Quick hello and a query!

krisspark · May 17, 2010

Hi Guys,

New on here and i have a query on a supply to a house......
Situation is this, i have a new build farm house and farm office to tender for and the new supply to the house has me scratching my head a bit!!
The SEB are to bring there new supply into the office building and terminate, the house is approx 80 meters away and the client wants me to install a 'sub main' with meter at office end, to the house.
I've never come across this situation before what with a house being supplied like this, i have done the calcs and the demand at the house end is 77a, the cable size i was going to run in was 35mm 2core and make the house a TT supply, being protected by a 80a switch fuse at the office end. I'm now wondering if this is sufficient? as 50mm would give more scope for additions in the futre but this does throw up termination issues at the house end?.........What i'm asking i suppose is if anyone else has come across this situation before and if they can pass on some of their valuable knowledge.

If any more info is required just ask as i'm keen to reach an answer on this or just to bounce a few ideas around.

Thanks in advance people

Kris

SirKit Breaker · May 17, 2010

As the 2 buildings are 80m apart, in my opinion it would make more sense to ask for seperate new supply to each building. This is what i would have asked for on the new connection paperwork. This way a fault in one wont impact on the other. You wont have to mess about with rods or exporting the PME etc etc etc and you wont be dealing with volt drop, big awkward cables and all that goes with it.

Cheers............Howard

krisspark · May 17, 2010

Hi,

Thanks for the reply howard, i've actually pushed this suggestion to the client and main contractor as it makes sense completely on all sides, however for some reason there not keen. The more i think about it the more it makes sense, i've explained the hassle factor to me and added cost and the view from an electrical point of view.....but....well i didn't get very far. I just wanted to explore the sub main angle and see if i was missing anything. I've got another meeting with the client and MC this week so will push the case for seperate supply to main house, thanks again for your reply.

Regards

Kris

SirKit Breaker · May 17, 2010

The other problem i can see is with your switchfuse. you are going to have to fit one within 3 metres of the incoming supply which i assume will be a 23KVa supply with 100a fuse. Therefore the switchfuse will be 80a. The links within the switchfuse will at best be 25mm but probably 16mm, therefore you will build up resistance and volt drop irrespective of the CSA of your 80m cable run. I cant see any other viable option except to have seperate supplies.