Hi, I'm planning to cut into the ground floor power cable ring and
extend it into the adjacent, integral garage. The concrete block walls
of the garage will make it necessary to run the cable in conduit
(plastic).

I intend to have one vertical run of 2.5M, with 3 x 2 gang boxes and
sockets contained within this run. I then want to elbow the top and
place another 2 gang box and socket at the end of a 1.5M horizontal
run, which will then form an inverted L shape. To maintain the ring
structure I'll need to return the cable to the extension starting
point.

Is it common practice to return the cable down the same conduit that
it came up in, or is it better to form a conduit loop?
The latter option is going to require twice as much conduit, so I'd
rather use the former method if practical.

--
Kind regards,
Geoff Mills

On Wed, 16 Sep 2009 16:09:50 +0100 someone who may be Geoff Mills
wrote this:-

Is it common practice to return the cable down the same conduit that
it came up in,

Yes.

Assuming metal conduit, if there is not a copper protective
conductor drawn into the conduit then you need to be particularly
careful about making proper joints to maintain the continuity of the
trunking which forms the protective conductor.


--
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

In an earlier contribution to this discussion,
David Hansen wrote:

On Wed, 16 Sep 2009 16:09:50 +0100 someone who may be Geoff Mills
wrote this:-

Is it common practice to return the cable down the same conduit that
it came up in,

Yes.

Assuming metal conduit, if there is not a copper protective
conductor drawn into the conduit then you need to be particularly
careful about making proper joints to maintain the continuity of the
trunking which forms the protective conductor.


He explicitly said he'd be using plastic conduit!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"Geoff Mills" wrote in message
...
Hi, I'm planning to cut into the ground floor power cable ring and
extend it into the adjacent, integral garage. ...

Is it common practice to return the cable down the same conduit that
it came up in, ...

It is acceptable, but if you are using twin and earth cable, rather than
individual conduit wires, you may find it a bit of a tight fit around elbows
in 20mm conduit. I prefer 25mm conduit if I am running two 2.5mm T&E cables.

Colin Bignell

On Wed, 16 Sep 2009 16:44:53 +0100 someone who may be "Roger Mills"
wrote this:-

He explicitly said he'd be using plastic conduit!

Apologies. I didn't spot the orphaned word.


--
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

On Wed, 16 Sep 2009 16:29:27 +0100, David Hansen
wrote:

On Wed, 16 Sep 2009 16:09:50 +0100 someone who may be Geoff Mills
wrote this:-

Is it common practice to return the cable down the same conduit that
it came up in,

Yes.

Assuming metal conduit, if there is not a copper protective
conductor drawn into the conduit then you need to be particularly
careful about making proper joints to maintain the continuity of the
trunking which forms the protective conductor.

Thanks,
I hadn't considered metal conduit before, nor that the conduit itself
could be used for earthing. Lots to learn.
--
Kind regards,
Geoff Mills

On Wed, 16 Sep 2009 18:01:10 +0100, "nightjar" cpb@insert my surname
here.me.uk wrote:


"Geoff Mills" wrote in message
.. .
Hi, I'm planning to cut into the ground floor power cable ring and
extend it into the adjacent, integral garage. ...

Is it common practice to return the cable down the same conduit that
it came up in, ...

It is acceptable, but if you are using twin and earth cable, rather than
individual conduit wires, you may find it a bit of a tight fit around elbows
in 20mm conduit. I prefer 25mm conduit if I am running two 2.5mm T&E cables.

Colin Bignell

Thanks, I started out with the idea that I'd be using T&E cable though
perhaps individual wires are more suitable. But then again, if that is
so, why would anyone be running 2 T&E cables through conduit?

--
Kind regards,
Geoff Mills

"Geoff Mills" wrote in message
...
....
Thanks, I started out with the idea that I'd be using T&E cable though
perhaps individual wires are more suitable. But then again, if that is
so, why would anyone be running 2 T&E cables through conduit?

Individual wires is the better choice. However, it probably depends upon
whether you are doing enough to justify buying three reels of conduit wire.

Colin Bignell

"Geoff Mills" wrote in message
...
On Wed, 16 Sep 2009 16:29:27 +0100, David Hansen
wrote:

On Wed, 16 Sep 2009 16:09:50 +0100 someone who may be Geoff Mills
wrote this:-

Is it common practice to return the cable down the same conduit that
it came up in,

Yes.

Assuming metal conduit, if there is not a copper protective
conductor drawn into the conduit then you need to be particularly
careful about making proper joints to maintain the continuity of the
trunking which forms the protective conductor.

Thanks,
I hadn't considered metal conduit before, nor that the conduit itself
could be used for earthing. Lots to learn.

Metal conduit is excellent if you need more mechanical protection than heavy
duty plastic offers, but it is not easy to work with. You need a pipe
threader and, if you want to make pretty shapes, which you can do with care
and a hot air gun in PVC, a pipe bender. As noted, the earthing it offers
can be unreliable, so I always run earth wires in it as well.

Colin Bignell

On Thu, 17 Sep 2009 08:28:30 +0100, "nightjar" cpb@insert my surname
here.me.uk wrote:


"Geoff Mills" wrote in message
.. .
...
Thanks, I started out with the idea that I'd be using T&E cable though
perhaps individual wires are more suitable. But then again, if that is
so, why would anyone be running 2 T&E cables through conduit?

Individual wires is the better choice. However, it probably depends upon
whether you are doing enough to justify buying three reels of conduit wire.

Colin Bignell

Are individual wires not usually sold by the metre? I like the idea of
these because only one earth wire would be needed. Trouble is the girl
who answered the phone at the local Peco said she'd never heard of
using individual wire. She always sells T&E for the purpose and this
with 20mm conduit, as 25mm is special order and only sold in bulk.
Fortunately there is a local Screwfix now.
--
Kind regards,
Geoff Mills

In article ,
Geoff Mills wrote:
I hadn't considered metal conduit before, nor that the conduit itself
could be used for earthing. Lots to learn.

Much stronger if in the sort of place where it could get bashed.
The minimum you'd need is a die to thread the cut ends. Assuming you can
do it all in straight runs.

--
*Nothing is foolproof to a sufficiently talented fool*

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

In article ,
Geoff Mills wrote:
Thanks, I started out with the idea that I'd be using T&E cable though
perhaps individual wires are more suitable. But then again, if that is
so, why would anyone be running 2 T&E cables through conduit?

Saves buying the singles? They have thicker insulation than stripped TW&E.
And IIRC only come in 100 mtr drums - dunno anyone that sells cut lengths.

--
*No hand signals. Driver on Viagra*

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

In article ,
Geoff Mills wrote:
Individual wires is the better choice. However, it probably depends
upon whether you are doing enough to justify buying three reels of
conduit wire.

Colin Bignell

Are individual wires not usually sold by the metre? I like the idea of
these because only one earth wire would be needed. Trouble is the girl
who answered the phone at the local Peco said she'd never heard of
using individual wire. She always sells T&E for the purpose and this
with 20mm conduit, as 25mm is special order and only sold in bulk.
Fortunately there is a local Screwfix now.

TLC cut most cables - but not this one. Probably no demand. You could
check Ebay, though.
Just for info you used to be able to get it in stranded too - which made
pulling through conduit that much easier. Dunno if you still can.

--
*It's this dirty because I washed it with your wife's knickers*

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

On Thu, 17 Sep 2009 08:40:14 +0100 someone who may be "nightjar"
cpb@insert my surname here.me.uk wrote this:-

As noted, the earthing it offers
can be unreliable, so I always run earth wires in it as well.

If it is installed and maintained improperly. However, that is true
of other ways of doing the same thing.


--
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

"Geoff Mills" wrote in message
...
On Thu, 17 Sep 2009 08:28:30 +0100, "nightjar" cpb@insert my surname
here.me.uk wrote:


"Geoff Mills" wrote in message
. ..
...
Thanks, I started out with the idea that I'd be using T&E cable though
perhaps individual wires are more suitable. But then again, if that is
so, why would anyone be running 2 T&E cables through conduit?

Individual wires is the better choice. However, it probably depends upon
whether you are doing enough to justify buying three reels of conduit
wire.

Colin Bignell

Are individual wires not usually sold by the metre?

I always buy frrom my local electrical wholesaler, who would probably give
me a very odd look if I asked to buy anything other than armoureed cable in
cut lengths. I usually buy conduit wire in 100m reels. I think 50m is also
available, but I used more than one of the 100m reeels last time I did a
factory rewire, so it wasn't worth buying less.

I like the idea of
these because only one earth wire would be needed. Trouble is the girl
who answered the phone at the local Peco said she'd never heard of
using individual wire. She always sells T&E for the purpose and this
with 20mm conduit, as 25mm is special order and only sold in bulk.

Again, my local electrical wholesaler (Newey & Eyre) will supply 25mm in
single lengths. It is to order only, but delivery is next day, to my
address.

Colin Bignell

"David Hansen" wrote in message
...
On Thu, 17 Sep 2009 08:40:14 +0100 someone who may be "nightjar"
cpb@insert my surname here.me.uk wrote this:-

As noted, the earthing it offers
can be unreliable, so I always run earth wires in it as well.

If it is installed and maintained improperly. However, that is true
of other ways of doing the same thing.

For the marginal cost of an extra wire run, it is safer to assume that it
will, at some point, not be properly maintained.

Colin Bignell

In article ,
nightjar cpb@insert my surname here.me.uk wrote:

"David Hansen" wrote in message
...
On Thu, 17 Sep 2009 08:40:14 +0100 someone who may be "nightjar"
cpb@insert my surname here.me.uk wrote this:-

As noted, the earthing it offers
can be unreliable, so I always run earth wires in it as well.

If it is installed and maintained improperly. However, that is true
of other ways of doing the same thing.

For the marginal cost of an extra wire run, it is safer to assume that it
will, at some point, not be properly maintained.

Yes. Conduit into BESA boxes will usually maintain good conductivity for
ages. The problem is with ordinary surface mount steel boxes etc where you
rely on a backing ring or nut.

--
*The longest recorded flightof a chicken is thirteen seconds *

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

To be blunt, I would no longer use steel conduit as the CPC, because
1) it must be maintained 2) too many 5-day people use 15mA EFLI
testers without understanding their limitations (namely that what
passes a 15mA test may not pass a 25A test).

Plastic conduit is fine with 6491X, FTE is an exercise in frustration
if you are a suitable masochist (6242YH is bad, 6242BH with its
tougher sheath would be friggin hilarious around a few bends).

You can buy cut lengths of 6491X online. TradingDepot, perhaps
AlertElectrical, Gil-Lec, TLC for gr/ye, a few others.

The problem with stocking cut lengths of 6491X is volume & having
sufficient reels set up to meet demands without wastage. Would be
better if they sold say 10m of large & 25m of small multiples which
would not be a bad idea (enough for a shed or garage basically which
is where 6491X does get used domestically).

If there is no real requirement to use conduit, I would use oval.

Where conduit & flexible conduit can come into its own - even with
6491X is for kitchens, particularly with stud walling. Very easy to
create an unpopulated network of conduit ready for any future changes
so making kitchen refurbs a lot simpler (remember tile trim for on
worktop so apes don't destroy the tiling). You could extend it to
network drops and throughout the house - even if not used the oval/
conduit saves plaster :-) Makes it a lot easier than "damn, I wished
I'd..." having decorated vs simply having to measure & cut out a box
over pre-existing oval/conduit.

On Thu, 17 Sep 2009 11:37:00 -0700 (PDT), "js.b1"
wrote:

...
You can buy cut lengths of 6491X online. TradingDepot, perhaps
AlertElectrical, Gil-Lec, TLC for gr/ye, a few others.

Thanks for the leads. I'll follow them up.

...

If there is no real requirement to use conduit, I would use oval.

Does oval marry up with the surface mounted back boxes in a similar
way to conduit?

Where conduit & flexible conduit can come into its own - even with
6491X is for kitchens, particularly with stud walling. Very easy to
create an unpopulated network of conduit ready for any future changes
so making kitchen refurbs a lot simpler (remember tile trim for on
worktop so apes don't destroy the tiling). You could extend it to
network drops and throughout the house - even if not used the oval/
conduit saves plaster :-) Makes it a lot easier than "damn, I wished
I'd..." having decorated vs simply having to measure & cut out a box
over pre-existing oval/conduit.

That is a state of excellence which I'm unlikely to achieve in this
lifetime. Fascinating to read though.
--
Kind regards,
Geoff Mills

On Thu, 17 Sep 2009 09:37:59 +0100, "Dave Plowman (News)"
wrote:

In article ,
Geoff Mills wrote:
I hadn't considered metal conduit before, nor that the conduit itself
could be used for earthing. Lots to learn.

Much stronger if in the sort of place where it could get bashed.
The minimum you'd need is a die to thread the cut ends. Assuming you can
do it all in straight runs.

Good points. I'm usually a belt and braces man but the relative ease
of working with plastic conduit is going to swing it on this occasion.
--
Kind regards,
Geoff Mills

On Thu, 17 Sep 2009 15:16:56 +0100, "Dave Plowman (News)"
wrote:

...
TLC cut most cables - but not this one. Probably no demand. You could
check Ebay, though.

Only found 100M drums of it so far on ebay. Thanks to this thread I
have a few more keywords for searches now, so I'll have another go.

Just for info you used to be able to get it in stranded too - which made
pulling through conduit that much easier. Dunno if you still can.

Stranded seems like a useful feature, though if it's possible to pull
2 T&E cables through the conduit, individual wires must be somewhat
easier by comparison.
--
Kind regards,
Geoff Mills

On Thu, 17 Sep 2009 18:21:03 +0100, "nightjar" cpb@insert my surname
here.me.uk wrote:

...
I always buy frrom my local electrical wholesaler, who would probably give
me a very odd look if I asked to buy anything other than armoureed cable in
cut lengths. I usually buy conduit wire in 100m reels. I think 50m is also
available, but I used more than one of the 100m reeels last time I did a
factory rewire, so it wasn't worth buying less.

The joys of being a pro. I'm barely a d-i-yer so I'll have to admire
that sort of relationship with wholesalers from afar.

I like the idea of
these because only one earth wire would be needed. Trouble is the girl
who answered the phone at the local Peco said she'd never heard of
using individual wire. She always sells T&E for the purpose and this
with 20mm conduit, as 25mm is special order and only sold in bulk.

Again, my local electrical wholesaler (Newey & Eyre) will supply 25mm in
single lengths. It is to order only, but delivery is next day, to my
address.

Colin Bignell

I'll renew my search for a similar local supplier.



--
Kind regards,
Geoff Mills

On Thu, 17 Sep 2009 09:41:44 +0100, "Dave Plowman (News)"
wrote:

In article ,
Geoff Mills wrote:
Thanks, I started out with the idea that I'd be using T&E cable though
perhaps individual wires are more suitable. But then again, if that is
so, why would anyone be running 2 T&E cables through conduit?

Saves buying the singles? They have thicker insulation than stripped TW&E.
And IIRC only come in 100 mtr drums - dunno anyone that sells cut lengths.

Is stripped T&E a realistic option for a small job? If so, does the
earth wire have to be sheathed throughout it's length?
--
Kind regards,
Geoff Mills

Geoff Mills coughed up some electrons that declared:

On Thu, 17 Sep 2009 11:37:00 -0700 (PDT), "js.b1"
wrote:

...
You can buy cut lengths of 6491X online. TradingDepot, perhaps
AlertElectrical, Gil-Lec, TLC for gr/ye, a few others.

Thanks for the leads. I'll follow them up.

...

If there is no real requirement to use conduit, I would use oval.

Does oval marry up with the surface mounted back boxes in a similar
way to conduit?

No - you'd probably want mini trunking for that.

Although you could use 20mm oval to 20mm round adapters and metal clad
surface boxes (with 20mm conduit knockouts) - though such adapters are as
rare as hen's teeth.

Also, oval conduit is not as robust as round - it really forms a tube in the
plaster. On the surface it would be easy to squidge.

Go buy John Whitfield electrical guide.
BS7671 OnSiteGuide is a good reference, not a guide.


Is stripped T&E a realistic option for a small job?
If so, does the earth wire have to be sheathed throughout it's length?

No.
- Singles (6491X) have thicker insulation than FTE
- Earth MUST be sheathed throughout its length


Does oval marry up with the surface mounted
back boxes in a similar way to conduit?

No.
- For surface sockets use round conduit or mini-trunking.
- Round conduit suits "warehouse bare brick" or looks odd.

Options...
- Run FTE in mini-trunking between surface backboxes
- Sink FTE into wall in ZONE between sunk backboxes w/grommets, cover
the plaster cutout cutout with flat wooden bead until redecorated

The latter is much prettier and "lower profile" than mini-trunking
which is a ghastly abomination even in d-line.



In general.
- Capping & Oval require sheathed cable (Flat Twin & Earth, FTE).
- Round Conduit can use singles (6491X) or sheathed cable (Flat Twin &
Earth, FTE).

- With oval fit a grommet to the backbox, butt the oval up against the
grommet
- With plastic round conduit fit female bushes into the backbox, slide
the conduit into the bushes
- With steel round conduit you need proper Die (£25) & Bender (Hilmor
£250)

- Conduit must be installed prior to cable draw in (so enforcing the
rule that if someone got the damn stuff in then when it goes time for
replacement someone else can get it out and back in again!)
- Conduit must be continuous where Singles (6491X) are used, you can't
stop the conduit short and use a grommet

Plastic conduit is only sometimes used in domestic, 20-25mm oval is
flatter.
Steel conduit is very rarely used in domestic re expensive tools &
labour.

You can buy 20mm oval-to-round adapters, MK do them.
- Trading Depot might list them, £0.80-1.00 each
- Cable only passes easily through them one way
- Ok for oval-in-plaster-to-round-in-stud-wall-cavity runs


If you need to run a cable outside a Zone.
1 - Consider if a wiring accessory can be added to create a Zone.
2 - Use BS8436 cable such as Prysmian Flexishield or Earthshield

The problem with BS8436 is £120-180 for 1.5-2.5mm/100m.

Example of where BS8436 is useful:
- Light switch below chimney, no-where else to fit it
- a) BS8436 b) MK Echo (£180) c) Occupancy PIR (£50 + £50 for spare)
- Option a) is best because a switch is more reliable

Example of where BS8436 is useful:
- Room has sloping ceiling so no 150mm HORIZONTAL zone, solid floor
- BS8436 is a lot simpler than wiring accesory route-markers
everywhere

TLC are not carrying BS8436 (I asked, they asked NICEIC). No-one else
does.
Surprised, because "25m" would be a low risk investment for someone to
carry.

OP questions indicate he needs to read John Whitfield's book. Go to
Amazon UK.

On Fri, 18 Sep 2009 06:35:30 -0700 (PDT), "js.b1"
wrote:

Go buy John Whitfield electrical guide.
BS7671 OnSiteGuide is a good reference, not a guide.


Is stripped T&E a realistic option for a small job?
If so, does the earth wire have to be sheathed throughout it's length?

No.
- Singles (6491X) have thicker insulation than FTE
- Earth MUST be sheathed throughout its length


Does oval marry up with the surface mounted
back boxes in a similar way to conduit?

No.
- For surface sockets use round conduit or mini-trunking.
- Round conduit suits "warehouse bare brick" or looks odd.

Options...
- Run FTE in mini-trunking between surface backboxes
- Sink FTE into wall in ZONE between sunk backboxes w/grommets, cover
the plaster cutout cutout with flat wooden bead until redecorated

The latter is much prettier and "lower profile" than mini-trunking
which is a ghastly abomination even in d-line.



In general.
- Capping & Oval require sheathed cable (Flat Twin & Earth, FTE).
- Round Conduit can use singles (6491X) or sheathed cable (Flat Twin &
Earth, FTE).

- With oval fit a grommet to the backbox, butt the oval up against the
grommet
- With plastic round conduit fit female bushes into the backbox, slide
the conduit into the bushes
- With steel round conduit you need proper Die (£25) & Bender (Hilmor
£250)

- Conduit must be installed prior to cable draw in (so enforcing the
rule that if someone got the damn stuff in then when it goes time for
replacement someone else can get it out and back in again!)
- Conduit must be continuous where Singles (6491X) are used, you can't
stop the conduit short and use a grommet

Plastic conduit is only sometimes used in domestic, 20-25mm oval is
flatter.
Steel conduit is very rarely used in domestic re expensive tools &
labour.

You can buy 20mm oval-to-round adapters, MK do them.
- Trading Depot might list them, £0.80-1.00 each
- Cable only passes easily through them one way
- Ok for oval-in-plaster-to-round-in-stud-wall-cavity runs


If you need to run a cable outside a Zone.
1 - Consider if a wiring accessory can be added to create a Zone.
2 - Use BS8436 cable such as Prysmian Flexishield or Earthshield

The problem with BS8436 is £120-180 for 1.5-2.5mm/100m.

Example of where BS8436 is useful:
- Light switch below chimney, no-where else to fit it
- a) BS8436 b) MK Echo (£180) c) Occupancy PIR (£50 + £50 for spare)
- Option a) is best because a switch is more reliable

Example of where BS8436 is useful:
- Room has sloping ceiling so no 150mm HORIZONTAL zone, solid floor
- BS8436 is a lot simpler than wiring accesory route-markers
everywhere

TLC are not carrying BS8436 (I asked, they asked NICEIC). No-one else
does.
Surprised, because "25m" would be a low risk investment for someone to
carry.

OP questions indicate he needs to read John Whitfield's book. Go to
Amazon UK.


Thanks, that's a lot of very good advice.
--
Kind regards,
Geoff Mills