Practical Real World Question

[steptoe]

OK,

in relation to an ongoing thread in another part of the forum I thought I'd put a question in here,

this is an actual real world situation, my own house, so, as you may have guessed I have already made the answer  up,

but, I would like you guys to tell me why, and how, and what you would do.

as an aside, the earthing arrangement is perfectly fine to export the TNCS on, if you need any more info regarding that particular aspect then I can provide that, but it is not relevant to the cable sizing , OCPD etc .

what size OCPD do I need to supply my shed?

what protection do i need to provide?

there will be a mini pvc CU fitted to the shed.

TNCS incomer

100A main switch

6mm T&E >50mm from the surface of any wall  [ 12m length ]

surface clipped not in contact with any insulation

changes to 10mm 4core SWA for outside run @ 12m length , 2 cores are redundancy so CANNOT  be used for anything else, but loading on them CAN be ignored for the purposes of this exercise.

the cable is already installed so is non change-able, you have to work out the max permissable loading and what protection I require.

 

[SLIPSHOD & SLAPDASH]

Does the number of beer cans in the fridge affect the resistivity of the copper thus loading up the PD on the cpc.

 

[steptoe]

Does the number of beer cans in the fridge affect the resistivity of the copper thus loading up the PD on the cpc.

probably,

but you already know you shouldnt be in here asking questions like that,

you are only allowed to point/push/prod the students into asking themselves more questions,

and no, the size of the beer fridge is irrelevant, that will be dependant on the size of the OCPD. 

 

[steptoe]

too much is never enough

its only correct if it works correctly

NO, Im fairly sure you had him for tea last night. 

 

[philbas]

OK I'll bite,  distend  to shed

 

[steptoe]

OK I'll bite,  distend  to shed

from where?

distance is stated.

6mm T&E is 12m long

10mm swa is 12m long

 

[philbas]

not that i can see

 

[steptoe]

Shed is 5m from the nearest point of the house.

 

[septiclecky]

Shed is 5m from the nearest point of the house.

 How far to the nearest street light

 

[steptoe]

30m to the wrong side of the house,

 

[wozz]

You need to give more info, like loading in the shed or you can't work out your volt drop, also size and length of cabling in shed, unless you are allowing the full % of volt drop on the submain.

Unless you are just looking at this from a Iz of the cable point of view?

 

[steptoe]

You need to give more info, like loading in the shed or you can't work out your volt drop, also size and length of cabling in shed, unless you are allowing the full % of volt drop on the submain.

Unless you are just looking at this from a Iz of the cable point of view?

well pointed out,

1.5kw compressor

140amp arc welder , can be taken as 16amp max.

small pillar drill <1kw

various hand power tools, grinder,drill etc

5 x 5' flourescents

2 x low energy outside lights

1 x natural daylight internal hand lamp, 3amp

NO electric heating under normal use so can be ignored.

radio, laptop, PC, phone charger etc etc etc

as you can see, no major loading really.

cabling within the shed can be ignored, that wont be the limiting factor.

 

[ProDave]

I think step's is saying "this is the cable e have and it's not being changed"

So what OCPD should it have and what load in the shed can is support?

Perhaps you should follow on with suggesting what circuits in the shed would work?

And discuss the pro's and con's and reg's about connecting the two "spare" cores in the 4 core SWA in parallel with the two in use. (though Step's says not to use them)

 

[SLIPSHOD & SLAPDASH]

well pointed out,

1.5kw compressor

140amp arc welder , can be taken as 16amp max.

small pillar drill <1kw

various hand power tools, grinder,drill etc

5 x 5' flourescents

2 x low energy outside lights

1 x natural daylight internal hand lamp, 3amp

NO electric heating under normal use so can be ignored.

radio, laptop, PC, phone charger etc etc etc

as you can see, no major loading really.

cabling within the shed can be ignored, that wont be the limiting factor.

You forgot the beer fridge & kettle in your list.

 

[steptoe]

You forgot the beer fridge & kettle in your list.

if I have the first why would I need the 2nd? 

well spotted though.

I think step's is saying "this is the cable e have and it's not being changed"

So what OCPD should it have and what load in the shed can is support?

Perhaps you should follow on with suggesting what circuits in the shed would work?

And discuss the pro's and con's and reg's about connecting the two "spare" cores in the 4 core SWA in parallel with the two in use. (though Step's says not to use them)

thats about it Dave,

the cable is already installed down the garden, and obviously the internal bit was put in when I rewired the house.

 

[Sharpend]

If you're having difficulty I recommend you call a qualified local electrician in to assist you!

 

[steptoe]

Im wanting to get it all in and connected up before I ring Deke to come and 'sign it off' for me,

and yes, I have used plenty of silicon on the swa glands that are outside,

should I tape a tesco bag around where its choc blocked to the T&E?

 

[kerching]

For protection I would advocate a bus shelter and a packet of three

Just proferring!

 

[wozz]

I cant find a limiting factor other than It, although this leaves next to nothing VD wise for the final circuits.  

Obviously cant do shock and thermal constraints.  

 

[SLIPSHOD & SLAPDASH]

.should I tape a tesco bag around where its choc blocked to the T&E?

No no no, they degrade far too quickly. Asda's are much more suitable. 

If you're having difficulty I recommend you call a qualified local electrician in to assist you!

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