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will this be alright? (Read 17397 times)
trowelhead
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will this be alright?
Oct 23rd, 2004, 4:50pm
 
Been to a customers today to price laying a patio.(great weather Angry)The customer has already laid the base(solid concrete, 12 inches thick!) and underneath has run the swa to feed his shed.(2.5mm only)
The swa is to be jointed into the utiliy room ring via a fcu,on this dedicated ring is washing machine and tumble dryer.Measurements as follows:-
cu to fcu point=15m
fcu to edge of patio = 4m
patio to shed =20m
All the elderly chap wants is to run 1 light and 1 double socket for his woodworking hobby,nothing to serious at all.
Question is,would this set up be alright for the full length in 2.5mm?
If not, could he do an external/underground joint from the edge of the patio and joint the 2.5 to two 2.5's (he has got enough left over,so therefore making the 20m run from the patio to the shed 5mm)
If none of the above look like a good idea then i'll have to do what i don't want to do,dig up his concrete base Shocked
Please bear in mind i'm only a humble brickie so if none of my ideas sound sensible,dont shout to loud! Embarrassed Embarrassed

    Thanks in advance.
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sparkyjonny
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Re: will this be alright?
Reply #1 - Oct 23rd, 2004, 5:03pm
 
You can't use two lengths of 2.5mm as a 5mm conductor.  However, the total run of 39m, all of which is wired in at least 2.5mm is sufficient to take a 3kW load (13A fuse in FCU).  The volt drop is 8.1v (according to tlc), which although some would argue is not ideal, is perfectly safe, within the regs, and will not present a problem.
Fit a consumer unit in the shed, make sure you earth the armour of the SWA well using glands (get a spark in if unsure), and that the shed has RCD protection (either in shed or house).
Good news that you won't have to dig up though!
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trowelhead
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Re: will this be alright?
Reply #2 - Oct 23rd, 2004, 5:15pm
 
thanks jonny,as long as i dont have to dig up and as long as his drill turns i'm happy Smiley
All the works are to be done by his sparkie (or himself,not me),i just didnt want a phone call after i'd finished asking me to dig up and re-lay the patio!I'll tell him the info and put the ball in his court,thanks again.
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trowelhead
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Re: will this be alright?
Reply #3 - Oct 23rd, 2004, 5:17pm
 
As i've said ,being a brickie and not overly tech minded can you tell me why 2x2.5 cables together will not work as a 5mm conductor?
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sparkyjonny
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Re: will this be alright?
Reply #4 - Oct 23rd, 2004, 8:24pm
 
They would have to be exactly equal lengths of cable, as if one was slightly longer, the majority of current would travel through the shorter, lower-resistance cable, potentially overloading it.  You've also got the issue of two seperate supplies terminating at one point.  The only option would be to treat each cable as a seperate supply, with an FCU for each, but you'd have to label the fact you have two incoming supplies in the shed.  This is feasible, but 13A should be sufficient for his needs anyway.
Glad you noticed the comment, i won't mention plumbers...!! lol!
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supersparky
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Re: will this be alright?
Reply #5 - Oct 23rd, 2004, 8:29pm
 
its not acceptable in any situation to double cable up weather they are the same length of not(exept rings and HV dist),
2.5mm is fine for the shed in this situation
if you wanted to be future proof you could stick some duct in along the surface- ie just cut a channel

ss
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HM
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Re: will this be alright?
Reply #6 - Oct 23rd, 2004, 11:14pm
 
[quote author=supersparky  link=1098546631/0#6 date=1098559778]if you wanted to be future proof you could stick some duct in along the surface- ie just cut a channel [/quote]

You are the expert so I'm not questioning the advice - but I thought the regs required cables to be buried at some depth and covered with warning tape etc?

Andrew
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JerryD
Re: will this be alright?
Reply #7 - Oct 23rd, 2004, 11:21pm
 
Yes, regs require (apart from earthed mechanical protection such as armouring) cables to be buried with warning tape or covers, all suitable identified.  Also cables must be buried to a depth to avoid being damaged by any forseeable disturbance to the ground.

(reg 522-06-03)

What does that last sentence actually mean??  Typical regs!!  Grin
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« Last Edit: Oct 23rd, 2004, 11:22pm by JerryD »  
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supersparky
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Re: will this be alright?
Reply #8 - Oct 23rd, 2004, 11:29pm
 
were talking at cross purposes here
look at my reply
then see the reg you quoted lol

its SWA so will have earthed protection

it will be buried to a depth to prevent damage in the future...its a patio and although this could be disputed, its not likly to be dug up every 5 mins

and the 'warning tape or other cover'
hence i said ducting



ss
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« Last Edit: Oct 23rd, 2004, 11:31pm by supersparky »  
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Re: will this be alright?
Reply #9 - Oct 23rd, 2004, 11:52pm
 
Thanks ss - just curious, not the sort of job I get involved with (but who knows who might want a patio in the future?).

Andrew
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Re: will this be alright?
Reply #10 - Oct 24th, 2004, 8:43am
 
The regs to recognise doubled up cables, but it is beond the scope of most people to fit such a system - and I wouldn't want to see it anyway.
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Re: will this be alright?
Reply #11 - Oct 24th, 2004, 2:29pm
 
same lec, as i see it, electrics need to be less prone to major faults as its oftern installed and forgotten

if one of the doubled up cables came out then its higher load on the others, and the chances of a T+I being done on time which might pick it up is unlikly Roll Eyes

not something id do

*Thinks of his 4 core...2 core shed supply.....not to be done by anyone*

ss
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Re: will this be alright?
Reply #12 - Oct 29th, 2004, 3:59pm
 
Doubling up cables...I can't believe I am reading this....Noone here can be any sort of qualified electrician, otherwise the penny would drop that they are talking about a perfectly standard ring main here...just configured in a slightly different way...no wonder you can't rely on the so called experts to do anything right...
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Re: will this be alright?
Reply #13 - Oct 29th, 2004, 4:02pm
 
*hides out the way for this one*
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Re: will this be alright?
Reply #14 - Oct 29th, 2004, 4:06pm
 
[quote author=qw  link=1098546631/0#13 date=1099061963]Doubling up cables...I can't believe I am reading this....Noone here can be any sort of qualified electrician, otherwise the penny would drop that they are talking about a perfectly standard ring main here...just configured in a slightly different way...no wonder you can't rely on the so called experts to do anything right... [/quote]

And where did you train?..

I strongly question your judgment!  Smiley
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Re: will this be alright?
Reply #15 - Oct 29th, 2004, 4:31pm
 
do you even know why 24 amp rated cable is allowed on a breaker exeeding the rating of the cable?
its not a ring cct its a submain as it supplys a consumer unit.
it is also serving one point only not multiple points.

ss
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trowelhead
Re: will this be alright?
Reply #16 - Oct 29th, 2004, 5:03pm
 
I must say that i asked a sensible(to me anyway ???) question and by consensus of opinion (ie the majority,if not all replies ) said or replied in the same way to it,so as far as i am concerned these respondees (where did i get that word from Roll Eyes) are correct.
 Now to all those, whom i gratefully respect, for answering,(as i've said before,i am just a bricky with VERY basic  knowledge of electricity ) can you explain what is the difference in what i thought could be done (connecting 1 feed to 2 cables to the shed) as opposed to a ring as qw says is all that i thought of!
As i have said,this isn't an 'argumentative' question,it's just not being a sparky,i can see where he's coming from! (even if the current crop of replies is  telling me he's talking tripe)
SO what exactly is the difference?
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