Hi Guys

I'm hoping someone will be able to help with the following (what to me is)
grey area.
Unfortunately I don't have the On Site Guide to hand, but I was looking at
this last night and the subject of a direct wired outside light was under
discussion.

Can't remember page references, think the clause was 3.5.2.
An illustration at the back of the guide shows an outside light, actually
illustrated as outside a remote shed rather than a house, and then refers
back to a clause (maybe 3.5.2).

This clause covers portable equipment etc, but the last entry is an outside
light and the general heading of the clause concerns items which need RCD
protection with a disconnect time of 0.4 ms. The clause also mentions light
fittings where conductive parts are accessible.

My questions a

If I am fitting an outside light where one has previously been fitted (i e a
ciruit already existed to supply this) do I need add RCD protection?
The outside light is part of a re-fit of a rear extension in which
additional circuits are not being added, but some damaged cabling is being
replaced and a return to the CU added for the power circuit (formerly run
radially!). The principle cable routing is not changing, so, in my opinion
the work does not fall under the remit of part P. However I will have
building inspectors around for other works, so comments welcome on the Part
P implications!
Does a light which is fixed direct to an outside wall, with a cable going
straight in from the back qualify for this protection, or is this really
aimed at remote lights, such as those used to illuminate pathways?
There is also a rider on this clause about the light being outside the
equipotential zone. Does this wall mounted fitting fall into this category
if the fitting is earthed back via the lighting to the CU?
If I fit a double insulated fitting will the requirement for RCD still hold?
(Not sure I would get away with a plastic fitting with SWMBO!)
If possible can respondents please include references to any answers given,
as I would like to have all amunition necessary in case this work is
questioned?

Thanks to anyone who's managed to get this far and more to anyone who can
shed light!


TIA

Phil

In message ,
"thescullster" wrote:

[outside light with ref. to sec 3.5.2 in the OSG]

This clause covers portable equipment etc, but the last entry is an outside
light and the general heading of the clause concerns items which need RCD
protection with a disconnect time of 0.4 ms. The clause also mentions light
fittings where conductive parts are accessible.

I can't see any explicit mention of light fittings, but the paragraph
does refer to any equipment with "exposed-conductive-parts" which will
include most metal-cased light fittings. It refers to regulation
471-08-03 in BS7671.

The requirement is *not* for 0.4mS disconnection, it is for 0.4S
disconnection (i.e. 400mS). The implication is that with correctly
specified circuits and protective devices it is possible to reach this
disconnection time without the use of an RCD. For example, with a fault
current of 30A or more flowing a 6A MCB will meet this requirement
(fig. 3.4 in BS7671). 30A is an earth fault loop impedance of about 7.5
Ohms or less which should be very easy to achieve if you have TN-S or
TN-C-S earthing. If you have an earth rod (TT system) then you will need
to use an RCD to meet this requirement.

If the light is connected via a fused spur to the sockets circuit with a
5A BS1361 fuse, a 22A current will do the trick (fig. 3.1 in BS7671).

If your circuits are protected by rewireable fuses to BS3036 then you
might have a bit more trouble meeting the disconnection times.

My questions a

If I am fitting an outside light where one has previously been fitted (i e a
ciruit already existed to supply this) do I need add RCD protection?

See above. If the earth-fault loop impedance is low enough then probably
not.

The outside light is part of a re-fit of a rear extension in which
additional circuits are not being added, but some damaged cabling is being
replaced and a return to the CU added for the power circuit (formerly run
radially!). The principle cable routing is not changing, so, in my opinion
the work does not fall under the remit of part P. However I will have
building inspectors around for other works, so comments welcome on the Part
P implications!

You can download Part P from the ODPM website. It has the list of exempt
works in it.

Does a light which is fixed direct to an outside wall, with a cable going
straight in from the back qualify for this protection, or is this really
aimed at remote lights, such as those used to illuminate pathways?

It seems to me to be aimed at all outside lights, but the 0.4S
disconnection time is a good thing to aim for for *all* electrical
equipment in the home, and most of it requires this timing.

[snip the rest, sorry]

I find it odd that you posted on the 30th and no-one has yet replied.
Hopefully this will have answered some questions, and if there are any
glaring errors I'm sure someone will pick them up.

If you are at all worried about Part P or similar then I'd suggest
mentioning it "in passing" to the Building Inspector when he visits to
look at other work, but before you've actually done anything to the
light. I'd suspect he'd be happy that you're replacing an
old/damaged/worn out fitting, but it rather depends how "jobsworth" he's
feeling that morning and whether his department has completed (or even
started) its Part P training yet.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Where do you find 100 talking invertebrates? The US Senate!

Martin

Thanks for response - yes I think others may have been put off by the essay!

I can't see any explicit mention of light fittings, but the paragraph
does refer to any equipment with "exposed-conductive-parts" which will
include most metal-cased light fittings. It refers to regulation
471-08-03 in BS7671.

No, in the paragraph, light fittings are not referred to, but I arrived at
these clauses as they are indicated as applicable to an outside light
(admittedly attached to a remote shed) in a diagram at the back of the On
Site Guide.

The requirement is *not* for 0.4mS disconnection, it is for 0.4S
disconnection (i.e. 400mS).

Sorry that was a typo!


The implication is that with correctly
specified circuits and protective devices it is possible to reach this
disconnection time without the use of an RCD.

From what you are saying I believe that an outside light fitting, even a
metal one, would be OK.
The feed to this light and internal lighting to the single room extension is
taken from a shared 6A type B MCB (this MCB also supplies the upstairs
lighting circuit for the main house).

if you have TN-S or TN-C-S earthing.

My house has TN-C-S earthing.

If you are at all worried about Part P or similar then I'd suggest
mentioning it "in passing" to the Building Inspector when he visits to
look at other work

As a matter of interest, the approvals recently received from building
control for the general structural alterations include in the conditions of
approval "means of compliance with Part P".
Examining the ODPM web site, I am confident, even though I am adding sockets
and reducing numbers of light fittings, that this phase of the work does not
fall into Part P - no additional circuits etc! Replacement of fittings is
specifically mentioned as NOT being elligible - see below link top right
hand note on affected areas

http://www.odpm.gov.uk/stellent/grou...reg_033485.pdf


I intend to declare this with my response to their conditions.

Phil

Martin Angove wrote:

If your circuits are protected by rewireable fuses to BS3036 then you
might have a bit more trouble meeting the disconnection times.

But not for a 5 A lighting circuit. BS 7671 Fig. 3.2A gives the min.
current to clear a 5 A fuse in 0.4 s as only 24 A - IOW the Zs only
needs to be 9.5 ohm (8 ohms measured on a cold test - OSG Table 2A).
That would imply a heck of a length of cable - over 200 m of 1 mm^2 T&E!
- and probable non-compliance on voltage drop.

[RCD required?]
See above. If the earth-fault loop impedance is low enough then probably
not.

Definitely not, IMHO (other than in TT-earthed installations, obviously).

You can download Part P from the ODPM website. It has the list of exempt
works in it.

As has been mentioned a few times now, the current issue of the IEE
publication /Wiring Matters/ gives guidance that installation of a light
fitting on an outside wall of a house is not notifiable under Part P,
provided that the supply is taken from an existing circuit and the
connection is not made in a kitchen or special location.

It seems to me to be aimed at all outside lights, but the 0.4S
disconnection time is a good thing to aim for for *all* electrical
equipment in the home, and most of it requires this timing.

And of course in the age of MCB protection everything gets it. BTW the
unit symbol for seconds is "s" (lower case), not "S" which refers to the
SI unit of conductance, the siemens (formerly known as the 'mho').

--
Andy

In message ,
Andy Wade wrote:

Martin Angove wrote:

If your circuits are protected by rewireable fuses to BS3036 then you
might have a bit more trouble meeting the disconnection times.

But not for a 5 A lighting circuit. BS 7671 Fig. 3.2A gives the min.
current to clear a 5 A fuse in 0.4 s as only 24 A - IOW the Zs only
needs to be 9.5 ohm (8 ohms measured on a cold test - OSG Table 2A).
That would imply a heck of a length of cable - over 200 m of 1 mm^2 T&E!
- and probable non-compliance on voltage drop.


Good point. Fired off the phrase without bothering to flip the page and
check :-)

[RCD required?]
See above. If the earth-fault loop impedance is low enough then probably
not.

Definitely not, IMHO (other than in TT-earthed installations, obviously).

You can download Part P from the ODPM website. It has the list of exempt
works in it.

As has been mentioned a few times now, the current issue of the IEE
publication /Wiring Matters/ gives guidance that installation of a light
fitting on an outside wall of a house is not notifiable under Part P,
provided that the supply is taken from an existing circuit and the
connection is not made in a kitchen or special location.


Been absent from the ng for a while so have missed most of the Part P
debate (semi deliberately). That is an interesting interpretation of the
rules. Has it been tested in a court yet?

It seems to me to be aimed at all outside lights, but the 0.4S
disconnection time is a good thing to aim for for *all* electrical
equipment in the home, and most of it requires this timing.

And of course in the age of MCB protection everything gets it. BTW the
unit symbol for seconds is "s" (lower case), not "S" which refers to the
SI unit of conductance, the siemens (formerly known as the 'mho').

OK. I used to have a reason for usion capital S for seconds, but I can't
remember it and given what you've said, I'll change :-)

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... CONgress (n) - Opposite of PROgress

Martin Angove wrote:

[light on outside wall not Part P notifiable]
Been absent from the ng for a while so have missed most of the Part P
debate (semi deliberately). That is an interesting interpretation of the
rules.

Yes, but appearing in an IEE publication, who are we to argue? The
advice, as an answer in a series of Qs & As, starts "The general view of
the ODPM is that it is not notifiable."

Another somewhat surprising one is:

"Q. If I replace an existing electric shower with a new electric shower
connected to an existing shower circuit is this notifiable work?

"A. No, providing the shower is a like for like replacement."

("The old shower was 4 kW and the new one's 10 kW and the existing
circuit is wired in bell wire - but that's near enough like-for-like
innit?...")

Has it been tested in a court yet?

I very much doubt it.

--
Andy

On Wed, 04 May 2005 17:56:39 +0100, Andy Wade
wrote:

Martin Angove wrote:

[light on outside wall not Part P notifiable]
Been absent from the ng for a while so have missed most of the Part P
debate (semi deliberately). That is an interesting interpretation of the
rules.

Yes, but appearing in an IEE publication, who are we to argue? The
advice, as an answer in a series of Qs & As, starts "The general view of
the ODPM is that it is not notifiable."

Another somewhat surprising one is:

"Q. If I replace an existing electric shower with a new electric shower
connected to an existing shower circuit is this notifiable work?

"A. No, providing the shower is a like for like replacement."

("The old shower was 4 kW and the new one's 10 kW and the existing
circuit is wired in bell wire - but that's near enough like-for-like
innit?...")

4kW - bloody 'ell - I thought my 7kW a few years ago was bad enough!

Has it been tested in a court yet?

I very much doubt it.

I thought that part P was to do with wiring rather than appliances,
so the actual appliance, be it a 4 kW or a 10 kW shower is
irrelevant..

Still, things "may" change as a result of changes in the next 24
hours...

--
Frank Erskine
MJBC, OETKBC

Frank Erskine wrote:

4kW - bloody 'ell - I thought my 7kW a few years ago was bad enough!

I recall using one of the original (c. 1970) instant electric showers -
3 kW! People who think today's 8, 9 or 10 kW jobs are poor should try
one of those...

I thought that part P was to do with wiring rather than appliances,
so the actual appliance, be it a 4 kW or a 10 kW shower is
irrelevant..

I suspect that was tongue-in-cheek but, FAOD, the suitability and rating
of the supply to fixed equipment is surely within the scope of Part P,
as is the work involved in making connection to same, in certain cases.

Still, things "may" change as a result of changes in the next 24
hours...

FSVO "may" with a probability of something less than
floating_point_underflow ever if there were to be a change of gov't,
which won't happen either...

--
Andy