Sub mains

[colin_scuba]

6 apartments on 3 floors being fed from switch room in cellar, maximum rating 80amp.
Can I use 16mm twin and earth as oppossed to armoured to save on costs?

 

[camerabloke]

dont see why not. volt drop taken into consideration?

 

[GLENNSPARK]

how is the cable to be run?..
riser?


or within a wall?

 

[Darkwood]

You need to assess the cable install methods and whether you require mechanical protection to void a 30mA front end rcd been a discrimination issue to the rcd's in the sub DB.. not fitting rcd coverage in the sub DB will be poor design as any earth fault would render the whole flat without power and resetting would be remote to the flat.

SWA with HRC fuse to 17th consumer unit is the best way and better for future proofing with less issues all round regardless if T&E is all surface and RCD not required.

 

[colin_scuba]

how is the cable to be run?..
riser?


or within a wall?

sub mains
will be run up a riser then into the ceiling to the consumer unit

 

[GLENNSPARK]

sub mains
will be run up a riser then into the ceiling to the consumer unit

go with a SWA...
as dark has said here...

SWA should be generally the cable of choice for buried subs & feeders...

 

[colin_scuba]

Many thanks Darkwood for your help

 

[Darkwood]

sub mains
will be run up a riser then into the ceiling to the consumer unit

This still dosn't answer what i asked 'Does it require mechanical protection' be it in the short run from the ceiling to the DB or from the source to the riser.

Also regarding the ceiling run i hope you have factored insulation into the equation if it will ever be fitted even at a future date (ignore if not a factor). If it is a thought then the cable size seems a little on the small side although info is limited.

Lastly what about your earth conductor CSA ensure you comply to BS7671 additional earth conductor may be required with the T&E option.

 

[GLENNSPARK]

if the client is too tite to see to specifying SWA..thats their problem isn`t it...

remember: costs come secondry to conformance...

 

[colin_scuba]

Thanks also Glennspark

 

[colin_scuba]

If we are going to use T+E then we are going to run a 10mm supplimentary
but I thinking of going for the option of armoured for the reasons you stated.

 

[GLENNSPARK]

If we are going to use T+E then we are going to run a 10mm supplimentary
but I thinking of going for the option of armoured for the reasons you stated.

and i doubt 80A will cut it either for 6 apartments.

i mean are there going to be any electric showers in these apartments?

- - - Updated - - -

what have you got coming in at the switchroom?

 

[Dizzy_Maskell]

Sorry may have have been discussed but need to verify earth will be big enough if using T&E as I have encountered issues with this method where earth cable was to small

 

[colin_scuba]

There is no electric showers there will be run off the boiler and now they are using gas for the cookers.
There will be 2 lighting, 2 ring mains and 2 16amp radial circuits max run is 45m . sub mains that is

 

[GLENNSPARK]

There is no electric showers there will be run off the boiler and now they are using gas for the cookers.
There will be 2 lighting, 2 ring mains and 2 16amp radial circuits max run is 45m . sub mains that is

well..
going by the finals in each apartment...comes out at 108A..
lets apply some diversity:
this number X.2 given that there wont be much usage of anything heavy in here by what you have said regards spec=21.6A...
so can you see that even with a very harsh diversity applied of .2 you will still be struggling at 80A..

you will need more juice than you are allowing for i`m afraid...