Kitchen Electrics FAQ?

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David W.E. Roberts

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Jul 28, 2007, 7:30:14 AM7/28/07
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Hi,

I have looked at the FAQ and there doesn't seem to be much electrical stuff
there - mainly a pointer to the wiring regs (or at least, where to buy
them).

I am now Googling through but there is a lot of chaff to winnow to find the
wheat.

Is the FAQ not populated with wiring answers because of potential legal
liability?

Even a few pointers to threads in Google Groups would make life a lot
easier.

I will carry on researching, and then post what I think I have learned in
the hope someone will be kind enough to cross check.

Cheers

Dave R
--

John Rumm

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Jul 28, 2007, 7:38:09 AM7/28/07
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David W.E. Roberts wrote:

> Is the FAQ not populated with wiring answers because of potential legal
> liability?

No. Just not a section there as yet...

There is more info in the wiki though:

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

> I will carry on researching, and then post what I think I have learned in
> the hope someone will be kind enough to cross check.

What do you actually want to know?

Kitchen electrics are not that much different to those in other rooms
(part p not withstanding).


--
Cheers,

John.

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

David W.E. Roberts

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Jul 28, 2007, 8:49:00 AM7/28/07
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John,

thanks for that.

I have just had the kitchen completely gutted (plaster off walls, ceiling
down) and am about to start on minor modifications to the wiring - or at
least this is what I thought until I started.

I have 4 * 13 Amp sockets in the kitchen; three doubles and one single which
is on the cooker point.

When I (fortunately) checked I found that they were all on different
circuits.

One double spurred off the garage.
One double spurred off the house 13 amp ring main (with another double
spurred off this going into the lounge).
One double spurred off a 20 amp circuit which I thought did a complete
kitchen spur, but turned out to do an extractor fan and one double socket.
[I am still trying to trace where this circuit goes because it is inside the
cavity and I haven't yet found where it exits.]
One on the dedicated cooker circuit which goes straight back to a 32 Amp
fuse.

Fixed(ish) electrical devices to go in the kitchen:
(1) Dishwasher
(2) Under the counter fridge
(3) Under the counter single oven
(4) Kick space heater (planned to be a fan and a radiator of the CH but a
2Kw all electrical jobbie may turn out cheaper).
(5) Power to the gas hob for the ignition circuit.

On-the-counter devices:

(1) Microwave (combination grill/microwave/oven)
(2) Kettle
(3) Bread Maker
(4) Digital phone handset
(5) Hand blender
(6) Towcester
(7) Possibly another toy or two if the mood takes us.

The other main things will be lighting under a row of wall cupboards, and
possibly low voltage lighting inside a glass wall cupboard.
I assume these should come off the ring main not the lighting circuit.

My current plan is to install a ring main horizontally above the worktop,
with spurs down to the under-the-counter devices.

Much good information has already been picked up.

I think I will retain my cooker circuit as it is in about the right place,
although I recognise that I could take it off the ring main as modern
cookers are low(ish) power and I don't have an electric hob.

I am undecided about the appliance spurs. The over engineer in me likes the
idea of an isolation switch for each appliance in clear view with an
unswitched socket inside the units, but I recognise that this is not
strictly necessary and can make the wall space look cluttered.

My current outstanding questions:

(1) When you put sockets for the spurs beneath the units, is it necessary to
mount them in the wall and then cut a hole in the back of the unit, or can
you surface mount a box inside onto the back board of the unit, with the
wire coming in through the void at the back?

(2) How high should the sockets be above the work surface?

(3) What is the minimum horizontal distance between a socket and the sink
(and is this from the bowl and taps, or from the edge of the drainer)?

(4) What is the minimum horizontal distance between a gas hob and a socket?

(5) Should I run my wiring in conduits - if so is plastic O.K. or should I
use metal so that future owners have some chance of locating the wires
before they drill in to fit spice racks, kitchen towel holders etc. ?

I haven't done my final sums yet to see if everything will fit on one ring
main - I have a few power hungry devices there - but my first guess is that
it should be O.K., especially if I put e.g. the combi microwave on the plug
on the cooker circuit.

I have 'gained' two 32 amp fuses in my fuse box - with the new combi boiler
I no longer need the immersion heater or electric shower circuits.

TIA

Dave R


"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:46ab2aa4$0$1632$ed26...@ptn-nntp-reader02.plus.net...

Andrew Gabriel

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Jul 28, 2007, 9:23:39 AM7/28/07
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I've done two kitchens in the last 8 years.
In both cases, I installed completely new circuits for the kitchen
(except lighting), and replaced the CU's to take the extra circuits.

o 30mA RCD protected ring which feeds all the portable appliances
and all easily accessible socket outlets.
o non-RCD protected ring which feeds stationary and fixed appliances
such as fridge, freezer, washing/dishwashing machines, boiler,
oven (with 13A plug). No easily accessible socket outlets, so
this circuit isn't used for portable appliances. This would also
be a good circuit for something like a fishtank life support
system, although I might use an RCD plug if the apparatus wasn't
all well double-insulated.
o Cooker circuit. In both kitchens, a gas cooker is fitted so this
wasn't needed, but it seemed silly not to make provision for an
electric cooker in the future. Outlet fitted with a 13A socket
for now so hob ignition can be powered from it, but it's in
a deep box and can be replaced with a high current flex outlet.
o Lighting -- at least two separately switched sets of lights so
that lighting level can be adjusted (without using dimmers).
Split into general room lighting, and worktop task lighting.
For task lighting over a sink, I used a pullcord switch fixed
under a nearby cupboard with a 4" string, so it's perfectly
safe to operate with wet hands.

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

John Rumm

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Jul 28, 2007, 9:42:54 AM7/28/07
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David W.E. Roberts wrote:

> One double spurred off the garage.
> One double spurred off the house 13 amp ring main (with another double
> spurred off this going into the lounge).
> One double spurred off a 20 amp circuit which I thought did a complete
> kitchen spur, but turned out to do an extractor fan and one double socket.
> [I am still trying to trace where this circuit goes because it is inside the
> cavity and I haven't yet found where it exits.]

Sounds like it could all do with a radical pruning and starting over.

> Fixed(ish) electrical devices to go in the kitchen:
> (1) Dishwasher
> (2) Under the counter fridge
> (3) Under the counter single oven
> (4) Kick space heater (planned to be a fan and a radiator of the CH but a
> 2Kw all electrical jobbie may turn out cheaper).
> (5) Power to the gas hob for the ignition circuit.
>
> On-the-counter devices:
>
> (1) Microwave (combination grill/microwave/oven)
> (2) Kettle
> (3) Bread Maker
> (4) Digital phone handset
> (5) Hand blender
> (6) Towcester
> (7) Possibly another toy or two if the mood takes us.

OK, that lot does not sound too bad. Many of the smaller appliances are
short term loads anyway (kettle, toaster etc)

> The other main things will be lighting under a row of wall cupboards, and
> possibly low voltage lighting inside a glass wall cupboard.
> I assume these should come off the ring main not the lighting circuit.

You can do either. If coming off a power circuit then you will need
additional fusing at the point you take the lighting feed usually.

> My current plan is to install a ring main horizontally above the worktop,
> with spurs down to the under-the-counter devices.

They could be switched feeds in some cases rather than spurs.

> Much good information has already been picked up.
>
> I think I will retain my cooker circuit as it is in about the right place,
> although I recognise that I could take it off the ring main as modern
> cookers are low(ish) power and I don't have an electric hob.

Do you need to power a cooker? A free standing gas cooker will only need
power for ignition and clock etc, so not a big load. Even a single
electric oven can be powered from a general purpose circuit.

> I am undecided about the appliance spurs. The over engineer in me likes the
> idea of an isolation switch for each appliance in clear view with an
> unswitched socket inside the units, but I recognise that this is not
> strictly necessary and can make the wall space look cluttered.

You want to make sure you have a way of isolating each appliance without
having to pull it out. This can mean above counter switches, or sockets
that are accessible in adjacent cupboards for example.

> My current outstanding questions:
>
> (1) When you put sockets for the spurs beneath the units, is it necessary to
> mount them in the wall and then cut a hole in the back of the unit, or can
> you surface mount a box inside onto the back board of the unit, with the
> wire coming in through the void at the back?

It is preferable to have fixed wiring fixed to the building and not the
furniture. However you can use common sense here. Sometimes surface
mounting (or using a drywall mattress) on the back of a cabinet will
make more sense even if not totally "right".

> (2) How high should the sockets be above the work surface?

Midway between top and bottom units looks about right. There are no hard
and fast rules. You can also use 45 degree sockets mounted at the top or
the bottom of the gap if you prefer.

> (3) What is the minimum horizontal distance between a socket and the sink
> (and is this from the bowl and taps, or from the edge of the drainer)?

Again it is not specified in the regs, but you need to use common sense.
Guidelines usually say 600mm is plenty, 300mm may be ok in many cases.

> (4) What is the minimum horizontal distance between a gas hob and a socket?

As above - no hard and fast rules, but you don't want to either melt the
socket, or have a trailing lead draped over the hob.

> (5) Should I run my wiring in conduits - if so is plastic O.K. or should I
> use metal so that future owners have some chance of locating the wires
> before they drill in to fit spice racks, kitchen towel holders etc. ?

If you follow the required zones (inline with accessories horizontally
or vertically, and within 150mm of a corner or ceiling) then you can
bury the cables directly. Since you are back to bare walls you may find
plastic capping over the wires is simplest and that will give them
protection when they are being plastered.

It is very hard to offer mechanical protection to wires anyway -
especially against a determined numpty with a power drill or a masonry
nail. Using RCD protection for all applicable circuits (i.e. not
fridge/freezer/boiler) is usually far more effective.

> I haven't done my final sums yet to see if everything will fit on one ring
> main - I have a few power hungry devices there - but my first guess is that
> it should be O.K., especially if I put e.g. the combi microwave on the plug
> on the cooker circuit.

The main loads are:

(1) Dishwasher 3kW perhaps - thermostatic control - shortish term
(3) Under the counter single oven 2kW thermostatic control


(4) Kick space heater (planned to be a fan and a radiator of the CH but

a 2Kw all electrical jobbie may turn out cheaper). Not when you include
the cost of running it! Having said that many kitchens require little or
no heating much of the time.
(1) Microwave (combination grill/microwave/oven) 2kW perhaps

So we are heading toward 9kW peak load, but with diversity and the
thermostatic control that should be ok on a single circuit.

(5) Power to the gas hob for the ignition circuit.

(2) Kettle 3kW - but very short term
(3) Bread Maker 600W
(4) Digital phone handset 10W
(5) Hand blender
(6) Towcester - could be 2kW - but short term


(7) Possibly another toy or two if the mood takes us.

If you have the electric kickspace heater then you may want to put that
on its own radial.

(2) Under the counter fridge 400W

Stick that on a non RCD radial - could be the same one as the heater.

> I have 'gained' two 32 amp fuses in my fuse box - with the new combi boiler
> I no longer need the immersion heater or electric shower circuits.

Another candidate for a non RCD protected feed.

Andy Wade

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Jul 29, 2007, 8:14:05 AM7/29/07
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John Rumm wrote:

>> (2) How high should the sockets be above the work surface?
>

> There are no hard and fast rules.

There is a recommendation in the IEE Electrician's Guide to the Building
Regulations (EGBR) that the horizontal centre line of such sockets
should be at least 150 mm above the worktop, and that other sockets
should be at least 450 mm above floor level. (IMO the latter
measurement should be to the bottom of the sockets, to align with the
Part M building regs requirements.)

>> (3) What is the minimum horizontal distance between a socket and the sink
>> (and is this from the bowl and taps, or from the edge of the drainer)?
>
> Again it is not specified in the regs, but you need to use common sense.
> Guidelines usually say 600mm is plenty, 300mm may be ok in many cases.

The EGBR says 300 mm min., and so does NICEIC guidance. 600 mm is
probably being over-cautious.

> [...]


> Another candidate for a non RCD protected feed.

Given that the 17th edition regs are likely to be in force in less than
a year and will require all sockets "intended for general use" to be RCD
protected I'd be inclined to put everything on a single 30 mA
RCD-protected ring circuit. Ideally a 32 A / 30 mA RCBO would be used
as the protective device. A possible exception is the heater if that
does end up as an electric heater rather than a fan-coil unit and is
likely to be used for long periods, in which case a separate 16 A radial
heater circuit may be justified on loading grounds.

To comply with the draft 17th ed. requirements any sockets which are
_not_ 30 mA RCD-protected should be specifically labelled ("or otherwise
suitably identified") and must be "provided for connection of a
particular item of equipment" [Reg. 411.3.3 in the draft 17th ed.]

--
Andy

John Rumm

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Jul 29, 2007, 9:13:57 AM7/29/07
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Andy Wade wrote:

> To comply with the draft 17th ed. requirements any sockets which are
> _not_ 30 mA RCD-protected should be specifically labelled ("or otherwise
> suitably identified") and must be "provided for connection of a
> particular item of equipment" [Reg. 411.3.3 in the draft 17th ed.]

I would assume the positioning of a socket at the back of a 600mm wide
gap under a worktop with connections for water and drainage etc, would
be a fairly good example of "provided for connection of a particular
item of equipment" - even without a label for the hard of thinking ;-)

(You can see it now: "How the heck do they expect I am going be able to
plug the kettle in with that poxy washing machine in the way?")

Andy Wade

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Jul 29, 2007, 9:59:52 AM7/29/07
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John Rumm wrote:

> I would assume the positioning of a socket at the back of a 600mm wide
> gap under a worktop with connections for water and drainage etc, would
> be a fairly good example of "provided for connection of a particular
> item of equipment" - even without a label for the hard of thinking ;-)

You could argue that the positioning alone constitutes suitable
identification, but then there's a counter argument that if no WM or DW
is fitted in said gap the socket becomes available for general use, so
perhaps a specific label is best, at least from an
electrician's-arse-covering POV, if there's no RCD. Doubtless suitable
ready-made labels will become available.

--
Andy

John Rumm

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Jul 29, 2007, 6:23:02 PM7/29/07
to

More than likely. I must admit that I do tend to print my own labels and
stick them on anything non obvious like this[1]. I also like to label
the above counter switches so that you know which appliance they isolate.


[1] I find a Brother laminated label maker very good for this, you can
get a wide range of colours and styles of tape, and the labels are very
resilient once stuck.

meow...@care2.com

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Jul 29, 2007, 6:39:06 PM7/29/07
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On 29 Jul, 13:14, Andy Wade

> I'd be inclined to put everything on a single 30 mA
> RCD-protected ring circuit.

that would be a recipe for problems, and probably increase risk more
than reduce it (food spoilage).

You can do it of course, but its not an option I'd choose.


NT

Andrew Gabriel

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Jul 29, 2007, 8:57:57 PM7/29/07
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In article <46ad1328$0$1614$ed26...@ptn-nntp-reader02.plus.net>,

John Rumm <see.my.s...@nowhere.null> writes:
> More than likely. I must admit that I do tend to print my own labels and
> stick them on anything non obvious like this[1]. I also like to label
> the above counter switches so that you know which appliance they isolate.
>
> [1] I find a Brother laminated label maker very good for this, you can
> get a wide range of colours and styles of tape, and the labels are very
> resilient once stuck.

I had about 20 MK logic double 13A sockets engraved some 10
years ago, and it only cost around £1 each (same wording
on each).

Andy Wade

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Jul 29, 2007, 9:06:42 PM7/29/07
to
John Rumm wrote:

> More than likely. I must admit that I do tend to print my own labels and
> stick them on anything non obvious like this[1].

<aol>Me too.</aol>

> I also like to label the above counter switches so that you know
> which appliance they isolate.

<aol>Me too.</aol> It's essential, I would say, to provide the clear
identification required by 514-01-01.

> I find a Brother laminated label maker very good for this, you can
> get a wide range of colours and styles of tape, and the labels are very
> resilient once stuck.

<aol>Me too.</aol> The black-on-clear tape works well on white wiring
accessories.

--
Andy

Andrew Gabriel

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Jul 30, 2007, 3:19:38 AM7/30/07
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In article <46ac850b$0$31716$db0f...@news.zen.co.uk>,

Andy Wade <spamb...@maxwell.myzen.co.uk> writes:
>
> To comply with the draft 17th ed. requirements any sockets which are
> _not_ 30 mA RCD-protected should be specifically labelled ("or otherwise
> suitably identified") and must be "provided for connection of a
> particular item of equipment" [Reg. 411.3.3 in the draft 17th ed.]

Nice to see the regs catching up with my standard practice for
the last ~10 years :-)

unop...@mail.com

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Jul 30, 2007, 3:36:23 AM7/30/07
to

There is another option, which is to use a latching (or passive) RCD.
It breaks the circuit on detecting a fault current, but on power fail
(rather than detected fault), will automatically re-make the circuit
when power is reapplied.

If you use two kitchen circuits, then the above-counter sockets can be
on a non-latching (active) RCD, and the below- counter circuits for
major appliances (including freezers) on latching (passive) RCDs.

Regards,

Sid

Andy Wade

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Jul 30, 2007, 5:41:54 AM7/30/07
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meow...@care2.com wrote:
> On 29 Jul, 13:14, Andy Wade
>>> I'd be inclined to put everything on a single 30 mA
>> RCD-protected ring circuit.
>
> that would be a recipe for problems, and probably increase risk more
> than reduce it (food spoilage).

This is just your normal paranoia about nuisance tripping which in
practice is simply not a problem if the fixed installation and
appliances are in good order. There are certainly good arguments though
for using multiple RCDs or individual RCBOs to give improved fault
discrimination, and it's to be hoped that the 17th edition will lead to
the wider use of RCBO (combined MCB and RCCB) devices.

--
Andy

Andy Wade

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Jul 30, 2007, 5:52:28 AM7/30/07
to
unop...@mail.com wrote:

> There is another option, which is to use a latching (or passive) RCD.
> It breaks the circuit on detecting a fault current, but on power fail
> (rather than detected fault), will automatically re-make the circuit
> when power is reapplied.

What are you on about? All DIN-rail RCDs for fixed installation use in
consumer units and dis-boards are of that type (TTBOMK). By "active
RCD" I presume you mean the type with a built-in no-volt release, as
found in plug-in RCD adaptors and some 'RCD spur' units. Obviously that
type would not be suitable except in special cases like workshops and
lab benches where manual reset after a power failure would be preferable.

--
Andy

unop...@mail.com

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Jul 30, 2007, 6:21:37 AM7/30/07
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On 30 Jul, 10:52, Andy Wade <spambuc...@maxwell.myzen.co.uk> wrote:

Thanks Andy. A good illustration of "if you want to get the right
answer on Usenet, post the wrong one and wait for corrections".

The above was not intentional.

I wasn't aware that "all DIN-rail RCDs for fixed installation use in
consumer units and dis-boards are of that type" i.e. passive, or
latching - so I've learned something. Plug in RCD adapters come in
both varieties (which I found out by fortuitous accident), and this is
often not made clear.

It strikes me that there is very little downside to RCD protecting
large appliances (even if double insulated) if DIN rail RCDs are
latching. But perhaps I'm equally wrong in that statement.

Regards,

Sid


Lurch

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Jul 30, 2007, 7:02:46 AM7/30/07
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On Mon, 30 Jul 2007 03:21:37 -0700, unop...@mail.com mused:

Depends on what large appliances you are referring to. A washing
machine left unattended for a couple of days after an RCD has tripped
without being noticed isn't a major hassle but a fridge\freezer would
be a bit of a pain.
--
Regards,
Stuart.

John Rumm

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Jul 30, 2007, 8:01:56 AM7/30/07
to
Andy Wade wrote:

>> I find a Brother laminated label maker very good for this, you can get
>> a wide range of colours and styles of tape, and the labels are very
>> resilient once stuck.
>
> <aol>Me too.</aol> The black-on-clear tape works well on white wiring
> accessories.

And the wide black on yellow tape works well for warning labels.

John Rumm

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Jul 30, 2007, 8:03:55 AM7/30/07
to
meow...@care2.com wrote:
> On 29 Jul, 13:14, Andy Wade
>
>> I'd be inclined to put everything on a single 30 mA
>> RCD-protected ring circuit.
>
> that would be a recipe for problems, and probably increase risk more
> than reduce it (food spoilage).

I would have thought 20mA leakage budget for just one circuit was plenty
- even if it does have a few heater elements in there.

unop...@mail.com

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Jul 30, 2007, 9:02:45 AM7/30/07
to
On 30 Jul, 12:02, Lurch <myrealn...@sjwelectrical.co.uk> wrote:
> On Mon, 30 Jul 2007 03:21:37 -0700, unope...@mail.com mused:

>
> >It strikes me that there is very little downside to RCD protecting
> >large appliances (even if double insulated) if DIN rail RCDs are
> >latching. But perhaps I'm equally wrong in that statement.
>
> Depends on what large appliances you are referring to. A washing
> machine left unattended for a couple of days after an RCD has tripped
> without being noticed isn't a major hassle but a fridge\freezer would
> be a bit of a pain.

Well, I suppose the question is: why did the RCD trip? We seem to
have ascertained that DIN rail RCDs do not stay tripped on power loss
only - they will re-energise the circuit after a power failure so long
as no fault is detected, so the RCD having tripped and stayed tripped
indicates a fault of some sort. Are you happy for your fridge freezer
to be on a faulty circuit?

Of course, if the fridge/freezer shares the circuit with other
appliances which may potentially generate leakage currents in excess
of the RCD trip margin, then I see the problem, so there is a good
argument for putting a fridge/freezer on its own spur from the
consumer unit.

I have received a mains shock off an appliance (in this case, a
washing machine) where the flex had worn entering the appliance,
rendering the casing live. It was not on an RCD protected circuit. I
don't know if that particular w/m was double insulated.

I don't know how much of a problem nuisance trips are in reality. It
would certainly be irritating to lose a freezer full of food as a
result of a nuisance trip just after you left for a fortnight's
holiday. Perhaps (taking things to extremes), one should have two
sockets - an RCD protected one for when you are in, and a non-RCD
protected one for when you are away for long periods. That said, the
British populace seem to have survived the decades without RCD
protection for their freezers quite well, so one might argue the
absolute level of risk is small enough to ignore. Your choice,
really. It is a perennial topic with no satisfactory resolution.

Regards,

Sid


John Rumm

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Jul 30, 2007, 10:34:31 AM7/30/07
to
unop...@mail.com wrote:

> It strikes me that there is very little downside to RCD protecting
> large appliances (even if double insulated) if DIN rail RCDs are
> latching. But perhaps I'm equally wrong in that statement.

Not wrong as such, but there are a couple of points to bear in mind.
Firstly there are some items of fixed equipment that you don't really
want to be disconnected unless there is a real fault. Freezers, boilers,
fish tank heaters, smoke alarms, life support systems etc.

Secondly some equipment like washing machines etc can have naturally
high leakage currents. If they are sharing a RCD with too many other
items you increase the nuisance trip likelihood since the extra leakage
can lead to sensitisation of the RCD.

Your post does raise an interesting point about the NVR function of some
plug in RCDs though. I will add that to the wiki on the subject:

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

Lurch

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Jul 30, 2007, 11:15:36 AM7/30/07
to
On Mon, 30 Jul 2007 13:01:56 +0100, John Rumm
<see.my.s...@nowhere.null> mused:

>Andy Wade wrote:
>
>>> I find a Brother laminated label maker very good for this, you can get
>>> a wide range of colours and styles of tape, and the labels are very
>>> resilient once stuck.
>>
>> <aol>Me too.</aol> The black-on-clear tape works well on white wiring
>> accessories.
>
>And the wide black on yellow tape works well for warning labels.

And if you're like me, you buy a new machine with 9, 12 and 24mm tape
in all different colours, use the appropriate colours as above then
when they start running out don't actually remember to replace them
and then just stick any colour anywhere. 24mm black on yellow looks
good for labelling spurs in kitchens. ;)
--
Regards,
Stuart.

Lurch

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Jul 30, 2007, 11:19:48 AM7/30/07
to
\On Mon, 30 Jul 2007 06:02:45 -0700, unop...@mail.com mused:

>On 30 Jul, 12:02, Lurch <myrealn...@sjwelectrical.co.uk> wrote:
>> On Mon, 30 Jul 2007 03:21:37 -0700, unope...@mail.com mused:
>>
>> >It strikes me that there is very little downside to RCD protecting
>> >large appliances (even if double insulated) if DIN rail RCDs are
>> >latching. But perhaps I'm equally wrong in that statement.
>>
>> Depends on what large appliances you are referring to. A washing
>> machine left unattended for a couple of days after an RCD has tripped
>> without being noticed isn't a major hassle but a fridge\freezer would
>> be a bit of a pain.
>
>Well, I suppose the question is: why did the RCD trip? We seem to
>have ascertained that DIN rail RCDs do not stay tripped on power loss
>only - they will re-energise the circuit after a power failure so long
>as no fault is detected, so the RCD having tripped and stayed tripped
>indicates a fault of some sort. Are you happy for your fridge freezer
>to be on a faulty circuit?
>

I never said I did, I meant if you for instance go away for a weekend
and the power trips out an hour after you leave. Obviously the circuit
would be repaired upon your return but I'd rather have a happily
working fridge\freezer on a slightly faulty circuit than a non working
fridge\freezer on a faulty circuit thawing the contents and pissing
itself all over the floor for 2 days.

>Of course, if the fridge/freezer shares the circuit with other
>appliances which may potentially generate leakage currents in excess
>of the RCD trip margin, then I see the problem, so there is a good
>argument for putting a fridge/freezer on its own spur from the
>consumer unit.
>

Yes.

>I have received a mains shock off an appliance (in this case, a
>washing machine) where the flex had worn entering the appliance,
>rendering the casing live. It was not on an RCD protected circuit. I
>don't know if that particular w/m was double insulated.
>

I don't think I've ever seen a class II washing machine.

>I don't know how much of a problem nuisance trips are in reality. It
>would certainly be irritating to lose a freezer full of food as a
>result of a nuisance trip just after you left for a fortnight's
>holiday. Perhaps (taking things to extremes), one should have two
>sockets - an RCD protected one for when you are in, and a non-RCD
>protected one for when you are away for long periods. That said, the
>British populace seem to have survived the decades without RCD
>protection for their freezers quite well, so one might argue the
>absolute level of risk is small enough to ignore. Your choice,
>really. It is a perennial topic with no satisfactory resolution.
>

Getting a bit over complicated now, bear in mind 99% of the UK
population do everything on price and don't care how well it doesn't
work or how many flaws a plan has, as long as it's cheap.
--
Regards,
Stuart.

David W.E. Roberts

unread,
Aug 4, 2007, 9:25:03 AM8/4/07
to
Thanks for all the useful advice so far - I have been ill (man flu) for a
week but have now resumed operations.

"David W.E. Roberts" <nos...@talk21.com> wrote in message
news:5h0nm7F...@mid.individual.net...

meow...@care2.com

unread,
Aug 4, 2007, 11:48:37 AM8/4/07
to

People dying by electrocution from ff casings: 0.
People getting ill and dying from dodgy food: many.

Odds of an electrically leaky ff killing you: from the above figures,
close to zero. There are other safety layers designed to take care of
such faults, maybe this is why.

Therefore as a safety measure fitting RCD ''protection'' to a ff feed
is counterproductive. Satisfactory resolution achieved.


NT

meow...@care2.com

unread,
Aug 4, 2007, 12:02:48 PM8/4/07
to
On 30 Jul, 10:41, Andy Wade <spambuc...@maxwell.myzen.co.uk> wrote:

> meow2...@care2.com wrote:
> > On 29 Jul, 13:14, Andy Wade

> >>> I'd be inclined to put everything on a single 30 mA
> >> RCD-protected ring circuit.

> > that would be a recipe for problems, and probably increase risk more
> > than reduce it (food spoilage).

> This is just your normal paranoia about nuisance tripping

no, on several counts.


> which in
> practice is simply not a problem

I wish


> if the fixed installation and
> appliances are in good order.

only if you define good order as not tripping an rcd, or having near
zero leakage, which I dont. I define it as safe, ie not killing
people. Millions of RCD tripping loads have been used perfectly safely
in both domestic and commercial premises, and a huge number are in use
today.

This is just another illustration of the difference between what one
might imagine and what electrocution figures tell about the real
facts. For some reason what people commonly imagine about electrical
safety tends to be unrealistic fairly often.


> There are certainly good arguments though
> for using multiple RCDs or individual RCBOs to give improved fault
> discrimination, and it's to be hoped that the 17th edition will lead to
> the wider use of RCBO (combined MCB and RCCB) devices.

Whats it going to cost to put these in every property in the land?
(added cost at rewire time only)
How many deaths per year will it prevent?
What does that cost the nation per life saved?
If youve answered those qs it should be fairly evident that other
measures using that money could save 100x as many lives.


NT

unop...@mail.com

unread,
Aug 4, 2007, 12:06:57 PM8/4/07
to
On 4 Aug, 16:48, meow2...@care2.com wrote:
> On 30 Jul, 14:02, unope...@mail.com wrote:
>
>
>
> > On 30 Jul, 12:02, Lurch <myrealn...@sjwelectrical.co.uk> wrote:
>
> > > On Mon, 30 Jul 2007 03:21:37 -0700, unope...@mail.com mused:
> > > >It strikes me that there is very little downside to RCD protecting
> > > >large appliances (even if double insulated) if DIN rail RCDs are
> > > >latching. But perhaps I'm equally wrong in that statement.

<snip>

> > That said, the
> > British populace seem to have survived the decades without RCD
> > protection for their freezers quite well, so one might argue the
> > absolute level of risk is small enough to ignore. Your choice,
> > really. It is a perennial topic with no satisfactory resolution.
>
>

> People dying by electrocution from ff casings: 0.
> People getting ill and dying from dodgy food: many.
>
> Odds of an electrically leaky ff killing you: from the above figures,
> close to zero. There are other safety layers designed to take care of
> such faults, maybe this is why.
>
> Therefore as a safety measure fitting RCD ''protection'' to a ff feed
> is counterproductive. Satisfactory resolution achieved.

Purely to satisfy my curiosity, could you say briefly what the other
safety layers are? I imagine they are quite effective. As a side note,
on my trips to visit friends and relatives abroad, I've noticed a lot
of equipment is not earthed/grounded and protected (apparently) only
by cartridge fuses. However, they do use washing machines (and dryers)
in (wet floor) bathrooms - and on inspection these use sockets that
are earthed/grounded and in addition come with warning labels to say
that only double insulated equipment should be used in them. (Belt &
braces?) On that basis, I think w/ms available in Europe are probably
double insulated.

Cheers,

Sid


Owain

unread,
Aug 4, 2007, 12:47:30 PM8/4/07
to
meow...@care2.com wrote:
>>There are certainly good arguments though
>>for using multiple RCDs or individual RCBOs to give improved fault
>>discrimination,
> Whats it going to cost to put these in every property in the land?
> (added cost at rewire time only)
> How many deaths per year will it prevent?
> What does that cost the nation per life saved?
> If youve answered those qs it should be fairly evident that other
> measures using that money could save 100x as many lives.

Yebbut nobbut Part P...

Owain

John Rumm

unread,
Aug 5, 2007, 8:12:14 AM8/5/07
to
meow...@care2.com wrote:

>>>>> I'd be inclined to put everything on a single 30 mA
>>>> RCD-protected ring circuit.
>
>>> that would be a recipe for problems, and probably increase risk more
>>> than reduce it (food spoilage).
>
>> This is just your normal paranoia about nuisance tripping
>
> no, on several counts.

My own experience with RCD protected systems is that with working
appliances and a well designed system, nuisance tripping is a non issue.

>> which in
>> practice is simply not a problem
>
> I wish
>
>
>> if the fixed installation and
>> appliances are in good order.
>
> only if you define good order as not tripping an rcd, or having near
> zero leakage, which I dont.

Zero leakage is not a requirement. Reasonable estimates of likely
leakage can be made, and adequate leakage budget allocated on the circuit.

> I define it as safe, ie not killing
> people. Millions of RCD tripping loads have been used perfectly safely
> in both domestic and commercial premises, and a huge number are in use
> today.
>
> This is just another illustration of the difference between what one
> might imagine and what electrocution figures tell about the real
> facts. For some reason what people commonly imagine about electrical
> safety tends to be unrealistic fairly often.

The electrocution figures tell us that injury of death resulting from
fixed wiring installations is a tiny proportion of total injuries and
fatalities. The vast bulk happening with portable appliances. This is
one area where changes to the fixed wiring (more widespread use of well
designed RCD protected circuits) could have a big positive impact on safety.

I understand that of all the accident and injury risks we face in our
homes, that of electrocution is one of the less likely ones. That does
not seem to be justification to abandon any efforts at improving the
electrical design and safety, just because you are more likely fall over
your part P extension lead, or lacerate yourself on your nanny approved
round ended kitchen knife.

>> There are certainly good arguments though
>> for using multiple RCDs or individual RCBOs to give improved fault
>> discrimination, and it's to be hoped that the 17th edition will lead to
>> the wider use of RCBO (combined MCB and RCCB) devices.
>
> Whats it going to cost to put these in every property in the land?
> (added cost at rewire time only)

As a proportion of the total cost of a rewire? Cube root of sod all.

> How many deaths per year will it prevent?

For each property equipped in this way, that is another one where it
would become very difficult to electrocute yourself with a faulty or
misused appliance.

> What does that cost the nation per life saved?
> If youve answered those qs it should be fairly evident that other
> measures using that money could save 100x as many lives.

I don't follow your argument really. If you are rewiring anyway you
*will* be including RCD protection in the required places since that is
a current regulatory requirement. All Andy is suggesting is that you opt
for better design practice and implement this in such a way as you
reduce the likelihood of, and impact from, any nuisance trip that does
occur.

The total cost difference between a basic compliant design, and a better
one with improved discrimination, is unlikely to be less than Ł100
extra. Looked at as a proportion of the cost for a full rewire at say
Ł2,500 - Ł4000 that is pretty insignificant.

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