Is it permissible to have 13A sockets on 2 different ring, (or a ring
and a radial) circuits serving the same area of the house? What
prompts this post is that IIRC it is standard advice that all
downstairs 13A sockets should be on an RCD circuit.

What I should like is to put sockets for electronics (computers, TVs,
clock radios etc) on separate circuit(s) to those used for kit which
is likely to trip RCDs. There would be 1 or 2 double 13A sockets on
this ring or radial in most rooms. I get a fair amount of tripping
from portable outdoor kit like hedgecutters - portable workshop tools
(sanders, planers etc) are another bane. So the 'electronic' sockets
would be run through a normal switch & cartridge fuse or MCB &
definitely nowhere near an RCD. The sockets would be suitably marked
& possibly be coloured (I've seen coloured 13A sockets - presumably
they are easily obtainable?). So is it possible to install this
scheme within the regs?

TIA

the yorkshire dalesman wrote:
Is it permissible to have 13A sockets on 2 different ring, (or a ring
and a radial) circuits serving the same area of the house? What
prompts this post is that IIRC it is standard advice that all
downstairs 13A sockets should be on an RCD circuit.

Yes, I don't think the wiring regulations say anything at all about
whether sockets in a room (or area) have to be supplied by a single
MCB.

There might be issues with different phases but that rarely applies in
a domestic supply.

--
Chris Green )

"the yorkshire dalesman" wrote
| Is it permissible to have 13A sockets on 2 different ring,
| (or a ring and a radial) circuits serving the same area
| of the house?

I think it is a rather sensible idea actually; it means that if one ring is
down you have somewhere close by to plug in the inspection lamp / hot air
gun / radio / teasmade / whatever.

The two caveats a

1. Phase separation - unlikely to arise in a domestic dwelling which are
normally not supplied 3-phase.

2. Clear labelling of circuits at the CU ot prevent confusion.

| What prompts this post is that IIRC it
| is standard advice that all downstairs 13A sockets should
| be on an RCD circuit.

That is because there is the possibility they may be used for outdoor
equipment. Sockets which 'may' be used to power outdoor stuff MUST be RCD
protected.

| What I should like is to put sockets for electronics (computers, TVs,
| clock radios etc) on separate circuit(s) to those used for kit which
| is likely to trip RCDs. There would be 1 or 2 double 13A sockets on
| this ring or radial in most rooms. I get a fair amount of tripping
| from portable outdoor kit like hedgecutters - portable workshop tools
| (sanders, planers etc) are another bane. So the 'electronic' sockets
| would be run through a normal switch & cartridge fuse or MCB &
| definitely nowhere near an RCD.

Whether or not you require RCD on sockets will depend on your installation
and its earth arrangements. If you require RCD protection to comply with the
disconnection time of 0.4s on a socket, you cannot omit that simply because
you want to plug your clock radio in.

The best thing to do would be to install dedicated circuits for your outdoor
and workshop sockets which do not run through the same RCD as your house
sockets but have their own RCD protection.

If you have a split load CU, you could take a supply using a spare circuit
on the non-RCD side to individual RCD-protected sockets or a new RCD for
that circuit only.

If you have a whole-house RCD, this should really be replaced as it is
unsafe (a fault in your workshop could leave you without lights and with a
power tool spinning down).

Owain

What I should like is to put sockets for electronics (computers,
TVs, clock radios etc) on separate circuit(s) to those used for
kit which is likely to trip RCDs.

You can. However, if your current installation is prone to tripping, then
something is wrong. You may find you have an appliance with a latent earth
fault, or a neutral/earth short somewhere. This should be fixed, rather than
bodged around, trying to find excuses not to have RCDs on sockets. Quite
frankly, all your socket circuits should have RCD protection, whether
required by regs or not. This is PARTICULARLY the case for anything that is
likely to see power tools. The only exceptions are special circuits for
systems that you don't want to fail when you are out, such as a dedicated
fridge/freezer circuit, or your central heating. You should install a
separate dedicated outside socket on its own 16A RCBO (or 16A MCB with RCD
built into socket). Your leaky hedge trimmers then get the benefit of RCD
protection without causing your computer to shut down when you cut the
cable, or get it wet. If you have a workshop in the attached garage, this
should have its own RCD protection from the rest of the house.

If you simply have too much equipment connected, then rather than installing
lots of cable into complex arrangements, which is expensive in terms of
time, I'd upgrade the consumer unit to something more tolerant. The best
solution here is to use a simple isolated consumer unit (not RCD or split
load) and use B32/0.03A RCBOs for socket circuits. This way, leakage on one
circuit won't make another circuit oversensitive to any increase in leakage
current.

Christian.



"the yorkshire dalesman" wrote in message
om...
Is it permissible to have 13A sockets on 2 different ring, (or a ring
and a radial) circuits serving the same area of the house? What
prompts this post is that IIRC it is standard advice that all
downstairs 13A sockets should be on an RCD circuit.

What I should like is to put sockets for electronics (computers, TVs,
clock radios etc) on separate circuit(s) to those used for kit which
is likely to trip RCDs. There would be 1 or 2 double 13A sockets on
this ring or radial in most rooms. I get a fair amount of tripping
from portable outdoor kit like hedgecutters - portable workshop tools
(sanders, planers etc) are another bane. So the 'electronic' sockets
would be run through a normal switch & cartridge fuse or MCB &
definitely nowhere near an RCD. The sockets would be suitably marked
& possibly be coloured (I've seen coloured 13A sockets - presumably
they are easily obtainable?). So is it possible to install this
scheme within the regs?

TIA

"Owain" wrote in message news:1070983973.25912.2@lotis...
"the yorkshire dalesman" wrote
| Is it permissible to have 13A sockets on 2 different ring,
| (or a ring and a radial) circuits serving the same area
| of the house?

I think it is a rather sensible idea actually;

many thanks for advice, Owain (& Christian) - part 1 of Q answered
100% - yes areas served by different ring may overlap, assuming single
phase supply.

as for part 2: your responses open a can of worms I fear:

first, in passing:
That is because there is the possibility they may be used for outdoor
equipment. Sockets which 'may' be used to power outdoor stuff MUST be RCD
protected.

that's what I understood, but if they are labelled 'indoor use by
computer/hifi/Tv only' & the sockets are a different colour (eg
yellow/blue/red) is that enough to make them 'not likely to be used
outside?




now you're ahead of me Orwain:

The best thing to do would be to install dedicated circuits for your outdoor
and workshop sockets which do not run through the same RCD as your house
sockets but have their own RCD protection.

If you have a split load CU, you could take a supply using a spare circuit
on the non-RCD side to individual RCD-protected sockets or a new RCD for
that circuit only.

The current set up is the front of house (including kitchen & HW) is
on a CU RCD: the rear (2 rooms & a workshop is on a fused CU (some
rewireable, some cartridge). Both connect into a single master
switch. (Don't ask why - reasons lost in the mists of time). Plan is
put it all on a sound footing asap, hence this post.

I've lost (open) files several times by running the computer off the
RCD circuit (eg Excel can corrupt files it has open if the switch is
thrown). Since moving it onto the fused ring there's never been any
trouble.

Both circuits test completely Ok for insulation & earth - neutral
short. Nuisance tripping comes mainly when certain tools (all double
insulated - so no earth) are run off the rear fused ring - only the
tools keep going but the front CU is the one that trips. Observation
suggests overload is the cause - an extra thick hedge twig or heavy
pressure on the hand sander.

So what's happening? & will Christian's solution of an RCBO for each
cct cure it?




If you have a whole-house RCD, this should really be replaced as it is
unsafe (a fault in your workshop could leave you without lights and with a
power tool spinning down).

Yes, It's not just the computer & the nuisance value of resetting
clocks. Having an RCD in the workshop perturbs me - a nuisance trip
could leave me in the dark with a powerful rotary saw still spinning.
So why is an RCD needed/recommended/required in a workshop? As for
distance from the supply source, most of the house is far further away
than the remotest cranny in my workshop.

"northern_relayer" wrote
Are you the OP formerly known as "the yorkshire dalesman"?
| That is because there is the possibility they may be used for
| outdoor equipment. Sockets which 'may' be used to power outdoor
| stuff MUST be RCD protected.
| that's what I understood, but if they are labelled 'indoor use by
| computer/hifi/Tv only' & the sockets are a different colour (eg
| yellow/blue/red) is that enough to make them 'not likely to be used
| outside?

I don't think it is. The colour of the socket is meaningless in terms of the
regulations and a 13A socket should be suitable for supplying any equipment
usually fitted with a 13A plug. This is why 13A sockets should not be fitted
to 6A lighting circuits for table lamps and the like.

The spirit of the regs is clearly to ensure that equipment used outdoors is
very likely to be plugged in to an RCD-protected outlet. If a dedicated
RCD-protected outlet marked 'for external equipment' is provided in
convenient places as required, that is likely to be used in preference to
any other and thus the reg will be satisfied, AIUI.

| I've lost (open) files several times by running the computer off the
| RCD circuit (eg Excel can corrupt files it has open if the switch is
| thrown). Since moving it onto the fused ring there's never been any
| trouble.

You might want to consider a small UPS for the PC, especially if you're in a
rural area where overhead line failures are foreseeably more common.

| Both circuits test completely Ok for insulation & earth - neutral
| short. Nuisance tripping comes mainly when certain tools (all double
| insulated - so no earth) are run off the rear fused ring - only the
| tools keep going but the front CU is the one that trips. Observation
| suggests overload is the cause - an extra thick hedge twig or heavy
| pressure on the hand sander.

Overload shouldn't trip an RCD because RCDs don't trip on overcurrent, only
on a current imbalance caused by earth leakage. Anyway, you obviously have
problems with your wiring and with rewireable fuses are well overdue for a
rewire.

| So what's happening? & will Christian's solution of an RCBO for each
| cct cure it?

RCBOs on each socket circuit ideal but a bit expensive. Split-load CU is
usually an acceptable compromise, especially if workshops and the like are
run from the non-RCD side and given their own local RCD protection.

You need an RCD on the workshop sockets for the same reasons as anywhere
else, only increased: handheld power tools, risk of abraded or cut flex, wet
hands, etc. Just don't have the lights on it.

Owain

In message ,
"Owain" wrote:

"northern_relayer" wrote
Are you the OP formerly known as "the yorkshire dalesman"?
| That is because there is the possibility they may be used for
| outdoor equipment. Sockets which 'may' be used to power outdoor
| stuff MUST be RCD protected.
| that's what I understood, but if they are labelled 'indoor use by
| computer/hifi/Tv only' & the sockets are a different colour (eg
| yellow/blue/red) is that enough to make them 'not likely to be used
| outside?

I don't think it is. The colour of the socket is meaningless in terms of the
regulations and a 13A socket should be suitable for supplying any equipment
usually fitted with a 13A plug. This is why 13A sockets should not be fitted
to 6A lighting circuits for table lamps and the like.

The spirit of the regs is clearly to ensure that equipment used outdoors is
very likely to be plugged in to an RCD-protected outlet. If a dedicated
RCD-protected outlet marked 'for external equipment' is provided in
convenient places as required, that is likely to be used in preference to
any other and thus the reg will be satisfied, AIUI.


How about installing special sockets for the IT equipment so that you
have to fit different mains plugs? It doesn't matter then if they're
not RCD protected - it's a faff to set up, but you're not going to be
able to plug your drill in. This is commonly done in offices with
sockets which have differently shaped earth pins for example. I've used
some really good (though expensive) "Electrak" sockets in the past for a
similar application (making sure plebs didn't plug a kettle into a
circuit supplied by generator).

The only thing to watch is that any plug for connection into a standard
domestic circuit *must* be fused, so no using any of those nice European
"Shuko" types :-)

Can't find the Electrak in CPC - I'm sure they used to do them! RS do do
them, or did last time I had access to a catalogue, but I find their
website a pain in the backside so I'm not going to look for them now :-)

Just an idea...

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Don't fight technology, live with it: http://www.livtech.co.uk/
.... (A)bort (F)ail (C)reate a holographic image in plasma memory?

"Martin Angove" wrote
| How about installing special sockets for the IT equipment so that
| you have to fit different mains plugs? It doesn't matter then if
| they're not RCD protected - it's a faff to set up, but you're not
| going to be able to plug your drill in. This is commonly done in
| offices with sockets which have differently shaped earth pins for
| example. I've used some really good (though expensive) "Electrak"
| sockets in the past for a similar application (making sure plebs
| didn't plug a kettle into a circuit supplied by generator).

That's one application for non-standard sockets, another related one is for
IT equipment with high earth leakage.

I really don't know whether that would actually be acceptable for a house;
you could still have the situation of a lead plugged in and live, and the
little holes on the free end of an IEC lead are so inviting to 3-year-olds
and paperclips :-)

The OP's argument is not with RCDs per se but with nuisance tripping. That
should be avoidable with proper discrimination between protected circuits.

| The only thing to watch is that any plug for connection into a standard
| domestic circuit *must* be fused, so no using any of those nice European
| "Shuko" types :-)

But it wouldn't be a "standard domestic circuit" (and anyway 5A plugs on
lighting circuits aren't fused) - all that is required is to ensure the
circuit is fused at an appropriate level for the flexes. An alternative
would be to use fused sockets.

| Can't find the Electrak in CPC - I'm sure they used to do them! RS do do
| them, or did last time I had access to a catalogue, but I find their
| website a pain in the backside so I'm not going to look for them now :-)

www.olson.co.uk do power strips with individual socket fuses if wanted and a
variety of non-standard plugs (Elektrak, MK, Wandsworth, etc).

Owain

"northern_relayer" wrote in message
snip

as for part 2: your responses open a can of worms I fear:

first, in passing:
That is because there is the possibility they may be used for outdoor
equipment. Sockets which 'may' be used to power outdoor stuff MUST be
RCD
protected.

that's what I understood, but if they are labelled 'indoor use by
computer/hifi/Tv only' & the sockets are a different colour (eg
yellow/blue/red) is that enough to make them 'not likely to be used
outside?


snip

I think that the easiest way to satisfy this requirement is to install some
weatherproof IPx6 sockets outside in areas that you would be normally using
the outdoor equipment - ie strategic places around the house.

Make sure this circuit is adequately RCD protected, and isolate the sockets
from switches inside if necessay (if you're worried about people nicking
your leccy!).

If there are sockets in sufficient positions for all round house access then
this would make it most unlikely that an internal socket was used for
external appliances, therefore to my reading of the regs you would not have
to protect the internal sockets.

I'm sure others will comment upon whehter this would be sufficient.

It's also very convenient, and means that you can do dusty/messy jobs
outside will all the doors/windows securely closed so you don't get
dust/grass clippings/etc migrating into the house...



--
Richard Sampson

email me at
richard at olifant d-ot co do-t uk

If there are sockets in sufficient positions for all round house
access then this would make it most unlikely that an internal
socket was used for external appliances, therefore to my reading
of the regs you would not have to protect the internal sockets.

On the other hand, I wouldn't dream of not protecting the inside sockets. I
think the regs should be changed to mandate the protection of inside
sockets, except in special circumstances (i.e. non domestic situations).
However, I agree that waterproof outside sockets should be provided with
independent RCD protection, as well.

Christian.

"Christian McArdle" wrote in message .net...
What I should like is to put sockets for electronics (computers,
TVs, clock radios etc) on separate circuit(s) to those used for
kit which is likely to trip RCDs.

You can. However, if your current installation is prone to tripping, then
something is wrong. You may find you have an appliance with a latent earth
fault, or a neutral/earth short somewhere.

many thanks for all replies - I see there is a parallel posting
running

OT - Fitting RCD in household mains supply

which goes into these issues in some depth.


Whilst I appreciate the benefits of appropriate fitting of RCDs, I'm
unconvinced that they are always appropriate. Safety is something
that has to be managed & you have to weigh up the pros and cons of the
different options.


Agreed, my elec installation is overdue for update - but that's how
this post started & renewal work is in slow progress. Nevertheless
what happens poses some curious Qs. eg:

1. The front of house RCD (30mA) CU CAN trip when a light bulb
blows or it can be the MCB in the lighting cct: both happen, though
perhaps the MCB trip is the more common.

2. The Hedgecutter fed off the rear fused cct (with or without an
in-line RCD socket) usually makes the front RCD trip - while the
in-line RCD stays on. ditto for the B&D sander & other m/c tools (but
less often). All these are double insulated with 2 wire cables - so
where is the earth leakage?

Some time ago I queried all this with an elec engineer who made the
helpful(?) observation that 'loops sometimes do funny things'

I'm far from convinced that there's a fault of the simple
shorting/leakage type. Seems to me more likely that the tripping is
due to

a) the L-N imbalance detected by the RCD must be something to do with
variations in power factor & not earth leakage - ie capacitances &,
perhaps, inductances in the motors & suppressors:

(b) the peculiar design of elec hand motor tools - which are not
straight forward inductance or synchronous motors - more some *******
style of ac commutator motor (I've only a very rough idea on these
things). Still leaves the mystery of why fusing light bulbs trip the
RCD (but answer may be in the parallel post).

Lastly I'm still slightly paranoid about maintaining supply the the
electronics around the house especially this computer which is on most
of te time, even if I'm out. The fitting a UPS would be 1 answer but
that is expensive & would still leave sockets (on the UPS) which are
effectively unprotected.

2. The Hedgecutter fed off the rear fused cct (with or without an
in-line RCD socket) usually makes the front RCD trip

There could be a neutral to neutral leak between the front and rear consumer
unit based circuits. This way, some of the neutral current could go through
the wrong RCD. The front RCD is then more sensitive and always blows first.
Just a thought.

Christian.