Ring or radial

[Farmelectrics]

Just done some small alterations to a training room it's a 4mm radial in dado trunking that was already there there is 7 pcs to be plugged into circuit I suggested making it into a ring but the engineer were working for says its ok I thought all pcs had to be on ring du to high integratity earthing

 

[KAS1]

I think there's a drawing in the OSG that should explain

 

[Farmelectrics]

Kas I've seen it not recently but sure all sockets for pcs need high integrity earthing

 

[KAS1]

BS7671 in there somewhere, you're correct but I don't think they have to be on a ring, 2 cpc's though (ringed as they say) one of which can be conduit

 

[Farmelectrics]

Ok Kas so if I or should I say we run a 4mm earth back to db connected in separate earths of course this would solve the issue just for the record though what spark would disconnect an earth of a live circuit any way and be on the end of the earh leakage from the pcs always baffled me this one

 

[Sintra]

This little pdf should explain the lot.

https://www.dropbox.com/s/lyekd609rxsmo78/High integrity .pdf

 

[Richard Burns]

Computers can generate leakage currents that can cause RCD tripping problems as they can also have functional earthing requirements that suppress noise on the computer supply.
If the leakage current is high, say with ten or more computers, then the cpc should be doubled and, for a radial run, in a ring, but the live conductors do not need to be in a ring, it is only to ensure that the cpc connection is not broken by accident (i.e. high integrity earthing).
The cpcs should also be terminate in the accessories separately.

 

[KAS1]

I didn't write the regs lol, personally I'd of put them on a ring, I've worked on contracts where they've specced 4mm rings as standard so I'd of gone with your suggestion for the sake of a bit a cable and you would of then achieved the high integrity earthing as well, but I can see no reg where computers have to be on a ring, it could be a radial with 2 cpc's with one being a conduit or trunking.

 

[Farmelectrics]

Thanks for the replays guys

 

[pete555]

radial ok high integrity earth needs to be installed as a ring

 

[GLENNSPARK]

Kas I've seen it not recently but sure all sockets for pcs need high integrity earthing

then make the high integrity earth a ring by all means....

 

[telectrix]

all you need to do is use both earth tags on each socket, then from the last socket on the radial, take a 4.0mm single g/y back to DB. terminate in a different hole.

 

[Farmelectrics]

Will do tel but if you didn't what problems could this cause and how would you ever come into contact with this earth leakage as you wouldn't disconnect the earths at the db nosing the circuit was live your thoughts please

 

[telectrix]

no problems with a radial only, the ringing of the cpc is belt and braces in case of a cpc snapping off at a terminal. you can measure the earth leakage with a clamp meter if you need to, a pc has a typical leakage of around 3mA.

 

[Farmelectrics]

I no that tel but could you explain to me how you could come into contact with this earth leakage