ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Pop Quiz V1.0

Guys,
Just want to add an element of quick quizzes to this particular Non-US Forum.
(If that is OK with PaulUK, of course!)
I have a cable, it is run from a Sub-Main to a submersible pump, that is 150m away from the panel/starter.(400V supply to the pump)
The cable terminates at the Weather-Proof Isolator where a flex, then feeds the pump, which is a 3 phase Delta-wired 3kW unit.
The cable is 3C SWA (or N/S) w/ Cu conductors.
The cable is buried direct for most of it's length.
Using your tables of Voltage drop, could you please submit a relevant cable size, for this installation?.
Please bear in mind, you are not doing cable calcs, that I cannot be bothered doing, it only looks like it!.

Trumpy.

eith a direct buried SWA cable to feed the pump via a TPN (triple pole n neutral) isolator,
then via a flex, or Kopex (flexible water proof tubing) to the pump.

Me personally would use 4.00mm 4 core SWA, and using the wire armour as a supplimentary CPC not primary.
John H

John,
Thanks for your input.
I done the calcs, not long before I posted this topic.
And for the length of run and current draw(in-rush included) I came up with 4mm2 too,
using 3C+N/S, buried direct, with no additional mechanical protection.
Having said that, I note your remark about using a core of the cable as an Earth Conductor, I don't personally like the idea of using the Armouring or screening(as the case may be) as the primary Earth conductor.
And using one of the cores in this fashion, means also, that it is easier to terminate at both ends!.

The question of whether to rely on the armor as the sole earth connection seems to be a little divisive at times.

The difference in price between 2-core and 3-core isn't that great, so in general I'll buy 3C for a single-phase line and use the spare as an earth (with the armor still grounded as well, of course -- I've seen SWA installed with the armor just left cut-off and disconnected at both ends!).