Ring main for computers

[sparks1234]

Assuming thet we are talking T & E, and as this is computer terminals with high protective conductor currents, who does what and why for their method of earthing?

2 seperate earths seperately terminated in the sockets?
Does anyone run an additional earth

You tell me

 

[Spudnik]

No need for separate earths, unless there is going to be a large amount of PC's.

I generally just use the "high integrity' method of splitting the cpc's at the sockets and CU/DB.

 

[sparks1234]

Yes thats what I do at the sockets, now, at the consumer unit / dis board end, how do you go about keeping them seperate? do you purchase another earth bar or ?

 

[Sintra]

Yes thats what I do at the sockets, now, at the consumer unit / dis board end, how do you go about keeping them seperate? do you purchase another earth bar or ?

You can either install a seperate earth bar or if you have several high integrity circuits you can put 1 cpc from ring 1 into terminal with 1 cpc from ring 2 etc. When doing either of these methods all cpc's must be correctly labelled with circuit No. and phase. A label should also be installed at DB / CU informing of all circuits with high integrity earthing.

 

[NoSparks]

That's news to me. I thought a ring was defined as starting from the same connection in the CU, line nutral and earth, or am I confused. Are you meaning you put the cpc at each end of the ring under a different connector on the same bar? shorly you would not put the cpc from 2 rings in the same connector?

Or you mention phase. is it different for 3 phase systems.

 

[sparks1234]

That's news to me. I thought a ring was defined as starting from the same connection in the CU, line nutral and earth, or am I confused. Are you meaning you put the cpc at each end of the ring under a different connector on the same bar? shorly you would not put the cpc from 2 rings in the same connector?

Or you mention phase. is it different for 3 phase systems.

The idea of the seperate connections for earths is to ensure if there is a loose earth then you still have one connection on to an earth bar, what was said earlier is that you do put 2 earths from different rings into one terminal but you must make sure you number it up correctly

 

[Spudnik]

No.

The line conductors are still connected in the same way on a socket or in the CU.

Its the CPC's that are connected into different terminals so that IF one cpc should, for WHATEVER reason become disconnected, then the other is still providing a continuous earth path.

^^^^he beat me to it

 

[Sintra]

That's news to me. I thought a ring was defined as starting from the same connection in the CU, line nutral and earth, or am I confused. Are you meaning you put the cpc at each end of the ring under a different connector on the same bar? shorly you would not put the cpc from 2 rings in the same connector?

Or you mention phase. is it different for 3 phase systems.

Sorry i mention phase as i normally work on 3 phase systems but that is not relevant.

For example if you have a 4 way CU with 4 high integrity ring circuits you can connect 1st leg of ring 1 cpc with 1st leg of ring 2 cpc in your No. 1 terminal. In No. 2 terminal connect 2nd leg of ring 1 cpc with 2nd leg of ring 2 cpc. In No. 3 terminal 1st leg ring 3 cpc with 1st leg ring 4 cpc. In No. 4 terminal 2nd leg of ring 3 cpc with 2nd leg of ring 4 cpc.

So yes you can put the cpc's from 2 rings in the same terminal but it is all about the circuit labelling on each individual cpc and in the CU as mentioned previously.

 

[sparks1234]

no.

The line conductors are still connected in the same way on a socket or in the cu.

Its the cpc's that are connected into different terminals so that if one cpc should, for whatever reason become disconnected, then the other is still providing a continuous earth path.

^^^^he beat me to it :d

hahaha

 

[NoSparks]

Assuming thet we are talking T & E, and as this is computer terminals with high protective conductor currents, who does what and why for their method of earthing?

2 seperate earths seperately terminated in the sockets?
Does anyone run an additional earth

You tell me

But to return to the original question. Yes I would use a high integrity earth at each socket. But is it still relevant? My understianding is that it was not the Computer that generated the earth current, but the VDU. In a VDU the CRT has an earth shield which helps to stablize the scan, but induces a current. My point is that there are very few VDU left now. Most have been replaced by LCD displays which do not have the same charateristics. So please tell me, is the concept of a computer circuit still relevant?

 

[sparks1234]

But to return to the original question. Yes I would use a high integrity earth at each socket. But is it still relevant? My understianding is that it was not the Computer that generated the earth current, but the VDU. In a VDU the CRT has an earth shield which helps to stablize the scan, but induces a current. My point is that there are very few VDU left now. Most have been replaced by LCD displays which do not have the same charateristics. So please tell me, is the concept of a computer circuit still relevant?

Good question,

 

[Spudnik]

Yes i agree.

Although isnt there a fair bit of earth leakage from the PSU??

Not really up on computers so be nice.

 

[NoSparks]

For example if you have a 4 way CU with 4 high integrity ring circuits you can connect 1st leg of ring 1 cpc with 1st leg of ring 2 cpc in your No. 1 terminal. In No. 2 terminal connect 2nd leg of ring 1 cpc with 2nd leg of ring 2 cpc. In No. 3 terminal 1st leg ring 3 cpc with 1st leg ring 4 cpc. In No. 4 terminal 2nd leg of ring 3 cpc with 2nd leg of ring 4 cpc.

So yes you can put the cpc's from 2 rings in the same terminal but it is all about the circuit labelling on each individual cpc and in the CU as mentioned previously.

I would have thought this would have violated what I thought was a requireemnt of BS7671 to maintain the nutral and earth connections in the same order, but I note you reference to labeling. How do you physically lable the cpcs? My wholesaler has no circuit identifying rings or tags (Ive asked) do I need a new wholesaler?

 

[sparks1234]

I would have thought this would have violated what I thought was a requireemnt of BS7671 to maintain the nutral and earth connections in the same order, but I note you reference to labeling. How do you physically lable the cpcs? My wholesaler has no circuit identifying rings or tags (Ive asked) do I need a new wholesaler?

Places like RS comp will always have them, I do believe on some boards you can install an additional earthbar

 

[Sintra]

I would have thought this would have violated what I thought was a requireemnt of BS7671 to maintain the nutral and earth connections in the same order, but I note you reference to labeling. How do you physically lable the cpcs? My wholesaler has no circuit identifying rings or tags (Ive asked) do I need a new wholesaler?

On 3 phase systems i put a band of tape of the relevant phase colour then i have number strips that you can buy from most suppliers. In the centre of the phase strip i apply the relevant circuit number.
On single phase supply i just number.