I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?
--
Mark Roberts

"mark" wrote in message
...
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?

Mark Roberts


Proper earth rods are only a metre in length, or there abouts, and you need to
join them together with the right kit. You also need to buy a driving stud that
screws on the end of the rod, so the hammering doesn't damage the thread of the
screwed end of the rod.

What were you thinking using instead?

"mark" wrote in message
...
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?

Mark Roberts


Found a link to a .PDF file that shows what proper earth ground rods look like
for you. You'll need a .PDF reader for the pages.

The link: http://www.keison.co.uk/furse/pdf/ea...thing_rods.pdf

mark wrote:
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.

And probably not much good either IME.

I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?

"Ufer grounds" are used in the USA (Google for the phrase) but they
don't seem common over here.

Burying several meters of copper pipe to mimic the old water main earth?

At my place, the ground is so rocky that even if you can get an earth
rod in, the resistance is too high to be useful. The water main is the
only effective earth connection.

If you bury a pipe to mimic a water main, it should be below the frost
line (just like a real one) because the resistance rises considerably
when the groundwater freezes.


--
Ian White

In message , BigWallop
writes

"mark" wrote in message
...
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?

Mark Roberts


Found a link to a .PDF file that shows what proper earth ground rods look like
for you. You'll need a .PDF reader for the pages.

The link: http://www.keison.co.uk/furse/pdf/ea...thing_rods.pdf


Thats very helpful.
But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.
I need more contact if you see what I mean with as much ground as
possible.
I'm sure there's a knowledgeable person somewhere who knows more about
this than I do.

--
Mark Roberts

"mark" wrote in message
...
Thats very helpful.
But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.
I need more contact if you see what I mean with as much ground as
possible.


Dig a pond and throw the wire in ?

In message , Mike
writes

"mark" wrote in message
...
Thats very helpful.
But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.
I need more contact if you see what I mean with as much ground as
possible.


Dig a pond and throw the wire in ?




I'd have to line it, how conductive is butyl?
--
Mark Roberts

On Tue, 17 May 2005 23:51:54 +0100, mark
wrote:

But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.

There's a US army kit perfect for installing such things. It involves a
shaped charge to blow a hole in any surface crust or concrete, then a
downwards-pointing rocket motor to drive the earth rod (or anything you
might like) deep under the surface.

I've only seen one of these things in the flesh, and they wouldn't let
me push the button 8-(

"mark" wrote in message
...
In message , BigWallop
writes

"mark" wrote in message
...
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?

Mark Roberts


Found a link to a .PDF file that shows what proper earth ground rods look
like
for you. You'll need a .PDF reader for the pages.

The link: http://www.keison.co.uk/furse/pdf/ea...thing_rods.pdf


Thats very helpful.
But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.
I need more contact if you see what I mean with as much ground as
possible.
I'm sure there's a knowledgeable person somewhere who knows more about
this than I do.


Mark Roberts


I'm sure if you go deep enough, three, four or five rods deep, you'll get
somewhere close to a proper earth ground connection. :-)

You can also use a ground plate to make a good earth ground source. Scrape the
top layers off, maybe two or three feet down, and lay in a steel plate to
connect the earth terminals to. Then fill it back over. A plate of four or
five foot square would probably be enough. Any scrap yards near you? Old flat
steel plate of something close to a half inch thick is what you want.

Or you could go with two or three rod sites to spread the load around them. You
have to use at least 25 mm csa' conductors to bond these sites together though.

(csa' = cross sectional area)

"Andy Dingley" wrote in message
...
On Tue, 17 May 2005 23:51:54 +0100, mark
wrote:

But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.

There's a US army kit perfect for installing such things. It involves a
shaped charge to blow a hole in any surface crust or concrete, then a
downwards-pointing rocket motor to drive the earth rod (or anything you
might like) deep under the surface.

I've only seen one of these things in the flesh, and they wouldn't let
me push the button 8-(


Sounds like a very handy kit. Where can I obtain them? :-)

In message , BigWallop
writes

"Andy Dingley" wrote in message
.. .
On Tue, 17 May 2005 23:51:54 +0100, mark
wrote:

But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.

There's a US army kit perfect for installing such things. It involves a
shaped charge to blow a hole in any surface crust or concrete, then a
downwards-pointing rocket motor to drive the earth rod (or anything you
might like) deep under the surface.

I've only seen one of these things in the flesh, and they wouldn't let
me push the button 8-(


Sounds like a very handy kit. Where can I obtain them? :-)


Ebay ? :-)
--
Chris French

"chris French" wrote in message
...
In message , BigWallop
writes

"Andy Dingley" wrote in message
.. .
On Tue, 17 May 2005 23:51:54 +0100, mark
wrote:

But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.

There's a US army kit perfect for installing such things. It involves a
shaped charge to blow a hole in any surface crust or concrete, then a
downwards-pointing rocket motor to drive the earth rod (or anything you
might like) deep under the surface.

I've only seen one of these things in the flesh, and they wouldn't let
me push the button 8-(


Sounds like a very handy kit. Where can I obtain them? :-)


Ebay ? :-)

Chris French


Got one on a Buy it Now, and the postage was free all the way from Iraq. The
sellers name was Sunny Shi'ite or somethin' like that. Brilliant!!! Everybody
should have one.

ROFLMAO!!!!

In message ,
mark wrote:

I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.

Just as a thought, do you *have* to install an earth rod? If the shed is
close enough to the house and you use thick enough wire you could quite
safely "export" the house earth under most circumstances, but it's a
function of impedance/distance etc.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Is this yours? Your dog left it on my lawn ...

mark wrote:
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?

[...]
But the problem is the rocky ground. A lot is made up ground and the
rest is shaley dry stuff. It's not the best stuff in the world for
conductivity.

Cancel my previous - if it's only made ground and "shaley dry stuff ",
you have a very good chance of sinking 1m rods using a 1000x10mm or
1000x12mm SDS bit to drill a pilot hole. The reason for recommending
drilling first is that it can easily break up stones that would stop an
earth rod if you simply tried to hammer it.

For driving the rod, use the SDS drill with rotary stop, and a 0.5in
square drive adapter. An appropriate sized socket will keep it centred
on the rod. This works *much* better than just 'itting it wiv an 'ammer.

However, the earth rod is typically 1.2 m long while the drill bit is
only 1.0m... so for that last 0.2m you're on your own. Be prepared to
cut your losses using an angle grinder.

If you feel the drill bit breaking up significant amounts of hard stuff
down to 1.0m, then you've no chance of being able to sink a
double-length rod. The only exception might be if you're going to break
through into softer, rock-free ground (eg if it's a layer of made ground
covering clean, soft clay).

I need more contact if you see what I mean with as much ground as
possible.

As much *wet* ground as possible, you mean. With really rocky ground, it
can actually get drier further down, with most of the groundwater
flowing in the looser top layers.

If that is the case for you, you would get a better earth connection
from two 1.2m rods than by making heroic efforts to sink a whole 2.4m.
(Space the 1.2m rods at least 2.4m apart, or else you'll not get full
benefit.) Better still, go horizontal as you yourself suggested.

In the end, it all depends on exactly where *your* groundwater is.



--
Ian White

In message , Martin Angove
writes
In message ,
mark wrote:

I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.

Just as a thought, do you *have* to install an earth rod? If the shed is
close enough to the house and you use thick enough wire you could quite
safely "export" the house earth under most circumstances, but it's a
function of impedance/distance etc.

You might be right there.
There is 12m of 25mm diameter armoured cable.
I guess if I clamp the armour in a brass gland in the steel consumer
unit box in the house and do the same at the shed (also a steel consumer
unit) it would suffice.
Would testing the earth; by seeing if an RCD works when connected in the
shed, prove the earth is sufficient?


--
Mark Roberts

Ian White wrote:

For driving the rod, use the SDS drill with rotary stop, and a 0.5in
square drive adapter. An appropriate sized socket will keep it centred
on the rod. This works *much* better than just 'itting it wiv an 'ammer.

Now that is a good idea! (I need to stick a rod in tommorow...)

Don't spose you know any good tips for making really sure you don't
stick it through either the gas or water mains?


--
Cheers,

John.

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

In message ,
mark wrote:

In message , Martin Angove
writes
In message ,
mark wrote:

I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.

Just as a thought, do you *have* to install an earth rod? If the shed is
close enough to the house and you use thick enough wire you could quite
safely "export" the house earth under most circumstances, but it's a
function of impedance/distance etc.

You might be right there.
There is 12m of 25mm diameter armoured cable.
I guess if I clamp the armour in a brass gland in the steel consumer
unit box in the house and do the same at the shed (also a steel consumer
unit) it would suffice.
Would testing the earth; by seeing if an RCD works when connected in the
shed, prove the earth is sufficient?


No, because testing the RCD doesn't test the earth at all. Most RCDs
don't even have an earth connection. A good first step is to do a few
calculations (see below). Testing with the proper gear is a good second
step. Getting it all certified as per Part P is the finishing touch.
(Usual disclaimer; you do realise that all outdoor work / new circuit
work now comes under Part P and should be notified to Building Control
before work is started?)

25mm diameter armoured cable is what csa per conductor? How many
conductors of what cross sectional area is the important question. 12m
doesn't sound too far to me, so long as the cable is chunky enough -
let's face it, there are likely to be circuits in your house with longer
runs than that. What earthing system does your house have? What size and
type is the protective device at the house end (i.e. fuse or MCB)? What
sort of distribution will you have at the shed (fuses/MCBs etc.)? To
what uses will the supply in the shed be put?

As for the actual earth connection, if it's two-core SWA and you are
using the armour as earth (easier to use 3-core) then you need to use
the proper glands and if you can't guarantee that the boxes are properly
connected to earth at each end (metal consumer units should be, but
worth checking) you'd be as well putting in a chunky wire too, connected
to a tag on the cable.

HTH

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... I am Popeye of Borg. Prepare to be askimilgrated.

John Rumm wrote:
Ian White wrote:

For driving the rod, use the SDS drill with rotary stop, and a 0.5in
square drive adapter. An appropriate sized socket will keep it centred
on the rod. This works *much* better than just 'itting it wiv an 'ammer.

Now that is a good idea! (I need to stick a rod in tommorow...)

Don't spose you know any good tips for making really sure you don't
stick it through either the gas or water mains?

Well, it is "tomorrow" now. Probably by the time you read this, it'll be
all over...

If we were talking about the main service earth spike on a TT system,
then that's a very good point, because in many cases all the services
tend to come in pretty close together.

And don't forget the sewer pipes and any soakaway drains.


--
Ian White

Ian White wrote:

Well, it is "tomorrow" now. Probably by the time you read this, it'll be
all over...

It would be if only it would stop peeing down for long enough for me and
my trusty SDS to venture out ;-)

If we were talking about the main service earth spike on a TT system,

yup

then that's a very good point, because in many cases all the services
tend to come in pretty close together.

yup!

Gas main rises right about level with the meter cupboard. One might
presume that it is safe to sink it behind this point, however a slight
concern is the neighbouring propery has a similar rising main a few feet
further back. Hence the question: how likely is it that they would feed
a pipe to ours, tee upward, carry on for a bit then turn right and head
over to the neighbours!

Water maiun must go past - but that is probably only half inch so a
smaller target!

And don't forget the sewer pipes and any soakaway drains.

I think I am clear of those in the intended position (although they
become more of an issue if I try to avoid the other services by going
further away)


--
Cheers,

John.

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

Martin Angove wrote:

Testing with the proper gear is a good second step.

In the absence of a fancy earth tester[1], the following simple DIY
procedure that I've posted a couple of times before will give results of
entirely adequate accuracy:

[Repost from 20/04/1998, Message-ID: 01bd6c2d$0cd8b9e0$LocalHost@dog40]
Anyone with a bit of electrical common sense, knowledge of Ohm's law,
and a decent multimeter can measure earth electrode resistance quite
easily. You need to isolate the electrode in question and then find a
way of getting some current to flow into it. A safe way to do this is
to use a double-wound mains transformer with a secondary voltage of
around 24 (exact value not critical). Connect one end of the secondary
via a suitable length of wire to the main earth terminal in the house
and connect the other end to your earth electrode via an ammeter.

Energise the primary of the transformer, and the secondary current which
flows will immediately give you a rough idea of the total resistance in
the circuit, most of which will be attributable to your electrode. For
a more accurate result, drive a second temporary earth electrode (a 2ft
offcut of 15mm water pipe will do) into the ground at a distance of 10m
or more from the one you're measuring. Then use the meter on volts to
measure the voltage drop between the two electrodes. Dividing this
figure by the electrode current measured earlier gives you the earth
resistance. (Reactance in the circuit will be negligible.) Move the
temporary reference electrode to a second position and repeat. Average
the two values obtained, but if they are significantly different, try
further positions for the reference electrode.


[1] Not to be confused with a loop tester for measuring earth fault loop
impedance, which *is* an indispensable piece of kit.

--
Andy

In article ,
mark wrote:
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?

Export the house earth using suitable cable? Ie perhaps 16mm?

--
*I feel like I'm diagonally parked in a parallel universe.

Dave Plowman London SW
To e-mail, change noise into sound.

In message ,
Andy Wade wrote:

Martin Angove wrote:

Testing with the proper gear is a good second step.

In the absence of a fancy earth tester[1], the following simple DIY
procedure that I've posted a couple of times before will give results of
entirely adequate accuracy:

[...]

I wasn't talking about testing an earth rod, I was talking about working
out if it was possible to export the house earth rather than having to
install a rod.


[1] Not to be confused with a loop tester for measuring earth fault loop
impedance, which *is* an indispensable piece of kit.


For which job a loop impedance tester would be extremely useful :-)

Interesting procedure of yours though; I'll hang on to that post.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Hard work never killed anyone but why take a risk?

In message , Huge
writes
"Dave Plowman (News)" writes:
In article ,
mark wrote:
I need to install an earth rod for an outhouse.
The ground is seriously rocky and getting an 8' rod into the ground is
not going to be easy.
I seem to remember reading that reinforcing bars in concrete provide a
pretty good earth, this would be a lot easier to achieve than drilling
an 8' hole in the ground.
Would several shorter rods wired together be sufficient?
Burying several meters of copper pipe to mimic the old water main earth?

Export the house earth

Not allowed under all circumstances.

OK folks. Thanks for the advice.
The shed (stone outbuilding build into an earth bank) itself was
originally very damp indeed. The single socket and light bulb in there
used to run form an old wylex board and this was earthed via the steel
armour of the 25mm swa running to the shed.

I have since demolished the old shed and rebuilt it to the same
dimensions, reusing the old stone to reproduce the outward appearance.
Internally its block built with dpm, drainage & insulation pipes to keep
it all dry and snug.
Because the cable was buried under things I don't want to dig up putting
a new cable in or adding a new earth cable was not an option I wanted to
use.
I was a little worried about using the armour for an earth as I hadn't
come across it before. Asking a few electricians came up with some very
different answers from what I've read here.
I have now decided to use the swa as an earth (only 12m long) but I will
be adding shrouds and washers with tags to bolt short lengths of heavy
earth cable connected to the earth bars on the CU's at each end.
No earth spike.
Previously at the house end the swa was relying on the brass glands
connection via the painted steel consumer box and the bolt holding the
earth bar onto the box for the earth path. No attempt at removing paint
though.
At the shed end the armour had been manipulated so that it occupied
several different screw down terminals on the earth bar of the wylex
box.

Anyways Ta very much

I will of course be ensuring that my Part P capable professionally
qualified person will be doing the job right.



--
Mark Roberts

In message ,
(Huge) wrote:

Martin Angove writes:
In message ,
Andy Wade wrote:

Martin Angove wrote:

Testing with the proper gear is a good second step.

In the absence of a fancy earth tester[1], the following simple DIY
procedure that I've posted a couple of times before will give results of
entirely adequate accuracy:

[...]

I wasn't talking about testing an earth rod, I was talking about working
out if it was possible to export the house earth rather than having to
install a rod.

If you have PME, it is not permitted to export the house earth. Outbuildings
must have their own.

Huh?

Sorry, not met that one before. Can you point me in the direction of the
appropriate regulation?

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... I'm leaving my body to science fiction.

In article ,
Huge wrote:
I wasn't talking about testing an earth rod, I was talking about
working out if it was possible to export the house earth rather than
having to install a rod.

If you have PME, it is not permitted to export the house earth.
Outbuildings must have their own.

OK. But in my ignorance I'd say exporting the house earth with a suitable
cable - even 2000 mm might just work.

--
*Confession is good for the soul, but bad for your career.

Dave Plowman London SW
To e-mail, change noise into sound.

In message ,
"Dave Plowman (News)" wrote:

In article ,
Huge wrote:
I wasn't talking about testing an earth rod, I was talking about
working out if it was possible to export the house earth rather than
having to install a rod.

If you have PME, it is not permitted to export the house earth.
Outbuildings must have their own.

OK. But in my ignorance I'd say exporting the house earth with a suitable
cable - even 2000 mm might just work.

I still don't know where Huge has this idea from. I can see how the
logic *might* work, but I'm blowed if I can find any reference to it in
the regulations or in the OSG.

But it's been less than two days since he posted so I'm going to give
him a bit longer to respond :-)

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... See that Abacus, That's your hard drive that is.

Huge wrote:

If you have PME, it is not permitted to export the house earth. Outbuildings
must have their own.

That is not the case. This is a matter at the designer's discretion,
the main criterion being the feasibility of implementing an
equipotential zone in the outbuilding in question.

--
Andy

Martin Angove wrote:

I wasn't talking about testing an earth rod, I was talking about working
out if it was possible to export the house earth rather than having to
install a rod.

Sorry, perhaps I got a bit lost there, but ISTM that you were talking
about "testing the earth" after pointing out to someone that the RCD
test button only tests the RCD's internal operation, not the earthing.

--
Andy

In message ,
Andy Wade wrote:

Martin Angove wrote:

I wasn't talking about testing an earth rod, I was talking about working
out if it was possible to export the house earth rather than having to
install a rod.

Sorry, perhaps I got a bit lost there, but ISTM that you were talking
about "testing the earth" after pointing out to someone that the RCD
test button only tests the RCD's internal operation, not the earthing.


Shows the dangers of not being absolutely precise in a text-only forum,
eh? The way I read the post it went like this (paraphrased, obviously!):

OP said: I need to install an earth rod.

I said: Have you thought about exporting the house earth?

OP said: You might be right. Could I make the connections and then test
it using the RCD test button?

I said: No, you'd need to do the calculations and then test using the
proper equipment.

Never mind. I still haven't worked out exactly what sort of SWA (i.e.
csa) the OP has for the job, nor what earthing system his house has, so
this is all a bit academic really.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... 'Windows'. wipes away those stubborn BBS's !

In message , Martin Angove
writes
Never mind. I still haven't worked out exactly what sort of SWA (i.e.
csa) the OP has for the job, nor what earthing system his house has, so
this is all a bit academic really.

2 cores of multi-stranded copper about 5mm diameter. Spiral strands of
steel wire as armour making a cable that is about 25mm diameter total.
The house has an earth that is a big yellow and green cable from the
earth bar in the CU connected to a strap on earth connector on the main
cable coming into the house.
--
Mark Roberts

Martin Angove wrote:

Shows the dangers of not being absolutely precise in a text-only forum,
eh? The way I read the post it went like this (paraphrased, obviously!):

OP said: I need to install an earth rod.

I said: Have you thought about exporting the house earth?

OP said: You might be right. Could I make the connections and then test
it using the RCD test button?

I said: No, you'd need to do the calculations and then test using the
proper equipment.

OK - makes sense when you put it that way. I think I've been sampling
the group at somewhat less then the Nyquist rate lately...

--
Andy

mark wrote:

2 cores of multi-stranded copper about 5mm diameter. Spiral strands of
steel wire as armour making a cable that is about 25mm diameter total.

2-core SWA (to BS 5467), if really 25mm o/d, would be 50mm^2 CSA, which
seems a little excessive. Perhaps you're over-stating the o/d a bit
(easily done). An accurate o/d measurement with vernier callipers is
needed to identify the size - although you may find this embossed on the
sheath [1] along with manufacturer's name, year of manufacture, BASEC
approval and British Standard number.

The house has an earth that is a big yellow and green cable from the
earth bar in the CU connected to a strap on earth connector on the main
cable coming into the house.

TN-S.


[1] Usually in a format like 2 x 16.0 (i.e. no. of cores x CSA in mm^2).

--
Andy

"Andy Wade" wrote in message
...
mark wrote:

2 cores of multi-stranded copper about 5mm diameter. Spiral strands of
steel wire as armour making a cable that is about 25mm diameter total.

2-core SWA (to BS 5467), if really 25mm o/d, would be 50mm^2 CSA, which
seems a little excessive. Perhaps you're over-stating the o/d a bit
(easily done). An accurate o/d measurement with vernier callipers is
needed to identify the size - although you may find this embossed on the
sheath [1] along with manufacturer's name, year of manufacture, BASEC
approval and British Standard number.

I read the post as 25mm OD over the outer PVC sheath which without taking
detail from a cable chart I would have guessed at about 6 to 10 mm^2
conductors, maybe at a maximum 16? Bigger sizes may be involved if shaped
conductors are involved.

The house has an earth that is a big yellow and green cable from the
earth bar in the CU connected to a strap on earth connector on the main
cable coming into the house.

TN-S.

Andy Wade wrote:

OK - makes sense when you put it that way. I think I've been sampling
the group at somewhat less then the Nyquist rate lately...

or was it your alias? ;-)


--
Cheers,

John.

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

John wrote:

I read the post as 25mm OD over the outer PVC sheath which without taking
detail from a cable chart I would have guessed at about 6 to 10 mm^2
conductors, maybe at a maximum 16?

According to the Pirelli data sheet for 2-core XLPE SWA to BS 5467 the
o/d's are as follows:

CSA O/D
mm^2 mm
--- ----
1.5 11.5
2.5 12.9
4 14.4
6 15.6
10 16.8
16 19.6
25 20.9
35 23.0
50 25.3

[... continues to 400mm^2, 54.7 mm o/d, beyond most DIY requirements :-)]

Bigger sizes may be involved if shaped
conductors are involved.

Shaped conductors come in from (and including) 25mm^2, IIRC.

--
Andy

In message , Andy Wade
writes
mark wrote:

2 cores of multi-stranded copper about 5mm diameter. Spiral strands
of steel wire as armour making a cable that is about 25mm diameter
total.

2-core SWA (to BS 5467), if really 25mm o/d, would be 50mm^2 CSA, which
seems a little excessive. Perhaps you're over-stating the o/d a bit
(easily done). An accurate o/d measurement with vernier callipers is
needed to identify the size - although you may find this embossed on
the sheath [1] along with manufacturer's name, year of manufacture,
BASEC approval and British Standard number.

It may well be excessive. I put the thin in 15 years ago when we moved
here as I had a huge drum of it

Still have.

The house has an earth that is a big yellow and green cable from the
earth bar in the CU connected to a strap on earth connector on the
main cable coming into the house.

TN-S.


[1] Usually in a format like 2 x 16.0 (i.e. no. of cores x CSA in mm^2).


--
Mark Roberts

In message , Andy Wade
writes
John wrote:

I read the post as 25mm OD over the outer PVC sheath which without
taking detail from a cable chart I would have guessed at about 6 to
10 mm^2 conductors, maybe at a maximum 16?

According to the Pirelli data sheet for 2-core XLPE SWA to BS 5467 the
o/d's are as follows:

CSA O/D
mm^2 mm
--- ----
1.5 11.5
2.5 12.9
4 14.4
6 15.6
10 16.8
16 19.6
25 20.9
35 23.0
50 25.3

[... continues to 400mm^2, 54.7 mm o/d, beyond most DIY requirements :-)]

Bigger sizes may be involved if shaped
conductors are involved.

Shaped conductors come in from (and including) 25mm^2, IIRC.


Http://www.tlc-direct.co.uk/Products/SW16slash2.html

and according to my vernier it is 21.9mm .
The drum was not new when I got it so it could well be just PVC cable
(rather than this thermo setting stuff)
According to my maths it must be 16mm csa as the cores are made up of
strands that altogether are about 5mm across.




--
Mark Roberts

mark wrote:

and according to my vernier it is 21.9mm .
The drum was not new when I got it so it could well be just PVC cable
(rather than this thermo setting stuff)
According to my maths it must be 16mm csa as the cores are made up of
strands that altogether are about 5mm across.

Yes 21.9 mm o/d agrees exactly with a table I've got for 16mm^2 2-core
PVC insulated SWA to BS 6346. (And the TLC site is in error for not
having updated the dimension after the change to XLPE.)

In which case the armour CSA is 46 mm^2 and the armour resistance at 20
degC is 3.5 milliohm/m. Someone else can do the design calculations
this time...

--
Andy

In message ,
Andy Wade wrote:

mark wrote:

and according to my vernier it is 21.9mm .
The drum was not new when I got it so it could well be just PVC cable
(rather than this thermo setting stuff)
According to my maths it must be 16mm csa as the cores are made up of
strands that altogether are about 5mm across.

Yes 21.9 mm o/d agrees exactly with a table I've got for 16mm^2 2-core
PVC insulated SWA to BS 6346. (And the TLC site is in error for not
having updated the dimension after the change to XLPE.)

In which case the armour CSA is 46 mm^2 and the armour resistance at 20
degC is 3.5 milliohm/m. Someone else can do the design calculations
this time...


So to summarise what we know so far, the OP has:

TN-S earthing

A metal-cased CU at the house

Device protecting SWA to shed not known (type, rating)

12 meters of 16mm2 SWA.

Unknown CU at shed

Unknown circuits at shed end, though implied small loads.

I would have thought that that spec of cable is going to be fine in
terms of both loop impedance and voltage drop but I don't have time to
work on the details right now :-)

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Don't drink and park, accidents cause people

Martin Angove wrote:

So to summarise what we know so far, the OP has:
TN-S earthing
A metal-cased CU at the house
Device protecting SWA to shed not known (type, rating)
12 meters of 16mm2 SWA.
Unknown CU at shed
Unknown circuits at shed end, though implied small loads.

I would have thought that that spec of cable is going to be fine in
terms of both loop impedance and voltage drop but I don't have time to
work on the details right now :-)

Nor me, but later in the week, perhaps - by which time some of the
unknowns in your list above may be filled-in.

It would be particularly useful to have an answer to "device protecting
SWA to shed not known (type, rating)" (i.e. the device at the house end)
and also to know what sort of activities are to be carried out in the
outhouse/shed - IOW what is the electricity supply actually required /for/?

--
Andy