Electrical Distribution Help!!

[Ben Revell]

Well i'm a building services engineer but im not very experienced and have come across a problem.
As a ring main is generally only allowed to supply 100 sq m. I have a building that is about 70m long and the bottom 2 rooms are roundly about 50 sq m each. The DB board is at the top end of the building, the current wiring is a 2.5mm ring main from the DB board.

The Current wiring provides me with a voltage drop of roughly 30v. Which is very excessive for a final circuit not to mention the extrememly high earth fault impedance.

To solve this problem i have estiamted in a 40A MCb and the DB then a 16 sq mm cable running up to the end of the building and maybe a mini DB board or even just a fused 32A switch then the 2 rings coming off that.

I need to try and keep as much of the exisiting 2.5mm cable in as i can.

Thank you in advance for your help.

 

[davelerave]

30v is big volt-drop

you sure that's installation voltage drop

 

[Guest123]

30V VD on a ring final....do any of the lights in those rooms work???

Installing a large SWA sub-main would be the best way out no doubt, size it large enough to give you plenty of scope for VD on any future circuits that may get installed. A secondary DB is a better option than a single "fused switch" as the rings are seperate circuits, and you will also have the scope for future additions.

 

[ezzzekiel]

Well i'm a building services engineer

why would an engineer be asking us lowly electricians
as lenny said run a submain in or otherwise you gonna need big cables for the ring

 

[High Tower]

Sod all the sub main malarky just re-wire the ring in 10mm t&e

 

[ezzzekiel]

thats in the 18th edition - all circuits require 25mm swa cabling