200a tpn for house?!

[J.C.E]

Can i scratch your head (bare in mind biggest i have done is 25mm 4core ?)

I am tendering for a big house new build

I think they already have 100tpn
(But in a kiosk 40m away from house)

And i think they are doubting its big enough now (they sent max demand table below)

So they are asking for a price for 200a tpn sub mains to house if they upgrade from 100a to 200a tpn.

Am i right that the swa from kiosk to house (40m through underground duct)

Will need to be 150mm 4c with a 120mm cpc

And its just bad design that the income is so far from the house and needs a swa sub main!

 

[westward10]

If you have only ever put in 25.0 then 120.0 is going to be a whole new experience over 40m. Personally I would use parallel 70.0s and that is still a task there are however companies you can sub this out to who have all the equipment and specialise in just this kind of thing.

 

[pc1966]

Another option is tripled cables? Looking at OSG table F3 grouping would be 0.7, so per-cable CCC needed is just under 96A for 200A total. That is met for 70C at 35mm (or at 90C for 25mm).

You would need fairly big duct to get 3 * 4C 35mm + a 35-70mm CPC run through, but if you end up doing it without a lot of experienced/tooled-up help it might save you a lot of pain even though cost is not hugely different to a 4C 120mm solution.

The problem with cable CCC is the loss is I2R so for a given ability to get rid of heat you need 4 times the CSA for double the current. It is not always quite so bad as bigger cables can get rid of heat faster, but that depends to a degree on the surface area which goes up roughly with sqrt(CSA) and might well be further restricted by the overall size of duct, etc, so you still see a painful increase in cable size, cost and wrangling difficulties.

Edit: Just to add 35mm should meet adiabatic for 200A fuse so fancy protection for members of the paralleled set should not be required.

 

[pc1966]

I guess taking this to its logical conclusion, how about 4 * 95mm AWA single core copper cables and a 50mm CPC in suitably sized twin-wall duct (e.g. 160mm OD / 140mm ID)?

You would need non-ferrous gland plates and to carefully identify each conductor, etc, as well as checking the gland type for use with aluminium armour, but each conductor is going to be far easier to wrangle and you don't have any issues of how to terminate 2 or 3 parallel conductors at the end points.

 

[UKPN]

I haven't calculated it but 240.0 sounds well oversized. For ease of installation parallel cables are often better and I would have thought a pair of 70.0s would suffice but it needs calculating using a 2% vd. The cpc size will need calculating and it must be of a csa to support the main protective bonding but again 185.0 seems oversized.

240 oversized, bigger than the street cable! more info needed!

 

[James]

240mm took me 2 days to terminate the ends, as mentioned above, a whole different game to playing with 50 and under .

 

[pc1966]

Any update on this project @J.C.E ?

While I personally hope never to have to wrangle more than 50mm (unless tri-rated!) I would be interested how things worked out.