MCB tripping - why?
 

Hi, the MCB on my split circuit consumer unit is tripping
sporadically, sometimes when nothing is connected to the downstairs
socket circuit. The MCB protects the RCD protected circuits (upstairs
and downstairs sockets, cooker, hot tank, kitchen sockets). The hot
tank and cooker circuits are turned off at the rcd and are not
connected used/connected yet.The light (non-RCD'd) circuits stay on
when the RCD trips.

Please can someone tell me what causes an MCB to trip, other than
overcurrent, and not trip an RCD, and hopefully some possible things
to check in order to locate the fault.

This 'may be' heating associated but does happen when the heating is
off and the boiler is off i.e. could it be associated with hot pipes
near a cable?

Many thanks.

MCB tripping - why?
 

On Tue, 29 Dec 2009 02:41:08 -0800, nafuk wrote:

Hi, the MCB on my split circuit consumer unit is tripping sporadically,
sometimes when nothing is connected to the downstairs socket circuit.
The MCB protects the RCD protected circuits (upstairs and downstairs
sockets, cooker, hot tank, kitchen sockets). The hot tank and cooker
circuits are turned off at the rcd and are not connected used/connected
yet.The light (non-RCD'd) circuits stay on when the RCD trips.

Some confusion he one generally has an RCD giving residual-current
protection to one or more MCB-protected circuits, not the other way round.
Please can you confirm your layout of MCBs and RCDs?

(The RCD is the one with the 'TEST' button.)

Please can someone tell me what causes an MCB to trip, other than
overcurrent, and not trip an RCD, and hopefully some possible things to
check in order to locate the fault.

Overcurrent is the only thing that causes an MCB to trip. A difference in
current between live and neutral causes an RCD to trip. Thus a fault that
causes excess current to flow (slightly excess for a long period or gross
excess for a short period) trips an MCB (or other over-current device
such as a fuse). A few tens of milliamps leakage to earth trips an RCD -
even touching neutral and earth together on a circuit switched off at the
MCB or other single-pole switch in the circuit can cause enough earth-
loop current to flow to do it.


--
John Stumbles -- http://yaph.co.uk

Xenophobia? Sounds a bit foreign to me.

MCB tripping - why?
 

"John Rumm" wrote in message o.uk...
nafuk wrote:
Hi, the MCB on my split circuit consumer unit is tripping
sporadically, sometimes when nothing is connected to the downstairs
socket circuit. The MCB protects the RCD protected circuits (upstairs
and downstairs sockets, cooker, hot tank, kitchen sockets). The hot
tank and cooker circuits are turned off at the rcd and are not
connected used/connected yet.The light (non-RCD'd) circuits stay on
when the RCD trips.

Please can someone tell me what causes an MCB to trip, other than
overcurrent, and not trip an RCD, and hopefully some possible things
to check in order to locate the fault.

This 'may be' heating associated but does happen when the heating is
off and the boiler is off i.e. could it be associated with hot pipes
near a cable?

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:

http://wiki.diyfaq.org.uk/index.php?title=RCD


--
Cheers,

John.

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

--
Graham.

%Profound_observation%

MCB tripping - why?
 

Graham. wrote:
"John Rumm" wrote in message o.uk...
nafuk wrote:
Hi, the MCB on my split circuit consumer unit is tripping
sporadically, sometimes when nothing is connected to the downstairs
socket circuit. The MCB protects the RCD protected circuits (upstairs
and downstairs sockets, cooker, hot tank, kitchen sockets). The hot
tank and cooker circuits are turned off at the rcd and are not
connected used/connected yet.The light (non-RCD'd) circuits stay on
when the RCD trips.

Please can someone tell me what causes an MCB to trip, other than
overcurrent, and not trip an RCD, and hopefully some possible things
to check in order to locate the fault.

This 'may be' heating associated but does happen when the heating is
off and the boiler is off i.e. could it be associated with hot pipes
near a cable?
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:

http://wiki.diyfaq.org.uk/index.php?title=RCD


--
Cheers,

John.

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

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.

[g]

MCB tripping - why?
 

Overcurrent is the only thing that causes an MCB to trip. A difference in
current between live and neutral causes an RCD to trip. Thus a fault that
causes excess current to flow (slightly excess for a long period or gross
excess for a short period) trips an MCB (or other over-current device
such as a fuse). A few tens of milliamps leakage to earth trips an RCD -
even touching neutral and earth together on a circuit switched off at the
MCB or other single-pole switch in the circuit can cause enough earth-
loop current to flow to do it.



thats waht i was trying to say before i read this!
[g]

MCB tripping - why?
 

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

Thank you for the info and pointers..

MCB tripping - why?
 

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

http://groups.google.co.uk/group/uk....54f4f84f46148f

Now fixed.

Brendan

MCB trips as soon as a water heating coil is used.
 

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

MCB trips as soon as a water heating coil is used.
 

On Thu, 9 Feb 2017 01:10:39 -0800 (PST), wrote:

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.

--
Cheers
Dave.

MCB trips as soon as a water heating coil is used.
 

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

MCB trips as soon as a water heating coil is used.
 

On 09/02/2017 09:10, wrote:

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

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

--
Regards,
Martin Brown

MCB trips as soon as a water heating coil is used.
 

In article ,
wrote:
presently there is an C6 MCB can I replace it to 16 to resolve this
problem

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

--
from KT24 in Surrey, England

MCB trips as soon as a water heating coil is used.
 

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

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
wrote in message
...
presently there is an C6 MCB can I replace it to 16 to resolve this
problem

MCB trips as soon as a water heating coil is used.
 

On 09/02/2017 09:10, wrote:
presently there is an C6 MCB can I replace it to 16 to resolve this problem




Is this a free-standing heating coil such as
http://www.amazon.in/Bajaj-Immersion-1500W-1500-Watt-Heater/dp/B00ABMASXG?


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


--
Robin
reply-to address is (intended to be) valid

MCB trips as soon as a water heating coil is used.
 

In article ,
wrote:
presently there is an C6 MCB can I replace it to 16 to resolve this
problem

Sounds like you need to get a pro in.

--
*My luck is so bad that if I bought a cemetery, people would stop dying.

Dave Plowman London SW
To e-mail, change noise into sound.

MCB trips as soon as a water heating coil is used.
 

On 09/02/2017 09:10, wrote:

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

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)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

MCB trips as soon as a water heating coil is used.
 

John Rumm wrote:
On 09/02/2017 09:10, wrote:

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

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?

MCB trips as soon as a water heating coil is used.
 

MCB trips as soon as a water heating coil is used.
 

Dave Liquorice wrote:

On Thu, 9 Feb 2017 01:10:39 -0800 (PST), wrote:

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.

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

--

Roger Hayter

MCB trips as soon as a water heating coil is used.
 

In article ,
Bob Minchin wrote:
One has to wonder why a type C is being used instead of the more usual
type B for domestic circuits?

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

--
*If at first you don't succeed, try management *

Dave Plowman London SW
To e-mail, change noise into sound.

MCB trips as soon as a water heating coil is used.
 

On 09/02/2017 11:19, Bob Minchin wrote:
John Rumm wrote:
On 09/02/2017 09:10, wrote:

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

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?

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].


[1]
http://wiki.diyfaq.org.uk/index.php/...Loop_Impedance

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

MCB trips as soon as a water heating coil is used.
 

On Thursday, 9 February 2017 12:23:54 UTC, Harry Bloomfield wrote:
expressed precisely :
presently there is an C6 MCB can I replace it to 16 to resolve this problem

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

Ah. I wouldn't expect a 6A mcb to be powering a 16A capable cable, so no, doing that would be unwise. What power is this water heater?


NT