new one. I have 8 earthing points installed 10 years back. On 1st day of every month, I pour around 5 lts of water to each of these earthing points. (which means I have poured water for 10 years * 12 months = 120 times)

    Q1. Now the voltage between Phase and Neutral is 230 Volts; between Phase and Ground is 220 Volts; And between Neutral and Ground is 50 Volts. Can you tell me why this 50 V difference is there and why not Near-Zero volts difference between Neutral and Ground ? And is there any problem in it ?

    … Next … I have installed a 2 KW Solar Inverter in my pent house. I use almost all my electrical items through this Solar Inverter. They include LED lights, Fans, Chimney, TV, Computer and Internet, Exhaust Fan, Fridge, Washing Machine, Water Purifier etc. The Electrical wiring connection is as under:

    a. From Main Meter to MCB near the Meter box … say MCB1.
    b. From MCB1 ==> One circuit is connected to another MCB … say MCB2. From this MCB2, a 15 A circuit (4 sq mm wire) is drawn. As of now I use only my Dish Washer in this circuit. I have couple of spare 15 A socket points in this circuit, for any later use.
    c. From MCB1 ==> One more circuit is connected to the above mentioned 2 KW Solar Inverter. The out put of this Inverter is connected to several MCBs … say MCB3, MCB4, MCB5, MCB6 etc. 5 A circuit (2.5 sq mm wire) is drawn from each of these MCBs. And each of these circuits cater to the Rooms, Hall, Kitchen etc. All the above mentioned loads (LED light, Fan, Fridge etc) are connected through these MCBs. They are all 5A loads only.

    The house wiring is completely/permanently done. These MCBs, Inverter etc connections are temporarily done. It will be done permanently waiting for an expert advice/guidance from you.

    Q2. Now I want to connect an RCCB to my house. Can you tell me where I have to connect the RCCB in this wiring ?

    Waiting for your reply for both the queries. Thanks in advance to both of you.

    BP Bhat

    • https://www.bijlibachao.com Abhishek Jain

      Here is my response:

      1. The voltage difference between neutral and earth arises when there is load imbalance at your end. The imbalance load current circulate between the closed loop of ground and neutral. This results in voltage of neutral to rise. The neutral voltage is generally about 15-20 V. In your case it is very high. This can be if the feeding sub-station where the neutral is solidly earthed is located far off from your house resulting in higher resistance of neutral. You are keeping good earth pit but it is not sure whether the substation is also maintaining of similar order. The problem arises mainly on this account.

      2. RCCB is always connected at the distribution panel at the incomer. Now you have two incomers, one local supply and another from inverter. The RCCB shall be connected at the outgoing of the change over towards load so that load integrity continuously.

      3. It is always advisable to contact licensed electrician for the finer details. It is always important to have physical verification of the site before taking decision of changes in the electrical wiring.

    • b p bhat

      Thanks a lot AJ.

      With regard to Ans1, based on your reply, I think I can do the needful myself, by exploring more.

      Some confusion in your Ans2. Do I need to install 2 RCCBs, one for 15A circuit (after the MCB2); … and … the other one for 5A circuit (after 2KW Solar Inverter, but before MCB3-6) ?. Kindly give me a detailed reply.

      Q3. Is it possible to manage with only one RCCB ?. If yes, then where I must connect the same ?

      Q4. You may also give me the ratings of the RCCBs in both the cases.

      Waiting for you reply.

    • https://www.bijlibachao.com Abhishek Jain

      Hello Mr Bhat,

      Apologies for the delayed reply. I was out of town and could not respond. Regarding your query, there are many issues in your query which are not clear, namely:

      1. I understand you are having single phase 2 kW inverter and the incoming power supply from utility is 3 phase. You will need single phase RCCB for the load connected on solar circuit and 3 phase on the overall system separately.

      2. I unable to understand the connections, considering that it is a grid connected arrangement. There are always intricacies in electrical systems particularly of how neutral is connected. I will suggest to consult the electrician to make the arrangement.

      3. The RCCB ratings are in range 16A-100A; and select based on the maximum transient load that will come based on the start of the appliance sensitivity; 30mA, 100mA and 200 mA. 30mA will cause unnecessary tripping and 100mA may be selected. No. of poles; i.e. 2 for single phase and 4 for three phase circuit.

    • B P Bhat

      Hai AJ,

      Even though it was a belated reply, thanks a lot for the same.

      In fact I was running out of time. So I consulted a couple of other people. (And our collective decision, matched with your answer in #1 above) And I connected the load with an RCCB.

      But now I am facing the problem of RCCB Tripping. As my wiring is over, my this set of questions become infructuous now.

      I will be observing and analysing the wiring and load vis-a-vis tripping for a couple of days. After that I will ask a new question with some different details.

      Thanks a lot for your help so far.


    • BP Bhat

      Any chance of getting a reply, Sir ?

    • https://www.bijlibachao.com Abhishek Jain
    • B P Bhat

      Thanks again.

      I have mailed my contact number. But I will observe my load for a couple of days and will raise the question later.

  • Soham Chandra

    Abhishek Ji, I come from a remote background where no electrician has till date installed RCCBs! My question is can I use a 4 pole RCCB in place of a 2 pole RCCB for the time being, as in near future the supply will get converted to 3 phase line from 1 phase line! Please help as quickly as you can.What is the ideal sensitivity for a household RCCB to ensure no “false” trips (I have seen, after installation, Havells’ wires “leak”, but I can’t change all the wires due to financial shortage )? Will 30 mA do?
    I have “normal” appliances (single phase supply) and air conditioner (3 phase supply), provide me with a solution to connect RCCBs as required and will be the best according to you, in detail so that I can instruct the electrician to do that.

  • dixit kohli

    mr. abhishek ji
    Kindly suggest for single phase connection, to protect from high voltage(double phase)
    which device we should use for protecting our appliances

  • Sai Prasad

    Mr Abhishek Jain– Does the tripping of the ELCB also trip the MCCB? When i press the reset/test button on the ELCB it trip both the ELCB and the CCB.

    • https://www.bijlibachao.com Abhishek Jain

      Is it MCB or MCCB? I understand it is MCB because in household application MCB is used. MCB is provided for each circuit in the house. When there is high resistance fault, RCCB will trip the power supply. When there is high current fault, the respective MCB will trip, which may be associated with or without the RCCB tripping. Does all the MCB are tripping with the tripping of RCCB/ELCB or a particular MCB. I will suggest to get the circuit on your panel checked by an electrician as it is difficult to interpret the problem like this.

  • Swapan

    1. Is RCCB be of any use in a house where earthing is absent? Will RCCB provide any protection to residents and appliances if there is no earthing?
    2. My electrician says that this thing is a nuisance because of so many unwanted factors being there in majority of the houses( example- dampness in walls) and poor work / practices of electricity department related to supply. He is a sharp guy & really good in his job and convinced me not to have one installed.
    Then I read your article and I surely require your expert opinion. Please guide.

    • https://www.bijlibachao.com Abhishek Jain

      1. RCCB will be use in a house where earthing is absent because it measure the difference of current between two phases. If there is a difference of current, means some current is leaking out through fault returning to the supply neutral through earth. Earlier earth leakage detectors used to be provided which use to measure the leakage current and were prone to unwanted tripping.

      2. Let me give a situation which can be fatal in your house. Some one in your house touches the phase wire, the fault current will pass through its body. The MCB provided in the mains will trip immediately because the current drawn is high. Suppose you are wearing sleepers which reduces the fault current but not sufficient enough to give you a shock, than MCB will not trip. What is the protection? In such cases it in RCCB which will protect you.

      3. Your electrician may be a sharp guy but having knowledge of the appliances which were in market 10-15 years ago. RCCB is latest development and will protect you and your house. My advise is to provide this in your house and having medium sensitivity.

    • ss

      Thankyou Abhishek ji for your valuable suggestion.

      In this case , will it be suitable to provide a single RCCB of 30 ma in the mains only( no earthing is there). What about its type, AC or A etc? Simply, please suggest which RCCB to install, brand and model.

      Will the RCCB trip in case of faulty neutral or floating neutral or neutral wire disconnection from outside (no earthing)?

      Lastly, this is not related to the topic but I hope you may be able to guide me.
      I read about 4 pole MCB and that it is installed where particular type of earthing is present. But I couldn’t find out if it can be installed if there is no earthing. I think 4 pole MCB gives protection to neutral wire.
      I don’t require explanation on this. I simply want to know if 4 pole MCB can be put where there is no earthing and will it be useful against neutral wire disconnection or faults?

      I don’t have any problem in neutral wire at present but I know a case where electricity department connected neutral wire carelessly while doing repairs or changing meter and later it broke. I don’t trust those guys and want to do something about it.

      Please reply or I won’t be able to decide or do anything regarding this.


    • https://www.bijlibachao.com Abhishek Jain

      Yes it is ok but always better to consult the technician available at the shop selling the product about its suitability for the location
      Havell’s/Schneider are good brand. This will work if the neutral is also disconnected from the mains.
      MCB is a current protection device. The current in the neutral circuit when all the phases are balanced is almost negligible. All the four MCB shall be mechanically coupled means, if there is a fault in one phase, all the phases shall tripped along with disconnection of neutral wire. Care is required that if the neutral contacts become defective and does not make a contact (very remote situation) that you have the same situation of neutral disconnect in your house.
      Better go for RCCB in your house and simultaneously operated 3 or 4 pole MCB.

    • imran

      hi i am imran khan from tirupur tamilnadu ,,, i read your information regarding RCCB its was very nice and useful ,, thank you abhishek ji ,, well done

    • https://www.bijlibachao.com Abhishek Jain

      Thanks Imran. I am glad that you found it useful.

    • Anil

      Dear abhishek Ji,
      I want to consult a strange condition occurred in my house circuit. I have installed RCCB in main line then MCB for all seprate rooms. I put on one of my CFL of a 85 watts with 20 watts cfl total load was 105 watts after an hour I saw that wire of cfl 85 watts start heating up and got burnt all of my rooms circuit. But it was strange that none of the RCCB and MCB switches off. My circuit I have to put them off. Please guide me what should I do to not to encounter such problem in future. As RCCB is tripping off well now.
      [email protected]

    • https://www.bijlibachao.com Abhishek Jain

      If RCCB is tripping off well then it means that it is OK. But the real problem is that why it failed when the wire got burnt. This can only happen if the current flowing through the phase wire returned back through neutral without getting earthed. There is no absolute protection for such cases because MCB setting is generally more than what is required to protect in such situation. It can only be prevented if you provide a fuse wire in the low wattage circuits. I also think that the current rating of the wire is poor or of poor quality as it started burning even with a small load connected.

      The open cables should be laid in metallic conduit so that the smoke does not let the fire to continue and also it will get earthed for RCCB to trip. The concealed cables do not catch fire due to non availability of oxygen and will only be cut.

      So your problem appears to be of inadequate cross-section of cable or poor quality of cable. Ensure open cables to be laid through metallic conduit.