I have recently been informed that all ml installations should be earthed. I spoke to an electrician who reckons as it is a low voltage cable it should not be earthed to comply with regulations.

Does anyone know if this is the case and if it isnt how it should be earthed ( from the nearest socket , from consumer unit or other?) 

Thanks

The Masterlink is not intended to be earthed and as your electrician correctly points out this should not be done.

As with most electronic retail consumer products sold today, they do NOT have a earth connection.

There are a few situations where you are forced to add a "clean" earth to products which would normally not be earthed and this usually occurs when long cables such as active speaker cables are connected to the equipment which pick up RF interference on cable screens where they act as an aerial. In these cases it is acceptable to earth the incoming screen to stop the problem.

Earthing and earth related issues is actually quite a complex subject and there are different rules for different situations. For example in the US the incoming power into most homes is in fact 220 volts which is split making two 110 volt equipment feeds meaning the voltage potential to earth if a fault occurs can be very different depending which part of the phase is supplying your product.

As a general guide, if an earth is not required by a product, don't add it. If you have a problem where earthing part of the circuit may resolve a problem, get advice first. If you have an "Earth Leakage Breaker" on your incoming consumer unit, then this is likely to trip in some circumstatnces where an earth has been added.

Thanks Keith for the reply, they are saying all ML cables should be earthed ( even just between two products). If this has to be a "clean" earth presumably it will require a seperate earth rod etc. which will add expense and may be impossible in some situations ie. flats etc.

Regards Simon 

Simon,

You said

they are saying all ML cables should be earthed

Who are "they" your dealer ?

If two products are connected and the only route to earth is the screen on your low voltage Masterlink cable and a fault occurs, it can potentially destroy both products as they don't have an earth of their own. I am sure your electrcian friend will be able to show you the chapter in Edition 17 of the Electrical regulations which highlights this potential hazard and the do's and dont's related to it.

Keith,

b&o technical

Regards Simon

sgresswell:

Keith,

b&o technical

Regards Simon

Simon,

Did they recommend you do this in response to a particular problem you were having? What were the circumstances in which they made this recommendation?

It was a 5 room ML setup, all was well but then had various strange probs. System would go into standby, only radio available in link rooms etc. Tested ML with b&o tester- all ok then told to try earthing. It turned out to be a fault on the vision 7 motor stand which was swapped. But have since been advised that all ML networks should be earthed. I'm just concerned about the safety/legal issues.

Regards Simon

Simon,

So, your Beovision 7 motor stand had a fault, it was swapped and that resolved the problem, so why would you wish to earth the Masterlink when the fault has been resolved and given my previous statements about earthing.

sgresswell:

But have since been advised that all ML networks should be earthed. I'm just concerned about the safety/legal issues.

Regards Simon

Advised by whom?

No earth is shown in B&O user manuals where ML is discussed. In fact, I can't remember an instance where Earth and ML have ever been mentioned together. In my experience of course!

Richard,

Earthing the coax on your Sky Box is sometimes needed when there is high RF interference. This will not trip your earth leakage breaker.

Thanks for the reply Keith .

Richard

Hi Gents,

Just to emphasise Keith's comments, earthing and equi-potential bonding is a very complex subject and short circuits to mains earth should not be added from electrical equipment or cabling without taking professional advice (ideally from someone with suitable insurance cover who has physically seen the equipment installation).

I have seen occasions where badly earthed metal equipment stands have resulted in electrical noise being transmitted onto Powerlink cables, but this should not be a problem with Masterlink, due to the use of balanced audio signals and the high common-mode rejection ratio of the baluns used in modern B&O equipment.

Basically, if there isn't an earth connection in place from the factory as standard, don't add one!  By the way, don't confuse earthing with screening or shielding.  The former ties all bonded metalwork in a room to the same voltage to prevent electrical shocks.  The latter provides a barrier to restrict the growth of induced electrical fields within a cable or circuit.  (Keith: please correct me if my description is poor!)  B&O Technical may have asked you to check the screening on the Masterlink cables, as these conductors help to reduce spurious noise on the data lines within the cable.

Hope this helps,

Steve.