I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

Because of the construction of the garage, it would be easiest to run the
wiring at head height, and run down trunking to the places where sockets are
wanted. There are roughly two options:

1. A radial around three sides, with the sockets on essentially long loops
down from the ceiling. This is just an extension of the existing radial.

2. A ring main around at ceiling level. The simplest way would be for each
socket to be spurred off, but I understand spurs aren't well received. An
alternative would be to use a variation of 1) where the ring takes a long
loop down to each socket


The natural way to do this would seem to be a ring with spurs, but if spurs
aren't recommended then a ring or radial with loops would seem a sensible
option. In that case, would it be sensible to have a long run of cable at
ceiling level, with a pair of junction boxes for each socket downlead, ie:

-----+ +----
| |
| |
socket

where + is a junction box?

Also, Part P wise, am I right in thinking that extending a radial is OK but
converting a radial to a ring is notifiable?

Finally, is it acceptable to cable-clip T&E cables (bearing in mind the new
rule to use metal clips occasionally) in an outbuilding, or is additional
protection (trunking) needed (even at ceiling level)?

Thanks
Theo

On 27/08/2019 22:53, Theo wrote:

I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

Approx how many sockets in total?

What do you anticipate running from them?

(i.e. do you need the extra power available from a 32A ring rather than
a 16 or 20A radial)

(and for the pedants, yes you could run a 32A radial in 4mm^2, and spur
each socket in 2.5mm^2(

Because of the construction of the garage, it would be easiest to run the
wiring at head height, and run down trunking to the places where sockets are
wanted. There are roughly two options:

Have you considered dado trunking?

1. A radial around three sides, with the sockets on essentially long loops
down from the ceiling. This is just an extension of the existing radial.

You can do that - or the backbone and branch style with spurs from the
radial.

2. A ring main around at ceiling level. The simplest way would be for each
socket to be spurred off, but I understand spurs aren't well received.

In a conventionally wired ring its usually better to start with few
spurs, however its equally valid to take a design decision to use spurs
exclusively if it makes more sense.

An
alternative would be to use a variation of 1) where the ring takes a long
loop down to each socket

Tis probably what I would do, or, drop down to the first socket on the
wall, then run horizontally between them, and back up to the ceiling at
the last one.

Also, Part P wise, am I right in thinking that extending a radial is OK but
converting a radial to a ring is notifiable?

No. Adding a whole new circuit would be notifiable (if anyone actually
cared!) Extending one is ok, and arguably still ok if the extension
takes it back to the CU.

Finally, is it acceptable to cable-clip T&E cables (bearing in mind the new
rule to use metal clips occasionally) in an outbuilding, or is additional
protection (trunking) needed (even at ceiling level)?

Depends on what you are doing in there, and what the likely risk of
mechanical damage is.




--
Cheers,

John.

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

On 27/08/2019 23:14, John Rumm wrote:
On 27/08/2019 22:53, Theo wrote:

snip

Also, Part P wise, am I right in thinking that extending a radial is
OK but
converting a radial to a ring is notifiable?

No. Adding a whole new circuit would be notifiable (if anyone actually
cared!) Extending one is ok, and arguably still ok if the extension
takes it back to the CU.

Are you certain, not that I would worry, but isn't any change of (or
new) cable route notifiable. If you don't tell anyone ............

Or have the rules changed?

Finally, is it acceptable to cable-clip T&E cables (bearing in mind
the new
rule to use metal clips occasionally) in an outbuilding, or is additional
protection (trunking) needed (even at ceiling level)?

Depends on what you are doing in there, and what the likely risk of
mechanical damage is.

It's more down to what would happen to the cable if the clips melted.
Some form of retention over a doorway would be appropriate to stop it
sagging and blocking an exit.

On 27/08/2019 23:41, Fredxx wrote:
On 27/08/2019 23:14, John Rumm wrote:
On 27/08/2019 22:53, Theo wrote:

snip

Also, Part P wise, am I right in thinking that extending a radial is
OK but
converting a radial to a ring is notifiable?

No. Adding a whole new circuit would be notifiable (if anyone actually
cared!) Extending one is ok, and arguably still ok if the extension
takes it back to the CU.

Are you certain,

Yes

not that I would worry, but isn't any change of (or
new) cable route notifiable. If you don't tell anyone ............

If the work were on a circuit in a special location, then changes other
that like for like swaps would be notifiable - and hence in that
situation an extension to a circuit could be notifiable. However in the
general case it has never been so.

(This was one of the original criticisms of the system - that is made
extensions to existing circuits easier to do than add new ones, even in
cases where a new circuit would be a better technical solution)


Or have the rules changed?

There have been various changes to part P over the years (the most
recent ones being the most significant by removing many previously
notifiable activities from the list, and providing for the first time a
route to third party certification). However I can't immediately think
of changes on this bit. The current wording in the 2013 version[1] is:

"12.€”(6A) A person intending to carry out building work in relation to
which Part P of Schedule I imposes a requirement is required to give a
building notice or deposit full plans where the work consists of€”
(a) the installation of a new circuit;
(b) the replacement of a consumer unit; or
(c) any addition or alteration to existing circuits in a special location."

[1]
https://www.planningportal.co.uk/inf...ctrical_safety

(and kitchens are no longer special locations)

Finally, is it acceptable to cable-clip T&E cables (bearing in mind
the new
rule to use metal clips occasionally) in an outbuilding, or is
additional
protection (trunking) needed (even at ceiling level)?

Depends on what you are doing in there, and what the likely risk of
mechanical damage is.

It's more down to what would happen to the cable if the clips melted.
Some form of retention over a doorway would be appropriate to stop it
sagging and blocking an exit.

I think we are talking at crossed purposes.

Adequate cable support is required in all cases. However enclosing it in
conduit for example is not necessarily required (and if the conduit is
plastic, would not alone meet the requirements for retaining cables in
the event of a fire).

So for example - surface run cables in a garage where all that is needed
is somewhere to plug in an inspection lamp or battery charger, are not
going to require additional mechanical protection. However in a garage
used as a workshop where materials are handled and moved about, or say
welding is done, then some mechanical protection would be advised to
protect the cables from impact damage or contact with hot sparks / metal
splatter.


--
Cheers,

John.

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

On Tuesday, 27 August 2019 22:53:56 UTC+1, Theo wrote:

I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

Because of the construction of the garage, it would be easiest to run the
wiring at head height, and run down trunking to the places where sockets are
wanted. There are roughly two options:

1. A radial around three sides, with the sockets on essentially long loops
down from the ceiling. This is just an extension of the existing radial.

2. A ring main around at ceiling level. The simplest way would be for each
socket to be spurred off, but I understand spurs aren't well received. An
alternative would be to use a variation of 1) where the ring takes a long
loop down to each socket


The natural way to do this would seem to be a ring with spurs, but if spurs
aren't recommended then a ring or radial with loops would seem a sensible
option. In that case, would it be sensible to have a long run of cable at
ceiling level, with a pair of junction boxes for each socket downlead, ie:

-----+ +----
| |
| |
socket

where + is a junction box?

Also, Part P wise, am I right in thinking that extending a radial is OK but
converting a radial to a ring is notifiable?

Finally, is it acceptable to cable-clip T&E cables (bearing in mind the new
rule to use metal clips occasionally) in an outbuilding, or is additional
protection (trunking) needed (even at ceiling level)?

Thanks
Theo

Any of those options is compliant. Rings have a slight advantage in safety & reliability over radials, and of course use thinner wire for a given rating, though more of it.

Metal cable clips: Just enough are required to stop the wiring collapsing onto someone in a fire, most clips can be plastic.


NT

Also, brick built but is it detached from the house or part of it?
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Theo" wrote in message
...
I'm speccing up installing sockets in a brick garage. It currently has a
CU
with an adjacent pair of double sockets on a short radial. I want to put
some
sockets at various points around the far sides.

Because of the construction of the garage, it would be easiest to run the
wiring at head height, and run down trunking to the places where sockets
are
wanted. There are roughly two options:

1. A radial around three sides, with the sockets on essentially long loops
down from the ceiling. This is just an extension of the existing radial.

2. A ring main around at ceiling level. The simplest way would be for
each
socket to be spurred off, but I understand spurs aren't well received. An
alternative would be to use a variation of 1) where the ring takes a long
loop down to each socket


The natural way to do this would seem to be a ring with spurs, but if
spurs
aren't recommended then a ring or radial with loops would seem a sensible
option. In that case, would it be sensible to have a long run of cable at
ceiling level, with a pair of junction boxes for each socket downlead, ie:

-----+ +----
| |
| |
socket

where + is a junction box?

Also, Part P wise, am I right in thinking that extending a radial is OK
but
converting a radial to a ring is notifiable?

Finally, is it acceptable to cable-clip T&E cables (bearing in mind the
new
rule to use metal clips occasionally) in an outbuilding, or is additional
protection (trunking) needed (even at ceiling level)?

Thanks
Theo

John Rumm wrote:
On 27/08/2019 22:53, Theo wrote:

I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

Approx how many sockets in total?

'Lots'

Possibly on surface power/data trunking in one corner.

What do you anticipate running from them?

(i.e. do you need the extra power available from a 32A ring rather than
a 16 or 20A radial)

Nothing particularly power hungry - soldering irons, wall warts, AA battery
chargers kind of thing - lots of sockets but only taking a few watts each.
A bit of future proofing might be useful in case someone (possibly
me) wants to use more power tools in there. I suppose one way to do that
would be to spec a 16A radial and then leave the option of closing the far
end to make a 32A ring.

(I'll have to check the CU - any Part P implications if changing the MCB for
a different current?)

(and for the pedants, yes you could run a 32A radial in 4mm^2, and spur
each socket in 2.5mm^2(

Because of the construction of the garage, it would be easiest to run the
wiring at head height, and run down trunking to the places where sockets are
wanted. There are roughly two options:

Have you considered dado trunking?

For above work surfaces, yes. But I don't want to disrupt other uses of the
walls (eg shelving) by running wiring at waist level.

1. A radial around three sides, with the sockets on essentially long loops
down from the ceiling. This is just an extension of the existing radial.

You can do that - or the backbone and branch style with spurs from the
radial.

How should I calculate the wire sizes on that setup? Assume all the current
is taken from the branch furthest away?

2. A ring main around at ceiling level. The simplest way would be for each
socket to be spurred off, but I understand spurs aren't well received.

In a conventionally wired ring its usually better to start with few
spurs, however its equally valid to take a design decision to use spurs
exclusively if it makes more sense.

Why are spurs generally disliked? Because the spur itself only has one
route for the current?

Finally, is it acceptable to cable-clip T&E cables (bearing in mind the new
rule to use metal clips occasionally) in an outbuilding, or is additional
protection (trunking) needed (even at ceiling level)?

Depends on what you are doing in there, and what the likely risk of
mechanical damage is.

No heavy industry. I assume placement matters too (ie protection from
solder splashes at bench level might be useful, but not much point at
ceiling level)

I'm sort of leaning towards on running a 16/20A radial around the ceiling,
with spurred pendants in trunking. Anyone who wants to bump up the current
capacity can convert it to a ring and double up the pendants (easy given
it's all surface wiring), but on the KISS principle that will do for the
time being...

Thanks for your help (and everyone else too)
Theo

On 28/08/2019 10:09, Theo wrote:

John Rumm wrote:
On 27/08/2019 22:53, Theo wrote:

I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

Approx how many sockets in total?

'Lots'

Possibly on surface power/data trunking in one corner.

What do you anticipate running from them?

(i.e. do you need the extra power available from a 32A ring rather than
a 16 or 20A radial)

Nothing particularly power hungry - soldering irons, wall warts, AA battery
chargers kind of thing - lots of sockets but only taking a few watts each.
A bit of future proofing might be useful in case someone (possibly
me) wants to use more power tools in there. I suppose one way to do that
would be to spec a 16A radial and then leave the option of closing the far
end to make a 32A ring.

By the sounds of it, a fairly small load overall.

If running radials for general purpose socket circuits, there is little
point in speccing 16A since the cables you would typically install will
be fine with 20A as well in most cases, and that gives you a bit more
wiggle room in case you do need to run a 3kW kettle or a fan heater plus
other stuff.

(I'll have to check the CU - any Part P implications if changing the MCB for
a different current?)

There are no implications that I can think of...

(and for the pedants, yes you could run a 32A radial in 4mm^2, and spur
each socket in 2.5mm^2(

Because of the construction of the garage, it would be easiest to run the
wiring at head height, and run down trunking to the places where sockets are
wanted. There are roughly two options:

Have you considered dado trunking?

For above work surfaces, yes. But I don't want to disrupt other uses of the
walls (eg shelving) by running wiring at waist level.

1. A radial around three sides, with the sockets on essentially long loops
down from the ceiling. This is just an extension of the existing radial.

You can do that - or the backbone and branch style with spurs from the
radial.

How should I calculate the wire sizes on that setup? Assume all the current
is taken from the branch furthest away?

The cable will need to be able to take the full nominal circuit design
load "as installed" (i.e. including any de-rating factors). So for a 20A
radial, the normal choice would be 2.5mm^2 T&E unless there is some
reason (e.g. high ambient temp, or running through insulation etc) to
de-rate it below 20A.

2. A ring main around at ceiling level. The simplest way would be for each
socket to be spurred off, but I understand spurs aren't well received.

In a conventionally wired ring its usually better to start with few
spurs, however its equally valid to take a design decision to use spurs
exclusively if it makes more sense.

Why are spurs generally disliked? Because the spur itself only has one
route for the current?

Partly that, also on a ring circuit the B32 MCB normally provides both
overload and fault protection. In the case of a spur, it can still
provide fault protection, but can no longer do overload protection
(since the single length of 2.5mm^2 cable is good for 27A at best - less
than the MCB rating), so you have to rely on the restriction of one
single or double socket per unfused spur.

Having lots of spurs then makes it difficult to further extend the
circuit, since what may be a natural place to make a connection turns
out to already be a spur, and hence not available unless you also
convert it to a fuse spur. That also has disadvantages. Also more spurs
means more connection points with three or more sets of cable connected
to one point, which is more difficult to wire, and more complex to test
and maintain.

So for new ring circuits is preferable to start with few or no spurs,
and that gives the best scope to allow it to grow and adapt according to
need.

Finally, is it acceptable to cable-clip T&E cables (bearing in mind the new
rule to use metal clips occasionally) in an outbuilding, or is additional
protection (trunking) needed (even at ceiling level)?

Depends on what you are doing in there, and what the likely risk of
mechanical damage is.

No heavy industry. I assume placement matters too (ie protection from
solder splashes at bench level might be useful, but not much point at
ceiling level)

Manual soldering etc is unlikely to pose a problem - but then again that
is the place dado trunking might be good anyway.

I'm sort of leaning towards on running a 16/20A radial around the ceiling,
with spurred pendants in trunking. Anyone who wants to bump up the current
capacity can convert it to a ring and double up the pendants (easy given
it's all surface wiring), but on the KISS principle that will do for the
time being...

If going that route, then a lap of 4mm^2 at ceiling level, looping
through 30A JBs at each socket location would be easiest. Then install
2.5mm^2 drops to each socket. You are then free to protect it at
whatever current limit you want (up to 32A), and future additions would
be easy - add new JB and drop wire.

(you could also in theory add a "sub" ring to the backbone - say drop
down to some dado trunking, run through half a dozen sockets, and then
back up at the other end).


--
Cheers,

John.

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

On 27/08/2019 22:53, Theo wrote:
I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

What's the feed to the CU? Is this a stand-alone installation with its own
supply company feed and meter? There would be no point me wondering about
a 32 A ring in my garage as it only has a 16 A feed from the house.


--
Graham Nye
news(a)thenyes.org.uk

On 28/08/2019 11:38, John Rumm wrote:
On 28/08/2019 10:09, Theo wrote:



(I'll have to check the CU - any Part P implications if changing the
MCB for
a different current?)

There are no implications that I can think of...

Unless there is some existing certification to say that it was an
exiting radial who would know...


Or care as long as the new work is done properly?

--
Adam

On 28/08/2019 11:40, Graham Nye wrote:
On 27/08/2019 22:53, Theo wrote:
I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

What's the feed to the CU? Is this a stand-alone installation with its own
supply company feed and meter? There would be no point me wondering about
a 32 A ring in my garage as it only has a 16 A feed from the house.




Such a simple answer.

Well done sir.

--
Adam

Graham Nye wrote:
On 27/08/2019 22:53, Theo wrote:
I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

What's the feed to the CU? Is this a stand-alone installation with its own
supply company feed and meter? There would be no point me wondering about
a 32 A ring in my garage as it only has a 16 A feed from the house.

It's an 80A MCB on the CU in the garage - I'm not sure how it's hooked
into the main CU, but it isn't a separate feed. I'll see if I can find out
what the MCB on the other end is.

Theo

On 29/08/2019 10:15, Theo wrote:
Graham Nye wrote:
On 27/08/2019 22:53, Theo wrote:
I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

What's the feed to the CU? Is this a stand-alone installation with its own
supply company feed and meter? There would be no point me wondering about
a 32 A ring in my garage as it only has a 16 A feed from the house.

It's an 80A MCB on the CU in the garage - I'm not sure how it's hooked
into the main CU, but it isn't a separate feed. I'll see if I can find out
what the MCB on the other end is.


An 80A MCB? I may well be missing something but I'm left wondering:

a. are the sockets in the garage connected direct to that MCB or to
another - lower rated! - one?

b. does the supply definitely come from the house into the garage or
does it possibly go /from/ the garage /to/ the house?


--
Robin
reply-to address is (intended to be) valid

On 28/08/2019 21:16, ARW wrote:
On 28/08/2019 11:40, Graham Nye wrote:
On 27/08/2019 22:53, Theo wrote:
I'm speccing up installing sockets in a brick garage. It currently has a CU
with an adjacent pair of double sockets on a short radial. I want to put some
sockets at various points around the far sides.

What's the feed to the CU? Is this a stand-alone installation with its own
supply company feed and meter? There would be no point me wondering about
a 32 A ring in my garage as it only has a 16 A feed from the house.

Such a simple answer.

Well done sir.

That's kind of you. I was vaguely wondering if this is a garage next to (or
part of) a house or a separated garage with its own supply, but that's too
wide ranging a question. All that's necessary is to establish that the feed
to the CU can support the rating of the desired new circuit.



--
Graham Nye
news(a)thenyes.org.uk

On 29/08/2019 10:15, Theo wrote:
Graham Nye wrote:

What's the feed to the CU? ...

It's an 80A MCB on the CU in the garage - I'm not sure how it's hooked
into the main CU, but it isn't a separate feed. I'll see if I can find out
what the MCB on the other end is.

80 A is an unusually high rating for a domestic MCB. Are you sure it is a
MCB? Could it be either a main switch or a RCB with an 80 A rating?

If you're not sure, take a clear picture of it, share it somewhere
(e.g. imgur.com) and post a link here.

Checking the source end of the feed would definitely be useful.

What protective device(s), if any, are on the radial circuit feeding
your existing pair of double sockets?


--
Graham Nye
news(a)thenyes.org.uk

On 29/08/2019 10:46, Robin wrote:
On 29/08/2019 10:15, Theo wrote:
Graham Nye wrote:
On 27/08/2019 22:53, Theo wrote:
I'm speccing up installing sockets in a brick garage.Â* It currently
has a CU
with an adjacent pair of double sockets on a short radial.Â* I want
to put some
sockets at various points around the far sides.

What's the feed to the CU? Is this a stand-alone installation with
its own
supply company feed and meter? There would be no point me wondering
about
a 32 A ring in my garage as it only has a 16 A feed from the house.

It's an 80A MCB on the CU in the garage - I'm not sure how it's hooked
into the main CU, but it isn't a separate feed.Â* I'll see if I can
find out
what the MCB on the other end is.


An 80A MCB?Â* I may well be missing something but I'm left wondering:

a.Â*Â*Â* are the sockets in the garage connected direct to that MCB or to
another - lower rated! - one?

b.Â*Â*Â* does the supply definitely come from the house into the garage or
does it possibly go /from/ the garage /to/ the house?



80A RCD not MCB at a guess.

--
Adam

On 29/08/2019 18:29, ARW wrote:
On 29/08/2019 10:46, Robin wrote:
On 29/08/2019 10:15, Theo wrote:
Graham Nye wrote:
On 27/08/2019 22:53, Theo wrote:
I'm speccing up installing sockets in a brick garage.Â* It currently
has a CU
with an adjacent pair of double sockets on a short radial.Â* I want
to put some
sockets at various points around the far sides.

What's the feed to the CU? Is this a stand-alone installation with
its own
supply company feed and meter? There would be no point me wondering
about
a 32 A ring in my garage as it only has a 16 A feed from the house.

It's an 80A MCB on the CU in the garage - I'm not sure how it's hooked
into the main CU, but it isn't a separate feed.Â* I'll see if I can
find out
what the MCB on the other end is.


An 80A MCB?Â* I may well be missing something but I'm left wondering:

a.Â*Â*Â* are the sockets in the garage connected direct to that MCB or to
another - lower rated! - one?

b.Â*Â*Â* does the supply definitely come from the house into the garage
or does it possibly go /from/ the garage /to/ the house?



80A RCD not MCB at a guess.


Ah, yes; it's so obvious when it's someone who knows what they're
talking about

--
Robin
reply-to address is (intended to be) valid