Swa flat cable help

[danny124]

Hi wondering if someone can help, I left my BRB in my office and stuck on job trying to work out a few things.


I need the CCC of 16mm flat SWA 2 core cable, armoured is takin earth from meter cupboard to flat on 2nd floor. roughly a 15m run as its already a exisiting installation, it grouped with 5 other supplied feeding other flats from there own independant switch fuses....
Main system is TNCS PME... Ze at switch fuse is 0.09 Ze at CU 0.12.

But my client has decided to get her builder in to refurbish the bathroom and already plumbed in a wacking 9.5kw shower (41amps) so a 45 amp mcb needed for this, then decides to call me in to connect up power to it and change board....


She got 32a cooker mcb, 32amp for ring, 16a for standby immersion, 6 amp for lighting.....and now a
My concern is the CCC will be able to cope with her new max demand of approx 79 amps
32+32+16+6 x 0.4 + 45 = 79.4


I already have one issue with her old MEM 60amp (Ceramic Rewireable) switch fuse that needs upgrading to at least 80amp.... (In main meter cupboard) EDF have given me permission to change this, but im assuming the main switch is rated 60 amp too so there fore EDF have got to change it as its tails are from meter.

But my main issue is the CCC of the existing SWA.


Cheers guys sorry if some dont make sense, written really quick on mobile....

 

[Guest123]

Clipped direct is 89A

Are they on tray or clipped direct etc???

 

[danny124]

As for as i can see Clipped direct, the dissapear up into a foot square cavity.

 

[Guest123]

Well I would apply the grouping factor (Cg) of 0.60 which gives an Iz of 89 x 0.60 = 53.4A


This is obviously based on the 5 cables touching, not on a tray or ladder and more or less equally loaded.

There may be other factors such as insulation properties, temperature, and you also mention a re-wireable fuse which has it's own factor, but you are changing that.

 

[danny124]

cheers Lenny, Even without the rewirable factor my clients in trouble then.....

Thanks mate