Cable length

[Mac]

Personally i wouldn't rely on the armour sheathing as an earth.I would run a separate earth from the hut to the house.

 

[Keith the beef]

i feel the same way, however it would mean a trench digging across patio's and beautiful lawns, i am a little uncertain as what to do for the best, ie if i drop the supply fuses down to 80A i am in my earth loop for overprotective device tolerances whearas at the minute it doesn't comply

 

[Mac]

i feel the same way, however it would mean a trench digging across patio's and beautiful lawns, i am a little uncertain as what to do for the best, ie if i drop the supply fuses down to 80A i am in my earth loop for overprotective device tolerances whearas at the minute it doesn't comply

Is the armour not in a duct.Can you not put a spike in mate,saves all the hassle of digging the garden up.

 

[Keith the beef]

No duct as far as i can see,
Do you mean drop a spike in the ground near the house distribution board to lower the Ze? thus making 100A acceptable?

 

[Mac]

No duct as far as i can see,
Do you mean drop a spike in the ground near the house distribution board to lower the Ze? thus making 100A acceptable?

Yes mate

 

[Keith the beef]

it's one of the options i'm considering.
Mac i must thank you, you've stuck with me one this to the end, not a very exciting subject i know, we've suffered confusion, trying to explain via typing it's not easy sometimes.
Thanks again
Keith

Now lets talk about cheer leaders and motorbikes!

 

[Mac]

it's one of the options i'm considering.
Mac i must thank you, you've stuck with me one this to the end, not a very exciting subject i know, we've suffered confusion, trying to explain via typing it's not easy sometimes.
Thanks again
Keith

Now lets talk about cheer leaders and motorbikes!

Definitely mate

 

[Keith the beef]

Re this subject i have emailed the company who made the cable, they reckon as it's external diameter is 32mm it will be a 50mm 4 core swa, now the calcs begin!

 

[crabapple]

50mm2 = 0.387 mohms/m

length 100-150 m (assume its 150)

max conductor op temp for XLPE = 1.28

total R1+R2 = (0.387*0.387) * 150m * 1.28/1000 =28.756/1000 = 0.0287 ohms

Zs = Ze + total R1 + R2

Ze = 0.28 and 100A bs 88
Zs = 0.28 + 0.0287 = 0.3087

Ia=Uo/Zs

fault current is;

240/0.3087 =777.5 A

t = 1s (BRB pp248 bs 88 100A fuses in 1s with Ia of 790A !)

S = sqr rt(Ia^2*t)/k

k = 143
t =1s

sq rt(778*778*1)/143 = sq rt(605284)/143 =778/143 =5.44mm2



sorry, just couldnt rsist, sorry keith ignore me