To use a 5 amp socket?

[pasty-man]

Afternoon gentlemen!
A brief rundown:

Submain run to outbuilding, 6mm T&E from CU to adaptable box, crimped to 2 cores of 4 core 6mm SWA terminating in 2 way rcd protected CU in outbuilding. Remaining 2 cores in SWA used as remote switching for garden lighting circuit fed from outbuilding CU (6A MCB), 10A plateswitch, 1.5mm T&E.

This switchable circuit (In the 230V side) is only required to carry (at present) 300w of lighting via a ELV transformer inside the outbuilding, which is the only device on this circuit. This transformer came supplied with flex & 13A plug, which at present I have chopped and wired into an FCU & fused at 3A.

Is this the best approach or would I be better using a 5A socket? keeping the FCU as transformer fuse protection??

And before anyone asks why I didnt just make a 16A single socket radial and plug the transformer in, its to avoid the the possible future scenario of what could happen with remote switching of a 13A socket....

One more quicky..how would you have joined the 6mm SWA cores to 1.5mm T&E. I've used connector strip , folded over the 1.5 and fed both in 'all the way' from either side of strip, ie overlapping.

Thanks for any comments.

 

[ban-all-sheds]

Submain run to outbuilding, 6mm T&E from CU to adaptable box, crimped to 2 cores of 4 core 6mm SWA terminating in 2 way rcd protected CU in outbuilding. Remaining 2 cores in SWA used as remote switching for garden lighting circuit fed from outbuilding CU (6A MCB), 10A plateswitch, 1.5mm T&E.

I'm confused already.

You've got an adaptable box with 6mm² T/E from the CU joined to 2 cores of the SWA, which supply a CU in the outbuilding, and a 6A circuit from that goes to a switch, then back along the other 2 cores of the SWA to the adaptable box?

This switchable circuit (In the 230V side) is only required to carry (at present) 300w of lighting via a ELV transformer inside the outbuilding, which is the only device on this circuit. This transformer came supplied with flex & 13A plug, which at present I have chopped and wired into an FCU & fused at 3A.

Maybe it's just me, but a diagram would be very useful..

Is this the best approach or would I be better using a 5A socket? keeping the FCU as transformer fuse protection??

Nothing wrong with a flex-outlet FCU.

And before anyone asks why I didnt just make a 16A single socket radial and plug the transformer in, its to avoid the the possible future scenario of what could happen with remote switching of a 13A socket....

Which is?

One more quicky..how would you have joined the 6mm SWA cores to 1.5mm T&E. I've used connector strip , folded over the 1.5 and fed both in 'all the way' from either side of strip, ie overlapping.

How have you connected the armour to the 6mm² cpc, the 1.5mm² cpc and the earth bar in the outbuilding CU?

 

[pasty-man]

A picture says more than a thousand words.....
And no it wasnt done by a small child, and you have to imagine the neutral bar & neutrals at the outbuilding cu, and all earths, and, and.....
But you'll get the idea im bloomin sure.

Quote:
And before anyone asks why I didnt just make a 16A single socket radial and plug the transformer in, its to avoid the the possible future scenario of what could happen with remote switching of a 13A socket....

Which is?

Future householder, using powertool in said socket. Someone else accidentaly flicks switch in house. Tool isnt unplugged, fiddled with, power restored again.

How have you connected the armour to the 6mm² cpc, the 1.5mm² cpc and the earth bar in the outbuilding CU?

Waved my magic wand and said 'Izzy wizzy......' I wish.
The way you have worded the question implies that the 6mm t&e AND the 1.5mm are both presented at the outbuilding or that I was using an additional conductor of the swa as the cpc. Not the case. This may be clear with the piccy now. The swa armour is banjo'd/crimp hoop/flying leaded at both ends with the outbuilding terminating into a terminal bar and the adaptable box cpc's crimped.
My 'concern' was with the joining of the 1.5mm to the 6mm in the fashion I previously described.

 

[Pensdown]

I can see what you've done and why you've done it but it's not ideal.

How far away is the outbuilding from the main CU?

The reason I ask is you may have a volt drop problem as you have effectively tripled the length of run to you lights. The feed goes to the outbuilding CU then back to the switch then back again to the CU and then onto the lights. The 1.5mm cable to the switch will also add a further volt drop to the system.

You have also shown single cables to the lights, I assume they enclosed in something?

Joining the flex to the 6mm in terminal block is fine.


IMO a better way of doing it would be to fit a small din rail mounted contactor either in the CU (depending on make and size) or in an enclosure adjacent. Run the light feed through the contactor and switch the coil via the switch in the house.

http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Hager_Rcd_s_and_Contactors/index.html

 

[pasty-man]

Volt drop shouldn't be a problem. Without being aware of distances involved I would make similar comment to someone.
The cable lengths involved are:
Main cu to outbuilding cu 11m

Total path taken from main cu via switching & back to transformer approx 36m, which should be less than 2% volt drop at the max circuit current.

Singles are run in conduit system.

I don't believe that using a din rail mounted contactor would really be appropriate or neccessary here as the currently used switchplate is in fact (omitted from drawing) one gang on a 4 gang plate that is intentionally easily accessible (as opposed to the cu) & only 3.5m from the cu anyway. Bearing this in mind along with the fact its only a 6a circuit what do you think? Would you have achieved the same in a different way?

Have you any comment on the use of an fcu where connected to transformer? Would it be waste of time in using a 5a socket here.

 

[Pensdown]

There is no need for an FCU on a 6amp circuit so yes, a 5amp weather proof plug and socket is fine - a weather proof switch is fine - a weather proof joinction box is fine..you choose

 

[pasty-man]

There is no need for an FCU on a 6amp circuit so yes, a 5amp weather proof plug and socket is fine -

This transformer came supplied with flex & 13A plug, which at present I have chopped and wired into an FCU & fused at 3A.

Is this the best approach or would I be better using a 5A socket KEEPING the FCU as transformer fuse protection??

 

[ban-all-sheds]

Maybe I'm still missing something, but (assuming no suitable RCD circuit in the house CU), wouldn't this have been easier:

?

It also assumes that you can't find a switched RCD FCU - if you can then you don't need the switch as well.

 

[Adam_151]

I assumed / read it as, that he was looking at adding additonal circuits onto the submain eventually...

EDIT: Ban, surely an RCD is a waste on that, just protecting the primary side of a transformer...

 

[pasty-man]

I agree Ban, that would be the simplest IF I was ONLY looking to achieve that. However, things aren't always as straightforward and other factors existed that I had no need to mention initially; The main cu is full(12 circuits) with the outbuilding submain taking the last way and there are 3 circuits off of this.

I concede that I could have used the last circuit in the cu as you have described and split the tails pre main cu for the submain, but this in my eyes would unnecessarily have introduced extra cost for rcd protection for this lighting circuit which already existed in the outbuilding cu & I didn't want to take the circuit from an rcd protected way in the main cu. Again I could have used an RCBO but its incurring unnecessary cost when everything I required Is already in place to support other circuits.

Anyway, I do thank you for analysing my design !

 

[pasty-man]

Quite right Adam. It would have been pretty pointless running the submain just for these lights! But then again I admit I did assume that it was sort of obvious. Sorry.

Then again, I did only post with the enquiry of how I 'should' connect the transformer, bearing in mind it was fitted with a 3a fused 13a plug and no integral fuses.
Ban wrote:

Nothing wrong with a flex-outlet FCU.

Pensdown wrote:

There is no need for an FCU on a 6amp circuit so yes, a 5amp weather proof plug and socket is fine - a weather proof switch is fine - a weather proof joinction box is fine..you choose

So do I ditch the fcu and rely only on the 6a circuit mcb?
ps. I never said the transformer was outside(only the elv side is), so weatherproof not needed.[/quote]

 

[Pensdown]

Quite right Adam. It would have been pretty pointless running the submain just for these lights! But then again I admit I did assume that it was sort of obvious. Sorry.

Then again, I did only post with the enquiry of how I 'should' connect the transformer, bearing in mind it was fitted with a 3a fused 13a plug and no integral fuses.
Ban wrote:

Nothing wrong with a flex-outlet FCU.

Pensdown wrote:

There is no need for an FCU on a 6amp circuit so yes, a 5amp weather proof plug and socket is fine - a weather proof switch is fine - a weather proof joinction box is fine..you choose

So do I ditch the fcu and rely only on the 6a circuit mcb?
ps. I never said the transformer was outside(only the elv side is), so weatherproof not needed.

[/quote]

You can use a FCU but there is no need. If you've used one keep it - it's fine for the application (now we know most of the facts)