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David Hearn
 
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Default Consumer unit wiring

I'm trying to add some sockets to a bedroom upstairs, and I'm in the process
of working out how best to break into the ring and extend it by a socket or
two. (We have 1 double socket in each of the two larger bedrooms and a
single socket in the small bedroom! What a waste of a 32A MCB)

Anyway, something I've been wanting to figure out for a while is what's on
each circuit. A picture of my CU can be found at
http://www.swampie.org.uk/consumerunit.jpg

From left to right I have:

32A - Shower
32A - Downstairs ring. This also runs the extension/conservatory light
(plus probably 1 double socket), floodlight and garage (via FCU). I believe
there may be a spur also (hence 3rd live wire) which is the wire running
diagonally up to the right at the edge of the picture - I think this goes to
a single socket into the old larder (currently running freezer + microwave).
32A - Upstairs ring
6A - Downstairs lights + landing light (two way switch)
16A - Upstairs lights
6A - unknown

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the two
sockets together to rejoin the ring).

Also - any ideas what size wiring I've got based on that picture? The 2nd
32A MCB seems to have a thicker wire going into it - which would be the
spur. Unless of course, the spur is for the conservatory/extension which
then has a FCU running to the garage.

Also, any idea of the size of the wiring for the shower circuit? Its an
8.5kW shower and it would be interesting to know if they installed a large
enough wire to go to 9.5kW maybe in the future.

Thanks

D


  #2   Report Post  
David Hearn
 
Posts: n/a
Default Consumer unit wiring


"David Hearn" wrote in message
...
I'm trying to add some sockets to a bedroom upstairs, and I'm in the

process
of working out how best to break into the ring and extend it by a socket

or
two. (We have 1 double socket in each of the two larger bedrooms and a
single socket in the small bedroom! What a waste of a 32A MCB)


snip

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the two
sockets together to rejoin the ring).


When putting the wires under the floorboards are there any preferences with
repect to how I should route it? Currently all the wiring appears to go
into channels cut into the joists between the nails! I can now see how some
people can put nails through such wiring. Anyway, to avoid me having to
take up more floorboards than I may need to, what is the opinion of drilling
a hole through a joist and running a wire through that? I realise that this
will stop me from being able to move the wires around once all the boards
are up (whereas in channels they can just be layed down - possibly done that
way for ease of installation) - but realistically, when's that going to
happen?

Thanks.

D


  #3   Report Post  
Frisket
 
Posts: n/a
Default Consumer unit wiring


"David Hearn" wrote in message
...

"David Hearn" wrote in message
...
snip

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the

two
sockets together to rejoin the ring).


2.5mm twin & earth


When putting the wires under the floorboards are there any preferences

with
repect to how I should route it? Currently all the wiring appears to go
into channels cut into the joists between the nails! I can now see how

some
people can put nails through such wiring. Anyway, to avoid me having to
take up more floorboards than I may need to, what is the opinion of

drilling
a hole through a joist and running a wire through that? I realise that

this
will stop me from being able to move the wires around once all the boards
are up (whereas in channels they can just be layed down - possibly done

that
way for ease of installation) - but realistically, when's that going to
happen?

Thanks.

D

Chopping the top out of joists was a hideous practise that, rightly, is
frowned on - drilling a hole is the accepted way to do it.
The picture of your CU worries me tho' - the cable to all the fuses, apart
from the shower, all look the same size... Are they? or is it just my boggly
old eyes?
HTH, Richard


  #4   Report Post  
Andy Hall
 
Posts: n/a
Default Consumer unit wiring

On Fri, 10 Oct 2003 19:50:42 +0100, "David Hearn"
wrote:


"David Hearn" wrote in message
...
I'm trying to add some sockets to a bedroom upstairs, and I'm in the

process
of working out how best to break into the ring and extend it by a socket

or
two. (We have 1 double socket in each of the two larger bedrooms and a
single socket in the small bedroom! What a waste of a 32A MCB)


snip

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the two
sockets together to rejoin the ring).


This should be 2.5mm T&E.

However, looking at your picture, something appears to be wrong with
cable sizings.

The first position does appear to have the thickest cable - which it
should, but I can't easliy tell whether it is 4mm^2 or 6mm^2.
The second position appears to have 2.5mm T&E.

However, I am concerned about everything to the right of there - it
appears to use a small cable, possibly 1.5mm^2. Certainly this is
not enough for a 32A ring circuit, or even a 16A circuit.

Generally, the immersion heater, if there is one is run from a 16A
(blue) MCB. You wouldn't normally use 16A for a lighting circuit.
I would expect the two white carriers to be the lights at 5A each.
Could you re-check that.....



When putting the wires under the floorboards are there any preferences with
repect to how I should route it? Currently all the wiring appears to go
into channels cut into the joists between the nails! I can now see how some
people can put nails through such wiring.


Exactly. Apart from being a bad idea for the joists, it is not
allowed in the wiring regulations either. You should drill a hole
through each joist at least 50mm down from the floor and 50mm up from
the ceiling below to avoid the risk of nails reaching the cable.



Anyway, to avoid me having to
take up more floorboards than I may need to, what is the opinion of drilling
a hole through a joist and running a wire through that?


That is what you should do.

I realise that this
will stop me from being able to move the wires around once all the boards
are up (whereas in channels they can just be layed down - possibly done that
way for ease of installation) - but realistically, when's that going to
happen?

Thanks.

D


..andy

To email, substitute .nospam with .gl
  #5   Report Post  
BigWallop
 
Posts: n/a
Default Consumer unit wiring


"David Hearn" wrote in message
...
I'm trying to add some sockets to a bedroom upstairs, and I'm in the

process
of working out how best to break into the ring and extend it by a socket

or
two. (We have 1 double socket in each of the two larger bedrooms and a
single socket in the small bedroom! What a waste of a 32A MCB)

Anyway, something I've been wanting to figure out for a while is what's on
each circuit. A picture of my CU can be found at
http://www.swampie.org.uk/consumerunit.jpg

From left to right I have:

32A - Shower
32A - Downstairs ring. This also runs the extension/conservatory light
(plus probably 1 double socket), floodlight and garage (via FCU). I

believe
there may be a spur also (hence 3rd live wire) which is the wire running
diagonally up to the right at the edge of the picture - I think this goes

to
a single socket into the old larder (currently running freezer +

microwave).
32A - Upstairs ring
6A - Downstairs lights + landing light (two way switch)
16A - Upstairs lights
6A - unknown

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the two
sockets together to rejoin the ring).

Also - any ideas what size wiring I've got based on that picture? The 2nd
32A MCB seems to have a thicker wire going into it - which would be the
spur. Unless of course, the spur is for the conservatory/extension which
then has a FCU running to the garage.

Also, any idea of the size of the wiring for the shower circuit? Its an
8.5kW shower and it would be interesting to know if they installed a large
enough wire to go to 9.5kW maybe in the future.

Thanks

D



The 32 amp is running a whole house ring by the look of the picture. The 16
amp is for a water heater or something. (?)


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  #6   Report Post  
Chris Oates
 
Posts: n/a
Default Consumer unit wiring


"David Hearn" wrote in message
...
I'm trying to add some sockets to a bedroom upstairs, and I'm in the

process
of working out how best to break into the ring and extend it by a socket

or
two. (We have 1 double socket in each of the two larger bedrooms and a
single socket in the small bedroom! What a waste of a 32A MCB)

Anyway, something I've been wanting to figure out for a while is what's on
each circuit. A picture of my CU can be found at
http://www.swampie.org.uk/consumerunit.jpg

From left to right I have:


The CU is wired the wrong way around !!
all those red ways should be nearest the switch.


32A - Shower
32A - Downstairs ring. This also runs the extension/conservatory light
(plus probably 1 double socket), floodlight and garage (via FCU). I

believe
there may be a spur also (hence 3rd live wire) which is the wire running
diagonally up to the right at the edge of the picture - I think this goes

to
a single socket into the old larder (currently running freezer +

microwave).
32A - Upstairs ring
6A - Downstairs lights + landing light (two way switch)
16A - Upstairs lights
6A - unknown

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the two
sockets together to rejoin the ring).

Also - any ideas what size wiring I've got based on that picture? The 2nd
32A MCB seems to have a thicker wire going into it - which would be the
spur. Unless of course, the spur is for the conservatory/extension which
then has a FCU running to the garage.

Also, any idea of the size of the wiring for the shower circuit? Its an
8.5kW shower and it would be interesting to know if they installed a large
enough wire to go to 9.5kW maybe in the future.


The shower feed looks like 4mm but should be 6mm for an 8kw and 10mm
for 9kw - that means the shower cables should look like the tails that feed
the WHOLE box.



  #7   Report Post  
BigWallop
 
Posts: n/a
Default Consumer unit wiring


"Chris Oates" wrote in message
. ..

"David Hearn" wrote in message
...
I'm trying to add some sockets to a bedroom upstairs, and I'm in the

process
of working out how best to break into the ring and extend it by a socket

or
two. (We have 1 double socket in each of the two larger bedrooms and a
single socket in the small bedroom! What a waste of a 32A MCB)

Anyway, something I've been wanting to figure out for a while is what's

on
each circuit. A picture of my CU can be found at
http://www.swampie.org.uk/consumerunit.jpg

From left to right I have:


The CU is wired the wrong way around !!
all those red ways should be nearest the switch.


I'd agree with this.



32A - Shower
32A - Downstairs ring. This also runs the extension/conservatory light
(plus probably 1 double socket), floodlight and garage (via FCU). I

believe
there may be a spur also (hence 3rd live wire) which is the wire running
diagonally up to the right at the edge of the picture - I think this

goes
to
a single socket into the old larder (currently running freezer +

microwave).
32A - Upstairs ring
6A - Downstairs lights + landing light (two way switch)
16A - Upstairs lights
6A - unknown

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the

two
sockets together to rejoin the ring).

Also - any ideas what size wiring I've got based on that picture? The

2nd
32A MCB seems to have a thicker wire going into it - which would be the
spur. Unless of course, the spur is for the conservatory/extension

which
then has a FCU running to the garage.

Also, any idea of the size of the wiring for the shower circuit? Its an
8.5kW shower and it would be interesting to know if they installed a

large
enough wire to go to 9.5kW maybe in the future.


The shower feed looks like 4mm but should be 6mm for an 8kw and 10mm
for 9kw - that means the shower cables should look like the tails that

feed
the WHOLE box.





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  #8   Report Post  
froggers
 
Posts: n/a
Default Consumer unit wiring

What I'm after really is an idea of the size of wiring I need to use to
extend the ring (I'm planning on just breaking into it at an existing
socket, and then taking one wire to a new socket, and then joining the

two
sockets together to rejoin the ring).




A spur for a double ganged socket outlet should be wired from a ring main in 4 mm (or
bigger) cable
or, alternatively, continue the ring through the new socket, IMHO.

Professionals? - comment please ?

Nick



  #9   Report Post  
BigWallop
 
Posts: n/a
Default Consumer unit wiring

The consumer unit should have 16mm double insulated tails from the meter,
but yours has only got double insulated on the black phase and the red phase
is open to being more easily damaged and exposing the bare conductor. They
are all 16mm though, so are normal for this type of installation.

The fuse configuration I'd say is back to front, with the heaviest load
appliance (shower) being taken from the furthest point from the supply side
of the bus bar. This can cause lights to dim a bit more than they should
when the shower is switched on and off, and can also cause heating along the
full bus bar because all the heaviest use loads are furthest from the
supply.

Working from the switch, the first white cartridge is lighting and looks to
have a 1mm cable which is normal. The blue cartridge is for a heater of
some sort (water) and looks to have a 2.5mm cable, this to is normal. The
second white fuse is also lighting and looks to have 1mm, which again is
normal and a good idea to separate lighting over two supplies in case one
pops, you have the other as a sort of backup for safety.

The first red holder from the switch looks to be a ring circuit due the two
red 2.5mm cables going to it, which is normal. The second red fuse seems to
be a ring circuit as well, but also has a spur off to somewhere (?) because
it has three red 2.5mm cables connected. The last red connection has a 6mm
cable attached, by the look of it. For a load of around 7 or 8 killowatts
over a short length of cable, then this guage would probably take it without
complaining to much. But I would not chance going any higher in the Watts
rating on this, no matter how short a run this cable is. I'd say it is
safer to go with 10mm on a load over 8 kW and reduce the effect of any
possible heating totally and completely, and also gives a less resistive
path back to earth with the thicker conductor that is already supplied in
it. But then I always err' on the side of caution with these things.

I'd also say the earthing conductor, which currently looks like a 16mm
cable, is also quite normal for this type of installation, but I'd like to
be able to see where it is connected at the other end.

All in all, it is a normal installation for this size of dwelling, but as I
said in the first paragraph, I think it is back to front. Although others
will probably disagree with this idea.


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ARWadsworth
 
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Default Consumer unit wiring


"froggers" wrote in message
...
What I'm after really is an idea of the size of wiring I need to use

to
extend the ring (I'm planning on just breaking into it at an

existing
socket, and then taking one wire to a new socket, and then joining

the
two
sockets together to rejoin the ring).




A spur for a double ganged socket outlet should be wired from a ring main

in 4 mm (or
bigger) cable
or, alternatively, continue the ring through the new socket, IMHO.

Professionals? - comment please ?

Nick


A 2 gang socket can be run as a spur from a ring using 2.5 T&E, but the OP
is proposing to extend the ring not add spurs.

Adam




  #11   Report Post  
Chris Oates
 
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Default Consumer unit wiring


"froggers" wrote in message
...
What I'm after really is an idea of the size of wiring I need to use

to
extend the ring (I'm planning on just breaking into it at an

existing
socket, and then taking one wire to a new socket, and then joining

the
two
sockets together to rejoin the ring).



2.5mm


A spur for a double ganged socket outlet should be wired from a ring main

in 4 mm (or
bigger) cable
or, alternatively, continue the ring through the new socket, IMHO.


You could use 4mm but 2.5mm will do.
4mm would be needed for a radial circuit though.


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David Hearn
 
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Default Consumer unit wiring


"BigWallop" wrote in message
...
The consumer unit should have 16mm double insulated tails from the meter,
but yours has only got double insulated on the black phase and the red

phase
is open to being more easily damaged and exposing the bare conductor.

They
are all 16mm though, so are normal for this type of installation.


Erm - could you explain that a little simpler (I did do an Elec Eng degree
though - honest!). Is it the tails that's a problem, or the design of the
CU itself?

The fuse configuration I'd say is back to front, with the heaviest load
appliance (shower) being taken from the furthest point from the supply

side
of the bus bar. This can cause lights to dim a bit more than they should
when the shower is switched on and off, and can also cause heating along

the
full bus bar because all the heaviest use loads are furthest from the
supply.


The lights do dim/brighten when the shower is turned on/off - so that might
explain why its more noticable than I might have expected.

Working from the switch, the first white cartridge is lighting and looks

to
have a 1mm cable which is normal. The blue cartridge is for a heater of
some sort (water) and looks to have a 2.5mm cable, this to is normal. The
second white fuse is also lighting and looks to have 1mm, which again is
normal and a good idea to separate lighting over two supplies in case one
pops, you have the other as a sort of backup for safety.


The blue 16A MCB most certainly does the upstairs lighting - someone (when I
enquired about this before) wondered if someone had accidentally swapped the
lighting and the immersion heater over (which is fed from a single socket in
the airing cupboard). This is possible, and I will check this sometime by
plugging a light into that socket and turning off the 6A MCB and see if it
goes off (which is pretty much how I've worked out which circuit goes
where). This socket though used to be attached to the wall at some point in
history, now its lying on the bottom of the airing cupboard and rattles - so
I've avoided using it because a.) I've no idea what's inside (ie. conductive
or not conductive), b.) there's holes in the back of the socket which are
accessible and c.) We get plenty of water from our central heating! It's on
my job list of things to check out though!

Further (larger, less compressed) pictures of the CU can be found at:

http://www.swampie.ukfsn.org/ConsumerUnit1.jpg
http://www.swampie.ukfsn.org/ConsumerUnit2.jpg
http://www.swampie.ukfsn.org/ConsumerUnit3.jpg
http://www.swampie.ukfsn.org/meter.jpg

The first red holder from the switch looks to be a ring circuit due the

two
red 2.5mm cables going to it, which is normal. The second red fuse seems

to
be a ring circuit as well, but also has a spur off to somewhere (?)

because
it has three red 2.5mm cables connected.


This could either be a single socket, or maybe the feed to the garage (via a
FCU at the end of the kitchen).

The last red connection has a 6mm
cable attached, by the look of it. For a load of around 7 or 8 killowatts
over a short length of cable, then this guage would probably take it

without
complaining to much. But I would not chance going any higher in the Watts
rating on this, no matter how short a run this cable is. I'd say it is
safer to go with 10mm on a load over 8 kW and reduce the effect of any
possible heating totally and completely, and also gives a less resistive
path back to earth with the thicker conductor that is already supplied in
it. But then I always err' on the side of caution with these things.


That's fine - the shower is working fine at the moment and we've got no
plans to change it. It was more of a "I wonder..." type thought.

I'd also say the earthing conductor, which currently looks like a 16mm
cable, is also quite normal for this type of installation, but I'd like to
be able to see where it is connected at the other end.


http://www.swampie.ukfsn.org/earthing.jpg

All in all, it is a normal installation for this size of dwelling, but as

I
said in the first paragraph, I think it is back to front. Although others
will probably disagree with this idea.


Its an old-ish install in a 1930's semi. We've got no plans to replace the
CU (if we did replace it, I'd probably do it myself, but planning on doing
nothing other than just a new CU and swap circuits over (no plans on
rewiring etc - plenty of other jobs needed) - which probably isn't really
worth it - except maybe like to put RCD's onto the rings + shower (I know
about freezers being tripped!) ) I take it that it would just be a job of
putting a 2nd set of tails from the meter output (there's a few spare holes
to add some more tails) and wire it to a new CU. Then move a circuit across
at a time. Of course, remove the incoming main fuse first though!


So - can I expect that the immersion circuit and the upstairs lighting
circuits are the wrong way around? Should it be 2.5mm cable for the
immersion heater, and 1mm (or more) for the lighting? If the blue MCB has
1mm wiring and the white one has 2.5mm then its probably wired wrong, if
they've all got 1mm then I'm stuck. I guess its hard to see the difference
in the pictures (hence putting up uncompressed pictures).

And I'll drill through the joists to add my ring extension, using 2.5mm.

Thanks for your (and everyone else's) help.

D


  #13   Report Post  
BigWallop
 
Posts: n/a
Default Consumer unit wiring

The blue 16 amp definitely has 2.5mm connected to it. It is clear that the
cable connected to it a heavier guage than in the two white 6amp cartridges.


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