Network Cable in conduit under screed

[John Williamson]

I am building an extension which is going to have a multi-media cinema and will require a large amount of network cabling.

Do regulations on running cable through conduit under screed apply to low voltage network cable?

I would ideally like to bury some flexible (non metallic) conduit under the screed to avoid going through the rafters in the ceiling.

Does anyone have a better (tidy) solution? I understand the risks of if the buried cable breaks but I could easily thread new cable through with fishing tape to fix or upgrade the cable.

Many thanks in advance for the advice.

 

[PrenticeBoyofDerry]

Do regulations on running cable through conduit under screed apply to low voltage network cable?

How deep is the conduit to be? And what regulations are concerned about?

 

[RF Lighting]

Be very careful. Flexible conduit is not as easy as you'd expect to pull cables through once it's installed.

Other than that I can't see any issues with it.

 

[PBC_1966]

I'd agree about being careful with flexible conduit. Better to run solid PVC conduit, and if you're not confident about bending it where necessary, it's easy enough to use ready-made bends with couplings.

 

[John Williamson]

Thanks so much for the replies, I'm a bit of a novice so may be worried about nothing:

How deep is the conduit to be?

I would place it under the screed and insulation in the concrete slab so about 140mm deep. This is because the screed will hold wet underfloor heating and I want to prevent the heat from affecting the network cables.

And what regulations are concerned about?

BS 3036
522-06-04 A wiring system buried in a floor shall be sufficiently protected to prevent damage caused by the intended use of the floor.

Thanks so much for the warnings about the flexible conduit. I was concerned about that. Are the ready made bends too tight for CAT6 which has a minimum bend radius of 25mm?

 

[PBC_1966]

BS 3036
522-06-04 A wiring system buried in a floor shall be sufficiently protected to prevent damage caused by the intended use of the floor.

I think you meant BS7671. BS3036 is a standard for rewireable fuses.

Are the ready made bends too tight for CAT6 which has a minimum bend radius of 25mm?

Plenty large enough, even in the smaller 20mm conduit size:

https://www.tlc-direct.co.uk/Products/MT20BNDslashS.html

 

[John Williamson]

Hmmm, mixing my BS. Never a good idea. Thanks once again. Will probably go for a 50mm just in case. Should give me a little more wiggle room in any case.

 

[sparkwright]

Not sure how many cables you will have in the conduit (you may want to add some).

Perhaps two or three seperate 25 mm flexible or rigid conduits may be an idea.

With 20 mm or in some cases 25 mm conduit, you have a better chance of connecting it to a metal box flushed into the wall, meaning there would be no disruption if you need to draw in extra cables.

As said, rigid conduit is better for drawing in cables than the flexible.

If you do use the flexible, put in a draw wire, or the cable you want, before screeding over.

A draw wire AND the actual cable would be an idea while you have the chance.

 

[ban-all-sheds]

I understand the risks of if the buried cable breaks

Why/how on earth would it?

 

[PBC_1966]

A draw wire AND the actual cable would be an idea while you have the chance.

And if you ever do need to draw in another cable, pull in a fresh draw line with the new cable so that there remains a draw line there to repeat the process in the future, unless the conduit is at capacity and/or you're absolutely certain you'll never want to add another cable sometime.

 

[ban-all-sheds]

Be very careful. Flexible conduit is not as easy as you'd expect to pull cables through once it's installed.

Pliable should be easier. Tends to have a smaller ID though.

 

[Lectrician]

I would opt for rigid conduit, 25mm, and a couple runs if required. Rigid can still arc and bend a little, and pulled bends with a spring could be added if required. Secure it down with galv saddles (less the spacer bar).

Flexible would be a pita.

 

[John Williamson]

I understand the risks of if the buried cable breaks

Why/how on earth would it?

From experience, a builder going through a cable with a screw. Happened to me with an HDMI cable embedded in a ceiling which is one of the reasons I am looking at conduit this time round

 

[John Williamson]

Be very careful. Flexible conduit is not as easy as you'd expect to pull cables through once it's installed.

Pliable should be easier. Tends to have a smaller ID though.

That's very interesting. I haven't seen this before. I like the fact that the turns are smoother so should be easier to fish. Will have to speak to my builder to see if he is happy to bend the rigid and if not this would be a great backup plan.

A draw wire AND the actual cable would be an idea while you have the chance.

And if you ever do need to draw in another cable, pull in a fresh draw line with the new cable so that there remains a draw line there to repeat the process in the future, unless the conduit is at capacity and/or you're absolutely certain you'll never want to add another cable sometime.

Yes absolutely. I know somewhere down the line I am probably going to upgrade to Cat7 so essential that I always pull a draw line.

 

[ban-all-sheds]

I know somewhere down the line I am probably going to upgrade to Cat7.

Why?