flour.tube batten 2way+interm. in plastic cond.-how to wire?

[Adam_151]

I mean if you sum all the currents in all the conductors in a cable/conduit... eg, phase might be carrying 5A, but neutral is carrying 5A in the opposite direction to phase, so if you put a clamp meter on both you'd get 0A because they cancel / sum to zero, if the phase and neutral take different routes then the contents of the indivual cables/ conduits won't sum to zero, which can cause problems with interference to electronic devices, and if a group of conductors which don't sum to zero are totaly surrounded by metal (metal conduit, or metal holes in boxes*) then it can cause issues with eddy currents as it forms an unintentional shorted transformer... (though with a small lighting load the currents involved probably arn't going to be high enough to warm it noticeably...)

*A quick solution to if say phase and neutral have to enter a metal board through separate holes due to physical reasons, would be to cut a small slot between them, and the cables arn't indivudally surrounded by metal; the two holes are effectivly one hole surrounding both cables now

Sorry if this sounds patronising or anything, thats certainly not the way it was intended, I'm most certainly not the best person at getting a point across in an elegant way

 

[Bright_Spark]

Adam, i know what your saying Re: having cables summing to zero and the possibility of eddy currents accuring.

but in this case, the task in hand is for the 2330/2 assessment where you are given 10 hours to install and test different circuits using recognised methods.

the fella will be using plastic conduit for the lights and probably metal clad switches and boxes. for purposes of this installation, at that stage in 2330 what you described is not an issue.

they are looking for high standards in the physicalities of the install - eg. have you made the conduit bends at 90 degrees, have you mitred your trunking properly along with demonstrating that you have the know how to install/terminate an electrical circuit and that you know how to carry out basic testing - R1+R2, ins res, polarity, continuity and that you can identify electrical accessories such as knowing the CSA'a of your cables and being able to identify and use correct valued 3036 fuses etc.

all will become clear when you start your college course adam, because i dare say that you will be doing something very similar, if not the same for your assessment.

 

[scousespark]

Got what you were referring to Adam. The OP was referring to plastic conduit so did not think about eddy currents. As Bright Spark said at 2330 level the emphasis is on how to do things and you won't be going into the depths of electrical physics. Only when you get into large scale commercial/industrial builds will you deal with the issues you refer to.

 

[Spark123]

I don't quite understand why this thread went this way, just to clarify a metal conduit wiring system should have the wires drawn in so the resultant current in any given piece of pipework is zero. This can be given by both the phase and neutral being in the same conduit or both the phase and switched return being in the same conduit, (the current in both the cables is the same but flowing in the opposite direction.) Problems can occur when phase and neutral or phase and switched return are run in separate metal conduits.

 

[Spark123]

A sketch of a conduit 2 way intermediate lighting system using singles: