Hi,

I'm planning on building myself a large shed at the bottom of the garden. I
need to understand how I provide an electricity supply within regs.

I've broken my query down in to a few categories. I've check on the FAQ and
googled previous posts and not found quite what I'm after. I guess I'm
after some expert reassurance that I'm thinking along the right lines too.

My consumer unit is to the front of my house, and I've just got a new
driveway - so I need to avoid any digging to the side of the house, meaning
a section of the run will be internal, the rest will be 3 core SWA.

RCD:
I have a few options here, and I need to understand which is best..
a) Use existing RCD in consumer unit, put some breakers in shed
b) Install new RCD inside house via 30a breaker in existing consumer unit,
again breakers in shed
c) RCD and small consumer unit in shed with connection to a 30a breaker in
existing consumer unit


Cable:
As I need to run a section inside the house, I need to understand a) if this
is OK, or whether the SWA should run all the way to the fuse board, and b)
what cable size (as I want 30a supply over 30m I understand 6mm T&E is
required)?

Assuming I can do this, then can I run the T&E in to one of these
http://www.tlc-direct.co.uk/Products/LB9065.html mounted on the outside wall
to meet the SWA? Can I add a spur with an external socket at this point?

Where the SWA leaves the house I understand it needs to be protected.
What's the best way to do this?

I also understand that the depth at which the cable is run is fairly
discresionary. I'm thinking 20-30cm under the patio (patio yet to be laid),
then 50cm under the lawn.


Paperwork:
I've not done any electrical work since December 03, so I've no experience
with the new Part P regs. What testing and paperwork do I need to get done
so it's all legit? Are there any indicative/ball park costs?


Many thanks for your help...
Brett

Brett Jackson wrote:

I'm planning on building myself a large shed at the bottom of the
garden. I need to understand how I provide an electricity supply within
regs.

I've broken my query down in to a few categories. I've check on the FAQ
and googled previous posts and not found quite what I'm after. I guess
I'm after some expert reassurance that I'm thinking along the right
lines too.

Have you read through:

http://wiki.diyfaq.org.uk/index.php?...ricity_outside

If there are still bits unanswered then post about them here, and we can
update the document to add clarifications where required.

My consumer unit is to the front of my house, and I've just got a new
driveway - so I need to avoid any digging to the side of the house,
meaning a section of the run will be internal, the rest will be 3 core SWA.

Do you need 3 core? (two plus armour is usually enough)

RCD:
I have a few options here, and I need to understand which is best..
a) Use existing RCD in consumer unit, put some breakers in shed
b) Install new RCD inside house via 30a breaker in existing consumer
unit, again breakers in shed
c) RCD and small consumer unit in shed with connection to a 30a breaker
in existing consumer unit

See wiki article on this...

Cable:
As I need to run a section inside the house, I need to understand a) if
this is OK, or whether the SWA should run all the way to the fuse board,
and b) what cable size (as I want 30a supply over 30m I understand 6mm
T&E is required)?

You need to look at voltage drop for you maximum design current for the
whole length of the circuit - including allowing enough for the wiring
in the outbuilding.

Assuming I can do this, then can I run the T&E in to one of these
http://www.tlc-direct.co.uk/Products/LB9065.html mounted on the outside
wall to meet the SWA? Can I add a spur with an external socket at this
point?

Yes. A short section on conduit would probably be easiest and an
external socket. Note however doing this may limit your RCD positioning
choices. See the wiki section on design. You could also use a external
socket with integrated RCD see http://wiki.diyfaq.org.uk/index.php?title=RCD

Where the SWA leaves the house I understand it needs to be protected.
What's the best way to do this?

Protected in what way?

I also understand that the depth at which the cable is run is fairly
discresionary. I'm thinking 20-30cm under the patio (patio yet to be
laid), then 50cm under the lawn.

Under a patio there is little to no chance that it will be dug over.
Hence it can be quite shallow. Much the same probably applies under a
lawn etc. You need to use common sense and cable warning tape!

Paperwork:
I've not done any electrical work since December 03, so I've no
experience with the new Part P regs. What testing and paperwork do I
need to get done so it's all legit? Are there any indicative/ball park
costs?

You would have to speak to your building control department and ask. You
may need to argue your case since they ought not charge any more than
their normal building notice fee based on the commercial value of the
work being done. They should provide a completion certificate when done.



--
Cheers,

John.

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

Brett Jackson wrote:
snip

I have a few options here, and I need to understand which is best..
a) Use existing RCD in consumer unit, put some breakers in shed
b) Install new RCD inside house via 30a breaker in existing consumer
unit, again breakers in shed
c) RCD and small consumer unit in shed with connection to a 30a breaker
in existing consumer unit

I am no expert on this, but I would go for option c). That way, you can
keep the shed lighting on after a fault, if you wire them up before the
RCD. My house is wired up so that the lights go out when the RCD trips.
It's a PITA.

Dave

"John Rumm" wrote in message
...
Brett Jackson wrote:

I'm planning on building myself a large shed at the bottom of the garden.
I need to understand how I provide an electricity supply within regs.

I've broken my query down in to a few categories. I've check on the FAQ
and googled previous posts and not found quite what I'm after. I guess
I'm after some expert reassurance that I'm thinking along the right lines
too.

Have you read through:

http://wiki.diyfaq.org.uk/index.php?...ricity_outside

If there are still bits unanswered then post about them here, and we can
update the document to add clarifications where required.

No, but I will do. I had just seen the old FAQ before, the wiki is new to
me.


My consumer unit is to the front of my house, and I've just got a new
driveway - so I need to avoid any digging to the side of the house,
meaning a section of the run will be internal, the rest will be 3 core
SWA.

Do you need 3 core? (two plus armour is usually enough)

I've read that requirements may vary in different parts of the country! I
thought it best to be safe and go for 3 core. If 2 core is definately
sufficient then I'll use that.


RCD:
I have a few options here, and I need to understand which is best..
a) Use existing RCD in consumer unit, put some breakers in shed
b) Install new RCD inside house via 30a breaker in existing consumer
unit, again breakers in shed
c) RCD and small consumer unit in shed with connection to a 30a breaker
in existing consumer unit

See wiki article on this...

Cable:
As I need to run a section inside the house, I need to understand a) if
this is OK, or whether the SWA should run all the way to the fuse board,
and b) what cable size (as I want 30a supply over 30m I understand 6mm
T&E is required)?

You need to look at voltage drop for you maximum design current for the
whole length of the circuit - including allowing enough for the wiring in
the outbuilding.

I've measured the voltage in my house a few times before, it's consistently
been 248 volts (there's a substation 25m from my house). I calculated the
voltage drop on the TLC-direct web site and I'm well within the 230v +/-
10%.


Assuming I can do this, then can I run the T&E in to one of these
http://www.tlc-direct.co.uk/Products/LB9065.html mounted on the outside
wall to meet the SWA? Can I add a spur with an external socket at this
point?

Yes. A short section on conduit would probably be easiest and an external
socket. Note however doing this may limit your RCD positioning choices.
See the wiki section on design. You could also use a external socket with
integrated RCD see http://wiki.diyfaq.org.uk/index.php?title=RCD

Where the SWA leaves the house I understand it needs to be protected.
What's the best way to do this?

Protected in what way?

Sorry, I wasn't very clear. I was referring to the bit of SWA between the
junction box and the ground. I'm assuming it may need some extra protection
above ground?



I also understand that the depth at which the cable is run is fairly
discresionary. I'm thinking 20-30cm under the patio (patio yet to be
laid), then 50cm under the lawn.

Under a patio there is little to no chance that it will be dug over. Hence
it can be quite shallow. Much the same probably applies under a lawn etc.
You need to use common sense and cable warning tape!

Paperwork:
I've not done any electrical work since December 03, so I've no
experience with the new Part P regs. What testing and paperwork do I
need to get done so it's all legit? Are there any indicative/ball park
costs?

You would have to speak to your building control department and ask. You
may need to argue your case since they ought not charge any more than
their normal building notice fee based on the commercial value of the work
being done. They should provide a completion certificate when done.


Yes, I was looking at the way it's charged and it seems to depend on the
cost of the job as done by a professional. This would vary wildly based on
the amount of work falling outside the regs I did myself (e.g. dig trench,
clear route/drill holes for cabling internally etc). I imagine I could do
enough myself to get the cost of a professional down below £200, if not
less.



--
Cheers,

John.

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


Thanks for your help.
Brett

Brett Jackson wrote:

Have you read through:

http://wiki.diyfaq.org.uk/index.php?...ricity_outside

If there are still bits unanswered then post about them here, and we
can update the document to add clarifications where required.

No, but I will do. I had just seen the old FAQ before, the wiki is new
to me.

There is a fair bit of electrical stuff on there now. Much of it has
been peer reviewed by the more electrically oriented folks on the group,
so should be reasonably reliable by now - but if in doubt its worth
checking on the group.

I've read that requirements may vary in different parts of the country!
I thought it best to be safe and go for 3 core. If 2 core is definately
sufficient then I'll use that.

Two core should be fine for any size you are likely to need in a
domestic environment.


You need to look at voltage drop for you maximum design current for
the whole length of the circuit - including allowing enough for the
wiring in the outbuilding.

I've measured the voltage in my house a few times before, it's

The actual voltage at your house is not really relevant in this case.
You need to designed to keep your voltage *drop* at 4% of nominal supply
or less. That gives you 9.2V to play with.

So you mentioned 30m and a design load of 30A. So say you used 6mm^2
cable, that would be a drop of 7.9 mV/A/m = 0.0079 * 30 * 30 = 7.11V,
which is OK and leave a little for the wiring in the outbuilding.

consistently been 248 volts (there's a substation 25m from my house). I
calculated the voltage drop on the TLC-direct web site and I'm well
within the 230v +/- 10%.

The required limits on the supplier are actually 230V +10%/-4%

Where the SWA leaves the house I understand it needs to be protected.
What's the best way to do this?

Protected in what way?

Sorry, I wasn't very clear. I was referring to the bit of SWA between
the junction box and the ground. I'm assuming it may need some extra
protection above ground?

Not really, unless it is a in a place where it is likely to get hit
repeatedly. SWA is robust and not affected by UV exposure.

Yes, I was looking at the way it's charged and it seems to depend on the
cost of the job as done by a professional. This would vary wildly based
on the amount of work falling outside the regs I did myself (e.g. dig
trench, clear route/drill holes for cabling internally etc). I imagine
I could do enough myself to get the cost of a professional down below
£200, if not less.

Sounds a bit on the low side - you will probably spend a good proportion
of that on materials even if you DIY the whole job.

--
Cheers,

John.

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

"Brett Jackson" wrote in message
...

"John Rumm" wrote in message
...
Brett Jackson wrote:

I'm planning on building myself a large shed at the bottom of the
garden. I need to understand how I provide an electricity supply within
regs.

I've broken my query down in to a few categories. I've check on the FAQ
and googled previous posts and not found quite what I'm after. I guess
I'm after some expert reassurance that I'm thinking along the right
lines too.

Have you read through:

http://wiki.diyfaq.org.uk/index.php?...ricity_outside

If there are still bits unanswered then post about them here, and we can
update the document to add clarifications where required.

No, but I will do. I had just seen the old FAQ before, the wiki is new to
me.


My consumer unit is to the front of my house, and I've just got a new
driveway - so I need to avoid any digging to the side of the house,
meaning a section of the run will be internal, the rest will be 3 core
SWA.

Do you need 3 core? (two plus armour is usually enough)

I've read that requirements may vary in different parts of the country! I
thought it best to be safe and go for 3 core. If 2 core is definately
sufficient then I'll use that.

Not explicitly mentioned in your OP or in any reply though it is in the
wiki, is earthing, which is a big topic in itself. The 2 or 3 core debate
has run before, 2 core with the armour as an exported earth or 3 core using
a core as an exported earth. Not getting into that argument right now but
when I ran my shed cable I did as you suggested and used a junction box,
possibly the very same TLC box to transition from T/E to SWA. If I did the
job again I would run SWA all the way to the consumer unit to eliminate an
unecessary outdoors connection. Yes as the wiki points out the SWA is a bit
unweildy but less so stripped back.

If you particularly want an outside socket at the junction box you could run
an exterior RCD socket as a spur from a ring.

Jim A

On Sun, 14 Oct 2007 19:24:53 +0100 someone who may be "Brett
Jackson" wrote this:-

Do you need 3 core? (two plus armour is usually enough)

I've read that requirements may vary in different parts of the country! I
thought it best to be safe and go for 3 core. If 2 core is definately
sufficient then I'll use that.

Take a look at the electricity supply to buildings you know. If they
are in towns then it is highly likely that it will consist of a
cable with one or two cores and armour (providing the protective
conductor function). If there is only one core then the neutral and
protective conductor are combined, which is not something you should
experiment with inside a building (it is something for those who
know what they are doing and there are a number of strict
regulations for installing such wiring inside buildings).

I don't suggest that you (or anyone else) dismantle the supply cable
termination in such buildings, but that is what you would find if
you did. If you looked in a library you could probably find a book
with drawings/photographs of what is inside. There may even be
something on this new-fangled Interweb thingy.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"John Rumm" wrote in message
...
Brett Jackson wrote:

Have you read through:

http://wiki.diyfaq.org.uk/index.php?...ricity_outside

If there are still bits unanswered then post about them here, and we can
update the document to add clarifications where required.

No, but I will do. I had just seen the old FAQ before, the wiki is new
to me.

There is a fair bit of electrical stuff on there now. Much of it has been
peer reviewed by the more electrically oriented folks on the group, so
should be reasonably reliable by now - but if in doubt its worth checking
on the group.

I've read that requirements may vary in different parts of the country!
I thought it best to be safe and go for 3 core. If 2 core is definately
sufficient then I'll use that.

Two core should be fine for any size you are likely to need in a domestic
environment.


You need to look at voltage drop for you maximum design current for the
whole length of the circuit - including allowing enough for the wiring
in the outbuilding.

I've measured the voltage in my house a few times before, it's

The actual voltage at your house is not really relevant in this case. You
need to designed to keep your voltage *drop* at 4% of nominal supply or
less. That gives you 9.2V to play with.

So you mentioned 30m and a design load of 30A. So say you used 6mm^2
cable, that would be a drop of 7.9 mV/A/m = 0.0079 * 30 * 30 = 7.11V,
which is OK and leave a little for the wiring in the outbuilding.

consistently been 248 volts (there's a substation 25m from my house). I
calculated the voltage drop on the TLC-direct web site and I'm well
within the 230v +/- 10%.

The required limits on the supplier are actually 230V +10%/-4%

Where the SWA leaves the house I understand it needs to be protected.
What's the best way to do this?

Protected in what way?

Sorry, I wasn't very clear. I was referring to the bit of SWA between
the junction box and the ground. I'm assuming it may need some extra
protection above ground?

Not really, unless it is a in a place where it is likely to get hit
repeatedly. SWA is robust and not affected by UV exposure.

Yes, I was looking at the way it's charged and it seems to depend on the
cost of the job as done by a professional. This would vary wildly based
on the amount of work falling outside the regs I did myself (e.g. dig
trench, clear route/drill holes for cabling internally etc). I imagine I
could do enough myself to get the cost of a professional down below £200,
if not less.

Sounds a bit on the low side - you will probably spend a good proportion
of that on materials even if you DIY the whole job.

--
Cheers,

John.

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

Thanks all (esp. John) for your help.

Just one remaining question now...

I need to run some T&E under the stairs between the hall and kitchen. The
difficulty is that it's an external cupboard (old coal storage I think).

Do I need to run the T&E through trunking inside the cupboard, or is it
sufficient to use cable clips?


I appreciate I could use SWA all the way, but I have some fairly intricate
bends in the kitchen that I'm going to struggle getting the 6mm T&E through.


Brett

Brett Jackson wrote:

Just one remaining question now...

I need to run some T&E under the stairs between the hall and kitchen.
The difficulty is that it's an external cupboard (old coal storage I
think).

Do I need to run the T&E through trunking inside the cupboard, or is it
sufficient to use cable clips?

Well ask yourself if it needs extra protection.... If it is not going to
be exposed to sunlight, and its not going to be physically knocked or
otherwise abused then it ought to be ok clipped to the surface.


--
Cheers,

John.

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

On 14 Oct, 13:10, "Brett Jackson" wrote:
Hi,

I'm planning on building myself a large shed at the bottom of the garden. I
need to understand how I provide an electricity supply within regs.

in addition to other posters' advice, take a look at

http://www2.theiet.org/Publish/WireR...s_outdoors.pdf

This is from issue 16/summer 2005 of Wiring Matters, an advice leaflet
issued by the IEE as was - now the IET - every few months. They are
all easily readable, or perhaps I mean that if you find they don't
mean a thing to you then you might do infinitely better asking someone
else to do the job for you. But your post doesn't read like that ;-)
bash on!

It is quite possible you will pick up on several other relevant
aspects by looking at articles in other issues.

HTH

"Jim Alexander" wrote in
.uk:

... If I did the job
again I would run SWA all the way to the consumer unit to
eliminate an unecessary outdoors connection...

Indeed. That's what the contractor who did the electrical work for me
on my (almost finished, honest!) last renovation, ie our current
house. The sub-main to the shed was taken in SWA cable from the
existing consumer unit just inside the front door, through the
external wall by the front door, a short distance along the front of
the house (under the front step, which was being replaced in stone at
the time), back into the house and under a suspended floor, then into
a channel cut in the concrete floor at the rear of the house, out by
the back door, then (simplifying a little...) down the garden to a 4
way consumer unit in the shed.

Apart from the well-known unpleasantness of using an angle grinder
indoors when cutting the channel in the concrete floor, generally it
was pretty straightforward, if hard work.

Kind regards

--
Richard Perkin
To email me, change the AT in the address below
richard.perkinATmyrealbox.com

It's is not, it isn't ain't, and it's it's, not its, if you mean it
is. If you don't, it's its. Then too, it's hers. It isn't her's.
It isn't our's either. It's ours, and likewise yours and theirs.
-- Oxford University Press, Edpress News

"jim" wrote in message
ups.com...
On 14 Oct, 13:10, "Brett Jackson" wrote:
Hi,

I'm planning on building myself a large shed at the bottom of the garden.
I
need to understand how I provide an electricity supply within regs.

in addition to other posters' advice, take a look at

http://www2.theiet.org/Publish/WireR...s_outdoors.pdf

This is from issue 16/summer 2005 of Wiring Matters, an advice leaflet
issued by the IEE as was - now the IET - every few months. They are
all easily readable, or perhaps I mean that if you find they don't
mean a thing to you then you might do infinitely better asking someone
else to do the job for you. But your post doesn't read like that ;-)
bash on!

It is quite possible you will pick up on several other relevant
aspects by looking at articles in other issues.

HTH


That looks like a useful source of info, thanks.

I think I have just about everything I need now. Last remaining uncertainty
is how I run the cable behind the skirting in my hall - looks like inside
steel conduit is the only acceptable way...


Brett

Brett Jackson wrote:

I think I have just about everything I need now. Last remaining
uncertainty is how I run the cable behind the skirting in my hall -
looks like inside steel conduit is the only acceptable way...

Yup, behind skirting is not a recognised route. You could opt for deep
burial 50mm from either side, or you could find an alternative route
like up a corner and along just below ceiling level etc.

If there is an outside wall, another option is to drill through to the
outside and run SWA clipped direct to the outside.

Channel in the floor is another option (solid floor), or under if its a
suspended one.

--
Cheers,

John.

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