connections of cpc

[dave992]

hi,

Testing a job at the moment and a couple of DB have all there CPC connected in the trunking instead of the DB. There is a earh bar within the metal trunking but due to the trunking full of cables, unabale to gain access to the CPC. Due poor access to the CPC ive made a report on that but is the earh bar in the trunking ok?

Thanks dave

 

[Deleted member 72666]

Sounds like a strange setup, how old is the install?

 

[dave992]

Yh the installation is in a poor way, Looks like the CPC wasnt long enough for a new board change so all connection be made in the metal trunking with guar dthe cpcs.

 

[SirKit Breaker]

I would say that it isn't acceptable to have the earth bar in the trunking. I am not saying it is against the regs, but my concern would be the possibility of line and neutral conductors chaffing against the earth if the trunking is tightly packed as you say. I would extend them in to the DB somehow. How you do this will be down to you, as you can see the set up and not us. I would code it C3, it isn't C2 cos if something does chaff through it will trip something out i would hope.

Cheers…………Howard

 

[Pete999]

I would say that as well as being poor installation practice, it I think go against BS 7671, where the earth bar is after all acting as a junction box/enclosure, and with other circuits running adjacent to it in the trunking is a n0 no, thats what I think anyway others may have different ideas.
Pete999

 

[martinh89]

Im still only learning and personally i wouldnt terminate cpcs in the trunking on account of bad practice, but, on some installs the met isnt always in the d/b ie close to the meter. My question is (if not chaffing any cables) is there any lack of fault protection here? Id definitely snag it for lack access for testing and inspecting though

 

[SirKit Breaker]

I'd go with both of the above, terminations not accessible, well not easily accessible, C3.

 

[Engineer54]

If were talking about a full metal containment system installation here, there shouldn't be any need for individual circuit CPC's, the metal containment itself is the installations CPC!!

 

[sparks1234]

Old school stuff and its still found here and there, agree with eng 54 about the trunking being an earth but personally never liked it

 

[Engineer54]

Old school stuff and its still found here and there, agree with eng 54 about the trunking being an earth but personally never liked it

Explain to me what you don't like about a full metal containment system being the CPC for the circuits it's supplying??

Nothing old school about it, apart from being used for far more years than anyone here can remember, ....Why, because it works and works better than containment filling individual circuit CPC's!! The project i'm working on now, along with every other major project i've worked with, that has extensive metal containment systems throughout, have never included separate circuit CPC's.

I'd put bet's on, that the Zs values that i'm used to seeing, are far superior than anything you would typically expect to see!!

 

[pepparz]

for godsake dont knock eng or he'll turn on u

 

[joelypops]

I'm a big fan of full metal containment, during my apprenticeship we ran metal containment accross 4 floors and used conduit etc as cpc. No problems whatsoever! Biggest problem we come accross now is people adding extensions etc to these circuits but not continuing the earth path correctly

 

[Engineer54]

I'm a big fan of full metal containment, during my apprenticeship we ran metal containment accross 4 floors and used conduit etc as cpc. No problems whatsoever! Biggest problem we come accross now is people adding extensions etc to these circuits but not continuing the earth path correctly

They are called electrical trainee's Joe, and wouldn't know any different, let alone be able to work on any metallic containment systems!!

 

[LeeH]

Are there any manufactures data on the CSA of their containment?

 

[Engineer54]

Are there any manufactures data on the CSA of their containment?

Here you go.....

The first 2 tables are for conduit and trunking....

SWA CSA of Armour.pdf (58.0 KB, 907 views)