Round vs oval conduit

[DJ12345]

Hello guys! Just quick question, whats better to be buried inside the wall? Round or oval conduit for easy cable management and replacement? I have seen people using round conduit inside the wall but i am not sure if they are right as i have heard from other people that are oval conduit. Whats your thoughts?

Thank you!

 

[brianmoooore]

20mm oval conduit 99% of the time.

 

[littlespark]

I would think oval conduit was invented just for being buried in the wall. You wouldn’t run it surface as you would 20mm round.

Also, you don’t need to chase the wall so deep which could be structurally weakened if you go too far.

 

[HappyHippyDad]

Hello guys! Just quick question, whats better to be buried inside the wall? Round or oval conduit for easy cable management and replacement? I have seen people using round conduit inside the wall but i am not sure if they are right as i have heard from other people that are oval conduit. Whats your thoughts?

Thank you!

Oval conduit is easier as you don't have to chase out such a deep hole. Having said that, I have never tried round conduit in chases, perhaps it has some advantages that I am unaware of.
I 'think' the oval conduit may have an ever so slightly bigger cross sectional area as well.
CSA of 20mm round conduit is 31.4 sq mm
The CSA of an ellipse (a perfect oval) which has 25mm long side and 16mm short would also be 31.4 sq mm, but oval conduit has sharper corners than an ellipse, meaning slightly more area (I think, just by looking).

Also... The triple blade metabo wall chaser takes out a perfect 25mm to squeeze 25mm oval conduit into

 

[7029 dave]

IMO oval tube is used in domestic situations I always use it. If a client wanted the potential to be able to rewire with minimum disruption and mess I would use 20mm round full conduit system in singles. Only disadvantage with this is its much harder for any alterations not that its impossible. More expensive too

 

[Simon47]

Oval is a lot thinner wall as well. As said, designed to minimise the depth to bury it.
It's fairly easy to flex the oval, for example when you get to the box and need to bend it into the wall a bit to match the holes in the box - I NEVER stop the conduit short and dogleg the cables. Doing that with round would need somewhat more effort to set it.

 

[brianmoooore]

In most cases, I bring the oval conduit a few mm into the box, securing it with a dab of building adhesive if I think there's a chance it might get dislodged by 'other trades'.

 

[Simon47]

Nice to see I'm not alone

 

[7029 dave]

I will fess up when I bring the oval into a box a few mm in don't bother with a cromet

 

[Simon47]

If the conduit enters the box, a grommet isn't required as the conduit will provide protection from the (usually sharp) metal edge.

 

[brianmoooore]

More importantly, if there's no grommet there, it can't be dislodged.

 

[littlespark]

The old 12mm deep switch back boxes had a rolled edge to their oval hole on the top.
Didn’t need a gromet there.

 

[UNG]

The old 12mm deep switch back boxes had a rolled edge to their oval hole on the top.
Didn’t need a gromet there.

Not all of them did have the rolled edge it I remember it was only 1 or 2 manufacturers that did it

 

[littlespark]

You might be right. Some were rolled, some were an ovel knockout... which then needed a grommet....
Am i right in thinking there was oval grommets.... or just squashed round ones?

 

[UNG]

You might be right. Some were rolled, some were an ovel knockout... which then needed a grommet....
Am i right in thinking there was oval grommets.... or just squashed round ones?

Again I recall some did have a grommet already fitted when you purchased them if they were round grommets that had been squashed I don't know / can't remember

 

[brianmoooore]

Some had rolled edges, but the rest, to the best of my knowledge, came ready fitted with an oval rubber grommet.

 

[7029 dave]

Again I recall some did have a grommet already fitted when you purchased them if they were round grommets that had been squashed I don't know / can't remember

Yes some did have cromets already fitted

 

[Marvo]

I've never even seen oval conduit but I'm not a domestic sparky. How would you bend oval conduit, I'm assuming there's no such thing as an oval spring bender....?? Do you get oval male adaptors and other such fittings? I could see it reducing the depth needed for chasing but I'd imagine at a large trade-off.

 

[littlespark]

You don’t/ can’t bend oval conduit… and I think it was developed just for cable drops in chases as an alternative to capping over the top…. With the benefit of being able to rewire through it (if not too packed with cable)

 

[Marvo]

Ah..okay. When we wire a domestic house in conduit it's continuous PVC tubing between the back boxes so you can pull new wires between two sockets or switches or luminaires at any time in the future. Sounds like you don't use conduit that way. Are you guys using steel oval conduit drops as protection? I though that's what your cable zone rules were there for..??