Sub Main Supply

[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.

 

[snowhead]

Just use singles, not tails, providing you can get all the way in trunking.

 

[High Tower]

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

 

[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.

 

[Knobhead]

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

 

[londonlec]

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]

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.

 

[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.

 

[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]

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.

 

[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.

 

[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.

 

[MDJ]

so installing a cpc is wrong then tony?

 

[Bobster]

The metal containment is the cpc.

 

[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?