Can anyone tell me what the cable carrying capacity of 20mm conduit is?. The
conduit is PVC coated galvanised steel with an internal diameter of 17mm. I
need to know how many single core conduit cables (1.5mm or 2.5mm) I can run
in parallel (I assume this is based upon max current carrying capacity of
each core).

In article ,
"pls" writes:
Can anyone tell me what the cable carrying capacity of 20mm conduit is?. The
conduit is PVC coated galvanised steel with an internal diameter of 17mm. I
need to know how many single core conduit cables (1.5mm or 2.5mm) I can run
in parallel (I assume this is based upon max current carrying capacity of
each core).

There's a table in the IEE On-site guide, but I've lent mine
to someone. The limit is based on what you can pull in to the
conduit without risk of damage, and IIRC, it depends how long
the section of conduit between access points is and how many
bends you are pulling round.

There will also be the issue of derating the current capacity
of the conductors due to grouping.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Andrew Gabriel wrote:

There's a table in the IEE On-site guide,

Some of the cable factors and conduit factors info is on the TLC web
site here
http://www.tlc-direct.co.uk/Book/4.5.3.htm.

You can also use the older rule that the net space factor - i.e. the
total cable cross-sectional area, including insulation, should not
exceed 45% of the net internal CSA of the conduit.

There will also be the issue of derating the current capacity
of the conductors due to grouping.

Indeed. The Cg factors are here
http://www.tlc-direct.co.uk/Book/4.3.5.htm
(use the "enclosed" column).

--
Andy

"Andy Wade" wrote in message
...
Andrew Gabriel wrote:

There's a table in the IEE On-site guide,

Some of the cable factors and conduit factors info is on the TLC web site
here
http://www.tlc-direct.co.uk/Book/4.5.3.htm.

You can also use the older rule that the net space factor - i.e. the total
cable cross-sectional area, including insulation, should not exceed 45% of
the net internal CSA of the conduit.

There will also be the issue of derating the current capacity
of the conductors due to grouping.

When they talk about conduit diameter in these tables, do they mean outer
diameter of conduit or inner diameter? I plan on using PVC coated galvanised
steel which I suspect will have a smaller internal diameter than plain PVC.

pls wrote:
Can anyone tell me what the cable carrying capacity of 20mm conduit is?.
The conduit is PVC coated galvanised steel with an internal diameter of
17mm. I need to know how many single core conduit cables (1.5mm or
2.5mm) I can run in parallel (I assume this is based upon max current
carrying capacity of each core).

In practical terms, it depends on how long a run you have. But for any
reasonable length of run, you'll only get one 2.5 mm TC&E cable to easily go
down a 20 mm conduit. I'd be using one a lot bigger (32mm or more) & get the
cables pulled through more easily & a lot quicker. And of course, all cables
pulled at the same time, else one cable will rub the other

--
Karen

If you can't be a good example, then you'll just have to be a horrible warning.'
Catherine Aird

"pls" wrote in message
...
Can anyone tell me what the cable carrying capacity of 20mm conduit is?.
The conduit is PVC coated galvanised steel with an internal diameter of
17mm. I need to know how many single core conduit cables (1.5mm or 2.5mm)
I can run in parallel (I assume this is based upon max current carrying
capacity of each core).

I find the practical limit to drawing them through is the two sets of three
single core needed for a ring main feed and return to a socket outlet and
that only if you feed them all through together. It might be possible to get
more down a completely straight run, but mine always have an elbow or two.

Colin Bignell

On 04/04/2007 04:26, Duracell Bunny wrote:

In practical terms, it depends on how long a run you have. But for any
reasonable length of run, you'll only get one 2.5 mm TC&E cable to
easily go down a 20 mm conduit.

True enough, but the O/P was asking about singles rather than T+E.

Andy Burns wrote:
On 04/04/2007 04:26, Duracell Bunny wrote:

In practical terms, it depends on how long a run you have. But for any
reasonable length of run, you'll only get one 2.5 mm TC&E cable to
easily go down a 20 mm conduit.

True enough, but the O/P was asking about singles rather than T+E.

My mistake. This makes it worse, as there's a lot more insulation involved with
singe core as it has to be double insulated. You'd be lucky to get three single
cores in one 20 mm conduit, unless it's really short.

--
Karen

If you can't be a good example, then you'll just have to be a horrible warning.'
Catherine Aird

pls wrote:

When they talk about conduit diameter in these tables, do they mean
outer diameter of conduit or inner diameter?

O/D.

I plan on using PVC coated galvanised steel which I suspect will have
a smaller internal diameter than plain PVC.

I've never come across PVC-coated steel conduit. Is this tube you plan
to use a recognised electrical conduit type to a relevant British or
International standard? If not it's doubtful whether you'll comply with
the wiring regs (BS 7671), in particular Reg. 133-01-01 requiring good
workmanship and _proper_materials_ and Reg. 511-01-01 requiring
compliance with standards.

Also remember that when wired with 'singles' metal conduit is an
exposed-conductive-part (see definitions) and must be earthed,
regardless of whether or not it is also being used as the circuit
protective conductor. The insulation provided by a thin PVC coating
should not be relied on. It is also important that electrical
continuity is maintained through all joints, which is why only threaded
joints or "substantial mechanical clamps" are allowed [Reg. 543-03-06].

--
Andy

Duracell Bunny wrote:

My mistake. This makes it worse, as there's a lot more insulation
involved with singe core as it has to be double insulated.

Not in conduit, it doesn't. Single conduit wire (6491X or 6491B) with
only basic insulation is perfectly allowable, and indeed quite normal,
in conduit. If the conduit is metal it must be earthed, even if a
separate circuit protective conductor is provided in the wiring.

Also insulated and sheathed cables (6181Y) should not be described as
"double insulated" since they are not considered as being of Class 2
construction - see Reg. 471-09-04 in BS 7671. However metal conduit
wired exclusively in such cable, including ordinary T&E (6242Y), does
not need to be earthed [471-09-04 again], except where Reg. 522-06-06
(iii) applies - i.e. to provide protection for cables buried in walls
being run outside of the "safe zones".

--
Andy

"nightjar .uk.com" nightjar@insert my surname here wrote in message
...

"pls" wrote in message
...
Can anyone tell me what the cable carrying capacity of 20mm conduit is?.
The conduit is PVC coated galvanised steel with an internal diameter of
17mm. I need to know how many single core conduit cables (1.5mm or 2.5mm)
I can run in parallel (I assume this is based upon max current carrying
capacity of each core).

I find the practical limit to drawing them through is the two sets of
three single core needed for a ring main feed and return to a socket
outlet and that only if you feed them all through together. It might be
possible to get more down a completely straight run, but mine always have
an elbow or two.

Ok from working out the capacity I think I'm going to need 25mm diameter
conduit to be on the safe side.
Incidently, does the conduit have to be steel lined (its going to be buried
mostly under a patio) or can it just be standard flexible PVC conduit?
The steel lined one I've found is he
http://cgi.ebay.co.uk/30m-Length-of-...QQcmdZViewItem

pls wrote:

Incidently, does the conduit have to be steel lined (its going to be
buried mostly under a patio) or can it just be standard flexible PVC
conduit?
The steel lined one I've found is he
http://cgi.ebay.co.uk/30m-Length-of-...QQcmdZViewItem

Ah, flexible conduit and an underground application - two things you
hadn't mentioned before. What is it you're trying to do?

You shouldn't use flexible conduit underground unless it's a type
specifically designed for such use. Nor is it very sensible to be using
single conduit wire underground. Better to use SWA cable, which can
be buried directly, or a sheathed cable such as ordinary T&E or Hi-Tuf
in substantial plastic service duct.

--
Andy

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

Incidently, does the conduit have to be steel lined (its going to be
buried mostly under a patio) or can it just be standard flexible PVC
conduit?
The steel lined one I've found is he
http://cgi.ebay.co.uk/30m-Length-of-...QQcmdZViewItem

Ah, flexible conduit and an underground application - two things you
hadn't mentioned before. What is it you're trying to do?

You shouldn't use flexible conduit underground unless it's a type
specifically designed for such use. Nor is it very sensible to be using
single conduit wire underground. Better to use SWA cable, which can be
buried directly, or a sheathed cable such as ordinary T&E or Hi-Tuf in
substantial plastic service duct.

Ah so PVC coated galvanised conduit (as above link) won't cut it then? My
interpretation of the regs was as follows (taken from TLC site) "Any
suitable cable enclosed in conduit or duct which gives at least the same
degree of mechanical protection as an armoured cable."

The reason for using single core was that at the end of each run I will have
multiple circuits I need switching (deck lights, LED lights etc) which in
one case requires upto 4 seperate switched lives in one run.

I was told since the conduit was galvanised & PVC coated it would be
waterproof (& rustproof) therefore ok for underground use.

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

Incidently, does the conduit have to be steel lined (its going to
be
buried mostly under a patio) or can it just be standard flexible
PVC
conduit?
The steel lined one I've found is he

http://cgi.ebay.co.uk/30m-Length-of-...QQcmdZViewItem

Ah, flexible conduit and an underground application - two things
you
hadn't mentioned before. What is it you're trying to do?

You shouldn't use flexible conduit underground unless it's a type
specifically designed for such use. Nor is it very sensible to be
using
single conduit wire underground. Better to use SWA cable, which
can be
buried directly, or a sheathed cable such as ordinary T&E or
Hi-Tuf in
substantial plastic service duct.

Ah so PVC coated galvanised conduit (as above link) won't cut it
then? My
interpretation of the regs was as follows (taken from TLC site)
"Any
suitable cable enclosed in conduit or duct which gives at least the
same
degree of mechanical protection as an armoured cable."

The reason for using single core was that at the end of each run I
will have
multiple circuits I need switching (deck lights, LED lights etc)
which in
one case requires upto 4 seperate switched lives in one run.

I was told since the conduit was galvanised & PVC coated it would be
waterproof (& rustproof) therefore ok for underground use.



First scratch of the pvc will say goodbye to the waterproofing as the
various salts in the soil will locally disolve the zinc then the steel
in double quick time. I would echo the SWA or Hi-Tuf suggestion, or
consider putting normal solid pvc rigid conduit inside some other
protection such as 100mm soil pipe with both the conduit and the soil
pipe having glued joints.

AWEM

pls wrote:
The reason for using single core was that at the end of each run I will
have multiple circuits I need switching (deck lights, LED lights etc)
which in one case requires upto 4 seperate switched lives in one run.

You can get multicore SWA, e.g.
http://www.copper-cable.co.uk/produc...lds%5BID%5D=21

5-core would do what you're looking for and ought to be available to
order from a decent wholesaler. Alternatively find somewhere traffic
lights are being installed and try to cadge an 'offcut'. They use
multicore SWA (somewhere between 10 and 20 cores, IIRC) with an orange
sheath.

--
Andy

replying to Andrew Mawson, Adam wrote:
What about simply concrete around the pvc, like done in USA or Caribbean?
Although, there is a place somewhere that lists the rating of pvc schedule 40
as being the same in six inch concrete as buried at two feet

--
for full context, visit https://www.homeownershub.com/uk-diy...ty-386087-.htm

"Adam" wrote in message ...

replying to Andrew Mawson, Adam wrote:
What about simply concrete around the pvc, like done in USA or Caribbean?
Although, there is a place somewhere that lists the rating of pvc schedule
40
as being the same in six inch concrete as buried at two feet


A blast from the past - 2007 !!!!!!

Andrew

Yes Home Owners Club crappy message sorting strikes again. It actually is
on the page OK but people are not expecting the year to change. Why they
have not fixed the message sorting to include the year is beyond me.
If the admins are reading this on that web interface to usenet, please fix
it now or we will pur molten lead into your server bay.
brian

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

Blind user, so no pictures please!
"Andrew Mawson" wrote in message
news
"Adam" wrote in message ...

replying to Andrew Mawson, Adam wrote:
What about simply concrete around the pvc, like done in USA or Caribbean?
Although, there is a place somewhere that lists the rating of pvc schedule
40
as being the same in six inch concrete as buried at two feet


A blast from the past - 2007 !!!!!!

Andrew