high integrity earthing

[daveygh]

I'm currently running some radials for power poles in an office and the consultant has asked for high integrity sockets. i know that i have to run a seperate cpc back to the c/u and this cpc should be in seperate terminals at the socket, but if i'm running back to a standard merlin gerin distribution board can the cpc go in the same terminals and also what goes down on the EI cert as r1+r2? Also does it matter which terminal the back box fly lead goes to?

thanks

 

[Evans Electric]

Clean earth goes to the earth pin in the socket, normal earth wires go to the plate and back box. Most power pole boxes are plastic. Back at the board just stuff them in the same earth bar, what else can you do with them.

 

[NozSpark]

Deke.. he's on about high integrity earth, not a clean earth..

High integrity earths should go into seperate terminals, at the accessory and the CU

 

[Evans Electric]

Oh, why is he saying he is going to run a seperate earth back then , he,s got me mixed there methinks. :C

 

[NozSpark]

Yeh..

I thought that you could get away without an additional earth (in a ring final) so long as you put them under different terminals.

But if it were a radial then it would need an additional earth

 

[steptoe]

I honestly thought this stupid idea of hi integrity earths had been done away with a few years ago,

we recently (5/6 years ago) done a telecom exchange where every earth from every room was taken to an earth bar outside the room/in the corridor and was fed back to MET in 240mm earth,

hi integrity earthing really is an old fashioned way of thinking in this day and age with the speed at which our trade progresses IMHO .

 

[ianmacd]

I honestly thought this stupid idea of hi integrity earths had been done away with a few years ago,we recently (5/6 years ago) done a telecom exchange where every earth from every room was taken to an earth bar outside the room/in the corridor and was fed back to MET in 240mm earth,

hi integrity earthing really is an old fashioned way of thinking in this day and age with the speed at which our trade progresses IMHO .

Its more relevent now with large numbers of puters that leak to earth.

 

[initforthemoney]

I think its a very sensible idea and agree with the above member.

 

[steptoe]

Its more relevent now with large numbers of puters that leak to earth.

Im at a loss as to how that cures it.

ie, running a separate earth back.

you still have a circuit with high earth currents present, and you are still limited to the amount of points you can have on said circuit due to 30mA protection.

 

[Sidewinder]

Yes Steps, but with "high integrity" earthing, you have redundancy, in that if one cpc fails you still have another to carry the earth current.

Not perfect, not ideal, and perhaps even not good, but as I understand it this is the theory.

 

[initforthemoney]

Thats exactly how it is designed to work.

 

[Evans Electric]

Ah I didn't read the OP properly , its interesting though, a radial not a ring so does he install two earth cables back to the board or is that just a waste of time and materials.

I must admit I don't know the answer, Daveygh says "the consultant has asked for it" so I suggest ask him , let him earn his fee.

 

[initforthemoney]

In the case of socket radials, a separate cpc has to be run from the last socket back to the cu.

 

[Oracle]

correct -such that the cpc becomes a ring with the rest a radial.

Often with hi solutions they require/specify larger csa cpcs

O.

 

[steptoe]

so its name is a bit of a misnomer then, its really a supplementary earth for said circuit.

I understand it more now.

so if you have a lot to do you could install a "dirty" earth bar nearby, and use that (?)

 

[aptsys]

There's a 21 page thread on this at diynot. Lol.

 

[Sidewinder]

so its name is a bit of a misnomer then, its really a supplementary earth for said circuit.I understand it more now.

so if you have a lot to do you could install a "dirty" earth bar nearby, and use that (?)

Don't think so steps, IIRC the cct has to terminate at 2 seperate points in the DB also, just in case one falls out!

It it in GN8 not sure about how much detail is in brb.

 

[kme]

+1

 

[steptoe]

Don't think so steps, IIRC the cct has to terminate at 2 seperate points in the DB also, just in case one falls out!It it in GN8 not sure about how much detail is in brb.

I was meaning the earth bar for the supplementary earth.

as for 2 separate terminals, IMO that is just madness, we actually make a point of installing ring finals into the same terminal,

what about radial ccts too,

we are at risk of leaving the whole house/installation without an earth, maybe we should all start installing two "main" earths,

just in case one falls out.!

I know you are only quoting sidewinder, Im not having a go,

I just think a lot of this stuff is complete and utter madness,

maybe someone should ask whoever made this up what happens if the earthing conductor happens to fall out, or I suppose even the incoming neutral,

but that would/could never happen because we never lose a supply neutral.

this is what I sometimes hate about this job, people making rules as and when it suits them then they tell you to do this or that, but the rest of the time we know you are not going to have a cable fall out of a terminal,

bit like JBs really, maybe we should go back to using dogcocks.

X(

 

[ianmacd]

I believe the ethos behind it is that its easy to loose a cpc and no one notices (everything still works as before). I believe this was also the argument the DNO's used to try and force that badly implemented TN-C-S crap on us as you also loose your neutral so stuff stops working so someone notices. Would make more sence to fit a device that monitors the voltage from line to earth if they are really worried.