We woke up to a cold house this morning because the MCB on the ring main
to which the CH is connected had tripped in the middle of the night.

I reset it as soon as I realised, and it didn't trip again - so I'm
wondering what is likely to have caused it.

We're quite used to having 6A lighting circuit MCBs trip if a bulb fails
at switch-on, but this is different.

The one which tripped is a 32A MCB on a ring circuit which has no RCD
protection. According to a mains-driven clock, it appears to have
tripped at about 3AM. Nothing significant would have been happening at
that time. There are quite a few electronic devices on that ring -
mainly using wallwarts - but nothing using much current at that time of
night. [The freezers are on a different ring]. I can't find any device
which has obviously failed - but surely if a device had failed, its own
fuse would have blown rather than tripping the MCB?

Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article , Roger Mills
writes
We woke up to a cold house this morning because the MCB on the ring main
to which the CH is connected had tripped in the middle of the night.

I reset it as soon as I realised, and it didn't trip again - so I'm
wondering what is likely to have caused it.

We're quite used to having 6A lighting circuit MCBs trip if a bulb fails
at switch-on, but this is different.

The one which tripped is a 32A MCB on a ring circuit which has no RCD
protection. According to a mains-driven clock, it appears to have
tripped at about 3AM. Nothing significant would have been happening at
that time. There are quite a few electronic devices on that ring -
mainly using wallwarts - but nothing using much current at that time of
night. [The freezers are on a different ring]. I can't find any device
which has obviously failed - but surely if a device had failed, its own
fuse would have blown rather than tripping the MCB?

Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?

Switch on surge of your freeview equipment powering up to check for a
software update (only half tongue in cheek, 3am is the usual time).
--
fred
it's a ba-na-na . . . .

On 01/02/2014 21:00, fred wrote:
In article , Roger Mills
writes
We woke up to a cold house this morning because the MCB on the ring main
to which the CH is connected had tripped in the middle of the night.

I reset it as soon as I realised, and it didn't trip again - so I'm
wondering what is likely to have caused it.

We're quite used to having 6A lighting circuit MCBs trip if a bulb fails
at switch-on, but this is different.

The one which tripped is a 32A MCB on a ring circuit which has no RCD
protection. According to a mains-driven clock, it appears to have
tripped at about 3AM. Nothing significant would have been happening at
that time. There are quite a few electronic devices on that ring -
mainly using wallwarts - but nothing using much current at that time of
night. [The freezers are on a different ring]. I can't find any device
which has obviously failed - but surely if a device had failed, its own
fuse would have blown rather than tripping the MCB?

Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?

Switch on surge of your freeview equipment powering up to check for a
software update (only half tongue in cheek, 3am is the usual time).

Well, it's on the right ring - and about the only thing that *might* be
doing anything at that time of day. If you remove tongue from cheek, is
there any possibility that that (Humax HDR-FOX T2) could cause the MCB
to trip? The device itself (Humax) is working ok today, with no
intervention required.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article , Roger Mills
writes
On 01/02/2014 21:00, fred wrote:
In article , Roger Mills
writes

Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?

Switch on surge of your freeview equipment powering up to check for a
software update (only half tongue in cheek, 3am is the usual time).

Well, it's on the right ring - and about the only thing that *might* be
doing anything at that time of day. If you remove tongue from cheek, is
there any possibility that that (Humax HDR-FOX T2) could cause the MCB
to trip? The device itself (Humax) is working ok today, with no
intervention required.

It does seem unlikely. If it repeats though then it might be worthwhile
unplugging the HDR overnight and see if it makes a difference.

I've had a 32A MCB fail to close onto the load of a home office with a
few comps and a couple of hefty laser printers but that was closing onto
a heavy inrush rather than tripping from a load already connected and
one element going momentarily bad.
--
fred
it's a ba-na-na . . . .

One thing that happened to me some years back is that I had a surge
protector on my wander lead for the hi fi and computer. It was as far as I
could see, a medium sized resistor looking thing in the socket bar.
Apparently if the voltage exceeds whatever its set for it puts a momentary
short on the mains. This is definitely enough to trip things and more
worryingly reveal how many nasty over voltage pulses were cominginto the
house. Strangely, the device did not look stressed at all, and as it
stopped quite a few spikes, one assumes it is still ok.
Of late either its died or the spikes have gone away.

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"fred" wrote in message ...
In article , Roger Mills
writes
We woke up to a cold house this morning because the MCB on the ring main
to which the CH is connected had tripped in the middle of the night.

I reset it as soon as I realised, and it didn't trip again - so I'm
wondering what is likely to have caused it.

We're quite used to having 6A lighting circuit MCBs trip if a bulb fails
at switch-on, but this is different.

The one which tripped is a 32A MCB on a ring circuit which has no RCD
protection. According to a mains-driven clock, it appears to have
tripped at about 3AM. Nothing significant would have been happening at
that time. There are quite a few electronic devices on that ring -
mainly using wallwarts - but nothing using much current at that time of
night. [The freezers are on a different ring]. I can't find any device
which has obviously failed - but surely if a device had failed, its own
fuse would have blown rather than tripping the MCB?

Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?

Switch on surge of your freeview equipment powering up to check for a
software update (only half tongue in cheek, 3am is the usual time).
--
fred
it's a ba-na-na . . . .

On 01/02/2014 20:22, Roger Mills wrote:
We woke up to a cold house this morning because the MCB on the ring main
to which the CH is connected had tripped in the middle of the night.

I reset it as soon as I realised, and it didn't trip again - so I'm
wondering what is likely to have caused it.

We're quite used to having 6A lighting circuit MCBs trip if a bulb fails
at switch-on, but this is different.

The one which tripped is a 32A MCB on a ring circuit which has no RCD
protection. According to a mains-driven clock, it appears to have
tripped at about 3AM. Nothing significant would have been happening at
that time. There are quite a few electronic devices on that ring -
mainly using wallwarts - but nothing using much current at that time of
night. [The freezers are on a different ring]. I can't find any device
which has obviously failed - but surely if a device had failed, its own
fuse would have blown rather than tripping the MCB?

Not always guaranteed - there have even been rare cases where an
appliance fault has left its plug fuse and the circuit MCB untouched,
but blown the main incomer fuse!

Do MCBs sometimes trip for no good reason, or is there bound to be a

Not usually unless faulty. Perhaps in cases of parasitic heating from
adjacent "hot" heavily loaded MCBs.

genuine fault somewhere? If the latter, what should I be looking for?

Might be worth sticking a clamp meter round the circuit live or neutral
in the CU and checking the current draw is inline with your expectations...

Not powering an outside socket etc by any chance?

--
Cheers,

John.

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

John Rumm wrote:

Not powering an outside socket etc by any chance?

Got gypsies next door?

Bill

On 01/02/2014 23:54, John Rumm wrote:


Might be worth sticking a clamp meter round the circuit live or neutral
in the CU and checking the current draw is inline with your expectations...


Not easy to isolate a single conductor from that MCB, but when I put my
clamp meter on one of the tails feeding the CU in question, it measures
2.5 amps - and there are more things running than there would have been
at 3am - including some things on the other MCBs.


Not powering an outside socket etc by any chance?


Funny you should ask that! Yes, there is an outside circuit on that
ring, which powers the pond electrics (circulator pump and air pump) via
an RCD-protected spur.

The RCD had not tripped and the pond pumps are still working ok.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

Roger Mills wrote:

On 01/02/2014 23:54, John Rumm wrote:

Not powering an outside socket etc by any chance?

Funny you should ask that! Yes, there is an outside circuit on that
ring

Any neighbours with an electric car?

On 02/02/2014 16:58, Andy Burns wrote:
Roger Mills wrote:

On 01/02/2014 23:54, John Rumm wrote:

Not powering an outside socket etc by any chance?

Funny you should ask that! Yes, there is an outside circuit on that
ring

Any neighbours with an electric car?


Not as far as I know, and all the outdoor electrics are in the back
garden - a long way from where you could park a car. And the circuit
whose MCB tripped only has the pond electrics - with nothing accessible
to plug into.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

"Roger Mills" wrote in message
...


Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?


I would wait and see what happens. It could be a MCB on it's death bed.
Unless you have an old/odd CU then it should only be a few quid to swap the
MCB - that would be first my first suggestion - and if that fails then you
start to look for fixed wiring or appliance faults

BTW Did you get in touch with Geoff?

--
Adam

On 02/02/2014 09:09, ARW wrote:
"Roger Mills" wrote in message
...


Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?


I would wait and see what happens. It could be a MCB on it's death bed.
Unless you have an old/odd CU then it should only be a few quid to swap
the MCB - that would be first my first suggestion - and if that fails
then you start to look for fixed wiring or appliance faults

It's a Wylex CU which I fitted about 30 years ago. It originally had
re-wireable fuses, but I replaced them with MCBs later.

I do, in effect, have a spare MCB. When we moved the kitchen to the
other side of the house a few years ago, we had a new dedicated CU for
it. The MCB which used to power the cooker in the old kitchen is now
largely redundant - the cooker control box is still there but nothing is
connected to it. Its built-in 13A socket isn't used very often. So, if
it happens again, I'll swap the MCB with the old cooker one, and see
whether that makes any difference.


BTW Did you get in touch with Geoff?


Not yet, but I will. Would you care to send me a PM with the best email
address for him, so that my email won't get zapped by his spam trap?

[I was hoping for a few more responses to my OP - but yours is the only
one so far].
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

"Roger Mills" wrote in message
...
On 02/02/2014 09:09, ARW wrote:
"Roger Mills" wrote in message
...


Do MCBs sometimes trip for no good reason, or is there bound to be a
genuine fault somewhere? If the latter, what should I be looking for?


I would wait and see what happens. It could be a MCB on it's death bed.
Unless you have an old/odd CU then it should only be a few quid to swap
the MCB - that would be first my first suggestion - and if that fails
then you start to look for fixed wiring or appliance faults

It's a Wylex CU which I fitted about 30 years ago. It originally had
re-wireable fuses, but I replaced them with MCBs later.

I do, in effect, have a spare MCB. When we moved the kitchen to the other
side of the house a few years ago, we had a new dedicated CU for it. The
MCB which used to power the cooker in the old kitchen is now largely
redundant - the cooker control box is still there but nothing is connected
to it. Its built-in 13A socket isn't used very often. So, if it happens
again, I'll swap the MCB with the old cooker one, and see whether that
makes any difference.

That is the way forward,



BTW Did you get in touch with Geoff?


Not yet, but I will. Would you care to send me a PM with the best email
address for him, so that my email won't get zapped by his spam trap?

[I was hoping for a few more responses to my OP - but yours is the only
one so far].


I'll sort something out when I get to London later tonight. Is your email
valid?

--
Adam

On 02/02/2014 18:26, ARW wrote:
"Roger Mills" wrote in message
...
On 02/02/2014 09:09, ARW wrote:


BTW Did you get in touch with Geoff?


Not yet, but I will. Would you care to send me a PM with the best
email address for him, so that my email won't get zapped by his spam
trap?

[I was hoping for a few more responses to my OP - but yours is the
only one so far].


I'll sort something out when I get to London later tonight. Is your
email valid?


Ta! Yes the email is valid. [As I was typing this, a PM arrived from
John Rumm with an address for Geoff, so I'll try that].
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On Saturday, February 1, 2014 8:22:15 PM UTC, Roger Mills wrote:

which has obviously failed - but surely if a device had failed, its own
fuse would have blown rather than tripping the MCB?

no, MCBs are generally faster,so either can go.


NT

In article ,
writes:
On Saturday, February 1, 2014 8:22:15 PM UTC, Roger Mills wrote:

which has obviously failed - but surely if a device had failed, its own
fuse would have blown rather than tripping the MCB?

no, MCBs are generally faster,so either can go.

I've had table lamp bulbs blowing trip the 32A MCB.

I've even had the 15W oven lamp blow and take out the ring's 32A MCB,
and the plug fuse. It did cause the bulb to explode, and the force of
it blew the glass cover cross-threaded, so I had to take the whole
oven out so I could extract the fitting from the rear, and un-jam
the glass cover.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]