College assignment question

[SeánH]

Hi folks,

I have to draw a labelled diagram to show a 2 core pvc/swa cable being terminated into a polycarbonate 6 way distribution board with a 100 amp double pole isolator and assume the cable is the main incomer.

My question is, which way would the cable be installed i.e. from the top/bottom etc.

If anyone could point me in the right direction or provide an example of a diagram showing the above situation it would be much appreciated ray .

Thanks in advance

Sean

 

[sparkytim]

Could be either, but if it is a standard Consumer Unit then the supply L and N would be terminated into the L and N terminals of the main switch which are normally at the top with the bottom terminals feeding out to Circuit protective Devices and N connection bar.

If its 2 Core SWA then you will be using the Armour as a CPC (unless this is a segregated TT system), so don't forget to provide Earth conductor from the SWA Gland to the CU Earth bar.

 

[SteveT]

Tip : :If it comes through he wall above the CU i.e. as might happen in a garage, outhouse etc, run the SWA down the wall below the CU and then back up, only a small loop. When/if asked why = to allow for any water that may track from outside or condensation to drip off below CU.

Don't forget the Earth connection from SWA gland to Earth busbar, then wire as normal.

 

[SPECIAL LOCATION]

I have to draw a labelled diagram to show a 2 core pvc/swa cable being terminated into a polycarbonate 6 way distribution board with a 100 amp double pole isolator and assume the cable is the main incomer.

I get the impression that its the earthing of the SWA as one of the key points they are looking for on this question..

Specifically as it says its only 2-core..

so Armour probably earth... (unless TT? p'raps?)

But also you need to overcome any problems with a plastic enclosure...

e.g. getting a secure earth on your banjo when plastic could crack or deform if you over tighten the lock nuts on the gland.

I don't think top or bottom entry is that critical TBH...

as you can bring normal tails in comfortably form either top or bottom!

But then I may be completely wrong...

bin a few years since I did college assignments!?

:_|

 

[Evans Electric]

Must be the earth connection they want to see , picked up from the banjo . Just a tip with SWAs entering dist. boards, avoid the impulse to enter cable immediatly over the main terminals , you will often be struggling to connect the cores in the reduced space.

 

[SeánH]

Thanks for the replies, it doesnt state what earthing system it is. Just the details in my first post.

So am I right in saying that as long as I show a physical connection between the banjo and earth bar, as well as a neat route for the tails then all should be well?

Thanks in advance (again :worship)

Sean

 

[a1]

You could take them in either top or bottom, but when I was in college doing the 2330, it seemed that all Mock paper questions pointed to them coming in from the bottom.

May have had a question on that in my actual 2330 exam too, but I can't swear to it.

 

[SeánH]

Ive started doing a simple drawing with the cable coming in from the bottom, it's taking a while though trying to copy pictures from the net lol

 

[a1]

I would like to see that when it is done, Vinnie.

If that is alright mate.

 

[SeánH]

yeah i'll try and upload it when I'm done

---------- AUTO MERGE Post added at 16:30 ---------- Previous post was at 14:51 ----------

Heres the drawing I'm working on. Please feel free to blow it out of the water if its way off track ROTFWL

or just tell me what I need to change, add/take out, whatever takes your fancy :^O

Thanks again,

Sean



Uploaded with ImageShack.us

 

[Evans Electric]

Looks good to me Vinnie. Could be picky and say the tails usually go in the top of the main switch , but that would be harsh . I only added this before someone else did.

 

[SeánH]

Thanks for the reply, its an easy fix to swap it around

 

[Sidewinder]

Vinnie,

I rarely come in here, but seeing as its you!

Looks good a few points.

Terminating SWA into a polymer enclosure if fraught with problems.

One of the most overlooked is the cold flow of the plastic meterial where it is clamped up by the gland.

An option is 2 lock nuts, one not too tight to clamp the gland to the housing, the other tight as heck to clamp the banjo to the gland with a tail to the earthing bar.

This is a method "approved" by the NICEIC for what its worth.

There is another way, use the lock nut to clamp the cable to the plastic enclosure. Not too tight. Use a "Piranha Earth Locking Nut" with a tail to the earthing bar.

Another is to terminate into a metallic adaptable box, close coupled to the plastic enclosure, then sort the earthing from the gland out in there thus negating the possibility of long term damage to the plastic enclosure and take long tails into the CU.

Earth tail size must be correct too, don't forget, no good terminating a 16mm swa on a sub min into a box with a 1.5 tail from the banjo to the earth bar.

Drg looks OK though taking Deke's comments on board.

 

[SeánH]

Thanks for the input sidewinder, i'll take it into account whrn i modify the drawing when I get in

 

[SeánH]

Thanks for the help folks, I made modifications to the drawing and submitted it this morning, and all is well.

Thanks again

Regards

Sean Guinness