Eicr coding

[ses]

Interesting job doing a massive eicr on a factory
On a lot of the socket circuits the sockets are wired in singles in metallic trunking with the trunking being used as one of the cpc's it appears.

So two things are the trunking is also being used as cpc for lighting and some other circuits

And the drops from trunking to sockets are in plastic conduit with only one cpc in

Ideas on coding the above, can you use trunking to provide earthing for more than one circuit?

Also have quite a few boards and switchfuses fed direct from main switch incoming side i.e twinned with the incoming feed on another board coding ideas ?

 

[hermetic]

OK, difficult, but off the top of my head I would test earth continuity and resistance from each socket back to MET or distribution panel, and if it is within limits It passes. If there is a variation in readings, time to start checking connections, best way is probably to flag it up as potentially dangerous and recommend running a cpc in the trunking.

 

[ses]

Resistance is very low on every circuit major parallel earth paths maybe.
Zs all within as well.
Im more wondering about the 1 cpc on ring when socket circuit drops from trunking to socket outlets?

 

[hermetic]

Hi SES,

"Im more wondering about the 1 cpc on ring when socket circuit drops from trunking to socket outlets?"

I am having a bit of a senior moment with the above statement, can you explain a bit more? How old is the install, and what are the general ambient conditions like. If it is clean dry and warm, it is unlikely to give problems, but persistent ambient moisture plays hell with trunking and vertical conduit drops.

 

[KAS1]

I don't think it would be wise to run a separate trunking for each circuit lol "can you use trunking to provide earthing for more than one circuit?"

 

[ses]

Haha yes amazing constructive answer, what i mean is can the trunking be allowed to provide the cpc for every circuit run within it

 

[KAS1]

Why would you think it cannot?

 

[ses]

Sockets are a ring main 2x line 2x neutral and 2x cpc however the cpc is trunking as one leg and single as the other leg.
Now all the sockets are taken from the metal trunking in plastic conduit so at each socket outlet the is only one cpc not two as no path through the plastic conduit

 

[Deleted member 72666]

Nothing wrong with having metal trunking as a cpc and are you sure the sockets are on a ring as most often they are radials and the 1 cpc would then be a flylead from the skt to the trunking.

 

[ses]

I was asking if it could, if you get a bad joint somewhere between two sections then every circuit will loose its earth path. So for instance i have over 300 circuits

 

[Deleted member 72666]

I was asking if it could, if you get a bad joint somewhere between two sections then every circuit will loose its earth path. So for instance i have over 300 circuits

That's why you have to verify earth continuity!

 

[KAS1]

"And the drops from trunking to sockets are in plastic conduit with only one cpc in" from that statement it reads that each plastic trunking has 1 x cpc (if this was 1 x leg returning to the DB the conduits except the last socket on the ring would have 2 x cpc 1 in 1 out etc " so if only 1 x cpc in each drop what does that indicate to you .................

 

[ses]

Yes however every socket has one cpc in

 

[KAS1]

What is the size of the cpc I the plastic conduit?

 

[ses]

I have continuity on line to line and neutral to neutral and all on 32amp mcbs labelled as rings

 

[Guest55]

Sockets are a ring main 2x line 2x neutral and 2x cpc however the cpc is trunking as one leg and single as the other leg.
Now all the sockets are taken from the metal trunking in plastic conduit so at each socket outlet the is only one cpc not two as no path through the plastic conduit

theres something very wrong about this set up.
either youve incorrectly identified the cpc system or the design is a complete lash up.

if youre using metal containment for multiple circuit cpc , thats fine , so long as Zs complies for each individual circuit relying on the trunking for earthing then theres nothing to code.
But if thats how its to be done then i'd like to see totally connected
steel conduit drops to switches and sockets , not a mash up of steel and pvc , thats asking for trouble.
and if you want to use seperate cpc's for the rings , thats fine , but do it as a proper loop , 1 in , 1 out as you would with t&e , cant see how you can effectively use only 1 cpc and the trunking which is linear in its route.

seems "odd"

 

[ses]

2.5mm cpc at each outlet

 

[ses]

Yes thats what i thought
All zs are low,
R2s are very low as well

 

[Guest55]

All zs are low,
R2s are very low as well

then theres nothing to code , all values comply.
just put it down to a"weird" install and move on.
i guarantee you'll find worse things in the course of the inspection.
;-)

 

[KAS1]

Recommend as biff indicates "metal conduit drops" or 6mm cpc in plastic conduit bolted to metal trunking and code C3 (only a c3 if all Zs values are within limits) c2 if zs values are to high. Mind you I might change my mind in the morning lol

 

[ses]

Oh i have yes

 

[ses]

Ok thanks for help
I will recheck on monday when im back just in case i missed anything

 

[oldtimer]

Remember the 14th edition Electrically and Mechanically sound why because earths were never run as the containment was an earth . Noticing more often on this forum where people freak out when there is no earth. But I don't see the problem with it so you cannot fail it as that was the standard at the time

 

[Guest55]

Ok thanks for help
I will recheck on monday when im back just in case i missed anything

first thing i'd do is find out exactly where this 2.5 cpc starts and finishes.
if its not at the db i'd be recommending a new cpc leg be installed to each skt.

 

[Guest55]

Remember the 14th edition Electrically and Mechanically sound why because earths were never run as the containment was an earth . Noticing more often on this forum where people freak out when there is no earth. But I don't see the problem with it so you cannot fail it as that was the standard at the time

the problem is that pvc has been incorporated into the containment so not a continuos metal system

 

[ses]

Thanks biff

I wasnt freaking out with the no earth i was just asking if the containment system could provide earth to all circuits.
I appreciate all help advice and it doesnt hurt to check other peoples opinions on things.
When testing an installation as big as this 5 supplies over 500 hundred circuits its easy to miss things or look to much into things

 

[ses]

Its very odd when measuring cpc to metal trunking i got around 0.17 ohms suggesting thats a ring yet 1cpc at every socket suggests different unless somehow spured down from inside the trunking maybe

 

[Guest55]

was just asking if the containment system could provide earth to all circuits.

the csa of 100mm x 100mm trunking is 324 sq. mm.*
so that would be a yes.
;-)


* took me 5 seconds to google that.

 

[ses]

I should get more up to speed maybe

 

[GLENNSPARK]

Thanks biff

I wasnt freaking out with the no earth i was just asking if the containment system could provide earth to all circuits.
I appreciate all help advice and it doesnt hurt to check other peoples opinions on things.
When testing an installation as big as this 5 supplies over 500 hundred circuits its easy to miss things or look to much into things

well...look at it from this point of view:
mate of mine has a mill with a steel trunking that runs on both sides of each floor which is also used as the fault path...this has various connys coming off it that drop down to points (both lighting and power)....some single phase...others 3....
so whats the prob?
i think you`l find that the trunking will give a lower impedance path as well than any cores likely to be pulled into it...
i just cant get this `thing` that seems to do the rounds about containment being used as the CPC...
theres some that may argue the case for a G/Y conductor to be pulled in so if theres an interruption (damage to the containment)....but its not necessary...
surely as any damage to containment would be duely reported as well...
and this would/should be the case for those PVC conny drops...
do the adiabatic on the G/Y in them PVCs if your not sure (although i think you`l find `em ok)...