Premium Membership

Learn about power engineering and HV/MV/LV substations. Study specialized technical articles, papers, and electrical engineering video courses.

Home / Technical Articles / What is the difference between MCB, MCCB, ELCB, and RCCB

MCB (Miniature Circuit Breaker)

MCB (Miniature Circuit Breaker)

  • Rated current not more than 100 A.
  • Trip characteristics normally not adjustable.
  • Thermal or thermal-magnetic operation.

MCCB (Moulded Case Circuit Breaker)

MCCB (Moulded Case Circuit Breaker)

  • Rated current up to 1000 A.
  • Trip current may be adjustable.
  • Thermal or thermal-magnetic operation.

Air Circuit Breaker

  • Rated current up to 10,000 A.
  • Trip characteristics often fully adjustable including configurable trip thresholds and delays.
  • Usually electronically controlled—some models are microprocessor controlled.
  • Often used for main power distribution in large industrial plant, where the breakers are arranged in draw-out enclosures for ease of maintenance.

Vacuum Circuit Breaker

  • With rated current up to 3000 A,
  • These breakers interrupt the arc in a vacuum bottle.
  • These can also be applied at up to 35,000 V. Vacuum circuit breakers tend to have longer life expectancies between overhaul than do air circuit breakers.

RCD (Residual Current Device / RCCB(Residual Current Circuit Breaker)

RCCB - Residual Current Circuit Breaker

  • Phase (line) and Neutral both wires connected through RCD.
  • It trips the circuit when there is earth fault current.
  • The amount of current flows through the phase (line) should return through neutral .
  • It detects by RCD. any mismatch between two currents flowing through phase and neutral detect by -RCD and trip the circuit within 30Miliseconed.
  • If a house has an earth system connected to an earth rod and not the main incoming cable, then it must have all circuits protected by an RCD (because u mite not be able to get enough fault current to trip a MCB)
  • RCDs are an extremely effective form of shock protection

The most widely used are 30 mA (milliamp) and 100 mA devices. A current flow of 30 mA (or 0.03 amps) is sufficiently small that it makes it very difficult to receive a dangerous shock. Even 100 mA is a relatively small figure when compared to the current that may flow in an earth fault without such protection (hundred of amps)

A 300/500 mA RCCB may be used where only fire protection is required. eg., on lighting circuits, where the risk of electric shock is small.

Limitation of RCCB

  • Standard electromechanical RCCBs are designed to operate on normal supply waveforms and cannot be guaranteed to operate where none standard waveforms are generated by loads. The most common is the half wave rectified waveform sometimes called pulsating dc generated by speed control devices, semi conductors, computers and even dimmers.
  • Specially modified RCCBs are available which will operate on normal ac and pulsating dc.
  • RCDs don’t offer protection against current overloads: RCDs detect an imbalance in the live and neutral currents. A current overload, however large, cannot be detected. It is a frequent cause of problems with novices to replace an MCB in a fuse box with an RCD. This may be done in an attempt to increase shock protection. If a live-neutral fault occurs (a short circuit, or an overload), the RCD won’t trip, and may be damaged. In practice, the main MCB for the premises will probably trip, or the service fuse, so the situation is unlikely to lead to catastrophe; but it may be inconvenient.
  • It is now possible to get an MCB and and RCD in a single unit, called an RCBO (see below). Replacing an MCB with an RCBO of the same rating is generally safe.
  • Nuisance tripping of RCCB: Sudden changes in electrical load can cause a small, brief current flow to earth, especially in old appliances. RCDs are very sensitive and operate very quickly; they may well trip when the motor of an old freezer switches off. Some equipment is notoriously `leaky’, that is, generate a small, constant current flow to earth. Some types of computer equipment, and large television sets, are widely reported to cause problems.
  • RCD will not protect against a socket outlet being wired with its live and neutral terminals the wrong way round.
  • RCD will not protect against the overheating that results when conductors are not properly screwed into their terminals.
  • RCD will not protect against live-neutral shocks, because the current in the live and neutral is balanced. So if you touch live and neutral conductors at the same time (e.g., both terminals of a light fitting), you may still get a nasty shock.

ELCB (Earth Leakage Circuit Breaker)

ELCB (Earth Leakage Circuit Breaker)

  • Phase (line), Neutral and Earth wire connected through ELCB.
  • ELCB is working based on Earth leakage current.
  • Operating Time of ELCB: 
    • The safest limit of Current which Human Body can withstand is 30ma sec.
    • Suppose Human Body Resistance is 500Ω and Voltage to ground is 230 Volt.
    • The Body current will be 500/230=460mA.
    • Hence ELCB must be operated in  30maSec/460mA = 0.65msec

RCBO (Residual Circuit Breaker with OverLoad)

  • It is possible to get a combined MCB and RCCB in one device (Residual Current Breaker with Overload RCBO), the principals are the same, but more styles of disconnection are fitted into one package

Difference between ELCB and RCCB

  • ELCB is the old name and often refers to voltage operated devices that are no longer available and it is advised you replace them if you find one.
  • RCCB or RCD is the new name that specifies current operated (hence the new name to distinguish from voltage operated).
  • The new RCCB is best because it will detect any earth fault. The voltage type only detects earth faults that flow back through the main earth wire so this is why they stopped being used.
  • The easy way to tell an old voltage operated trip is to look for the main earth wire connected through it.
  • RCCB will only have the line and neutral connections.
  • ELCB is working based on Earth leakage current. But RCCB is not having sensing or connectivity of Earth, because fundamentally Phase current is equal to the neutral current in single phase. That’s why RCCB can trip when the both currents are deferent and it withstand up to both the currents are same. Both the neutral and phase currents are different that means current is flowing through the Earth.
  • Finally both are working for same, but the thing is connectivity is difference.
  • RCD does not necessarily require an earth connection itself (it monitors only the live and neutral).In addition it detects current flows to earth even in equipment without an earth of its own.
  • This means that an RCD will continue to give shock protection in equipment that has a faulty earth. It is these properties that have made the RCD more popular than its rivals. For example, earth-leakage circuit breakers (ELCBs) were widely used about ten years ago. These devices measured the voltage on the earth conductor; if this voltage was not zero this indicated a current leakage to earth. The problem is that ELCBs need a sound earth connection, as does the equipment it protects. As a result, the use of ELCBs is no longer recommended.

MCB Selection

  • 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 second characteristic 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 characteristic as follows:

    TypeTripping CurrentOperating Time
    Type B3 To 5 time full load current0.04 To 13 Sec
    Type C5 To 10 times full load current0.04 To 5 Sec
    Type D10 To 20 times full load current0.04 To 3 Sec
  • 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 Kilo amps (KA). In general for consumer units a 6KA fault level is adequate whereas for industrial boards 10KA fault capabilities or above may be required.

Fuse and MCB characteristics

  • Fuses and MCBs are rated in amps. The amp rating given on the fuse or MCB body is the amount of current it will pass continuously. This is normally called the rated current or nominal current.
  • Many people think that if the current exceeds the nominal current, the device will trip, instantly. So if the rating is 30 amps, a current of 30.00001 amps will trip it, right? This is not true.
  • The fuse and the MCB, even though their nominal currents are similar, have very different  properties.
  • For example, For 32Amp MCB and 30 Amp Fuse, to be sure of tripping in 0.1 seconds, the MCB requires a current of 128 amps, while the fuse requires 300 amps.
  • The fuse clearly requires more current to blow it in that time, but notice how much bigger both these currents are than the ’30 amps’ marked current rating.
  • There is a small likelihood that in the course of, say, a month, a 30-amp fuse will trip when carrying 30 amps. If the fuse has had a couple of overloads before (which may not even have been noticed) this is much more likely. This explains why fuses can sometimes ‘blow’ for no obvious reason
  • If the fuse is marked ’30 amps’, but it will actually stand 40 amps for over an hour, how can we justify calling it a ’30 amp’ fuse? The answer is that the overload characteristics of fuses are designed to match the properties of modern cables. For example, a modern PVC-insulated cable will stand a 50% overload for an hour, so it seems reasonable that the fuse should as well.

Premium Membership

Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! It helps you to shape up your technical skills in your everyday life as an electrical engineer.
More Information

Jignesh Parmar

Jignesh Parmar has completed M.Tech (Power System Control), B.E (Electrical). He is member of Institution of Engineers (MIE), India. He has more than 13 years experience in transmission & distribution-energy theft detection and maintenance electrical projects.


  1. Sivakumar
    Jan 15, 2021

    Thanks a lot

    Dec 26, 2020

    Good Explanation. MCB,MCCB,RCB,RCCB,RCBO,ELCB

  3. Sunny G Yakwai
    Dec 04, 2020

    This is just awesome. You explain everything in a single article. Thank you sir

  4. [email protected]
    Oct 13, 2020

    Thank you Jignesh for your detailed information.

  5. abdul-mumin halidu
    Sep 28, 2020

    thank you very much for your wonderful education

  6. Snehal Devda
    Aug 18, 2020

    Can you advice us ELCB is required if a MCB is attached.

      Oct 20, 2020


  7. M.M. Munas
    Jun 23, 2020

    Explain a case where both MCB and RCCB can trip.

  8. kumar
    Mar 28, 2020

    why the RCCB live-neutral should not be reversed. Please explain

  9. Aung Moe Oo
    Dec 04, 2019

    This is easy to understand for me.
    Thank very much, Sir.

  10. vijay
    Oct 11, 2019

    what You use ELCB or RCCB for own use
    why not publish RCCB internal

  11. Henry pius
    Sep 26, 2019

    Thanks so much for the explanation really appreciate

  12. Buhle
    Sep 23, 2019

    thank you for the clear explanation i will keep it at the back of my mind

  13. Sathish
    Sep 11, 2019

    Dear Sir,

    Thank you very much for valuable information

    Sep 09, 2019

    Hola muy buena información.

  15. Tirumaladevi mandalapu
    Sep 08, 2019

    In lt distribution system generally use fuse wires but they don’t blow off even conductor cut and fallen on Earth but at the same time when any one come into contact they Wii get shock some times even die why

    • Jovin
      Sep 13, 2019

      its because the flow of current during a short circuit (neutral to phase) is higher than neutral to earth so the fuse will be blown suddenly.

  16. Gajraj Singh
    Sep 08, 2019

    Very useful for Electrical field.

  17. Md. Ali Abuhanafiah Hj. Awg. Mukkim
    Sep 07, 2019

    Thanks for sharing with brief, simple, its operation and with its limitation. Highly appreciated with many thanks.

  18. Desmond
    Jul 31, 2019

    My freezer keep developing fault whenever I have a voltage drop despite it been connected to a stabilizer.what is the best protective device should I use.

  19. Raja Naveed
    Jul 24, 2019

    Dear Sir,

    Thanks for sharing great information .

  20. faiz
    Jun 20, 2019

    really informative… thanks

  21. simon senfuka
    May 21, 2019

    difference between dc cable and ac cable

    • Prak Dsouza
      May 28, 2019

      There is no difference and nothing as such. Only the voltage rating vary.
      Example 1000V AC (always in rms) rating cable would be rated as approx 700V DC.

  22. Gari Khudaverdov
    May 08, 2019

    Thanks for your work, it was very informative.

  23. ajay
    Dec 15, 2018

    can you please explain how mcb mccb elcb are selected,
    how ways of db are calculated

  24. ravi
    Dec 10, 2018

    what is the reason of mcb burning & melting issue in a panel & how we can stop it

    • ismaeel
      Mar 07, 2019

      I hope to get some important electrical information from this site …m

    • naya bharat
      May 31, 2019

      due to the less rating as compare to actual current

  25. OMER
    Nov 21, 2018


  26. Erric Ravi
    Sep 19, 2018

    An MCB operates as an automatic switch that opens in case of excessive flow of current. It is essential to install MCBs for better control and secure system. There are number of MCBs available based on their breaking capacity. Know more at – Schneider Electric India.

    Jul 08, 2018

    why the colour of wire red ,yellow & blue in electrical ,any standard is required for electrical

    Jul 08, 2018

    what is difference between pole & phase

    • Chun Sokha
      Dec 02, 2018

      1 phase of CB has 1 or 2 Poles to choose, (U can direct N or u can choose to disconnect both of P&N)
      3 Phase is the same (Have 3 or 4 poles to choose)

    Jun 27, 2018

    can you recheck the ELCB calculations.I think there are some mistakes with the current calculaton and the time of operating as current=voltage/resistance but while calculating you considered resistance/voltage also check the value and unit of operating time you calculated.

  30. Mark Kilburn
    Feb 20, 2018

    Your Maths seems to be in error’.. ohms law is (voltage / resistance) not as you have it “500ohms / 230volts”

    see the below extract from your text:
    Quote ” The safest limit of Current which Human Body can withstand is 30mA sec.
    Suppose Human Body Resistance is 500Ω and Voltage to ground is 230 Volt.
    The Body current will be 500/230=460mA.
    Hence ELCB must be operated in 30mASec/460mA = 65msec”

    Hope you are able to revise accordingly

    it strange how so many people missed this error.. on such a basic principle

    • Gaby Khairallah
      Aug 14, 2019

      he just permuted 230 and 500 but the values are correct

  31. vishnu
    Jan 17, 2018

    can any one help me with selecting the wire guage with respect to the load

    Dec 16, 2017

    What is the procedure to detect malfunctioning of RCCB/MCCB/MCB? What is the procedure to check the RCCB on installation ?

      Feb 07, 2018

      Completing installation of the RCCB and connection of incoming Phase and neutral wire as per marked ‘L’ & ‘N’ on RCCB than switch on main supply or TPN.

      To test the RCCB you can push test Button as on marked “T”.

      The RCCB will trip .

      And after that you can also test it by test lamp/short phase an earth point at any socket plug,bulb holder and light points connector.


      • Abraham
        Sep 08, 2019

        hi i am a certified electrical inspector engineer and i have a testing instrument to check RCB according to IEC procedure. all installations have to be checked by this type of instrument at least every 5 years for normal housings and once a year for industrial and public places. some public places are even compelled by law to check twicw a year. you shall be surprised of how many RCB i find out of range after 4 to 5 years
        according to manufactyrers instructions the test button MUST be pushed once a month. the RCB mechanical system tends to get stuck if not actuated for a long period

  33. Lou Hernandez, P.E.
    Oct 18, 2017

    The first two photos are be reversed with the black GE circuit breaker being the molded case CB and the white IEC circuit breaker is the miniature circuit breaker.

  34. Mohammed Asad
    Oct 14, 2017

    hello sir
    i need a just little help
    from some days my area electric transformer is giving high voltage,and my house electric applicens are totally gone bad. is not working of this problem. so i need any solution for recover this problem,or any power load tripper from out side.
    please give me a good and helpfull advice on my mail
    thnking u

    • rajesh joshi
      Dec 02, 2017

      dear install voltage stablizer of 3kva in home for all wiring

    • ketan patel
      Dec 06, 2017

      hello jigneshbhai how are you? I am an electrical technician most of working in gulf countries like (shell),which are following IEC standard of E&I field. could you give me the any resources or bibalogy to knoe this IEC standard. moreover could you give me information about COMPEx training ?

    • Madhav
      Jan 11, 2018

      Hello Asad,
      I think the solution to your problem lies in re-strengthening the transformer neutral earthing. Please check the neutral connection at your home and its continuity upto transformer neutral point. Also check if there are any bad joints. A floating neutral always lead to a dangerously high voltage (with respect to neural/ground) in one or more phases in a 3-ph, 4-w system where the neutral is solidly grounded.

  35. Mohammad reza Gharghaei
    Aug 30, 2017

    Thanks,much appreciated.

  36. Vasil Takev
    Aug 03, 2017

    An attempt for a simple summary but unfortunately technically not very correct. MCCBs could be up to 3200 A e.g. Tmax T8 and could have also microprocessor based release, MCBs could be up to 160 A, etc. Anyway, this is not the biggest problem. The main difference between MCCB and ACB in their construction, which ensures also different performance, different service capabilities etc.

  37. Dr.P.Aravindan
    Jul 20, 2017

    Really very useful technical information . Thanks Mr.Jignesh Parmar

  38. victor pinto
    Jun 06, 2017

    very good information for me. thank you

  39. laxman
    Jun 01, 2017

    Which is the best device to install at home? for avoiding shock & overload?

      Feb 07, 2018

      Just simply install a distribution board with RCCB (40 Amps) , MCB (6 amps) for each light ckts and MCB (16amp or 20amp) for each power ckts , like-minded fridge, AC, geyser etc.)

      Connection must be proper with RCCB MCB’s.

      If you have any confusion or needs more help than contact me through mail.


      • Michael
        Aug 19, 2019

        It is all over if you forget Ohms law, ( Over) V before R Ohms law is Voltage divided by Resistance

      Feb 07, 2018

      Just simply install a RCCB(40 amps) and MCB’s (6amp or 10 amps for light ckts and 16amps or 20 amps for each power ckts.)

      Thanks in advance.

  40. Yogesh Shah
    May 13, 2017

    Which is the best device to install at home? for avoiding shock & overload?

    For Eg. Today there was overload of current & our fuse didnt trip insted tubelight, laptop charger, mobile charger, routher charger got burnt also after some time when i tried to check the mobile charger by connecting to mobile the mobile device had live current & i suffered small scock. Luckily tv & fridge got saved in the nick of time.

    Pls suggest a good device

    • Jitendra jena
      Sep 08, 2019

      Avoid both over current and shock ELCB is most suitable for home.

  41. saeid
    Apr 08, 2017

    in the name of God

    that’s it
    thanks alot ma
    so useful

  42. Andrew
    Mar 16, 2017

    Why can a lower kA rated MCB be used downstream from a higher rated upstream fuse? How does the fuse limit the let through energy?

  43. shrikant nikam
    Mar 14, 2017

    Very good information Sir…

  44. saber
    Feb 28, 2017


  45. Hari Krishna
    Jan 30, 2017

    Nice Information Jignesh, does this mean that none of these (MCB/MCCB/ELCB/RCCB) protect the devices from high voltages coming from Grid. Voltages stabilizer provide stable output but not feasible to connect every appliance with this.

    Is there any device which protects from high voltages from grid adding over load and shock features.

    Any inputs on this is very much appreciated.

  46. Mohammed Mujeebuddin
    Aug 26, 2016

    If i have power watts and voltage how to know current (ampere) calculate the current

    • naganath
      Sep 02, 2016


  47. Myo
    Aug 12, 2016

    Hi Sir,
    May i know why MCB and RCCB tripped at the same time? What is the high chance of tripping in that situation? Please reply!

    Aug 02, 2016

    Dear Sir

    The newly wiring system in my home got burn when electrical people are connecting the meters at ground level. what will be reason and which one of the following is the suitable for homes to protect appliances and human from fault current MCB, MCCB, RCCB, RCD, RCBO

  49. alvin elias
    Jun 16, 2016

    is there any device to control the use of electricity. something like when too much power is used circuit should break. plz suggest

    • Bhavin Patel
      Jul 25, 2016

      Yes, You can control/restrict use of Electricity by using Meters with Output relay, which will trip MCB

    • Anurag
      Dec 29, 2016

      It’s very simple , you can use fuse for the high power.

  50. Er. B L Saini ITI Ratangarh
    May 17, 2016

    Thanx for this online knowledge sharing

  51. Rajni Verma
    Mar 31, 2016

    Dear Sir,

    Please suggest for switchgear BIS certificate requirement.
    Is BIS require for all switchgear like MBC,MCCB,RCCB…etc?

    • Bhavin Patel
      Jul 25, 2016

      Hi, BIS required with details as follows:
      MCB: IS 60898
      RCCB: IS 12640 Part 1
      RCBO: IS 12640 Part 2
      MCCB IS is not Compulsary, IS 60947 /IEC60947-2
      Hope this will suit to your requirements,
      Thanks in advance,

  52. Indrapal Singh
    Mar 18, 2016

    Thanku ji to provide information about MCB’s.

  53. sajana
    Mar 09, 2016

    Thank you very much. This article is more helped to know type of circuit breakers.

  54. Bhavin Patel
    Mar 02, 2016

    Dear Mr. Jignesh,

    Excellent Efforts, I have following Suggestions for Improvements:
    MCBs: Generally available upto 125A
    MCCB: Picture shown is of MCB not MCCB
    ACB: Available only upto 6300A,

    Hope to update,
    Thanks in advance,

  55. qyiph da silva
    Feb 03, 2016

    hi…i’d like to asking for spesification….
    how many ampere i should using the mcb for installation on elevator with max weight 600kg???
    and the motor is using 7.5 kw with max ampere is 28 A…

    please reply…

      Apr 07, 2016

      for a motor of 7.5kW with a maximum ampere of 28, use 40amp mccb

      • D.Balakrishnan
        Sep 24, 2019

        Harini Apartment, F2,First Floor, No:3/1515,Mugalivakkam Main Road, Madhanandhapuram, Chennai-600125.

    • Bhavin Patel
      Jul 25, 2016

      Dear Qyiph Da Silva,

      First of all, You have to define following in additions to provided,
      Where do you want to install ? As incomer of Control Panel/or only for Motor Protection,

      Ideal Selection Criteria:
      MCB Rating in A= Load (Motor) Rating in A

      In your case, Ideal selection is 32A for Control Panel, for only starter we have to use MPCB,

      Hope it will suit to your requirements,
      Do not hesitate to contact more information i required,
      Bhavin Patel

    Jan 30, 2016

    Good informnation

  57. ASIM
    Jan 24, 2016

    a 30-amp fuse will trip when carrying 30 amps. *will blown

  58. Marimuthu
    Jan 22, 2016

    thank you.. so much

  59. JOE JOSE
    Jan 20, 2016

    please explain the working of 3phase RCCB
    The neutral current is zero in case of balanced 3phase load, then how works RCCB

  60. naim
    Jan 18, 2016

    What is the difference between Earth Leakage Relay and Earth Leakage Circuit Breaker? Is it the operation? or maintenance wise?

      Feb 07, 2018

      Earth leakage relay or earth fault relay used to unit protection. (Like – in transformer etc)
      Earth fault relay connected between phase and ground and it’s work to ground the over voltage.

      ELCB used in wiring or appliances earth protection to trip the ckts if there is any connection phase with ground/earth.

      Thanks in advance.

  61. vetri HSE
    Dec 29, 2015

    Nice and Useful information

  62. Sachin Kulkarni
    Dec 19, 2015

    Nice Information…..Thank you…

  63. Chris
    Nov 10, 2015

    Your calculation of the time an ELCB must trip is incorrect.
    30maSec/460mA = 65msec

    That is 65mS, not 0.65mS.

  64. raj
    Oct 14, 2015

    Its uses where give details MCB rccb etc

  65. Dakshesh Shah
    Oct 09, 2015

    I am in the business of water pump. I want to protect our submersible water pumps up to1 HP, single phase. Can you advise what type of MCB, RCB or RCBO should be used by us for protecting our submerisble pump against short circuit in winding, overload. The full load current of our equipment is 3.6 Amp. Please suggest proper product with minimum space requirements.

    • Bhavin Patel
      Mar 02, 2016

      HI, Specific to Pump protenction MCB/RCCB/RCBO can’t be used as it has not been designed for that, You can choose MPCB’s (Thermal Magnetic Type) for Pump Protection which has adjustable overload settings based on Pumps winding Class & initial starting Torque, We also have to consider Reaction of product during fault, which has been defined in Coordination (Type 1/Type 2/Total),
      You can contact for further details if required,
      Thanks in advance,

    • rhea endaya
      Apr 07, 2016

      for 1 hp single phase motor, use 20 amp mccb fuji.

  66. guljinder singh
    Oct 08, 2015

    Good job

  67. greatmanifex
    Oct 06, 2015

    Good Job,please I want to know if it will be possible for me to download the materials and where I can do that,am using phone to check the information.thanks.

  68. Roger
    Oct 04, 2015

    Appalling English explanation of how an RCCB (RCD) works.

    • Augustine peter
      Aug 05, 2019

      Get electrical knowledge

  69. Bharat Bhandwalkar
    Oct 02, 2015

    Very good information Sir

  70. Sandeep Pandey
    Sep 24, 2015

    thancks alot sir ……

  71. Shwetank Dixit
    Sep 11, 2015

    Hi i’m Shwetank Dixit a student of volkswagen academy, Thanks for sharing so explain about electrical our citizen or country has very need to knowledge of hardware (electrical knowledge) as well as software also please more and more and some advance………like MPCB (Motor protection circuit breaker) and all that…….

  72. Mohamed Ismail.Sudan.gnpoc
    Sep 10, 2015

    I’m E&I engineer… thanks a lot for all these beneficial and valuable informations .
    I have a question : in the AC circuits normally we use a protection fuse at the line and the neutral directly wired ..why in DC circuit need to use 2 fuse for both (+) &(-) wires.

  73. Monty Doctor
    Sep 02, 2015

    Dear Jigneshbhai,
    I stay at Mangalore and I am a layman as far as Electricity is concerned, earlier I was staying at Ahmedabad where the electricity was of good quality. Your article was very informative.Here in Mangalore many times I have noticed that after a power outage when the power returns, there is current in the neutral line. It may be due to faulty re-connection by the electricity linesman. At this time if any appliance is on, it gets fried, also we get a shock on touching the appliance. Some of my appliances were destroyed because of this. I would like to know if I can use Residual circuit device(RCD) to prevent damage to appliances or will a 3 pin adapter with fuse will help. Or is there any other device that can help prevent damage to appliances when there is current in Neutral( as tested with a screw driver tester). Power outage occurs here at least 3 times a day!!
    Thanks in advance.

  74. satish n takalkar
    Aug 30, 2015

    Pl.send detail ELCB

    • sakthivel.k
      Oct 29, 2015

      ELCB (Earth leakage circuit breaker)it is working based on Earth leakage current, The safest limit of Current which Human Body
      EX:Many switch are connect in this ELCB circuit.any one switch to earth fault on human body touch on the time working ELCB is tripped.then totally off switch through to the ELCB circuit.this is ELCB function.

  75. Zarni
    Aug 28, 2015

    Thank you so much! Mr. Jignesh Parmar

  76. Sebastian Ngowo
    Aug 26, 2015

    I’m real aprisiate that electrical is every thing.. No electrical nothing can go on.

    Aug 21, 2015


  78. E.Kalithas.DEEE
    Aug 21, 2015

    i love Electrical….

  79. David
    Aug 12, 2015

    very useful. Thanks for the information.

  80. eng_ali_abdo
    Aug 07, 2015

    thanks very much useful information

  81. Gaurav sahu
    Aug 04, 2015

    But what about the earthing we use outside our home or commercial place? If we use RCCB ,really there is no use of earthing?

  82. jilly mcgoo
    Jul 28, 2015

    Basically it’s all a load of old toast

    Jul 23, 2015

    what is differential circuit breaker by 30ma. and what difference between mcb also

  84. Amol shinde
    Jul 21, 2015

    Nice artical just want to ask I have completed B.E.Electrical. Should I do M tech in power system ?

  85. Crown
    Jul 20, 2015

    Well articulated explanations. Kudos

  86. artv
    Jul 20, 2015

    Thank you for the information

  87. Nestor Lim
    Jul 16, 2015

    Our system in my province is Multi Ground – phase (live) and earth ( ground) without neutral. I recently purchased a Lighting panel in Australia fully assembled with RCCDs can I adapt this to be used in a multi ground system where we have no established neutral? Please advise. I was thinking of doing this with a transformer but still want a cheaper fix

    Jul 13, 2015


    • shailesh shete
      Aug 08, 2015

      Thank u sir for giving me knowledge about MCB types.
      Now I want information about power theft detection bcoz it is my final year project.
      Please share information with me on my email. Thank u.

  89. sadick Ramadhan
    Jul 08, 2015

    I am a Tanzanian man, electrical technician, thanks for your article

  90. suhas
    Jun 27, 2015

    Dear Sir ,
    I am working as maintenance Engineer ,
    I have facing one problem our 4 pole RCCB incoming terminal are frequently overheat or burn out . What are are the causes behind that ?
    Please guide and What should I check ?

    • blitz
      Jul 27, 2015

      RCDs detect an imbalance in the live and neutral currents. A current overload, however large, cannot be detected. It is a frequent cause of problems with novices to replace an MCB in a fuse box with an RCD. This may be done in an attempt to increase shock protection. If a live-neutral fault occurs (a short circuit, or an overload), the RCD won’t trip, and may be damaged. In practice, the main MCB for the premises will probably trip, or the service fuse, so the situation is unlikely to lead to catastrophe; but it may be inconvenient.
      It is now possible to get an MCB and and RCD in a single unit, called an RCBO (see below). Replacing an MCB with an RCBO of the same rating is generally safe.

  91. Mujammil sidddique
    Jun 19, 2015

    ELCB trip in over load yes or no?

    • Girish R Nair
      Jul 26, 2016

      A big NO NO NO

  92. Ravi Shankar Tiwary
    Jun 18, 2015

    We relay Appreciate with you and getting knowledge in our typical situation thanks.

  93. krishan kumar
    Jun 11, 2015

    Sir I have done 12class and it good site

  94. kashish
    Jun 08, 2015

    i am a second year ece engg student form NSIT

  95. N.Eeswaran
    May 18, 2015

    A clarification
    Reference my comments and questions on May 18,2015, Please note while using a Test Pen on a Phase wire causing a small current to flow thru our body to Earth, resulting in a bulb glowing, a resistor is connected in series to drop the Phase voltage, making it safe to touch. In case of an appliance malfunction, where the Phase voltage is present on the casing, touching it may cause an electric shock.

  96. N.Eeswaran
    May 18, 2015

    The RCCB will operate and cut off supply to the load if there is an unbalance (or difference) in the currents flowing thru the Phase (Line or Live) wire and the Neutral wire. In the Malaysian system, all equipment and utensils ( esp. those made of metal), the body or casing is connected to an Earth wire, which originates from the Main Switch Board. In the unlikely event of the Phase wire coming into contact with the body of the appliance (e.g. a bread toaster), a leakage current will flow from the body of the appliance to Earth, causing an unbalance in the RCCB and forcing it to trip and isolate the load.
    If an Earth wire system is not provided, the RCCB will trip only when a human touches the appliance, causing a current to flow thru him to Earth or Ground, resulting in an unbalance in the RCCB. An efficient RCCB needs to be sensitive to about 30mA leakage current and operate fast enough to avoid any hazard to the human.
    Am I right? I believe this is not dangerous as when we use a Test Pen on the Phase wire, a small current does flow thru our body to Earth causing the lamp to light.
    The doubt is whether the current thru our is the same in both instances.
    Thank you and hoping for some clarification on this matter.

  97. salman khan
    May 12, 2015

    Sir I have pasout in this year I want you help me increase my Knowledge.i m very thankful

  98. JOSEPH
    May 06, 2015

    Thanks for the helpful information, please can you kindly help me with information on how MCCB, MCB, RCCB, ACB, VCB etc. circuit breakers are rated.

  99. joy
    May 06, 2015

    Pretty good read

  100. satender kumar
    May 05, 2015

    I want extra knowledge in electrical engineering, so I want to subscribe your news letters

  101. satender kumar
    May 05, 2015

    I want to gain extra knowledge about electrical I want to subscribe your news letters.

  102. madhusudanan nair
    Apr 29, 2015

    Dear sir,
    A beautiful explanation to understand all thanks
    awaiting a lot from you!!!!!

  103. Mohankumar
    Apr 28, 2015

    Very simply and aptly explained. Superb.

  104. Paul
    Apr 27, 2015

    Hi. You have a typo under the ELCB comments. “The Body current will be 500/230=460mA.” That’s upside down, of course, it’s 230/500.

    Good post, by the way.

    • Firoz Ahmed
      Jul 30, 2015

      Right Paul, you are correct, as per ohm’s law V=IR so I=(V/R) in A, i.e. 0.46A
      I= 460mA

  105. SURAJ DAS
    Apr 12, 2015

    Thanks a lot for your topic.
    May I ask you on how to connect MCB and RCCB in residential wiring? Should L n N wires from Main Switch be put into RCCB and then to MCBs ? How to connect those for Inverter lines?
    What is different between B, C, D grade in MCB and which one do you recommend for rsidential purpose?For a 1.5 ton A.C. , what should be the grade and amp. of the MCB?
    Please, help me.

    • Steve
      Aug 06, 2015

      You can use C type,,

  106. Karthik R
    Apr 06, 2015

    Nice Article

  107. neeraj
    Mar 30, 2015


  108. neeraj
    Mar 30, 2015

    such kind of article ,generally not available,on site, it is very helpful.

  109. neeraj
    Mar 30, 2015

    very good and helping topic.

  110. Kamal Laha
    Mar 20, 2015

    Dear Jignesh
    I appreciate your valuable information.
    Kamal Laha FIEAust CPEng LifeFIE(I)

  111. Lars Jakobsson Sweden
    Mar 19, 2015

    Thank you sir for a very nice and useful artickle

  112. Dakalo
    Mar 18, 2015

    impressive site

  113. B p soneji
    Mar 15, 2015

    My rccb damaged & electrician has made electricity connection directly though mobs are there. Pl. advise me whether rccb is needed to install ? If i do not install rccb, what R the consequenc ?

    • Girish R Nair
      Jul 26, 2016

      MCB won’t cut the supply on an electrical shock to earth. Only a short from phase to neutral or overload it trips. So you should install rccb or elcb with 30mA best suits.

  114. kailash menaria
    Mar 14, 2015

    dear sir i appreciate your answer and your nature
    please give me suggestion. i completed diploma in electrical
    now i want to become a expertise in electrical field please suggest me
    what i have to do
    thanks and regards
    kailash menaria

  115. Suranjit
    Mar 14, 2015

    Sir why three point in battery terminal.

    • Girish R Nair
      Jul 26, 2016

      To take out two different volages. V2= 2 x V1

  116. vidyabhushan
    Mar 12, 2015

    sir, what is the connection and working difference of ELCB and RCCB.

  117. Rajaraman
    Mar 12, 2015

    Thank you very much sir

  118. ankit patel
    Mar 11, 2015

    Nice article…very useful..

  119. swarup shil
    Mar 11, 2015

    good thinking..

  120. Waterlot Frederic
    Mar 10, 2015

    Your picture of MCCB is not good ( it is a MCB) use a picture of NSX fron Schneider electric or similar.
    Best regards

  121. Sankar TL
    Mar 08, 2015

    Thank u v.much Sir. I’ve few doubts.. V r constructing a 2BHK house in Chennai. Can i re-use a 4yr old (was working) 40A AUTO PHASE CHANGER? I also have 25A Rotary phase changers (say RPC) in a box, and in same DB box, 12 LeGrand MCBs (2x c20,4x c16, 2x c10, 4x c6) r there.
    Shall i connect 3 parts/places(AC1, AC2, & Kitchen) to these RPCs via 63A RCCB in DB & again take back to DB & connect with MCBs?!! So that i can connect confidently all remaining divisions with AUTO-PHASE CHANGER.

    Also i’ll be glad if i get a chance to talk with you rgdg it. Am not comfortable in txting…
    Thank u
    Sankar TL: 8015666550

  122. anil samal
    Mar 07, 2015

    I like electrical

  123. sekhar
    Mar 06, 2015

    Nice information…..

  124. Ibrahim
    Feb 20, 2015

    thank you bro for this information

  125. Ayorinde Fajobi
    Feb 17, 2015

    Thank you sir for your complement. I will need more encouragement as a beginner.

  126. Mohamed
    Feb 14, 2015

    dear Sir

    appreciate your support to inform me what the reason for current leakage

    we installed RCCB 300 mA at our site GEDP (contain-Air condition CB and light-socket-emergency light-rectifier… etc.

    but RCCB down many times

  127. alli shaikh
    Feb 11, 2015

    Thank you sir

  128. Surendra R.
    Feb 10, 2015

    Thank you sir,
    For this information

  129. Ashok vastrad
    Feb 09, 2015

    Dear jignesh,

    We are using Mcb but in recently my oven blown due to over current even my oven switch was in off condition my advise me what typeople of protection device I should install, now a days hpl is advertising for over load current tripping mccb. Pl advise
    ashok vastrad

  130. Aaron Charles Smith
    Feb 01, 2015

    Finally a clear understanding of rcd / rcbo, totally transfixed by your clear explanation and I want to learn more. I’ve been an electrician for 8 years and never bore of the devices we trust and how they work in a changing industry.

  131. jay
    Jan 27, 2015

    dear sir
    please give me information about shock guard
    i want to make it at home
    so please give me suggestion with diagram

  132. siva ganesh
    Jan 25, 2015

    Hi ,Thank you for your valuable information

  133. gandhi.r
    Jan 25, 2015

    sir can you give the idea for this one,
    due to some return current r short ckt or leakage current is or high voltage is accrued we r using mcb but all the device get damaged.
    what kind of protective devices we can used to over come the problem
    and how to control the over voltage isues

  134. Abir Mahapatra
    Jan 23, 2015

    This is very much useful for me.

    Thanks & Regards

  135. selvan
    Jan 19, 2015

    Hi Jig, Thank u for the information..Recently i was attacked by electric shock and this time i felt the current flow entire body

    Jan 14, 2015

    I read these article about circuit breakers.I can acuuired many knowledge about that.Thank you for the valuable Informations.

    thanks & regards
    PH: 08281124775

  137. Mukesh Singh
    Jan 04, 2015

    Very usefull

  138. Muhammad Tahir
    Jan 03, 2015

    Dear Sir,
    By reading your article today I understood all kinds of breakers and their difference. Thanks for your article. Allah bless you.

  139. Prasanth
    Jan 02, 2015

    Really useful sir, helps me in procurement

  140. abhimanyu
    Jan 02, 2015

    very useful and unlike knlowdge

  141. ankur
    Dec 26, 2014

    Thanks for the practical information you have shared, especially the difference between all the circuit breakers. now i got to understand the major difference between different kind of circuit breakers.
    thanks again ….

  142. R .Padmanaban
    Dec 24, 2014

    Sir very useful at my sites

  143. DHINESH
    Dec 22, 2014

    Sir I got More information.In ELCB calculation is 230/500=460MA

  144. A.Mohamed Bilal
    Dec 13, 2014

    I learn lot from EEP .

  145. jerry quindara
    Dec 13, 2014

    how can!t i minimize the humming of circuit breaker

    • Girish R Nair
      Jul 26, 2016

      Most probable cause is some internal loose connections and or the loss of strong bonding between laminations of any magnetic path internal. Open out the breaker and look into

  146. Prasad rupe
    Dec 11, 2014

    I’m electrical

  147. James J Pullat
    Dec 10, 2014

    Very useful for practical tips & latest information

  148. samuel kamau
    Dec 03, 2014

    i like the way you teach can you help me in adding my electrical am electrical craftman

    Nov 25, 2014

    Its very useful. Though i am mechanical engineer but i can understand the function of the devices easily you describe.
    Heartily thanks Sir.

  150. D.R.Rajessh Kumar
    Nov 22, 2014

    dear ji,
    Could you explain me how to calculate the RCD rating in mA as my client is asking me to install 3P 150A Mccb with 300mA rating. I couldn’t find the list in the specification catalogue.

    • Girish R Nair
      Jul 27, 2016

      MCCB has no mA rating. Only A rating. Rccb or Elcb has MA rating too. For safety side MA should be as minimum as possible, but also have to consider the grading between upstream and downstream mA also. If no downstream and upstream problems, like in small houses etc. Please select mA as minimum as possible. But some machines like submersible pumps will again trip as they have already leakage currents in small quantities. In that case increase the mA . Typical mA are 39, 50, 100 etc.

  151. Suhas
    Nov 20, 2014


    I read it at a very timely instant, when I was installing MCB. Thanks a ton


  152. Deepak
    Nov 13, 2014


  153. Sujoy Basak
    Nov 12, 2014

    Thank you.

  154. cam cheema
    Nov 12, 2014

    Its nice.

    • cam cheema
      Nov 12, 2014

      please make correct the spelling of “might” in characteristics of RCD/RCCB.
      it’s not “mite”, its “might”.

      • parmjit singh
        Nov 14, 2015

        What is the means rccb mcb mccb elcb rcco

  155. Prateek
    Oct 30, 2014

    Nice but increase the amount of pictures and try to explain by diagrams

  156. Bhawani Khanal
    Oct 23, 2014

    Some how it’s helpful bt there is not enough discription…for elcb.

  157. Hadi
    Oct 19, 2014

    Thanks a lot for this information which is useful for safe precaution in projects …..Sinopec HSE Safety Eng

  158. ganesh
    Oct 18, 2014

    It’s really useful, but I am having small dout we using overhead crane in that we frequently facing drive failure. Below the hook welding work carried one also suggested the same ie due to welding operation Only these failure happened,any other cause????????

  159. Subrata Mukherjee
    Oct 17, 2014

    Our main is connected through RCCB ,when i Tested the Earth with a bulb ,by connecting Neutral with Phase our RCCB tripped,but no problem with other devices.Is it ok?or something wrong with connection.

  160. Nawas
    Oct 14, 2014

    it’s really useful article to me . thank you so much

  161. Domo Kamduk
    Oct 09, 2014

    Nice and simple- way to go !!!

  162. Beca junior
    Sep 25, 2014

    Nice job and well done

  163. sumit naudiyal
    Sep 13, 2014

    Its great thankss

  164. avidesh
    Aug 31, 2014

    thanks a lot Mr. PARMAR

  165. vijay wagh
    Aug 28, 2014

    Sir, i’m working in govt org. I have one problem. Our generator is turning off while running condition cause of unbalance load. Some people who using this load, they use water heater. We put the MCB 6 those circuit to reduse extra load. When 8-9 amp current flow throuw the mcb, it is not tripping. MCB condition is OK. Pls reply me.

  166. raj patel
    Aug 25, 2014

    please send me drawing of motor on/off every 5 minutes

  167. sandeep
    Aug 10, 2014

    I want a device which help in light cut between 160:260 voltageand shock proof suply

  168. V.T.Appuswamy
    Aug 09, 2014

    Complicated things made simple. You are making things easy for any engg studets /engineers to understand easily. Very nice.Easily digestable.Many a thanks. Regards Appu

  169. shital
    Aug 08, 2014

    it is very good ,useful and easily understandable information .
    thanks for that .
    i have question ,
    which is modern medium used in circuit breaker for arc extinction ?

  170. k.ramalingam
    Aug 02, 2014


  171. dileep
    Jul 27, 2014

    Dear Sir,
    Please explain me to how to select Barker for 20 KW load.

  172. Rahul Negi
    Jun 21, 2014

    hello sir.
    i our house there are new electronic meters installed, is there anyway i can reduse the speed of meter reading without tempering it..

  173. solomon
    Jun 14, 2014

    in India we get A type MCB, whereas in all websites only 3 type B C D types are discussed.

    How come A type is not discussed

    I will be thankful if the same is clarified

  174. DSP
    Jun 10, 2014

    dear sir,
    you said that
    For example, For 32Amp MCB and 30 Amp Fuse, to be sure of tripping in 0.1 seconds, the MCB requires a current of 128 amps, while the fuse requires 300 amps.

    can you justify this statement ?

  175. Rajesh
    Apr 17, 2014

    Hi thanks for the information provided for.

    • meter manager
      Apr 18, 2014

      hi Jignesh I was following through ur various posts on meter bypass. I have a scenario on which I would like ur valuable expert comments. I live in a multi storied government quarter. I would like to know how to bypass the single phase electronic meter. It is giving me sleepless nights. Presently both the live and the neutral from the meter goes to a MCCB which then terminates in our flats DP.One option I am considering is like using 2 wires from one live phase from main connection. One goes through the meter and other directly to the house. Since distance from the meter to our house is considerable I cannot discreetly lay a new line to the flat I plan to disconnect the neutral in the MCCB and connect the unmetered live wire to the neutral port of the MCCB. In this way 2 wires both having the same phase would be coming to my flat from a single MCCB. We have 2 separate earth connections to the flat. For neutral I plan to use the earth wire. The second earth will be used for the three pin connections so that they are secured. The metered live phase could be used for some very low load to ensure meter running for atleast the minimum units. The unmetered phase will be used for rest of the loads. My query is-
      1) Will the MCCB allow 2 live connections through it (both would of same phase so no 440 volts chance)?
      2) Can I install a MCB with the earth which I would using as neutral. IF so, of how much rating.
      3) What safety precautions should I take for preventing electrical shocks and equipment safety.

      Pse reply fast.

      With regards.

      • Dusan
        Aug 07, 2014

        @Meter Manager

        answers to your query:

        1) don’t even try to do that. you can’t connect 2 feeder cables to one MCCB. one of the resons is electric shock at the start point of cable although its feeding circuit breaker is disconnected. but, you can connect 2 cables from MCCB and supply 2 or more consumers.

        2) you can’t do that neither. if there is a RCD it will trip in that case, and earth conducter must not carry current in normal regime, only in case of fault.

        3) use appropriate protection (MCB, MCCB, RCD, RCBO, etc), cable sizing to match equipment needs, and use of appropriate IP rating for environment where equipment is installed.

  176. Manoj Khadilkar
    Mar 30, 2014

    Very good information & to the point.

  177. Mahesh Chauhan
    Mar 26, 2014

    Good information. Great work Jignesh.

  178. Shyam
    Mar 22, 2014

    Dear sir,
    i have doubt how does mcb trips. Is there any mechanisam is there in mcb to trip for certain rating plz reply me sir

    • Deshmukh
      Apr 20, 2014


      this is good information but i want 3 phase submersible pump’s ELCB/RCD Installation at agricultural basic so you sugges me in this both devices which is safe. Sugges me which capacity e.g 25a,63a for 3phase agricultural submersible pump.

      • Dusan
        Aug 07, 2014

        every pump should have its own protection (RCD, RCBO, MCCB, ELCB, etc) and nominal current should be choosen on basis of pump’s power consumption and power factor.

  179. ISHAQ
    Mar 16, 2014

    1.I think this information is not correct. Because there do exist MCCB of 1,2,4,6,10,16,20,25,32,40,50,63 amperes of Schneider and even ABB……..
    2. The figure which is shown(for MCCB) does not resemble to that of MCCB seems to be of MCB as per its looks.
    3.Please follow the below links and correct me if I am wrong:$file/1SXU000023C0202%20RevA_17%20MCCB.pdf

  180. Mahesh Deshmukh
    Mar 02, 2014


  181. Tayo
    Feb 28, 2014

    This is nice!thank u 4 dis!

  182. priya
    Feb 27, 2014

    want to know more abouy energy ditribution,d-regulation etc

  183. Thar Lin
    Feb 21, 2014

    I want to know LV design for building

  184. Thar Lin
    Feb 21, 2014

    Engineer ….not near engine

  185. shiv
    Feb 14, 2014


  186. prabhu r
    Jan 27, 2014

    me want to know dat how to calculate the energy meter constant…with example…and hw to know dat multifly of mf

  187. Safi Ali
    Jan 11, 2014

    Thank you…

  188. vidhnesh
    Dec 31, 2013

    hi, sir i m working as a TFO in bank . require EE information.

  189. Hemaanandan.V
    Dec 24, 2013

    thank you

    Dec 23, 2013

    This is really helpful. Thanx a lot.

  191. Kevin Rajan
    Dec 22, 2013

    Very helpful..simple to understand..thanks..

  192. Kevin Rajan
    Dec 22, 2013

    Very helpful..simple to understand..

  193. simanchal panigrahi
    Dec 16, 2013

    thank u for providing knowledge

  194. ASH
    Dec 16, 2013

    Brief, precise and superb information.

  195. devaprasad
    Oct 21, 2013

    thanks for giving super information

  196. Kishor parsond
    Oct 17, 2013


  197. HUN
    Aug 18, 2013

    thanks a lot

  198. Akhilesh
    May 13, 2013

    thank you sir especially for the RCBO and the difference between ELCB and RCCB.
    hopefully it is more then sufficient for my orals…….

  199. Donalex
    Jun 02, 2012

    ELCB as above; under ‘Operating Time’ – the left side of the equation for ‘Body Current’ is upside down and gives an answer of 2.17 amps and not 460 mA as stated.
    IIRC Ohms Law!

  200. Sourav
    Dec 03, 2011

    Thanks a lot

  201. Ibrahim Seder
    Nov 07, 2011

    Thanks a lot, but I think that you should include the earthing systems which affect some products above.

  202. sridhar
    Nov 03, 2011

    I liked all the topics listed above, based on my experience and usage of some of these equippments, i relaised that with ELCB, the current flow is better/optimistic in one direction and most preferrable for domestic applications. thanks for the article.

  203. abhay
    Oct 25, 2011

    Tjhanks a million…i just can’t tell u how much i needed dis…thanks a million….

Leave a Comment

Tell us what you're thinking... we care about your opinion!

EEP Academy Video Courses

The learning platform for LV/MV/HV electrical engineers. Learn from experienced engineers and sharpen up your knowledge.