Hi all, new to here.
Just designing a sub main, very long time since I have done this so just wanted some thoughts. Its to a summerhouse sort of set up that will be at the bottom of a very long garden at a later date (sockets, lighting and hot tub planned from the board). Patio is getting done soon so they are wanting the cable buried under that ready for when the rest of the garden is done, and it will be buried under the path that gets done.
Was thinking of installing 16mm 3 core XPLE SWA, fed from an 80amp DP switch fuse. The current meter tails are into a henley block before DB in house, so separate set of tails from the henley block to incoming side of switch fuse, and then sub main out.
The calc I have done is for part of the run, approx 58m which will be from an weatherproof box on the side of the house, down into the ground at a depth of 0.5m (internal of the house to the DB was going to calc down to a smaller cable given the run, clipped direct, and come in the back of the weatherproof box, so as not bringing a 16mm or bigger cable out the side and having to chop some of the render away as to get a decent bend). Cable will be grouped with another SWA for outside lighting on the patio (have accounted for cables touching).
Ib = I have allowed 15kw (not sure on ratings of hot tubs etc but thought I would allow more on this initial design) 15000/230 = 65.21amps
In = 80amp switch fuse (board in summerhouse will have a 63amp RCD incomer on 3/4 way board)
Factors of 1.03 (buried direct 0.5m) & 0.75 (cable grouping) assuming ground temp of 20 deg and thermal resistivity of soil of 2.5 both giving factor of 1
It = Ib/Cd*Cg = 65.21/1.03*0.75 = 84.41amps
Table 4E4A ref method D direct in ground is 16mm capable of 91amps
Volt drop = 5% so 11.5v therefore 65.21*58*2.9/1000 = 10.97v therefore acceptable
Is there anything I may have missed? Keep on second guessing myself.
PGA
Just designing a sub main, very long time since I have done this so just wanted some thoughts. Its to a summerhouse sort of set up that will be at the bottom of a very long garden at a later date (sockets, lighting and hot tub planned from the board). Patio is getting done soon so they are wanting the cable buried under that ready for when the rest of the garden is done, and it will be buried under the path that gets done.
Was thinking of installing 16mm 3 core XPLE SWA, fed from an 80amp DP switch fuse. The current meter tails are into a henley block before DB in house, so separate set of tails from the henley block to incoming side of switch fuse, and then sub main out.
The calc I have done is for part of the run, approx 58m which will be from an weatherproof box on the side of the house, down into the ground at a depth of 0.5m (internal of the house to the DB was going to calc down to a smaller cable given the run, clipped direct, and come in the back of the weatherproof box, so as not bringing a 16mm or bigger cable out the side and having to chop some of the render away as to get a decent bend). Cable will be grouped with another SWA for outside lighting on the patio (have accounted for cables touching).
Ib = I have allowed 15kw (not sure on ratings of hot tubs etc but thought I would allow more on this initial design) 15000/230 = 65.21amps
In = 80amp switch fuse (board in summerhouse will have a 63amp RCD incomer on 3/4 way board)
Factors of 1.03 (buried direct 0.5m) & 0.75 (cable grouping) assuming ground temp of 20 deg and thermal resistivity of soil of 2.5 both giving factor of 1
It = Ib/Cd*Cg = 65.21/1.03*0.75 = 84.41amps
Table 4E4A ref method D direct in ground is 16mm capable of 91amps
Volt drop = 5% so 11.5v therefore 65.21*58*2.9/1000 = 10.97v therefore acceptable
Is there anything I may have missed? Keep on second guessing myself.
PGA