Discuss Sub Main Supply in the Commercial Electrical Advice area at ElectriciansForums.net

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chris2139

Hello,

My boss is away and I'm trying to score a few brownie points if i can.

We are currently working for a plastic fabrication company who have just purchased a new building and we are starting the electrical instatation.

My question is. We have a Crabtree powerstar pannel board to feed 4 new 3 phase dis boards, one board is already fed with a 63A MCCB next to the pannel board. We have already fitted 150x150 galv trunking to allow hold the singles that will feed the sockets.

So, should we use SWA from the pannel board to the dis board clipped direct to the concreet wall or are we to use single tails within the trunking to feed the dis board that is appraxamatly 40m aways. Fed from a 100A MCCB?

This will allow me to get a quote from our suppler for when my boss gets back and earn my some brownie points as I'm trying to get a pay rise.

Thanks in advance.
 

High Tower

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Depends on the size of the installation, if it's biggish and you I visage the trunking being fairly full, taking into account trunking space ratios, then I would run it in armoured so as to free up some space
 
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chris2139

Ok I think I will get 2 quotes and see which is going to be the most cost effective.

Quote one, 40m 25mm 4 core SWA and 40m of 16mm Greeen & Yellow, a gland pack and cleets.

Quote two, not too sure, can I still use 25mm singles for the phases and neutral and a 16mm single for the earth or dose the earth have to 25mm as well, not 2/3 the size of the incomer.

Oh, thanks for the response.
 
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Knobhead

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

londonlec

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I'd get quotes for 50m of singles, you don't want to be short ;-)

Although obviously you can use the trunking as CPC, I would personally run a separate 25mm green/yellow as well as.
 

Brightspark2

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Id use SWA...

You may not need the separate 16mm either you could use the armour...

Sent from my Xperia S using next doors WIFI.
 
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MDJ

I know this thread isn't exactly new and sorry to re-post, however I thought I would post anyway haha sorry, I would definately run a seperate main earth with the single cables if you use them, don't rely on the trunking for an earth especially for a distribution board in this enviroment, I wouldn't be happy myself relying on a trunking even if earth tags are fitted for a sub main run.
 
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Engineer54

I know this thread isn't exactly new and sorry to re-post, however I thought I would post anyway haha sorry, I would definately run a seperate main earth with the single cables if you use them, don't rely on the trunking for an earth especially for a distribution board in this enviroment, I wouldn't be happy myself relying on a trunking even if earth tags are fitted for a sub main run.
Sometimes i just have to laugh at some of the posts i read here, and this is one of them....

Someone that obviously knows nothing about the attributes of metal containment systems, and probably no experience of them either. Let's hope he never goes to a factory, where the whole place has been wired in metal conduit and trunking and not a separate CPC conductor anywhere in sight!! Or perhaps he should, and let him see for himself the kind of Zs values he is likely to find, ....anywhere on the system, even after 40/50 years of not being touched!!....
 

darkwood

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While everyone is giving advice on the best earth i think it would be wise to ask the OP about Gas/water and structural bonding of the new building as this will have to be accounted for when sizing the earth, is Gas and/or water the same common source or is it independant of the original building.
 
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MDJ

Sometimes i just have to laugh at some of the posts i read here, and this is one of them....

Someone that obviously knows nothing about the attributes of metal containment systems, and probably no experience of them either. Let's hope he never goes to a factory, where the whole place has been wired in metal conduit and trunking and not a separate CPC conductor anywhere in sight!! Or perhaps he should, and let him see for himself the kind of Zs values he is likely to find, ....anywhere on the system, even after 40/50 years of not being touched!!....
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.
 
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Knobhead

I take it that applies to me as well. Like E54 I wouldn't consider a seperate CPC. But then I know the job would be done right.
 

Rob

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The metal containment is the cpc.
 
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MDJ

Hi-Rob, I'm aware of that fella, however theres no guarentee the trunking is up to the job really, and due to good paractice or at least I would like to think so running an earth wire around with the singles to supply the new board in my opinion is good practice, some trunkings in factories are not always in great condition are they? and the factory owner won't always pay for it to be sorted out, so covering yourself by ensuring a decent earth is connected to your new board can't be a bad thing surely, I am not saying it is something thats needs to be done, just good practice to do it In my view and am a little suprised engineer felt it a must to think it necassary to try to suggest I have no experience in metal contaiment due to my opinion about running a seperate earth, we all have our views and I personally prefer to know a good earth is connected, whats wrong with that?
 

Strima

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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?
 
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Knobhead

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

johnboy6083

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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
 
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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:
 
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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

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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.
 
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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
 
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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!!!
 
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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.
 
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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
 
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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!!
 
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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.)
 
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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.
 
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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

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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:

 
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Engineer54

Listen, your the idiot that started throwing personal insults around, if you cant take them, don't throw them...

Bighead is maybe how you see me, but then i don't go around giving duff responses to posts. I'm afraid i speak as i see it, i'm not going to change to suit You. I'm not into the looking/being cool bit, bit too old in the tooth for all that crap, much prefer to keep warm these days...lol!!!

Look at the end of the day, if you don't want to be pulled up on being wrong on here , make sure what your posting is at least half correct. There are others here far worse than me, ....just you wait and see ...lol!!!
 
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MDJ

Des it was the second post From Tony I was reffering to, and I think you know that fella.
 
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MDJ

your the one throwing insults not me, I gave a view, you had to reply with "I laugh at these posts and the guy knows nothing about the trade comments", as for duff comments, whats duff about suggesting running a seperate earth in a sub-main, your the one who has thrown around insults not me, I am just trying to defend my view against you and due to your personality have let you know you do not impress me, if you don't like it don't keep replying, I only ever wanted to suggest my view of running a earth was a good idea In my opinion, it seems to have made you into the incredible hulk hasn't it?
 

Des 56

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Des it was the second post From Tony I was reffering to, and I think you know that fella.
Apologies,I am just an observer and replied with what has been written

and I think you know that fella
No I didn't know that.
I only posted what I understood was intended
 
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MDJ

Listen, your the idiot that started throwing personal insults around, if you cant take them, don't throw them...

Bighead is maybe how you see me, but then i don't go around giving duff responses to posts. I'm afraid i speak as i see it, i'm not going to change to suit You. I'm not into the looking/being cool bit, bit too old in the tooth for all that crap, much prefer to keep warm these days...lol!!!

Look at the end of the day, if you don't want to be pulled up on being wrong on here , make sure what your posting is at least half correct. There are others here far worse than me, ....just you wait and see ...lol!!!
Look It is not imp[ressive or award winning to keep trying to win browny points, I would be far more impressed and indeed content if you made a constructive comment regarding my view about running an earth wire with sub main cables, If your right and there are indeed far worse people here that you ( I find that hard to believe) then this site which seems really good may as well shut down hadn't it, come on now stop trying to insult and win medals and just reply to views properly and be helpful, I'm sure there are quite a few people here who would appreciate a view rather than posting comments which are meant to sound insulting, please read your first reply to me and you may see what I mean.
 
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