Cable table which column to use

Use columns 2,4 or 6 as appropriate to your installation method

So I use the 2core column if I’m correct?

So I use the 2core column?

Yes, the three core columns are for three phase whether neutral is there or not. I suspect that the asterisk in other tables indicated a test house determination having included and omitted the earth core in their tests. Perhaps the same tests were not run on the swa cables in 4D4A as the earth was traditionally either the armour or a separate core. I an only offer my humble opinion that the inclusion of an integral core for earth in a single phase application would not have a detrimental effect on the current carrying capacity.

Thanks Lyle


Does this apply to all the tables, not just for SWA?


thanks


Peter

Does this apply to all the tables, not just for SWA?

I'd say so. As a general principle it's the current carrying cores that generates the heat - generally calculated on the number of fully loaded cores - hence a 4-core 3-phase cable has the same rating as a 3-core 3-phase cable - as the N current only carries the differences from the phases - so even in the worst case it's the same as three fully loaded cores.


But in all cases I'd say it's an approximation. The heat dissipation from say the centre core of a 3C+E flat cable won't be quite the same as from either core of a 2C+E flat cable - as it'll have the extra plastic surrounding the other outer core to contend with, but then once the heat's past that it'll have a larger surface area to dissipate from. Likewise the geometry of a 3-core SWA with two loaded cores isn't quite the same as a 2-core. But as long as you're got a few percent of the cable's rating as a safety margin, I doubt there's anything to worry about in practice.


   - Andy.

Yes, and of course these tables are for continuous operation in an ambient temperature of 30C so I would say for the vast majority of installations you have an appropriate inherent safety margin.

Thanks for your replies, 


On another note, in debating whether to use SWA or hi-tuff for a job I’m currently designing. As hi-tuff( that’s what it’s called in this area, I know others have different names for it) is basically pvc insulated cores with a tougher outer sheath, would table 4D2A be the correct one to use?


Thanks

That’s the one I would use.

HI Baldyhugh


If you look at the columns on table 4D4A  - Reference method C for example - column 2 is for single phase AC (It says this at the top of the column) and the next column 3 says that it is for three phase. 


Hope this helps ;-)


Kind Regards

Tatty