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Anonymous Poster

Difference of ELCB and RCD

05/17/2010 7:42 AM

Dear engineers. I want to know what is the difference of ELCB (Earth leakage circuit breaker ) and RCD (Residual current device) . For the installation how to select (ELCB or RCD)?

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#1

Re: difference of ELCB and RCD

05/17/2010 7:48 AM

Dear,,,

they're two sides of the same coin!!! ELCB, RCD & GFCI are the same!

Regards,,,,,,,,,,,,,,,,,,,,,

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#2

Re: difference of ELCB and RCD

05/17/2010 7:51 AM

Both mean the same, however, ELCB implies a device capable of breaking a certain value of current since it is a "Earth Leakage Circuit Breaker" whereas, anything that senses a 'residual' current (meaning earth leakage) and doing something with it, can be called 'RCD'.

In my apartment complex, the main incomer switchboard has a Earth Leakage Relay which trips the main MCCB in the event of any earth fault. i frankly don't know its sensitivity.

However, i have an ELCB installed in my home, set at 100mA sensitivity. This is for protecting all of us in the house.

Hope this helps a little?

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#3
In reply to #2

Re: difference of ELCB and RCD

05/17/2010 8:55 AM

Dude, i had been to schneider training on elcb or rccb and they told me tht human body s capable of withstanding a max of 30mA ...so wenever u install rcd for residential purpose see through tht ur main rcb s 30mA.............

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#6
In reply to #3

Re: difference of ELCB and RCD

05/17/2010 9:52 AM

It is a function of time and current, please see the IEC graph here. Also the very good paper

ect114

i may add that i have designed these things when i was with ABB and GE

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Anonymous Poster
#12
In reply to #2

Re: difference of ELCB and RCD

07/02/2010 12:58 AM

Please note that you should not use 100mA ELCB for homes, it should always be 30mA

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#15
In reply to #12

Re: difference of ELCB and RCD

02/23/2022 10:55 AM

Well, that depends upon the earthing arrangements for the supply.

  • It is commonplace for a whole-house protection on a TT supply arrangement to be 100mA, with 30mA on several sub-circuits.
  • The above would not apply with TN-S or TN-C-S supplies.
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#4

Re: Difference of ELCB and RCD

05/17/2010 8:59 AM

the purpose n principle of both devices r same.............but now rcbs are equipped wit OC/ SC protection....They r called rcbo.......i don think elcb these days r equipped wit overcurrent(OC) protection (not sure abt it).......

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#5

Re: Difference of ELCB and RCD

05/17/2010 9:48 AM

They mean the same. Different nationalities use different terminologies. That's that. Coming to selection,

i) The rated current of the ELCB/RCD should be equal to or more than the expected load current of the feeder it is protecting.

ii) The sensitivity should be selected from amongst 30mA, 100mA & 300mA;

30mA for Protection against Direct Contact Risk

100mA for Protection against Indirect Contact Risk

300mA for Protection against fire/explosion

iii) Polarity: 2 Pole for single phase applications & 4 Pole for three phase applications

I also suggest you read a Schneider Electric Publication called "Cahiers Techniques" Publication No. ECT 114 - Residual Current Devices in LV, which is an excellent study material on the subject.

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#7

Re: Difference of ELCB and RCD

05/18/2010 6:14 AM

Dear Sir,

Generally both the terms are used depending upon the user. The function

they perform is the same ie to prevent the loss of human life due to the passing of

electric current through our body - through direct or indirect contacts.

(1) Human heart can withstand 30 mA for two cycles ( @ 50 cycles per second)

only( 30 mA for 0.04 secs).

(2) For multiple user areas like Factory etc- 100 mA is recommended to avoid

nuisence tripping.

(3) For areas where works like welding etc take place 300 mA sensivity is used.

I am in the field of Flat construction and we provide 30 mA ELCB in each

phase circuit with 4 Pole MCB or 4 pole Isolator as the incomer and it

is in line with CEIG ( TN) norms guide lines.

Manroop.Chennai.

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Guru

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#8
In reply to #7

Re: Difference of ELCB and RCD

05/18/2010 9:14 AM

I beg to differ in your quoting "in line with CEIG (TN) norms. Any electrical inspection should be carried out in accordance with the Indian Electricity Rules, 1956 only and no state CEIG can have their own regulations. And, to quote from IE Rule No. 61A: "61. A. Earth leakage protective device:- The supply of Energy to every electrical installation other than low voltage installation below 5 KW and those low voltage installations which do not attract provisions of section 30 of the Indian Electricity Act,1910, shall be controlled by an earth leakage protective device so as to disconnect the supply instantly on the occurence of earth fault or leakage of current" As can be noted from the above, no guidance or stipulation on sensitivity is given in the IE Rules. This being so, how can CEIG (TN) have their "so-called" norms? And, how can one be "in-line" with such "norms" which cannot be traced back to the master (i.e.) IE Rules?

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#9
In reply to #8

Re: Difference of ELCB and RCD

05/18/2010 11:36 AM

Well, perhaps it is not a crime to over-specify something? If the provision of a 30mA ELCB in every house meets in principle the IE Rule 61A, and does something more, why not?

i understand some European countries have seriously started considering a 10mA standard for domestic supply, keeping in mind the low tolerance threshold of children. Just overheard, no authenticity yet.

i wish i could have used a 30mA ELCB. Unfortunately i had to settle between having power or not at my house

Anyways, i intend to put an additional one in the bathrooms rated 10mA after rewiring that portion.

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#10
In reply to #9

Re: Difference of ELCB and RCD

05/18/2010 9:21 PM

I agree, but we have to realise the ground realities in India. Normally we do not pay enough attention in procuring quality wires & accessories for our house wiring. We become so much cost conscious there and go for sub-standard items. In such a case, if we go for a sensitive ELCB for our domestic installations, it would trip spuriously due to leakage in the poor quality wire insulation. The very next day we ask the electrician to by-pass the ELCB. I have seen a number of such cases, where a "hi-fi" ELCB is provided and within a few days it is bypassed.

I only meant in my earlier posting that (TN) CEIG (or for that matter, any other CEIG) cannot have their own norms. Everybody has to follow the IE Rules only. Good practice is one thing and regulations are something different. One cannot quote the rules out of context.

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#11
In reply to #10

Re: Difference of ELCB and RCD

05/18/2010 9:35 PM

You are quite right here. Being a switchgear designer myself, i am embarrassed that i could not supervise the builder's electrical work, and ended up having >30mA leakage. I did get the best wires, MCBs, ELCBs etc, but the execution was below par. Well, c'est la vie

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#13

Re: Difference of ELCB and RCD

07/14/2015 11:06 AM

An ELCB detects current in the earthing system, and an RCD detects a difference in current between the "Phase" and "Neutral".

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#14

Re: Difference of ELCB and RCD

08/15/2015 10:09 AM

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#16

Re: Difference of ELCB and RCD

02/27/2022 6:30 PM

As it was explained to me years ago:

The GOAL is protection against earth leakage. But there are different METHODS of doing so. One of those methods is RCD, but there are others. So all RCDs are Earth Leakage protective devices, but not al Earth Leakage protective devices are RCDs.

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