Sub Main Supply

[Strima]

If you're not 100% on using the traywork/trunking as a CPC then why not just do a continuity test and go from there?

 

[Knobhead]

At the end of the day, it’s down to our elusive OP.

 

[johnboy6083]

Well, personally i would install a long submain in SWA 9 ttimes out of ten, as by the time you have derated the cable for the grouping factors, you will end up with a possibly much larger conductor size. Especially in a factory situation, where there maybe little diversioty on the loads. If did choose to use trunking, then i wouldnt have a problem using it as CPC, and i would supplement this with a bond to some local steelwork ect. I reckon that you will end up with some suprisingly low Zs on these systems I know what you are saying with regards to possible damage and corrosion, but those problems exist on all types of installation, and if designed and constructed properly, then a trunking system used as CPC will be fine

 

[MDJ]

I certainely wouldn't rule out an armoured either, if it was a single phase supply though I would use a 3 core, I suppose I have no idea about running these in either then according to engineer:laugh3:

 

[MDJ]

John I do understand what your saying and coming from fella, in an ideal situation your right, but a lot of factories I have worked in are old and the trunkings usually a right mess, if singles were used I am just saying I would run an earth with them, thats all, and recommended to the OP he do the same, were all here to give opinions, and of course I respect yours.

 

[Darkwood]

The arguments here seem to be all based on personal preference but regards old trunking installs yes seen a few knacked ones but the OP has given enough insight and explained the building is new, the trunking is a new install too and thus will have been sized with thought of the content including submains supply, there is nothing wrong with using said trunking then as the earth, why spend money when its not needed if OP were putting a price in to win the job such a cost for the extra earth cable could be the difference between winning and losing the contract.
We should be advicing the OP that it is a suitable recognised way of earthing with maybe a personel pref' comment after if you so wish, the install been new will be subject to EICR periodically and will be down to the owners to ensure this happens, this will highlight any issues with damaged trunking etc as it would with any other system chosen so as long as the install is worked out and fitted correctly i see no reason against the use of the trunking as the earth, but i stress it comes down to personal habits in fitting seperate earth but wouldn't be deemed bad practice to not do so.

 

[MDJ]

I suppose it is the way we down here are trained, I have never known a spark or company around here not pull in a seperate earth wire with any circuit wether fixed or distribution, all my career we have done this and been of the mind a seperate earth is important, indeed ALL of the specifications we recieve regarding new circuits insist on it, every engineer I have dealt with insist on an earth and always tell us what size (TBH they are over the top most of the time), however I have never come across an electrician who thinks it is hilarious to suggest a new member doesn't know anything about containment due to his view about main earths, perhaps I need to stick around here a bit more and learn from you guys who do not live around the west and work in our circles, we learn every day, thank-you for your help fella, much appreciated.

Kind Regards

Mike

 

[Engineer54]

I cannot imagine why a guy like you thinks it is hilarious to attemp to insult someone who suggests running a main earth in with single cables when installing a sub-main, firstly wrong I have worked in factories and installed cable trays ladders, trunkings etc, I see the state of them at times as well and know they can still do the job, however what is so laughable about advising someone to run an earth wire in as a main earth? just because you have the name engineer and a high postcount and a few friends on here it doesnt impress me sonny, i wouldn't employ you with that attitude thats for sure, why not run an earth? why risk the trunking if you don't need to? surely it is good practice to do this if possible!!!

one statement comes to mind with you

small mans syndrome

oh and stop following me around the forum.

I can assure you, i'm not your sonny, and you certainly wouldn't be able to afford me!! lol!!

Only the inexperienced, would suggest running a separate CPC in a metal containment system, they are just not needed and if anyone was foolish enough to provide a separate CPC for every circuit, the conduit and probably even the trunking system would need to be considerably larger as a result. Your basically a ''doom monger'' not trusting a full metal containment system, you see or make up problems that just aren't there. They have been around long before my time, and for good reason, .....They Work, and work dammed well too. The only time they can possibly fail, is when numpties start breaking into it, to run the only cable they know how to use, ....T&E!!!

A point in note, virtually all our final circuits and a good number of our local sub-mains on my present project, are run in just such metal containment systems, We are not and have never even thought about running separate CPC's. What's more, when it comes to testing and commissioning time, i already know, we'll not have any problems with Zs values, ....Anywhere on the system!!!

 

[MDJ]

once again your wrong sonny, I have been intalling for 29 years and in industry, you just don't impress me with your post count and insulting comments to a new member, please have an opinion, but don't patronise new members, you don't know me or any others, you have a view, please let me and others know but don't act like a clown.

 

[MDJ]

it is fine to have a view, i repect that, but to say any electrician installing an earth wire with the main phase cables in a system where a metal trunking is evident is in experienced just proves to me your in-experienced or do not like discussion regarding installation, there have been 3 or 4 other opinions here I am interested in and they didn't need to attempt to gain attention by trying to look the big man insulting a new member, (you can't afford me) probably the case, my firm only turns over 500k a year and is small compaired to most, one thing we don't do down here is cut corners on installations, right or wrong we always allow to install seperate earths in out fixed priced quotations, it doesn't mean we are thick, clueless and inexperienced.

Kind Regards

 

[Engineer54]

29 years a, and in the industrial side, and still know nowt about metal containment...lol!! I don't believe for a second that project consultants would be calling for separate CPC's to be pulled in to metal conduit and trunking systems, a complete waste of time and more importantly money!!!

Well with the suggestions you've made so far on this and other threads, your certainly not impressing me either.
I'm a lot of things to many people, but i can assure you i'm no-bodies clown!!

 

[Knobhead]

it is fine to have a view, i repect that, but to say any electrician installing an earth wire with the main phase cables in a system where a metal trunking is evident is in experienced just proves to me your in-experienced or do not like discussion regarding installation, there have been 3 or 4 other opinions here I am interested in and they didn't need to attempt to gain attention by trying to look the big man insulting a new member, (you can't afford me) probably the case, my firm only turns over 500k a year and is small compaired to most, one thing we don't do down here is cut corners on installations, right or wrong we always allow to install seperate earths in out fixed priced quotations, it doesn't mean we are thick, clueless and inexperienced.

Kind Regards

And thus spake the wisest fool in Christendom. (Refer. James VI of Scotland.)

 

[MDJ]

I'm not lying sonny, and I have never met an engineer yet who doesn't insist on a cpc in a sub main run, your a big headed no-body who likes to insult new members rather than get involved in a conversation, I don't like you and want you to avoid following me around the forum, I am just not impressed with you, 6000 posts or the fact you work in china, have a view, but use your head and get involved in conversation, not try to look cool, you just don't impress me at all, I have looked at your posts to, and big head is the way I see it lmao.

 

[MDJ]

Disappointed in you tony, I am only stating a view regarding running an earth wire with submain cables, theres no need to jump on the bandwagon, I would respect you more if you gave an opinion, I am not trying to cause any trouble here, but believe if the forum wants to grow it needs views from across the spectrum tony, and slating a new member with experience in the trade because he suggests to an OP running an earth wire is a good bet is quite frankly appalling.

whats the point.

 

[Des 56]

Disappointed in you tony, I am only stating a view regarding running an earth wire with submain cables, theres no need to jump on the bandwagon, I would respect you more if you gave an opinion, I am not trying to cause any trouble here, but believe if the forum wants to grow it needs views from across the spectrum tony, and slating a new member with experience in the trade because he suggests to an OP running an earth wire is a good bet is quite frankly appalling.

quote Tony
I would use singles keep everything contained and out of sight. The trunking if done properly should be your CPC.

I think he already did :flowers: