Grounding Armoured cable

[Deimos]

 Not something I'm thinking of doing myself but something a friend has had professionally done and is having problems.

A professional electrician has installed phone, network and electricity supply to an outbuilding. All three cables (separate cables !!) are properly armoured. thus ADSL modem in house, computers, phone and other electrical equipment in outbuilding. When some electrical devices are switched-on in the outbuilding the phone line (ADSL) stops working (ADSL modem in the house immediately loses sync). To my mind this has to be crosstalk from the main to the phone line. I'm sure I got the idea from somewhere that for a shielding (or metal armour) to work properly it needs to be grounded at one end. Is this the case as it might explain the ADSL loss as when crosstalk increases between the mains and phone cable.

Similarly, maybe if the mains shielding is connected to the phone line shielding, could this be causing the problem ?

Badly explained and hope it makes some sense (if not say so and I'll try and explain better).

Many thanks

Ian

[jxedwards]

Ian,

Yes confusing posting sorry.

Anyway you seem to be mixing up armouring and shielding. The metal armouring found on cables has to be earthed both ends. This armouring is purely a mechanical protection for the conductors  inside the the cable.

Shielding is totally different and is not a mechanical protection. You are correct this is normally 'grounded' at one end only.

However it sounds as if mains 220V cables have been run alongside telephone and ADSL cables. If this is the case you can possibly have electrical interference between the different voltages thus causing the problems that you are experiencing. Can you physically seperate the cables by 1/2 feet apart and see if the results are the same.

Hope this helps poit you in the right direction.

 

John

[Nick Price]

Do also check that you have installed either a central DSL filter on the incoming line prior to distribution to phones around the house or have fitted filters at each phone point. Missing or broken filters are common causes of DSL modem disconnection.

Nick