IT equipment & earth leakage

[RF Lighting]

I know there is no definative answer but does any one know the 'average' current leaked to earth by a PC and monitor?

I am currently locked in a vicious argument at work regarding RCD protection of a circuit supplying IT equipment.

We extended an existing high integrity earth ring circuit.

My boss wants RCD protection to be added to the circuit as it is on the ground floor of a small office, and there are no other circuits to supply equipment for use outdoors, but as I understand the regs 'IT' circuits should NOT be protected by an RCD.

Who is right? Are we both wrong?
Just after a consensus of opinion (and some hard facts) so we can carry on arguing tomorrow

 

[Adam_151]

approx 1ma per computer is the fiqure I got when I placed my multimeter in series with the earth conductor on a made up lead once when I was trying to fault find a nuisence tripping issue

EDIT: btw, the RCBO for the kitchen ring solved things in the end

 

[toasty]

It really does depend.
Modern monitors are much better from what I've seen.

However I would say as a rule of thumb that you won't get more than 10 PCs and monitors to work reliably on a single 30mA RCD.

So roughly speaking I'd say ~ 3mA leakage per computer (monitor and base unit)

 

[RF Lighting]

btw, the RCBO for the kitchen ring solved things in the end

Glad to be of assistance

 

[plugwash]

i had an old monitor at one stage that was fine on its own 30ma rcd (the place i was living in at the time insisted on use of 30ma plug in rcds on all equipment) but if it shared one with the computer (also quite old) then about half the time turning on the monitor would trip the RCD.

i've never had a problem since (can't remember what happened to the monitor but i no longer have it, it could only really do 640x480 anyway) but then i've never tried to set up lots of PCs on one rcd.

i'd say the correct approach here would be to provide RCD sockets near any likely flex exit locations and make sure it is put into the companies health and safety policies that theese should be used for outdoor equipment.

 

[nozspark]

but as I understand the regs 'IT' circuits should NOT be protected by an RCD.

Do you mean a circuit that supplies IT (computer) equipment, or an IT installation as opposed to TNS, TNCS or TT???

 

[securespark]

btw, the RCBO for the kitchen ring solved things in the end

Glad to be of assistance

Oh, boy! John WILL be pleased...!

 

[RF Lighting]

The question is regarding a circuit designed to supply computer type equipment, and not a system with an 'IT' earth arrangement.

BTW the system is TN-S

 

[Spark123]

This sound daft but IT (information technology) equipment with a leakage current of 3.5mA> must not be connected to an IT (Isolation Terra) system.
I can only ever remember seeing a couple of IT (Isolation Terra) systems in use, they were special systems designed for a testing environment.

 

[JohnD]

btw, the RCBO for the kitchen ring solved things in the end

Glad to be of assistance

Oh, boy! John WILL be pleased...!

RCBOs solve lots of problems

 

[Pensdown]

Although you are both right, IMO you are more right than your boss

A high integrity earthed ring should not be fed via an RCD but sockets that could used outside should be, but that does not mean the whole circuit.

I would install a few RCD sockets (if you spur them you can maintain the HI ring) on the HI ring for outdoor use. I would label any other sockets that could be used outdoors "not for outdoor use"

 

[plugwash]

surely the rest of the ring is still high integrity (since it has two earth paths) even if the sockets used for outdoor equipment only have one earth terminal.

 

[Pensdown]

Assuming the RCD socket is a single then yes it can have a single earth terminal and yes it can be wired on the ring. However, my own preference would be to leave the HI ring in tacked and feed the RCD sockets as spurs.