Hi all

Please can someone advise best practice for the following:

1970s extended property with subject extension to rear
Extension adjoins both the house and garage with fuse box located in garage
Currently the sockets in the extension are a radial spur from the breaker
covering the upstairs main house ring main
Similarly the extension lighting is a radial spur from the upstairs lighting
feed

My questions:

In an ideal world I suppose I would have a separate breaker covering the
extension supplies, or have them form part of the existing downstairs
ring/lighting.
Is it a big no-no to power more than one circuit from a single breaker?
There are currently 3 single sockets in the extension, so I presume that the
power to this room should be converted into a ring whether it returns to a
shared fuse or not?
There are currently no spare fuse ways in the CU so it would be an expensive
upgrade for one room to provide individual protection for these two
supplies.

Any comments on IEE Regs compliance welcome

TIA

Phil

TheScullster wrote:

Currently the sockets in the extension are a radial spur from the breaker
covering the upstairs main house ring main

A spur from the origin is perfectly valid, but to count as a
'conventional circuit' it should obey the usual spur rules, i.e. feed no
more than one single or double socket or else be fused down to 13 A.
Also the whole area served should remain within 100 m^2. You mention
three single sockets on this spur - are they wired in 2.5 mm^2 cable or
4 mm^2? The circuit would not comply with BS 7671 (== IEE regs. 16th
ed. as amended) if the former (unless it is a fused spur) but may comply
in the latter case as a special design. On the whole though it sounds
like a cowboy job as the rules hare haven't really changed since the
'60s (if not before).

Similarly the extension lighting is a radial spur from the upstairs lighting
feed

No problem there, necessarily, provided that the total load (assume 100
W per lampholder) stays within the cable and breaker ratings.
Nevertheless it is considered desirable to spread lighting over a
reasonable no. of separate circuits to avoid the problems of sudden
total darkness in the event of a fault or nuisance trip.

Is it a big no-no to power more than one circuit from a single breaker?

Whatever you feed from one breaker is /ipso facto/ a single final
circuit. What you have is composite circuits with multiple parts or
sections.

There are currently 3 single sockets in the extension, so I presume that the
power to this room should be converted into a ring whether it returns to a
shared fuse or not?

What floor area? A (separate) 20 A radial circuit would be OK for
general use if it's under 50 m^2. (Assuming no major kitchen/laundry
appliances or water heaters are involved.)

There are currently no spare fuse ways in the CU so it would be an expensive
upgrade for one room to provide individual protection for these two
supplies.

From the date I'm imagining a Wylex-type brown consumer unit with
rewireable fuses, or perhaps BS 1361 cartridge fuses. Nothing wrong
with those /per se/ until you start to run out of fuseways.

Perhaps it's time to bite the bullet and invest in an upgrade to a
modern split-load MCB consumer unit. Sort out the extension power
circuit and provide a few spare ways, and RCD protection for the socket
circuits too.

HTH
--
Andy

Andy

Apologies for delay!

Thanks for comprehensive response!
The room area is a maximum of 20 sq metres, intended as a teen chill out
zone for kids.

Your comments new CU are noted:

Perhaps it's time to bite the bullet and invest in an upgrade to a
modern split-load MCB consumer unit. Sort out the extension power
circuit and provide a few spare ways, and RCD protection for the socket
circuits too

This has already been done, with the RCD protection to the socket circuits.

Yes the feed to this additional room is only 2.5sq mm.
I believe this also supplies a double socket in the end wall of the garage
which adjoins this room.

So if I put a switched fused spur alongside the CU with a 13A fuse I can put
as many sockets in as I like and this will be regs compliant for a 2.5mm
spur?
I don't anticipate heavy loads to this supply, but do expect TV, audio,
computer type equipment and possibly the occasional vacuum!

Thanks for your help

Phil

TheScullster wrote:
Hi all

Please can someone advise best practice for the following:

Do you want 16th edn compliance, or making it work ok safely? Why?


1970s extended property with subject extension to rear
Extension adjoins both the house and garage with fuse box located in
garage
Currently the sockets in the extension are a radial spur from the
breaker
covering the upstairs main house ring main

if its from teh CU it could be put on its own breaker, although the
trip would have to be low current if its just 2.5mm. 2.5 radials are
not reg compliant afaik, but if MCBed at suitably low rating, and youve
not got all your lighting running off it, theyre safe and workable.


Similarly the extension lighting is a radial spur from the upstairs
lighting
feed

no problem with that.


My questions:

In an ideal world I suppose I would have a separate breaker covering
the
extension supplies, or have them form part of the existing downstairs
ring/lighting.
Is it a big no-no to power more than one circuit from a single
breaker?

More to the point I wouldnt put a 2.5 radial on a 30/32A mcb/fuse. Is
the 2.5 clipped direct, buried in thermal insulation, what? With that
info one can current rate it, thus know what fuse/mcb to put it on.
However its not gonna be reg compliant whatever you do with it, unless
you rewire it as a 2.5 ring or a 4mm radial.


There are currently 3 single sockets in the extension, so I presume
that the
power to this room should be converted into a ring whether it returns
to a
shared fuse or not?

In some cases you do need reg compliance, in some you dont. The regs
are mainly about safety, but not entirely. Theres nothing unsafe about
a 2.5mm radial circuit on a 16A breaker and RCD, but it might trip on
some heavy-startup loads, hence the need to not have all your lighting
on it.


There are currently no spare fuse ways in the CU so it would be an
expensive
upgrade for one room to provide individual protection for these two
supplies.

A split CU kit is only =A370, plus wiring it up, plus fixing the
inevitable problem circuits. Another 4 way Wylex fusebox is of course
much cheaper, if its that tight.

Any comments on IEE Regs compliance welcome

Do you need compliance in your case? Given what youve found though, I
would want to check the whole system over and see if any nastier bodges
have been done.


NT

Thanks, BigCat

Yes I want to be regs compliant and will look at running a return 2.5 for
the socket circuit.
I have found one or two nasties, mainly associated with extensions, the
original wiring seems sound.
Although the original 70s wiring can take some sorting on occasions, with
lives looped around switches and neutrals around ceiling roses - very
strange, but standard for the area and era apparently!

Currently the 2.5 is clipped along the inside wall of garage, through the
end wall between ceiling of extension and upper floor then down "top hat"
type conduit behind plaster to sockets.

What would you recommend to protect the 2.5 in the garage?
I am considering running the feed, return and lighting cable in some kind of
trunking.

TIA

Phil

TheScullster wrote:

Your comments new CU are noted:
[snip]
This has already been done, with the RCD protection to the socket circuits.

With the cowboy's spur not sorted out - oh dear. I take it there are no
spare ways in the new CU.

Yes the feed to this additional room is only 2.5sq mm.
I believe this also supplies a double socket in the end wall of the garage
which adjoins this room.

So four sockets (single or double) on a single unfused spur.

So if I put a switched fused spur alongside the CU with a 13A fuse I can put
as many sockets in as I like and this will be regs compliant for a 2.5mm
spur?

Well, yes and no. Yes, you can have as many sockets as you like on a
fused spur, but no in the sense that you must also consider whether such
a 13A rated sub-circuit is appropriate for the loads likely to be
connected. In your circumstances it would seem entirely possible that
two 2 or 3 kW electric heaters could be plugged in (e.g. central heating
breakdown) thus overloading the spur. Thus it's not an ideal
arrangement, but would still be better than what you have now.

I don't anticipate heavy loads to this supply, but do expect TV, audio,
computer type equipment and possibly the occasional vacuum!

Fair enough, but can you rule out the use of multiple heating appliances
on occasion?

--
Andy