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Why is a MCB important?

November 6, 2009

Hi!

Before explaining to you the actual concept of this post, let me share an incident with all of you.

One day, in the evening at around 9pm, my neighbor needed my help. After helping her, I was sitting reading a magazine. Then, her son came from outside and was feeling very tired. He wanted to take a bath. So he switched on the geyser and it caused an overload that left them in darkness. The sudden prolonged darkness caused a lot of problems as he couldn’t prepare properly for his exam which was the next day.

This can happen to anybody. But, do you know why this happened? This was because they were using a fuse and not a Miniature Circuit Breaker (MCB). Here, to fix the damage caused, they had to wait for an electrician till the morning, as it was already too late. If they would have used a MCB, it would have solved the problem. Unlike a fuse, a MCB can be reset immediately after the overload is detected and removed. So, in the above case, if a MCB was used, then it could have been reset immediately after the reason for overload was identified and isolated, and her son could have prepared properly for his exam, without facing such a problem.

Now let us come to our topic. Let me first tell you what a circuit breaker is. A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused due to excess passage of current. Its basic function is to detect a fault and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in various sizes, from small devices used to protect an individual household appliance up to large switchgear designed to protect high voltage circuits to supply an entire city.

A MCB is a mechanical switching device which is capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and automatically breaking currents under specified abnormal circuit conditions such as those of short circuit. In short, MCB is a device for overload and short circuit protection. They are used in residential & commercial areas. Just like we spend time to make a thorough check before buying appliances like washing machines or refrigerators, we must also research about MCBs. Also, if you are still using a fuse then you must replace it with MCB.

I’m sure you don’t need any more persuasion to install MCBs as soon as possible!

Other than a MCB, there are also some products like RCCB and RCBO that prevent you from electric mishaps.

I will tell you more about them in our future posts.

Till next time,

Elex – Your Electricity Expert

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52 Comments leave one →
  1. Thanigaivel permalink
    December 28, 2009 1:58 pm

    Hi Elex,
    Can you tell me about your “INDICATOR LIGHT” product. Does the light get damaged or it just starts working when there is a short circuit…

    • December 29, 2009 11:36 am

      Hello Thanigaivel,

      The light is an indicator only to tell you whether the supply is available or not.
      It is in no way concerned with short circuit or anything else.

      Regards,
      Elex!

  2. Sam permalink
    January 4, 2010 10:21 am

    Dear Elex,

    I am building a new home, want to protect me and my kids from electrical mishaps, Can you help me with good literature on earthing circuit, How to select MCB/ ELCB or RCCB. Best suggested practice while designing electric circuits ( I have 3 phase and all possible home appliances like A/C, Washing machine, Micro Oven, Electric hood, Vacuum cleaner, water heater etc), How should I plan for a balanced load in my home.

    Sam

    • January 6, 2010 7:08 am

      Hello Sam,

      MCBs or Miniature Circuit Breakers are intended to give protection against
      overloads and short circuits, which can cause damage to cables and
      equipment. They have current ratings (6A, 10A etc.) above that can
      open or trip and give protection to the equipment.

      – The first characteristic is the overload which is intended to prevent the
      accidental overloading of the cable in a no fault situation. The speed of
      the MCB tripping will vary with the degree of the overload. This is usually
      achieved by the use of a thermal device in the MCB.

      – The secondcharacteristic is the magnetic fault protection, which is intended to
      operate when the fault reaches a predetermined level and to trip the MCB
      within one tenth of a second. The level of this magnetic trip gives the MCB
      its type of characteristic as follows: – ·

      Type B – trips between 3 to 5 times full load current

      Type C – trips between 5 to 10 times full load current

      Type D – trips between 10 to 20 times full load current

      -The third characteristic is the short circuit protection, which is intended
      to protect against heavy faults maybe in thousands of amps caused by short
      circuit faults. The capability of the MCB to operate under these conditions
      gives its short circuit rating in Kiloamps (KA). In general for consumer
      units a 6KA fault level is adequate whereas for industrial boards 10KA
      fault capabilities or above may be required.

      MCBs are offered in types B , C and D characteristics. Where normal
      resistive loads are being fed the type B characteristic may be sufficient
      but in many industrial application motors, special lighting and data
      equipment which is being fed may adversely affect the MCBs at the start
      and therefore, it is necessary to use type C characteristic breakers.
      Use B curve MCBs for lighting loads & C curve for motors & inductive loads.

      For a Balanced Load for your home,
      First of all decide the total load of your home i.e. Total Wattage of your
      equipments based on equipments work on 1 phase or 3 Phase .
      Then divide the load on all three phases separately taking care of
      division as per rooms ,kitchen etc.
      Wiring for lighting loads & Power loads are done separately.

      For the selection of RCCBs,you can use RCCB 4P, 30 mA ,the Current Rating shall depend
      on your total load.

      For your System, first place an Isolator as Main Switch, then a MCB 3P+N for Overcurrent Protection
      wired up to RCCB 4P 30 mA for Residual Current Protection.
      After that wiring to the loads through respective MCBs should be done.
      For more protection from electric shock to individual circuits use
      RCBOs on individual circuits ( such as kitchen & washrooms).

      To know more about Earthing systems you can view Wikipedia, the link is as follows:
      http://en.wikipedia.org/wiki/Earthing_system

      And yes, I suggest that you consult an electrician for proper wiring &
      distribution circuits. In case you have any other queries, you can get in touch with me.

  3. April 16, 2010 4:26 pm

    Hello Elex…

    Can you tall me about your” MCB” product?what are the rating types of MCB, we can use for industrial purpose.like three phase induction motor(500 rpm,600 rpm,900rpm,1000rpm,1200rpm,1500rpm,3000rpm)?

    NIL

    • April 30, 2011 5:14 am

      Hey,

      A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.

      Havells is the largest manufacturer of MCBs in the country and 30% of the MCBs sold in UK are Havells manufactured. Our products are approved by international quality bodies such as KEMA, UL, CE, CSA and VDE and are as per IEC standards.
      Havells offers three kinds of MCB: Lower rating MCB, Mini MCB and Higher rating MCB.
      MCCB are used in high power application in generation station above 100A

      For any other query, do revert back.

      Regards
      Elex

  4. Jay Popat permalink
    May 4, 2010 2:43 pm

    Dear Havells

    I have installed a 1.5 ton Panasonic Split AC. I have been asked to install a MCB. I have 3 Phase. Which one of your MCB should be used and it will be helpful if you can advise an approx price for it.

    I have to install it tomorrow. Sorry for short notice.

    Awaiting your reply

    Regards
    Jay
    Ahmedabad.

  5. Jay permalink
    May 11, 2010 11:07 am

    Hi Elex

    Thank you for your lightening response. I really appreciated it.

    I was able to see the Chart. Mine is 1.5 Ton Ac and i did install a C series 16A MCB (MFG Date 2007) but the wire is of 2.5 sq mm.

    This raises few questions as below:

    1. Is it safe to use Havells 2007 MCB?
    2. Is it okay if I continue using 2.5 sq mm or shall I change it to 4 sq mm wire.
    3. I note that when AC runs, lights in others room flicker for a moment when AC restarts Automatically. My flat has 3 phase power and main board is having regular fuses.

    I am little concerned now.

    anxiously awaiting your reply.

    Regards

    Jay
    Ahmedabad.

    • May 12, 2010 5:20 am

      Dear Jay,
      It is safe to use 2007 mfg. MCB.

      The 2.5 mm cables are recommended for currents 13A- 20A & 4 mm2 cables are recommended for above 20A to 25A . The 4 sq mm cable shall have lesser heating than 2.5 mm2.
      Based on your current consumption and the loads you have connected you can decide accordingly.

      When the AC starts it draws higher current initially & because of which the voltage drop happens. If this flicker is momentary then it is fine otherwise get your wiring checked for voltage drop by an electrician.

      regards,
      Elex

  6. May 19, 2010 3:22 pm

    Sir,
    There are frequent power fluctuations in our power line. Is it advisable to go for an MCB and if so what rating?
    I have 230V single ph line. My friends advised me to go for HAVELLS MCB.
    Please advise me more on the ratings and preferences.

    Thanking you

    • May 26, 2010 6:06 am

      Dear FR,

      An MCB works for over current protection and does not give any voltage protection. For voltage fluctuations get the wiring of your house checked. Regarding the ratings of the MCB it will depend on the loads you have connected. For proper distribution of electricity you should consult an electrician.

      For any other query do get back to me.
      regards,
      Elex

  7. Ammit permalink
    May 23, 2010 7:59 am

    Can you please advice if a 16 Amp B series MCB is OK for a 1 Tonne Air conditioner?

    Thank you.

    • May 24, 2010 6:57 am

      Dear Ammit,

      Here is a Havells MCB selection chart for your air conditioner. This will be of great help to you. If any query do get back to me.

      regards,
      Elex- Your Electricity Expert

  8. September 9, 2010 4:10 pm

    Dear sir

    Can you send 3 no of mcb/mccb by carrier.

    Thanking you

    with best regard
    Bajaranglal Agawal
    mob-09437540752.

    • April 29, 2011 9:37 am

      Dear Sir,

      I hope your query has been addressed by our support staff. We’d like to know if you were satisfied with the experience or not. Do revert back.

      Regards,
      Elex – You Electricity Expert

  9. Neeraj kangar ror permalink
    September 26, 2010 5:44 am

    This is best site for gaining knowledge about mcb,rccb,elcb and all about other electrical appliances.

    • September 27, 2010 6:44 am

      Dear Neeraj,

      Thank you for the appreciation. Do let us know if you need any other information.

      regards,
      Elex- Your Electricity Expert.

  10. Shyam sunder permalink
    October 24, 2010 1:07 pm

    I want exceeding 600 W load MCB should trip tell me what MCB TYPE to buy ?

    • October 29, 2010 10:20 am

      Dear Shyam,

      Thank you for your query. Our representative will contact you to help you further.

      regards,
      Elex- Your Electricity Expert

  11. ashok mehta permalink
    December 12, 2010 7:12 am

    Hi,

    I have 3 phase supply at my home. I want to replace the old ceramic fuses with MCB.

    My phone number is Delhi 41661886. Can your representative give me a ring to guide me

    through the process including balancing the load between the 3 phases.

    Thanks.

    Ashok Mehta

    • December 13, 2010 6:12 am

      Hi Ashok,
      Thank you for the query, we will be glad to help you.
      Our representative will get in touch to help you your further.

      Regards,
      Elex – Your Electricity Expert

  12. subhash chandra gupta permalink
    January 31, 2011 5:03 pm

    I have installed a 295 to 280 line automatic voltage corrector having a very large transformer. My electrictric distribution system has 32A Havells MCBs B type. When the above AVR is started the above MCBs trips both on phase and netural. Now I have installed 63A C-type Havells MCB, the problem of tripping is over. Please tell me whether it is safe or otherwise what should have been better.

    • February 1, 2011 5:35 am

      Hi Mr. Subhash,
      Thank you for the query, we will be glad to help you.
      Please provide with your contact number so that our representative can get in touch to help you further.

      Regards,
      Elex – Your Electricity Expert

  13. saibaba k.v.n permalink
    April 11, 2011 10:09 am

    Sir, I have got 16 amp MCB for my water geyser of 3000 watts. It trips regularly after heating for 5 minutes. I changed the MCB thrice still the problem continues. What to do. How to determine correct MCB amp.

    • April 11, 2011 10:22 am

      Hi Saibaba,
      Thank you for the query, we will be glad to help you.
      Please provide with your contact number so that our representative can get in touch to help you further.

      Regards,
      Elex – Your Electricity Expert

  14. Amit Jaiswal permalink
    April 14, 2011 9:18 pm

    Sir,
    I am planning to Get a 1.5 Ton AC installed. The dealer have asked me to get a 32 A MCB. He have not specified about the Series (B or C). As per the chart the C series 16 A would be sufficient. Still the Dealer is recommending for 32 A MCB. Will not an over rated MCB (32A instead of 16A) fail in the purpose of protection.
    Please Reply asap.
    Regards
    Amit

    • April 16, 2011 12:21 pm

      Hi Amit,
      Thank you for the query, we will be glad to help you.
      Please provide with your contact number so that our representative can get in touch to help you further.

      Regards,
      Elex – Your Electricity Expert

  15. GP Singh permalink
    April 19, 2011 6:50 am

    I have 1.5 ton window ac having 20A MCB next to Mains supply socket and 20A MCB in distribution bof of my flat for this circuit. The supply is tripped occasisonly when the AC starts. Electricians and AC mechanics are advising me to change both MCBs to 32A. I am not convinced. Could you please help. I stay at Dwarka Sector 2 N Delhi. Mob 9871706386.
    Regards

    • April 28, 2011 10:28 am

      Hi Mr. Singh,
      Thank you for the query, we will be glad to help you.
      Our representative can get in touch to help you further.

      Regards,
      Elex – Your Electricity Expert

  16. Vikky permalink
    May 14, 2011 10:44 am

    Thanks for the details about MCB

    • May 16, 2011 11:51 am

      Hi Vikky,
      It’s our pleasure! Do get back to us, in case any more queries.

      Regards,
      Elex – Your Electricity Expert

  17. Rahul P permalink
    May 25, 2011 8:46 am

    Hey Elex,
    I have taken 4 KVA load and single phase electricity connection at my new home, Can you suggest and advice in detail if I can install 1.5 ton Split AC at this load & precautions if any.

  18. Pijush Maiti permalink
    June 20, 2011 1:53 pm

    Dear Elex,

    I would like to know:

    1. Cables of what cross-sectional area are suitable for the main line wiring of three 1.5 ton ACs.

    2. Which cable is suitable for this type of use—PVC or XLPE.

    Thanks and regards

    Pijush

  19. priya permalink
    June 28, 2011 2:31 pm

    can we use stebilizer instead of mcb..??could u tell me d diffrence between stebilizer and mcb??

    • July 4, 2011 8:06 am

      Hi Priya,
      Thanks for writing in. We ll get back to you on this shortly.

      regards,
      Elex – Your Electricity Expert

  20. mahadev singh permalink
    June 29, 2011 3:41 am

    dear sir,
    can you tell me difference between MCB and Relay. please

    thank you.

    • July 4, 2011 8:06 am

      Hi Mahadev,

      Thanks for writing in. We shall get back with the information, shortly.

      regards,
      Elex – Your Electricity Expert

  21. deepty sharma permalink
    June 30, 2011 12:18 pm

    hiii Elex
    i m doing training at Havels pvt. ltd. at baddi n as per d curriculum of my syllabus i have to make a report can u mail me a report based on mcb manfactured at baddi plant…

    • July 4, 2011 9:25 am

      Hi Deepty,

      Thanks for writing in. We shall get back to you with the information, shortly.
      You can also share your contact number, so that our representative can get in contact to help you further.

      regards,
      Elex –– Your Electricity Expert

  22. khushman taunk permalink
    July 16, 2011 8:05 pm

    hi there!
    I have to install a 1.5 Ton AC at my home and i will be using a separate wiring line directly from main meter for it. I am having single phase connection. I want to know what sort of MCB should i install for this wiring? Plz give the specifications for the appropriate MCB i.e whether it should be single pole, double pole or SPN; whether it shud be B,C or D type and of how much ampere it must be. ACs input power is 1800W and current is approx 8.15A. I am thinking to use a 40A isolator in place of the starter switch; is it ok to do so? Where must the isolator and the MCB be placed? My mobile no is 09547150515.
    Please reply soon as i need to complete the wiring very soon.

    • July 28, 2011 12:14 pm

      Hi Khushman,

      Thanks for writing in. We shall get back to you with the information, shortly.

      regards,
      Elex –– Your Electricity Expert

  23. bretjay permalink
    September 24, 2011 3:02 pm

    Is it safe to put the load of Geyser & A .C. on a single mcb.
    or else wht should i do.
    PLS HELP !

  24. bretjay permalink
    September 25, 2011 8:45 am

    Thanks Elex ! can u give me a MCB selection chart for fridge,wahing machine, water pump,geyser.

  25. bretjay permalink
    September 25, 2011 8:46 am

    Thanks Elex ! can u give me a MCB selection chart for fridge,wahing machine, water pump geyser.

  26. subu roy permalink
    November 11, 2011 1:34 am

    SUUGEST ME A MCB WHICH WILL REPLACE THE MAIN SWITCH IN OUR HOUSE,AS I ALSO WANT TO REPLACE MY MIAN SWITCH WITH A MCB.I MEAN THE TYPE OF MCB.PLEASE REPLY ME AS EARLY AS POSSIBLE

  27. ajay parmar permalink
    August 4, 2012 9:21 am

    wt is diff. between relay and mcb?

    • August 6, 2012 5:12 am

      Thank you Ajay Parmar for taking out time to reach us. Kindly find the below information–
      MCB: Mechanical switching device, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of short circuit.
      Over-current relay or release: relay or release which causes a mechanical switching device to open with or without time-delay when the current in the relay or release exceeds a predetermined value.
      Overload relay or release: over-current relay or release intended for protection against overloads.
      Hope we have managed to answer your queries effectively.

  28. Ritupan saikia permalink
    October 6, 2012 3:41 pm

    Hi
    i need put proper mcb and amp watt calculation plz give me

    • October 8, 2012 7:47 am

      Hi Ritupan Saikia,

      Kindly download the brochure of Building Circuit Protection from our website where in all the relevant information regarding MCB is mentioned. The link for the website is http://www.havells.com

      Also, for any further queries feel free to contact us on our Customer Care number: 1800 103 1313

      Thanks & Regards,
      The Havells Team

  29. May 11, 2010 10:26 am

    Dear Jay,

    Thank you for your feedback. You will be able to see the link now, if not you can check it here. Also your message has been passed on.
    If any other query feel free to get back.

    regards,
    Elex

  30. September 26, 2011 5:37 am

    Thanks for posting….we will write back soon!

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