sub main

[dochisholm]

Need to supply a sub main in a farm mechanical workshop need to work out cable size earthing isolation want to have about 40 amp supply about 5 meters run on catinary just wondered what would people do. Already have 8 way board with 30ma at end of circuit

 

[telectrix]

can you not run SWA buried? much neater job. 6mm or 10mm XLPE SWA.

 

[dochisholm]

Can't trench there is a weighbridge there

 

[telectrix]

so 6mm XLPE SWA, well capable of 40A. decent catenary. can you go high enough to be above wagons on the weighbridge?

 

[dochisholm]

Yeh that's ok would I have to go 10mm for 50 amp how would you supply sea and would you tt it or bring earth from cutout

 

[telectrix]

50A is borderline for 6mm. google AEI cables and use their cable finder wizard.it calcs VD as well could poss. get away with 6mm XLPE, allowing for diversity.10mm XLPE is rated 81A, be inclined to export earth from cut-out or you will have to RCD alll circuits to achieve disconnection times if TT.. 63A switch fuse at supply end (10mm) . CU and RCD/RCBOs workshop. bear in mind only sockets need RCD as long as other circuits are surface wired. (TN earting)

 

[dochisholm]

Regs state all circuits on agricultural land needs 300 ma protection

 

[dochisholm]

oobviously with 30 ma on sockets e.t.c

 

[telectrix]

300 ma??? what reg. is that?

 

[dochisholm]

Page 183 705.411.1 iii Ian all other circuits rcds with ma not exceeding 300 ma

 

[Des 56]

I would just string some 6mm twin+e enclosed in plastic conduit and tie it to the catenery wire
An swa cable would be better,but if it cant be buried,its weight on the catenary would outdo any advantages