A few weeks ago, our consumer unit tripped out at 5am - and it turned
out that a neighbour had had the same happen to them.

Had I been away for a couple of days or longer, I would have come back
to a fridge-freezer full of rotted food.

The Credit Card machine in the village shop helpfully reported three
power interruptions that night, and Central Networks (who distribute
electricity here in Derbyshire) having initially pretended to know of
nothing odd, have now belatedly accepted that something did happen -
they say that a neighbouring area's supply had tripped out and reset on
three occasions (timings match exactly), which might well have caused
variations in supply to our village - but all within their allowed
operating limits (of course!).

They are suggesting that I should spend money on getting my 7-year-old
consumer unit tested as it must be hyper-sensitive to have tripped out
on such minor provocation.

Should I believe them? What can I do?

John Geddes
Derbyshire

John Geddes wrote:
A few weeks ago, our consumer unit tripped out at 5am - and it turned
out that a neighbour had had the same happen to them.

Had I been away for a couple of days or longer, I would have come back
to a fridge-freezer full of rotted food.
Msnip
They are suggesting that I should spend money on getting my 7-year-old
consumer unit tested as it must be hyper-sensitive to have tripped out
on such minor provocation.

Should I believe them? What can I do?

Maybe.
I assume that your CU has a earth leakage detector, and that's what's
tripping, rather than anything else.

Depending on the design of this, and the way the network is setup, large
currents flowing in the ground (the large flattish thing the house is built
on, not electrical) can cause the leakage detector to trip.

This is not a fault in the CU - it's working as designed.
It _may_ be a fault with the installation.

Also, current flowing in the ground wire, from the electricity company,
can cause similar problems.

On Mon, 03 Apr 2006 18:22:48 +0000, John Geddes
wrote:

Should I believe them? What can I do?

I don't know if you should believe them or not, but if the problem is in
their distribution network then you're fairly powerless I reckon. We
have about 2 power-cuts a year on average at the sub-station up the
road, each lasting for about 45 minutes to an hour and affecting the
street-lights, and (at a guess) 150-200 houses. And this is on the
outskirts of London, not out in the sticks somewhere and has been going
on for about 8 years.

The 'leccy board clearly aren't interested in fixing whatever the real
root of the problem is, they just sent a man out to the substation each
time it happens to fix the effect rather than the cause. 2 hours outage
per year is probably within whatever service levels they're allowed to
get away with. I've given up complaining, and bought a couple of UPS's.
--
Chris Cowley

John Geddes wrote:
A few weeks ago, our consumer unit tripped out at 5am - and it turned
out that a neighbour had had the same happen to them.

Had I been away for a couple of days or longer, I would have come back
to a fridge-freezer full of rotted food.

The Credit Card machine in the village shop helpfully reported three
power interruptions that night, and Central Networks (who distribute
electricity here in Derbyshire) having initially pretended to know of
nothing odd, have now belatedly accepted that something did happen -
they say that a neighbouring area's supply had tripped out and reset on
three occasions (timings match exactly), which might well have caused
variations in supply to our village - but all within their allowed
operating limits (of course!).

They are suggesting that I should spend money on getting my 7-year-old
consumer unit tested as it must be hyper-sensitive to have tripped out
on such minor provocation.

Should I believe them?

no

What can I do?

nothing. This will happen with a whole house RCD, does everything go
off or just some things?

If you're willing, replacing single RCD with RCBOs would help. Cost
around £100 in bits. In principle replacing rcd with a v-elcb would
also fix it, but theyre no longer regs accepted.

Wiring, appliances and filters all have capacitance. Capacitance causes
low leakage at 50Hz. A glitch is much higher frequency, so leakage much
higher. Hence the RCD trips.

There is a chance youve got an oversensitive rcd, but thats probably
not it, more likely just a single 30mA rcd, which is poor circuit
design.


NT

Should I believe them? What can I do?

If you see dips on a regular basis, ask them to fit a voltage
recorder. There are guaranteed standard service level agreements that
cover this (although I forget the timescale involved) - I think they
should have one in within 7-10 days IIRC (I should know this :-} )

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2 hours outage per year is probably within whatever service levels
they're allowed to get away with

Correct - the current time period before you can start to claim
compensation for an outage is 18 hours.

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On Mon, 3 Apr 2006 23:52:57 +0100, Colin Wilson
wrote:

2 hours outage per year is probably within whatever service levels
they're allowed to get away with

Correct - the current time period before you can start to claim
compensation for an outage is 18 hours.

Ah, I suspected as much - you'd have thought it'd work out cheaper for
them in the long run to diagnose and fix it properly, but I guess they
have bigger fish to fry.

I keep trying to convince SWMBO that buying a small-ish generator for
the back garden would be a good idea (mainly so I could tinker with it),
but she doesn't seem impressed with the idea.
--
Chris Cowley

Ah, I suspected as much - you'd have thought it'd work out cheaper for
them in the long run to diagnose and fix it properly, but I guess they
have bigger fish to fry.

I`m not sure whether multiple outages of a shorter period may class as
claimable under the guaranteed standards for loss of supply - IIRC any
more than 4 outages in a year bags you a payment, but you have to
claim it yourself - its not an automatic payment.

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Colin Wilson wrote:
Ah, I suspected as much - you'd have thought it'd work out cheaper for
them in the long run to diagnose and fix it properly, but I guess they
have bigger fish to fry.


I`m not sure whether multiple outages of a shorter period may class as
claimable under the guaranteed standards for loss of supply - IIRC any
more than 4 outages in a year bags you a payment, but you have to
claim it yourself - its not an automatic payment.

It's not the outages that are the problem. We get a couple per year and
you cope with this (learning not to buy mains-only telephone answering
machines for example). The point is that a normal outage sees the power
restored to everything in the house when the main supply is restored.

It is having the consumer unit trip off that is the bigger worry. Even
if the main supply comes back after 30 seconds outage, if the consumer
unit has tripped, then there is no power to anything in the house until
someone realises there is a problem and manually resets the consumer unit.

And if there is nobody at home when the unit trips, the house stays
unpowered until someone comes back - to find everything in the freezer
wrecked if they have been away for more than about 24 hours.

John Geddes

"John Geddes" wrote in message
...
...
It is having the consumer unit trip off that is the bigger worry. Even if
the main supply comes back after 30 seconds outage, if the consumer unit
has tripped, then there is no power to anything in the house until someone
realises there is a problem and manually resets the consumer unit.

And if there is nobody at home when the unit trips, the house stays
unpowered until someone comes back - to find everything in the freezer
wrecked if they have been away for more than about 24 hours.

Years ago, when industrial disputes were producing regular four hour power
cuts, the electronics magazines were full of designs for standby power
supplies, usually run off a car battery, to keep freezers and gas or oil
boilers running. It sounds as though you need something similar, perhaps a
really big UPS?

Colin Bignell

In article ,
John Geddes wrote:
A few weeks ago, our consumer unit tripped out at 5am - and it
turned out that a neighbour had had the same happen to them.
[snip]
They are suggesting that I should spend money on getting my
7-year-old consumer unit tested as it must be hyper-sensitive to
have tripped out on such minor provocation.

Do you by any chance have one of those filter plus
surge protection devices, plugged in anywhere?
The sort of thing that is built into an enlarged
13A plug top and used to power things like computers
or modems, etc.

The one I have has the normal filter components
and then a 270V VDR directly across Line-Earth.
This VDR appears to do nothing until there is an
overvoltage surge, at which time it conducts
and pulls an unbalance current through the RCD,
tripping it OFF to disconnect the surge.

Do you have anything like this, that may have
responded to an overvoltage surge as the power
wobbled from being connected/disconnected?

--
Tony Williams.

Chris Cowley wrote:
On Mon, 03 Apr 2006 18:22:48 +0000, John Geddes
wrote:

Should I believe them? What can I do?

I don't know if you should believe them or not, but if the problem is in
their distribution network then you're fairly powerless I reckon. We
have about 2 power-cuts a year on average at the sub-station up the
road, each lasting for about 45 minutes to an hour and affecting the
street-lights, and (at a guess) 150-200 houses. And this is on the
outskirts of London, not out in the sticks somewhere and has been going
on for about 8 years.

The 'leccy board clearly aren't interested in fixing whatever the real
root of the problem is, they just sent a man out to the substation each
time it happens to fix the effect rather than the cause. 2 hours outage
per year is probably within whatever service levels they're allowed to
get away with. I've given up complaining, and bought a couple of UPS's.

It happens here every time the wind blows or we get a thunderstorm..the
power overheads get shorted by tree branches and strikes, and the
automatic trips go out, then attempt automatic reset, and if the branch
is still there, trip again,and reset again.

The voltage surges are quite injurious and I have learnt NOT to set the
computer to 'autoboot' on restoration of power..the quickest way to head
crash a hard disc is to remove power when its loading up the operating
system doing lots of reads..

And a massive switch on transient is almost guaranteed to flip a 30mA
'whole house'RCD...which is why I stuck a 100mA in mine...

Christian McArdle wrote:
A few weeks ago, our consumer unit tripped out at 5am - and it turned
out that a neighbour had had the same happen to them.

Can you tell us exactly what is written on the switch that tripped.

I'm looking for anything like:

RCD/MCB/RCBO/ELCB/16A/32A/100A/63A/30mA/100mA/0.03A,0.1A

Christian.


A bit off subject perhaps. We also frequently get power cuts here.
However yesterday the voltage dropped for about 4hours such that lamps
were just glowing, the microwave thought it needed setting up, the
'fridge was grumbling, and the burglar alarm became confused! So I
switched everything off. Now my question is could low voltage cause any
harm, like damage motors that are trying to run but failing?

On Tue, 04 Apr 2006 09:39:59 +0100, The Natural Philosopher wrote:

It happens here every time the wind blows or we get a thunderstorm..the
power overheads get shorted by tree branches and strikes, and the
automatic trips go out, then attempt automatic reset, and if the branch
is still there, trip again,and reset again.

We get the same occasionally, the auto recloser tries three times within
a minute to re-enstate the power before locking out. Once locked out it
requires a man to come out, isolate/reroute power around the fault (there
are two ways of feeding every where around here), find and fix the fault
and reset the recloser. This normally takes 6 to 8 hours... Fortunately
it doesn't do it every time the wind blows, very few trees along the line
routes. B-)

We did have one spate, which was a tree, that would trip the recloser but
not often frequently enough for it to lock out. off 2s, on 60s, off 2s,
on 300s, off 2s, on 90s, off 2s, on 600s, off 2s, etc it did eventually
clear (ie burn the branch back on the tree) but only after about 30 mins
of this cycling...

The voltage surges are quite injurious and I have learnt NOT to set the
computer to 'autoboot' on restoration of power...

I have a small UPS that will supply power long enough to shut down the
PCs gracefully it then powers the iPBX until flat (up to 12hrs or so,
depending on how quick I can switch the PCS off). The UPS doesn't restart
on power return until it has got back at least 15% battery capacity.

And a massive switch on transient is almost guaranteed to flip a 30mA
'whole house'RCD...which is why I stuck a 100mA in mine...

A "whole house" RCD should be a 100mA time delayed one, so that you
maintain descrimination between the whole house 100mA one (there for
circuit/fault protection due to poor earth provision) and 30mA
non-delayed ones for shock protection.

--
Cheers
Dave. pam is missing e-mail

Now my question is could low voltage cause any harm, like damage
motors that are trying to run but failing?

Yes, although most modern things should be designed for it. Indeed, many
(not all) switched mode supplies won't even care and will work normally down
below even 100V.

Christian.

Broadback wrote:

A bit off subject perhaps. We also frequently get power cuts here.
However yesterday the voltage dropped for about 4hours such that lamps
were just glowing, the microwave thought it needed setting up, the
'fridge was grumbling, and the burglar alarm became confused! So I
switched everything off. Now my question is could low voltage cause any
harm, like damage motors that are trying to run but failing?

fridge & freezer compressors.

NT

Christian McArdle wrote:
Now my question is could low voltage cause any harm, like damage
motors that are trying to run but failing?

Yes, although most modern things should be designed for it. Indeed, many
(not all) switched mode supplies won't even care and will work normally down
below even 100V.

Christian.


I once worked on a unit that was specified as 48-400V DC or AC up to
400HZ :-)

On Tue, 04 Apr 2006 09:39:59 +0100, The Natural Philosopher
wrote:

It happens here every time the wind blows or we get a thunderstorm..the
power overheads get shorted by tree branches and strikes, and the
automatic trips go out, then attempt automatic reset, and if the branch
is still there, trip again,and reset again.

All the power 'round here is underground, but there was a big
underground fire a few years ago (way after the sub-station first began
tripping). I rather optimistically hoped that the work carried out after
the fire would solve the problem, but it didn't.

There's a small company up the road who manufacture, refurbish and test
electricity meters and I harbour vague (and probably completely
unfounded) suspicions that this problem is being caused by them in some
way.

The voltage surges are quite injurious and I have learnt NOT to set the
computer to 'autoboot' on restoration of power..the quickest way to head
crash a hard disc is to remove power when its loading up the operating
system doing lots of reads..

Oh yes, I've experienced the same thing. It used to be that whenever the
supply was first restored, it would go off again after 10 seconds or so
before coming back on permanently (or what passes for permanently around
here). Just long enough for my hard disks to spin back up before having
the rug pulled again...

--
Chris Cowley

On Tue, 4 Apr 2006 02:23:00 +0100, Colin Wilson
wrote:

Ah, I suspected as much - you'd have thought it'd work out cheaper for
them in the long run to diagnose and fix it properly, but I guess they
have bigger fish to fry.

I`m not sure whether multiple outages of a shorter period may class as
claimable under the guaranteed standards for loss of supply - IIRC any
more than 4 outages in a year bags you a payment, but you have to
claim it yourself - its not an automatic payment.

Ta. I reckon there have been times in the past where we'd have qualified
for that. Sounds like more trouble than it's worth though. I'd rather
they just traced and fixed the problem!
--
Chris Cowley

Christian McArdle wrote:
A few weeks ago, our consumer unit tripped out at 5am - and it turned
out that a neighbour had had the same happen to them.


Can you tell us exactly what is written on the switch that tripped.

I'm looking for anything like:

RCD/MCB/RCBO/ELCB/16A/32A/100A/63A/30mA/100mA/0.03A,0.1A

Christian.


RCD 80A, 0.03A, 240v - Made by GE ref 304/28031-601 if that helps

John Geddes

RCD 80A, 0.03A, 240v - Made by GE ref 304/28031-601 if that helps

Yes. I wouldn't put a freezer on a 30mA RCD. OK, it might have also tripped
a 100mA, but it is less likely.

I don't know what earthing system you have. If you have TT currently:

You should probably upgrade to a 100mA time delay RCD split load or RCBO
system, with the freezer on its own dedicated MCB circuit covered only by
the overall 100mA trip.

An even better alternative is to enquire if your supplier offers TN-C-S
earthing. Then you can have the freezer circuit with no RCD at all. Then you
can pretty much guarantee it will get power after reconnection.

If you have TN-C-S or TN-S earthing:

You seem to have a non split load consumer unit with all circuits RCD
protected. This is no longer current practice partly for the reasons you
have found. You should change to a split load unit (or RCBO system) with
lighting and a dedicated freezer circuit NOT RCD protected.

Christian.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember John Geddes
saying something like:

It is having the consumer unit trip off that is the bigger worry. Even
if the main supply comes back after 30 seconds outage, if the consumer
unit has tripped, then there is no power to anything in the house until
someone realises there is a problem and manually resets the consumer unit.

And if there is nobody at home when the unit trips, the house stays
unpowered until someone comes back - to find everything in the freezer
wrecked if they have been away for more than about 24 hours.

You need a non-RCD (or non-ELCB) protected spur to your freezer.
--

Dave

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember The Natural Philosopher
saying something like:

It happens here every time the wind blows or we get a thunderstorm..the
power overheads get shorted by tree branches and strikes, and the
automatic trips go out, then attempt automatic reset, and if the branch
is still there, trip again,and reset again.

The voltage surges are quite injurious and I have learnt NOT to set the
computer to 'autoboot' on restoration of power..the quickest way to head
crash a hard disc is to remove power when its loading up the operating
system doing lots of reads..

And a massive switch on transient is almost guaranteed to flip a 30mA
'whole house'RCD...which is why I stuck a 100mA in mine...

That exact thing happened to me a few years ago and wrecked a PC. Every
major component within it failed over the next year. The motherboard was
dead at once, but subsequent failures of the salvaged components
convinced me that the surges were to blame.

I bought a decent UPS and it's paid for itself since, many times over.
--

Dave

"nightjar" nightjar@ insert my surname here.uk.com wrote:

"John Geddes" wrote in message
...
...
It is having the consumer unit trip off that is the bigger worry. Even if
the main supply comes back after 30 seconds outage, if the consumer unit
has tripped, then there is no power to anything in the house until someone
realises there is a problem and manually resets the consumer unit.

And if there is nobody at home when the unit trips, the house stays
unpowered until someone comes back - to find everything in the freezer
wrecked if they have been away for more than about 24 hours.

Years ago, when industrial disputes were producing regular four hour power
cuts, the electronics magazines were full of designs for standby power
supplies, usually run off a car battery, to keep freezers and gas or oil
boilers running. It sounds as though you need something similar, perhaps a
really big UPS?

Or a relatively small UPS, and several car batteries from the scrappies,
along with blower to keep the UPS cool.