sub boards

[beech1984]

hello there everyone just got a quick question in regards to a new installation i am doing at the moment it is a manor house 20m in length.


i was wondering whats the best way to go about it i would like to put a domestic board on each of the 3 floors and one in the basement is it best to come off the main service board with a 100a breaker to first board then from second with 100a.


any ideas???

the incoming supply is single phase 100a/125a

 

[davelerave]

if you run a separate distribution circuit to each board it's tricky-you have to calculate demand for each etc.
on a small supply

a ring-main would be efficient (if rules allow)

 

[SirKit Breaker]

hello there everyone just got a quick question in regards to a new installation i am doing at the moment it is a manor house 20m in length.


i was wondering whats the best way to go about it i would like to put a domestic board on each of the 3 floors and one in the basement is it best to come off the main service board with a 100a breaker to first board then from second with 100a.


any ideas???

the incoming supply is single phase 100a/125a

Did a similar job a few years back in the 16th edition days. big board in cellar 17 way if i remember. Used this board for all circuits in cellar and ground floor. Used 40a MCB's to feed boards on each of the top 3 floors wired in 10mm T&E plus an additional 6mm earth. each floor only had lighting and sockets, and some fancy bathroom lighting set up with inset lights, spa bath etc so no big loads. Customer didnt want to be going to cellar in the event of a trip. You could i suppose do same using RCBO's etc to make it 17th compliant. If i remember i put in 6 way boards on each floor, 100a main switch, 6a mcb, 63a 30ma RCd, 32a mcb.

Cheers........Howard

 

[davelerave]

ya- if it's just lights and sockets on top 2 floors should be straightforward

apartments are prob simpler as the demand is prob the same for each

 

[High Tower]

Problem is that if you have a sub main per floor then you have the problem of either mechanical protection, or RCD discrimination.

Either sub mains would all have to be on their own time delayed RCD or would have to be in SWA.

If the sub was RCD time delayed then a fault on a light circuit on one of the floors would take out the T/D RCD on the dist board and take out the whole floor

 

[davelerave]

forgot that we don't have that here

do you have to rcd it if it's ran between joists and rises in pvc trunking ya

if so swa glanded supply side -or you'd have to 30mA rcbo final circuits i suppose

 

[SirKit Breaker]

When i have done flats and apartments there has always been a switch room with incoming 3 phase into a bemco unit, the meters and isolators already fitted. I have then run 16mm SWA to each unit and connected CU to it, and connected circuits as normal in each flat. The last one I did was a block of 12 on 3 floors, It was amusing watching the cable jointers in the pouring rain, 6ft down a hole.

Funny how you never meet an old cable jointer, and if you do they have fingers missing

Cheers........Howard

 

[mogga]

if there is a "Riser" cupboard on each floor you could use split concentric cables but the phase balancing would be hellish to work out

 

[High Tower]

It's a manor house not flats so it's not going to have risers

Swa is gunna be a pain to chase

 

[beech1984]

thanks to all your replies. the 16mm s.w.a will be on cable tray above a false ceiling so do you think it would be possible to sub it then. i was thinking with it being a house and not flats there wont be a great demand for load at the same time.

 

[High Tower]

No problems then

Use 3 core swa earth the swa for mech protection and use 3rd core for cpc