low voltage cables

[wolfiehogan]

hi guys
just a quick question for you.
i know not to mix low voltage cables with mains voltage and to keep them seperate. but why exactly is this??.is it because there a magnetic field set up around the mains cables??
in my brothers house he wants an alarm cable brought down the same conduit as the switch. in normal circumstances i would not do this but as its my brother i cant see the harm. could this cause problems and why??

 

[Adam W]

hi guys
just a quick question for you.
i know not to mix low voltage cables with mains voltage and to keep them seperate. but why exactly is this??.is it because there a magnetic field set up around the mains cables??
in my brothers house he wants an alarm cable brought down the same conduit as the switch. in normal circumstances i would not do this but as its my brother i cant see the harm. could this cause problems and why??

Why is that?
Check 528.1.

 

[acvc]

Hi chaps.

I'm getting confused messages about this issue.

As standard I keep separate 240V from data/phone/alarm cabling, but three times in the last couple of months I've had the ELV contractors telling me it's rubbish, even when i've got the OSG out and showed them it in black and white. And they've then proceeded to run their cables in alongside mine!!!

Am I missing the point here? I'm talking about intruder alarm, data, cat5 cabling, telephone .........

Help!

 

[Risteard]

They should be segregated AC/VC. Although if the cables are rated to the maximum voltage present then this may not be required.

 

[electricAl]

You aren`t missing the point.

Fact is, Band I & Band II should be seperated by the stated distances, unless the Band I (ELV) cabling is insulated to that of the higher voltage Band II, or a seperating pane of equal insulating properties is interspersed.

If some numbskull comes along later & fires in some twisted pairs without a thought, be it on their head, not yours

 

[acvc]

Yeah that's what I thought! Ta.

Obviously the 6242Y insulation does the job, but does anyone know what the cat5 insulation can insulate against ...... just so that I can tell the cheeky ******s next time!

 

[Golden_Boy]

Yeah that's what I thought! Ta.

Obviously the 6242Y insulation does the job, but does anyone know what the cat5 insulation can insulate against ...... just so that I can tell the cheeky ******s next time!

I carried out a 500 volt IR test on a full box of CAT5 ( 250 metres ) with a cm500. Result 299+ Megs.
Measured between the blue and blue striped wire..

 

[acvc]

Wow! That's interesting! Well that would suggest that cat5 is suitable to run alongside 240V cable.

Goldenboy: would you do it?

 

[Golden_Boy]

Wow! That's interesting! Well that would suggest that cat5 is suitable to run alongside 240V cable.

Goldenboy: would you do it?

Not if I could help it...

I am not an electrian but DO work with networks every day... I have never ( hand on heart) had any problems with cables being in close proximity to mains or even 3 phase supplies. Singles not grouped together may produce a small induced voltage but its never been a problem as far as I have found...

 

[Spudnik]

Surely it may have some sort of effect on the data being carried by the cat5?

I could of course be talking complete ****

 

[Golden_Boy]

Surely it may have some sort of effect on the data being carried by the cat5?

I could of course be talking complete ****

As ordinary twin and earth cable carries the same current but in opposite directions there is very little magnetic fields produced as they cancell one another out. Thats why I mentioned singe conductors !!
At the data transfer speeds of 100mb/second there is very little if any effect at all. I can remember one site where someone " qualified" had jammed a 6mm twin and earth into trunking that was already bursting with data and phone cables... Didnt make a bit of difference. Fibre optics are now widely used and there is NO way they are affected by anything less than a pair of cutters
Next time you are in a position to do so just pop your head above a suspended ceiling in a large offfice. The mind boggles.............