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elementps
Hi all, just after some help with the following, i have use the cable cals template as seen inthe sticky at top of forum.
Have been asked to price for a sub-main to a new shed/office being installed in garden.
TNCS system at moment, ze unknown, but have used max of 0.35 for calcs
cable run to outbuilding is 30m
Planning to install a 20a radial and 6a lighting circuit so design current max 26a, 32a breaker
Correction factor of 0.9 for burried cable, comes out at 35.55a
so i use a 40a breaker???
from table 4e4a, 4mm burried will carry 43a
vd = (30x26x12)/1000 = 9.36v within limit of 11.5v
max zs for 40a EN60898 is 1.15*0.8 = 0.92
zs = 0.35 + (9.22x30x1.2)/1000 = 0.33 + 0.35 = 0.68
Now here's where I am unsure...
fault current = 230/0.68 = 338.24a
min cpc size = square root of (I2xt)/k
do i use 0.4 or 5 for my t value?
Please advise, sorry if long winded, any help much appreciated.
Have been asked to price for a sub-main to a new shed/office being installed in garden.
TNCS system at moment, ze unknown, but have used max of 0.35 for calcs
cable run to outbuilding is 30m
Planning to install a 20a radial and 6a lighting circuit so design current max 26a, 32a breaker
Correction factor of 0.9 for burried cable, comes out at 35.55a
so i use a 40a breaker???
from table 4e4a, 4mm burried will carry 43a
vd = (30x26x12)/1000 = 9.36v within limit of 11.5v
max zs for 40a EN60898 is 1.15*0.8 = 0.92
zs = 0.35 + (9.22x30x1.2)/1000 = 0.33 + 0.35 = 0.68
Now here's where I am unsure...
fault current = 230/0.68 = 338.24a
min cpc size = square root of (I2xt)/k
do i use 0.4 or 5 for my t value?
Please advise, sorry if long winded, any help much appreciated.