Hi,

I see you can buy a conduit bending spring. Does this work with
plastic and metal conduit? What a shame the conduit is 20 or 25mm and
not 22mm otherwise one spring could be used for plumbing and conduit.
I dare say there are proper conduit benders but for one-off use, a
spring is probably the only sensible way forward. Do you use them as
you would with copper pipe: insert spring, bend over knee, and then
bend back slightly to release the spring?

I would have thought that big angles, say 90 degrees, were asking for
trouble: presumably you make the bends as gentle as possible to aid
cable threading?

Is it a good idea to bend conduit or it it better to buy the joins?
The corner pieces usually have a lid that unscrews, which enables you
to help push cables round the corner when installing/removing them.

What if the conduit was buried inside a wall. Wouldn't I need
something behind a blank plate, not only so that I could access the
bend but also to show that the cable changes direction? I thought
there had to be an "accessory" wherever the cable changed direction?

TIA

John Rumm
wibbled on Thursday 29 April 2010 20:02

Fred wrote:

Hi,

I see you can buy a conduit bending spring. Does this work with
plastic and metal conduit? What a shame the conduit is 20 or 25mm and

Just plastic - and the tick walled stuff is best.

not 22mm otherwise one spring could be used for plumbing and conduit.

And it doesn't really matter with plastic - use a 3/4" or a 22mm spring if
you have either to hand - no need to go and buy a special one. Plastic is
less fussy than copper - you're just trying to stop it kinking.

Have you tried bending modern half hard copper with a spring? Not
advised for those wanting to remain sane!



I dare say there are proper conduit benders but for one-off use, a
spring is probably the only sensible way forward. Do you use them as
you would with copper pipe: insert spring, bend over knee, and then
bend back slightly to release the spring?

Basically yes, but warm the pipe first. The traditional method being
rubbing it vigorously with a cloth (kind of like conduit wanking!)

|~O

I would have thought that big angles, say 90 degrees, were asking for
trouble: presumably you make the bends as gentle as possible to aid
cable threading?

Yup. Bear in mind that conduit is primarily designed for singles and not
cable anyway. Feeding a snake first can help greatly, as can drawing a
wire through it first.

I've not found it an issue with a snake. I have a bit that goes up the right
side of a bay window, 90 degree bend[1] plus a couple of minor offsets to
get round wood, then across on the horizontal in the bay ceiling[2] and
couple of wiggles plus 90 degree bend[1] and down to the left side. I tried
a test pull of 2.5mm2 T+E with snake and provided the T+E was fressh off
the drum and helped in one end, it pulled fine despite the tortuous route.

[1] I used solvent couplers near each 90 degree bend - you do have to wtach
the joints - any excess gunk or not pushing the coupler "home" and leaving
a stepped gap can cause the cable to snag while pulling.

[2] That ceiling is not coming down for anyone. If T+E now fails to pull,
I'll use singles on that leg!!


http://wiki.diyfaq.org.uk/index.php?...ords_.2F_tapes

Is it a good idea to bend conduit or it it better to buy the joins?
The corner pieces usually have a lid that unscrews, which enables you
to help push cables round the corner when installing/removing them.

A combination is often the answer - with access bends etc every so often.

Agreed - if the bend is accessible, an access bend is good as it gives
another pulling point. If the bend is not accessible, it's better not to
use an access joint as it's one more place for the cable to snag.

What if the conduit was buried inside a wall. Wouldn't I need
something behind a blank plate, not only so that I could access the
bend but also to show that the cable changes direction? I thought
there had to be an "accessory" wherever the cable changed direction?

Yes and no... you could legitimately for example run up a wall from a
socket, and then turn and run horizontally close to the ceiling and
still remain in the permitted zones. It would not be a very conventional
way of doing it though.

For concealing in a wall oval trunking is more commonly used than conduit.


--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

Fred has brought this to us :
Hi,

I see you can buy a conduit bending spring. Does this work with
plastic and metal conduit?

Plastic only.

You can make bends in steel conduit using a piece of timber with
suitable hole in it. The hole size and shape is critical. It needs to
be tight in width, to prevent the conduit crushing, yet with a slot in
the height to allow it to bend - plus lots and lots of practice.

Do you use them as
you would with copper pipe: insert spring, bend over knee, and then
bend back slightly to release the spring?

Pretty much.

I would have thought that big angles, say 90 degrees, were asking for
trouble: presumably you make the bends as gentle as possible to aid
cable threading?

Yes.


Is it a good idea to bend conduit or it it better to buy the joins?

That will depend upon quantity. The more bends you need, the cheaper
the spring will become.

The corner pieces usually have a lid that unscrews, which enables you
to help push cables round the corner when installing/removing them.

Elbows - they are very tight, but you can also buy less severe 'bends',
with or without inspection covers.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In article ,
Fred wrote:
I see you can buy a conduit bending spring. Does this work with
plastic and metal conduit?

No. Steel conduit requires a mandrel bender.

--
*You are stuck with your debt if you can't budge it*

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

On Thu, 29 Apr 2010 20:02:45 +0100, John Rumm
wrote:

Have you tried bending modern half hard copper with a spring? Not
advised for those wanting to remain sane!

22mm? Once but thereafter I used elbows

A combination is often the answer - with access bends etc every so often.
[...]
For concealing in a wall oval trunking is more commonly used than conduit.

I need a 90 degree bend (because the stairs are in the way); I don't
know how I could do that with oval conduit.

I did think I would bend the conduit but I don't want to have to rip
the wall out if the wire gets stuck, so I'm thinking some sort of
access would be a good idea. The problem is that conduit accessories
don't look very pretty and I don't want to see them sticking out of
the wall. I think the best way would be to use a 1G blank plate. Even
that's not pretty but its the lesser of all the other evils. But what
to put behind it?

I can't use traditional dry wall boxes because they only seem to allow
cable to enter from top or bottom, not the sides. But if I use a
traditional galvanized back box, wouldn't I need to earth it, even
though the cables are only "passing through"?

I have seen some conduit boxes but they only have knock outs top and
bottom; not at the side, and I tried drilling both a proper conduit
box and a "normal" pattress box and both were brittle and broke ;(

Help!

Fred
wibbled on Friday 30 April 2010 14:46


I need a 90 degree bend (because the stairs are in the way); I don't
know how I could do that with oval conduit.

Only 2 ways I know of: Bending oval is just about possible with the
application of a hot air gun - but it is very difficult to stop it
collapsing. I've put offsets in it but never a 90 degree bend. With enough
fiddling about it may be possible but will take a lot of fiddling.

The other way is to joint it into 20mm round using some rather rare
adaptors.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

On Fri, 30 Apr 2010 16:20:18 +0100, John Rumm
wrote:

Perhaps I am missing something, but why do you need conduit at all? can
you not either set the cable directly into the chase and plaster over,
or use capping and plaster over? Is there a particular need to be able
to pull new wires later? If there is a potential need for additional
wires later, could you not lay in spare cable now?

It's a stud wall but I was trying to be neat and hide all the cable
inside. It has to bend because of the stair case. You are quite right,
I could put the cable in and board it up, job done. In many ways that
would be so much simpler. I just wanted to future proof it. The
problem is that not having a crystal ball, I don't know what I might
want to add later and you can guarantee that I will need one more wire
than I have added! So I just thought using some sort of conduit would
allow me to make changes later without having to change the wall the
wall later.

No. You only usually earth back boxes when you will have live
connections contained in them.

Thanks. That is what I wanted to hear. It makes sense to only earth
them when there is a possibility that an exposed conductor might touch
them.

Fred
wibbled on Friday 30 April 2010 16:58

On Fri, 30 Apr 2010 16:20:18 +0100, John Rumm
wrote:

Perhaps I am missing something, but why do you need conduit at all? can
you not either set the cable directly into the chase and plaster over,
or use capping and plaster over? Is there a particular need to be able
to pull new wires later? If there is a potential need for additional
wires later, could you not lay in spare cable now?

It's a stud wall but I was trying to be neat and hide all the cable
inside. It has to bend because of the stair case. You are quite right,
I could put the cable in and board it up, job done. In many ways that
would be so much simpler. I just wanted to future proof it. The
problem is that not having a crystal ball, I don't know what I might
want to add later and you can guarantee that I will need one more wire
than I have added! So I just thought using some sort of conduit would
allow me to make changes later without having to change the wall the
wall later.


Can you not use round conduit then?

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

Tim Watts formulated the question :
Only 2 ways I know of: Bending oval is just about possible with the
application of a hot air gun - but it is very difficult to stop it
collapsing.

Filling with water and freezing would help stop it collapsing, or
packing with sand.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Dave Plowman (News) expressed precisely :
No. Steel conduit requires a mandrel bender.

You can actually bend 20mm conduit around your knee, if you are careful
and don't get it too tight.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk