Computer sockets (split earths)

[Boaky]

Can any of you guys explain why we split the earths in sockets when installing
A ring main for computers. Please explain in lehmanns terms thanks

 

[Guest77]

The idea is if one becomes loose then there is still an earth connected.

 

[Andy78]

Can any of you guys explain why we split the earths in sockets when installing
A ring main for computers. Please explain in lehmanns terms thanks

Use the computers to rack up debts into the billions of dollars then file for bankruptcy.

 

[Darkwood]

As simple as MJD explains but remember the earths have to have separate terminals even in the DB, the computers use the earth to dump electrical noise, if the earth path is ever broken then any metalwork on the computer can have a floating voltage that can be dangerous... this is why its called a functional earth... the more computers plugged in the higher the current flow .. Ive seen offices have 30+ amps flowing down the main earth so imagine breaking that ...every computer would be floating a voltage with a large current waiting to ground down possibly through an unsuspecting user. Its also not good for the electronics if they can't effectively sump the noise down the earth.

 

[Boaky]

As simple as MJD explains but remember the earths have to have separate terminals even in the DB, the computers use the earth to dump electrical noise, if the earth path is ever broken then any metalwork on the computer can have a floating voltage that can be dangerous... this is why its called a functional earth... the more computers plugged in the higher the current flow .. Ive seen offices have 30+ amps flowing down the main earth so imagine breaking that ...every computer would be floating a voltage with a large current waiting to ground down possibly through an unsuspecting user. Its also not good for the electronics if they can't effectively sump the noise down the earth.

Thanks dark wood that's exactly the explanation I needed

 

[Darkwood]

Its a slightly confusing regulation because most people look for the electrical advantage of separate terminals but its really a mechanical advantage that a loose earth terminal on one earth will not disconnect both earth wires meaning an alternative route should still be tight in the other terminal.

 

[andybrown]

thanks @Darkwood for telling us such a use full information

 

[Farmelectrics]

it is a good explanation darkwood but 30 amps leakege is that right allways thought pcs could possibly have mili amps leakage

 

[telectrix]

you only need a hundred or so computers/printers/etc. to build up leakage to amps rather than miliamps.

 

[bigdavs83]

The 30 amps leakage he means would be on the main earth for the building not per PC. I've seen buildings at 20 odds but not as high as 30. Must've been a big building.

 

[Darkwood]

It was an office block and yes plenty servers, computers and floors, + lighting to factor in might have added if electronic. If parallel paths are not available and you disconnect the Main Earth you can imagine that all the frame works will be floating with a large combined current but in reality parallel paths are common but a loose main earth can see say a parallel path subject to a maintained current it wasn't designed for, Ive seen idiot sparkies disconnect main earths while buildings are powered and wonder why it flashes and arcs when touching down like a shorted car battery.. I just facepalm and walk away and wonder what they have actually been trained to be; because it aint competent in their job.

 

[cobrauk]

Years ago when installing ring mains for computer circuits in banks we use to run what was call a clean earth to all the sockets as well as the normal ring main circuit cpc I could never figured out why they asked for that as both earths come from the same DB ?

 

[DPG]

Or is it a 'clean earth' system that is being specified? Daz

 

[DPG]

Sorry Cobra, you must have posted while I was still typing. Daz

 

[Farmelectrics]

Maybe in a ideal world you should only have a dozen pcs per circuitcircuit

 

[Farmelectrics]

Got the stutters there ha ha

 

[Engineer54]

Years ago when installing ring mains for computer circuits in banks we use to run what was call a clean earth to all the sockets as well as the normal ring main circuit cpc I could never figured out why they asked for that as both earths come from the same DB ?

The term ''Clean Earth'' is an old fallacy, in reality there is no such thing as a clean earth. The closest thing to a so-called clean earth is a separate TT ground field that can, if you are extremely careful isolate the inherent noise etc, of say a distribution network earth that is provided by the electrical supplier...


But then, as soon as you connect an IT installation to that isolated earthing system, it itself becomes dirty or noisy through the high leakage currents associated with IT components etc!!