Cable size sub main

[MATTMGM]

Hi all, looking for a bit of guidance/help please..... I have been asked to confirm the correct cable size on a sub main that supplies the communal area of a block of flats (4 flats in total).

All that is supplied from the consumer unit under the stairs is a 2kw heater, led lights x 6, 2 x cleaners sockets, socket for tv/sky and circcuit for smoke alarms.

The cable is swa buried underground in a duct 25m long.
Consumer unit (under stairs) is 100amp main switch with 63amp rcd.

I have done cable calcs but my calculations seem to be equalling to a small csa.

Thanks for your help.

 

[Darkwood]

Hi MATMMGM if you don't mind posting your calculations up and results this way any errors can be quickly identified for you and pointed out

 

[Spoon]

As above mate. If you post up your calculations we can tell you if your are right or where you went wrong. There is no learning in us just telling you the correct size.

 

[malcolmsanford]

Is the heater going into a socket or is it going to be fixed via spur.......... separate circuit or coming off the cleaners circuit that is the first thing 16amp MCB?
2 cleaners socket on a radial 16amp MCB?
6 LED lights on a radial 6 amp MCB?
1 socket for sky is this going onto a separate circuit or are you taking it off the cleaners?
FA circuit 6amp MCB?

So next questions are

• What are you connecting your SWA to ?
• What is the protection device for the SWA?
• Are you expecting that all these circuits are going to be energized at the same time?
• Are you going to apply diversity and therefore size your SWA CPD to that?

 

[MATTMGM]

Hi MATMMGM if you don't mind posting your calculations up and results this way any errors can be quickly identified for you and pointed out

Hi, thanks for your reply

i am am at work at the moment but the cable size I got was 2.5mm SWA. Seems a bit small for me ???

 

[Spoon]

Hi, thanks for your reply 

i am am at work at the moment but the cable size I got was 2.5mm SWA. Seems a bit small for me ???

And how did you get to this size? Show us your calculations mate.

 

[HandySparks]

What overcurrent protection does this distribution cable have?

 

[Leesparkykent]

How long is the lighting circuit for the 6x led lights?

 

[MATTMGM]

What overcurrent protection does this distribution cable have?

32 amp MCB

 

[Leesparkykent]

32 amp MCB

2.5mm SWA on a 32amp MCB?

 

[Darkwood]

You also need to give a little room for expansion or additions, once you find the correct size cable for the small cost difference I would be sizing up a submain supply in your situe', its not just about what you can get away with cable size wise.