Separating data and power in containment

[Jon Lester]

I was told today that I should install a hep2o pipe ( plastic plumbing pipe ) inside a conduit as a way of separating power and data cables . I’m not sure this is correct and am asking if anyone has any thoughts / answers on the matter ?

 

[Jon Lester]

There are two issues to consider :

Interference. For a short run, and fairly benign loads (you don't tend to have big welders at the tills ?) it's not going to be an issue. I imagine that these days it's probably just one ethernet cable for data.

Safety. What you don't want is (e.g.) the cables getting hot, insulation softening, and your data connections getting connected to the mains. You could consider over-sleeving either the mains or data cable with a length of high-temperature sleeving and that would completely eliminate that risk without adding too much bulk.
It still leaves the risk of "a sharp object" bridging the cables, but again that's a minimal risk, especially in a metal tube.
Back when telecoms de-regulation came around, the rules for phone wiring was either a 2" separation or a solid insulating barrier between phone cables and power cables - BT would be considering mostly the safety of their guys working on the wiring, and the risk of damage to their plant.

In terms of space, you probably want a larger tube anyway, and you definitely want something where you can protect the cables from the sharp edge (notice you've shaved the white pipe ?). I've observed (yes, I'm that sort of person) that the chromed pipes they use in our local ASDA are quite large - between 2 and 3 inch.

The white pipe is a plastic pipe and it hasn’t been shave , I just cut a length to fit in the tube as a trial . The size of the chrome pipe is 25mm . It’s all a tight fit.

 

[Simon47]

Look again, it's been shaved by the sharp edge of the outer pipe - the swarf is clear to see.

 

[Strima]

BT would be considering mostly the safety of their guys working on the wiring, and the risk of damage to their plant.

The actual frame at the exchange would rise to mains voltage and as thousands of other phone lines are connected there potentially there could be a very serious issue. TBH with volt drop etc on the cables the voltage wouldn't be at mains RMS but would still nip a bit.

 

[Jon Lester]

Look again, it's been shaved by the sharp edge of the outer pipe - the swarf is clear to see.

Oh that was me trying to feed the data down the chrome pipe . Had to move plastic pipe backwards and forwards to get 4th data down ! Just trialing in . Hard to do when it’s in a vice , let alone up in a ceiling void

 

[Simon47]

The actual frame at the exchange would rise to mains voltage and as thousands of other phone lines are connected there potentially there could be a very serious issue.

These days I'd expect all the ports on the line cards to include surge suppressors which will clamp the incoming AC and stop it spreading to other lines. Without that, they'd have fried cards every time there was a fault like that, or a thunderstorm.
As you say, the wiring resistance will limit the current - one advantage of thin cables.