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Discuss 110 metre submain for 4/5 bed new build? in the Electrical Forum area at ElectriciansForums.net

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BillyH

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What size swa would be needed for a 4/5 bed new build property submain burried direct in ground?
 
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P

Plonker 3

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  • #2
Do the calculations for Volt drop, design current etc and you will have your cable size.
 
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BillyH

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  • #3
table 4D4B HAS 3 columns r, x and z. Which column do i use?
 
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Octopus

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  • #5
Astonishing.

Do you think you're ready for such jobs?
 

telectrix

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Arms
Esteemed
and if there are 4/5 en-suite showers with 4/5 teenage daughters, then it's do the calcs. and X by 3.
 
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BillyH

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  • #9
Astonishing.

Do you think you're ready for such jobs?
Been a long day . Out the house a 5.30 this morning and just got in.Don,t really need "help" like this. I know i should be able to do this in my sleep ( kinda feels like i am) but a little guidance might be more constructive
 
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Octopus

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  • #10
Been a long day . Out the house a 5.30 this morning and just got in.Don,t really need "help" like this. I know i should be able to do this in my sleep ( kinda feels like i am) but a little guidance might be more constructive
Maybe your post could have been worded in such a way to encourage people to help you.
 

Amp David

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Arms
Have never yet specced any cable size going off how many bedrooms a house is to have.

80 amp cut out lets say 50mm
 
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BillyH

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  • #13
Maybe your post could have been worded in such a way to encourage people to help you.
Sorry,should've been a bit clearer. I had an answer phone message on the way home asking for this info so just wanted a quick answer so i could knock off.
 
That's a very vague design...

Max demand = 4/5 bedroom house?

Don't know if that's accepted under bs7671. Any clues on run load ect
 
B

BillyH

  • Thread Starter Thread Starter
  • #18
Sorry for the vague info, i will explain more.The supply is for a 4 or maybe a 5 bed house (100A). Allowing for a 5% vd the cable size would be 50mm.

0.94x110x100/1000 = 10.34

Am i close
 

telectrix

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Arms
Esteemed
close, but VD for lighting is 3%, so i'd err on the side of caution. better to install a slightly oversized cable than have to dig out and replace an undersised one.

i got 70mm based on 80A demand.

5.6V drop.
 
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sedgy34

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  • #20
my apprentice wouldnt ask that question
 
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SPARTYKUS

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  • #21
Thats a big run. And a big cable. Will need jacks and strong blokes!
 
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BillyH

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  • #22
I just got an email from the guy. This is the only info i have. I know nothing about whats on site whatsoever so can't comment further .It reads as follows;


I need to put in 5 supplies. One each for the 3 units - these will all be say 3 bed, and no electric heating or showers. They each have a cable run of 75 metres.
One run needs to go to the house - this will be about 110metres, and it will be a 4/5bed house.
The other one needs to go to the sewage treatment plant, which is again about 120 metres, but only needs to run a 200 Watt pump.
Everything single phase.

Why would this be preferable to getting the board in to give new supplies?
 

Amp David

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Mentor
Arms
close, but VD for lighting is 3%, so i'd err on the side of caution. better to install a slightly oversized cable than have to dig out and replace an undersised one.

i got 70mm based on 80A demand.

5.6V drop.
Just a guess at 50mm, close though damn!!!LOL
 
S

sedgy34

  • Thread Starter Thread Starter
  • #24
I just got an email from the guy. This is the only info i have. I know nothing about whats on site whatsoever so can't comment further .It reads as follows;


I need to put in 5 supplies. One each for the 3 units - these will all be say 3 bed, and no electric heating or showers. They each have a cable run of 75 metres.
One run needs to go to the house - this will be about 110metres, and it will be a 4/5bed house.
The other one needs to go to the sewage treatment plant, which is again about 120 metres, but only needs to run a 200 Watt pump.
Everything single phase.

Why would this be preferable to getting the board in to give new supplies?
you need a site meeting mate and deisgn it correctly, also submains are cheaper than paying the dno
 
B

BillyH

  • Thread Starter Thread Starter
  • #25
my apprentice wouldnt ask that question
Nor mine. Its been over thirty years since i did my time so i think i'm entitled to be be a bit rusty,forgetful,senile or whatever.I'm not proud of asking such basic questions but if you're not sure its best to ask, is it not?
 

topquark

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Mentor
Arms
table 4D4B HAS 3 columns r, x and z. Which column do i use?
The r, x and z colums are values for resistance and corrections when taking into account reactance and impedance respectively. Only need worry about reactance and impedance over about 16mm.
 

UKMeterman

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Arms
For the big cables, ask the DNO for a quote if you agree to dig the trench for them, or use a contractor they normally use such as Murphy or similar.
 

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