MCB tripping - why?

I am guessing that you have transposed the terms RCD and MCB here, and what you actually have is a nuisance RCD trip. You will need to be methodical to track down the cause of this. Some advice is given in the nuisance trip section of this article:

you actually have is a nuisance RCD trip. You will

the nuisance trip section of this article:

I am confused by his post too. If the individual circuits are protected by RCBOs rather than RCDs it begins to make more sense

you actually have is a nuisance RCD trip. You will

in the nuisance trip section of this article:

i think an rcd/rcbo can trip even if the circuit is turned off, if its a singlepole switch and only cutting power to the live wire, because a leak from the neutral to earth would trip the rcd as neutral and live would then be unbalanced.

so maybe disconnect some neuatralsl and see if that stops it.

Sorry, I do have my MCB and RCD's mixed up.

Thank you for the info and pointers..

I recently had the same problem and got some excellent advice from this forum, see my post:

Brendan

presently there is an C6 MCB can I replace it to 16 to resolve this problem

Assuming that you really mean MCB then you need to find the reason for the instant overload.

What is your "water heating coil"? What checks have you done on it?

Did it work in the past? Why is it tripping? Have you checked earth leakage?

What are you doing with a water heating coil on a lighting circuit?

Kind of lacking in information to make such a decision unless you are of the kill or cure type. IE insert six inch nail and see what goes bang. Brian

Is this a free-standing heating coil such as ?

Are you in the UK or are you elsewhere - eg in India?

Sounds like you need to get a pro in.

What kind of water heating coil are we talking about?

(A 6A MCB sounds rather low for most heating circuits - that would limit the heater power to about 1300W - however you can only substitute a higher trip current MCB if the cable size is large enough to remain protected)

One has to wonder why a type C is being used instead of the more usual type B for domestic circuits?

snipped-for-privacy@gmail.com expressed precisely :

The sent from IP seems it might be Shertallai, Kerala, in India.

If it is a two or three kilowatt heater the result is unsurprising.

Not that uncommon on lighting circuits with lots of LV stuff - especially when transformer fed.

I normally spec a type C for lighting circuits since it makes them less likely to trip on a filament lamp failure IME. Not really any downside in doing so as long as you make sure the ELI at the furthest part of the circuit is less than 3.64 Ohms[1].