electrical

[caretaker]

I am a health and safety officer at work and have just had a contractor wonting to run a telephone cable through the basement but would like to tie the cable to trunking on the out side of it with plastic ties.
Is this allowed?

 

[StevieB]

What is in the conduit? Telephone cable does not carry a charge so I cannot see a problem with this from an electrical point of view. Not quite sure how it would contravene H&S requirements either? I am also H&S officer at work and havent been told its a no-no.

Steve.

 

[andrewm]

I don't know about H&S but you (or he) may want to check the Wiring Regulations regarding separation between telecoms and electrical cables. I don't have mine to hand but seem to remember something along the lines of 50mm spacing required between the two with some allowance for physical separation - so the trunking might be OK. Just because a telephone cable carries little (not no) current doesn't mean that a high current cable next to it cannot induce unwanted currents - even if they only result in hum. I think the bigger concern is a fault condition that could put 240v on the phone socket.

Andrew

 

[OLD]

I think the key here is voltage withstand the telephone cable will not stand 240 volts but it is separated by conduit which will withstand it so all is well.
Telephone cable is manufactured to deal with induction from AC by using twisted pairs for the circuits .

 

[Lincolnshirebodger]

I am a health and safety officer at work and have just had a contractor wanting to run a telephone cable through the basement but would like to tie the cable to trunking on the out side of it with plastic ties.
Is this allowed?

When I was involved in installing network infrastructure in schools, we were not allowed to run copper outside, we had to switch to fibre optic and back

 

[Steve Maskery]

Telephone cable is manufactured to deal with induction from AC by using twisted pairs for the circuits .

Quite true, but that doesn't mean it eliminates interference entirely. I'm not an expert on telecoms, but I did install Cat5 for many years. Computer cables carry a more sophisticated signal which is more sensitive to 240 noise than a crude voice signal, so I may be over-egging the pudding here, but we used to try to clear 240 runs by 6". That was generous, there was a recommended minimum, but I can't for the life of me remember what it was.

I don't see any problem with tying the cable to trunking per se, but if there is trunking there, and it's not 240V, why can't he run it inside the trunking? If it is 240V, I'd say that was too close, not on H&S grounds, just on sensible working practice for performance.

S

 

[caretaker]

Just found out a bit more.
The trunking that is about 3inches square and metal with lid, about 60 feet long, has mains cables for the heating and cold air switches to two upper floors but the cable that they GPO will fix is fiber optic but will feed not phones but a large computer network, so I believe, something to do with band width so the contractor said.
I got the impreshion he wonted to make it as easy for him self as possible.
When I said GPO, that was writen on the box that it was coming from outside, it will not be the GPO but a private contractor.
When this cable gets to the top floor they will lay it on top of a suspended ceiling then it will go to a large cabnet.
All in one day.

 

[Woody Alan]

Typical contractor type installation. All fibre optics should be installed on a seperate tray for the purpose. No telecom/cat5 should be attached/strapped to electrical trunking as there is no seperation for interference (minimum 150mm) no cables should be allowed to lay across suspended ceiling, for more than one reason firstly the loading of the false ceiling, secondly anyone who needs access to the void doesn't know what they are likely to find when releasing a tile, thirdly it is simply outside specification...that includes the spec that the contractor has signed up to, despite what they may say.
P.S the GPO ceased to exist in 1984 . (actually a little before that but..)


Alan

 

[Grinding One]

While I have been out of the loop per say since 2003....I used to lay Primary cables right along side telephone cables in the same trench 8" wide.Both cables were insulated very well.But we used to get talking on our secondary wires sometime while trying to locate the bad wire...(Underground Fault).So I guess there could be cross talk in England as well...But our system was grounded every 100 ft.so no induction was there also the telephone company did the same thing with their wire in our trench.More grounds at pedestals and transformers and entrances of customers houses.Telephone likewise was grounded at various points.Fiber optic was just starting when I retired.Now I get Telephone,computer,and long distance phone on the hard line.
In all of the faults I was involed in repairing I never came upon a burn into a telephone cable from a power line.

 

[Steve Maskery]

If it's a fibre optic cable you will get no interference at all from neighbouring copper.

If it's going over a suspended ceiling it should be supported every 300mm, or preferably continuously in a tray.

S