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.

Conclusion

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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40 comments

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1

Hello Abhishek,

I have a new Construction that has just got ready to get its electrical wiring done. I came across this article after getting to know about RCD aka RCCB, & I noticed that the Site Electrician didn't mention any RCD/RCCB requirement, So having known its importance, I would like to get this added to the Main Box.
But I have some questions, & I'll be grateful to you If you can please answer them ASAP.

1. I have a Basement & Ground Floor Plan so should I be using two RCCB's , one for each Floor or more or less.
2. I want to minimize faulty tripping so would you recommend 30mA or 100 mA.

Before asking third & fourth question, I would like to brief about the equipment to be installed:

a). Basement will have 4*1.5 Ton Ac + 7 Fans + ~21 Concealed LED Bulbs + 5*25 mA Socket & Switch & possibly Inverter will also be installed here only(although might have its separate wiring idk.).
b). Ground Floor will have 3-4*1.5Ton AC + 8-9 Fans + 3 Geysers + 1 Washing Machine + 1 Fridge + 1 Microwave + other Kitchen Appliances(RO, Food Processor, etc) + ~ 50 LED Bulbs +6-8*25 mA Socket & Switch + other misc stuff.
c). My House is somewhat midway or far from the feeder step down transformer, & there are close to 15 houses or more before the main line reaches my house.

3. Now what Ampere RCCB should be used as per your answer to Question 1, like 32A or 40A or 63A?
4. Which type of RCCB should be used, a Type AC which covers Alternating Current only, or a Type A which covers Alternating Current & Pulsating Current with DC Component?

Thanking you beforehand as I know you will surely answer or recommend the correct place or person to find the answer.

2
Abhishek Jain (Mod)

When there is leakage of current through a high resistance path, the same can not be detected by MCB, and RCCB provides protection detecting the difference in outgoing and incoming current. Since you have large number of appliance, it is preferable to go for sensitivity of 100 mA. RCCB is generally provided at the incoming board from where the supply is distributed. You may consider providing two numbers of RCCB one at each floor, so that if it trips, the identification of defect is limited to that floor only. The identification of defect is done by switching off the MCB, one by one and finding out the MCB which trips and one should try to find out the defective appliance in that circuit.

From my calculation, you should go for 100 mA and 63A, AC type RCCB.

While buying this product, please read the literature, rating etc. carefully and the warranty slip. In case there are spurious tripping, report the matter to the manufacturer and call for checking.

3

Thanks a lot Abhishek. As expected, got all my queries answered :)

4

sir i have some information abut plant opperator

5

Sir,

1 need an advice from you regarding installation of RCBO ( Over Load Protection ) of my Single Phase Current. Presently I have installed only a 32 A ANchor make DP Switch with a Pulse make ELCB+MCB of 32 A. Due to heavy over current fluctuations some times with GEB Power, I would like to go in for installing a 40 A-30mA RCBO by removing the present Anchor 32 A DP Switch and Pulse ELCB + MCB 32A box. After removing these two PULSE and ANCHOR accessories, If I install 1 No. 2 pole 40A RCBO, then is it necessary I should install a 2 Pole 40A MCB also along with RCBO. I read in inter-net Wasim Khan articles he has given drawing that MCB should also be installed with RCBO of same rating. Pls. clarify Sir.

6
Abhishek Jain (Mod)

RCBO is a combination of MCB and RED (residual current detector). Pl be sure why there are trippings, ie MCB or ELCB. ELCB is generally the reason and if you replace ELCB by RCCB, it should be Okay. You may also use 40A RCBO without removing DO switch. I don't think u need ME with RCBO, but yes with RCCB. Read DP in lieu of DO.

7

Hi Abhishek,

1. I read in an online discussion that installing RCCBs for each rooms seperately is better. They said instruments like computers produce harmonic distortion (or something like that, I don't remember the exact word), so they'll trip the RCCB frequently if not set in correct mA. So do I need to connect RCCB to the main or sepeeate RCCBs for each rooms?

2. Legrand DX3 FP RCCB(63A 30mA) https://www.amazon.in/dp/B00P8YYBSU/ref=cm_sw_r_cp_apa_i_AAsvzbHGB4CJF
Is this a good product?

8
Abhishek Jain (Mod)

Harmonic distortion shall result in the leakage of the current. RCCB detects if there is difference between the input and output current which happens due to leakage of part of the current through earth. There is no harm in providing RCCB in each room and in that way it will trip the room which has any earth fault and not from the mains.

Legrand is a good brand value and stated to be a good product. you may go for sensitivity lower than 30 mA to avoid spurious tripping i.e. more than 30 mA.

9

First of all RCCB is not new, I am using it from past 15 years. If there is a short-circuit in an appliance it will detect and trips but if you touches a live phase wire and gets shock from completing a circuit it will not trip. If you short neutral and earth the rccb will trip but if you take a bulb and put its terminal in phase and earth the bulb will glow without rccb tripping. Also Havells RCCB is so fragile its internal components specially its mechanical spring lock which engages the RCCB circuit is so poor. I have wasted 3 havells 4 POLE RCCB. Very poor mechanism .

10
Mangalore Cafe

I have a question regarding MCBs.
My house is 10 years old and it has just one MCB(I hope it is an MCB as my electrician keeps calling it Tripper) It has 32 written on so I am assuming its 32Amps.
Now from this one MCB all wiring is taken plus 3 plugs which are 15amps. One each for the TV Fridge and AC. I bought a 2200 watt Blender so I told my electrician to add a 15AMP plug. He just came and fixed and was done in 10 minutes.
I was under the impression that he will bring with him a 15amp MCB I wanted to tell him to get a 45AMp one and put 3 15 amp switches, as I plan to buy an oven later and just wanted to keep one spare because I also assumed he would buy a high guage wire too I thought he would pull the new wire through the electricity pipes. So thought no harm in putting an extra one.
but he just added this and assured me it will take the load.
When I asked him about the wire he said that normally electricians earlier used to put very high guages wires for the entire house and said that my wiring was such. They do this to avoid confusion and also if the customer needs new plugs of high amps they wont have to pull new wires everytime.
I was like how does it work on 32 amps. He said you don't use everything at the same time.
But everything is working fine. The blender runs well. And it is a high speed blender so it not used for more than 1 minute mostly 30 seconds.
So this has always been bugging me.
He said new apartments give a MCB for each room and each board.
But earlier nobody did this.
And he seems very lazy. Actually all the electricians here are lazy. He said we cant pull the wire we will have cut in the wall if you want to to put a new MCB with for these 15 amp plugs.
Obviously that would cost a lot but would also be a big mess.

So that is my question is this ok. Will it be safe to run an oven. Maybe I would have to be careful not run it simulteneously with the blender.

Also this might purely manual work labour question but I always thought that to change a wire you tied the new wire to the old wire at one end and pulled it out the other end and that is how you replace it without having to cut through the wall or make a new cut.
So correct me if I am wrong or is my electrician just discouraging me from doing so because maybe he is lazy or he want to charge me more cause making new cut in the wall with all the work he could give me a higher bill.
thanks

11
Abhishek Jain (Mod)

It is always advisable to split the circuit into two with each protected by a separate MCB. It is possible to pull another wire in the existing conduct. At every turn, one opening is given to ease the pulling process. You may separate AC circuit which takes more load and pull wire for this circuit. I will suggest to use RCCB for protection against high resistance fault. MCB protects when the current drawn is high, whereas RCCB trips when the current leaks out from the appliance to the earth through high resistance circuit.

12
Muhammad Dessouky

Sir, I have another troubling question that I've not been able to find an answer to it over the Internet, why is the neutral wire grounded at the source of the supply? and how does the current flow back to the power source and not to the ground, and when the current alternates (i.e. change direction) why doesn't it flow to earth instead of flowing to the consumer's utility (as this earth path has the lower resistance)?

I know the question might be irrelevant to the topic but sir I'm desperate.

13
Abhishek Jain (Mod)

When neutral at the supply point is not connected to earth

In case, a fault does not take place any where in the circuit, it is OK. Also, even if there is only one fault, in one line or any load, than also it is OK.

Just imagine, if there are two faults, than the fault current will flow through another fault and makes a short circuit and this will not be detected. In case, there is one fault and a person touches live wire, the circuit will get complete through the earth and he will get a shock. In view of this, this system is not followed for power supply distribution to residential houses.

Solid neutral connected is required to hold the voltage between phase and neutral same even when of the phase is earthed, a common feature.

Now in case, a part of the equipment get grounded with a high resistance path, the current will flow back to the supply through the ground and balance of the current through the neutral. RCCBs are used to detect such high resistance fault because very low current is returning through the earth and balance through netural.

In case, there is dead short circuit, the whole of the current will flow through the earth and negligible through neutral. Such faults are detected by RCCBs as well as MCBs.

Note that, the current through the earth flows which is a fault current and not the current which is providing a function to the appliance.

Flow of current through earth is taken as fault current. In earlier days, earth was used as a return conductor particularly communication line with one wire on the poles and return through earth. Return current flowing through earth has many disadvantage in modern days of causing erosion of all service utility that it encounters in its return path because the earth current travels through these service utility provided underground such as metallic pipe line, metal parts.

14
Muhammad Dessouky

Well sir, I'm a mechatronics engineer with no practical experience whatsoever in electrical engineering and power systems. First I wanna thank you for your precious time but unfortunately I did't get the answer well, so could you please simplify/elaborate (as needed) the answer or something?

15
Abhishek Jain (Mod)

I will suggest you to study and read the content on
https://en.wikipedia.org/wiki/Earthing_system and it should clear your doubts.

16
Muhammad Dessouky

Thank you sir, I'm on it.

17
Muhammad Dessouky

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

18
Abhishek Jain (Mod)

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.

19
Muhammad Dessouky

Thank you so much!

20

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

21
Abhishek Jain (Mod)

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.

22

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.

23
Abhishek Jain (Mod)

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.

24

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.

Regards

25

Any chance of getting a reply, Sir ?

26
Abhishek Jain (Mod)

On second thoughts, if you can send us your phone number at [email protected] , someone from our team will contact you and talk to you in detail.

27

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.

28

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.

29

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

31

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.

32
Abhishek Jain (Mod)

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.

33

Hi,
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.

34
Abhishek Jain (Mod)

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.

35

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.

Swapan

36
Abhishek Jain (Mod)

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.

37

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

38
Abhishek Jain (Mod)

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

39

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.
Regards
Anil
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40
Abhishek Jain (Mod)

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.

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