Same Phase Wires in Single Conduits

It may be from a practical point of view.. Your loads are all single phase. Why do you want to bring the other two phases in the line with the additional risks.

The wirings also from MCB will be a bit less complex.

Also if we feed the phases to zones, say room1,2 phase R, Rooms 3,4 Phase Y etc, the identifications of faults may be easy.

At least that is the idea I got from electrician when he did my home wiring (3 phase).

Dear Guest,

What you are saying is contrary to good practice. If you split the phases between conduits, you invite the generation of large circulating currents in the conduit and in any metal surfaces (eg switchboard panels) the conductors pass through. These circulating current will cause significant heating issues, and will use energy that will add to the power charges.

Good practice is to put all three phase conductors, and the neutral if one is ionstalled, in the same conduit. If you need multiple conductor sets, you should put each complete set into its own conduit.

On single phase loads, it is OK to tun one phase per conduit as long as the neutral wire is included in the same conduit. Also make sure that the load is supplied by the same neutral wire as the one running in the phase conduit. If you use the neutral from another conduit, you will have circulating current loops and EM problems.

To avoid this problem, make sure the different phases supply geographically separated sections of the building. E.G. one phase per floor.

G'Day Prashanth, You bring us a very interesting question.

On a humorous note, I first thought to post that someone has been reading "Wiring For Dummies", but decided against that since In the translation the humor could be missed.

On a serious note, if only one phase is run in the conduits, there will be a higher cost in wire since each run must also have an accompanying neutral. Two or three different phases can share the same neutral without increasing the size of the neutral.

I can only presume that someone has instituted this method for circuit organizing reasons. Either they mistakenly thought this a good electrical choice due to lack of short circuit possibility, or the color of the wire may not be the actual phase indicator.

It is possible to use red conductors for all three different phases within the building so as to group conductors by panel or purpose rather than by phase. If so this will be quite confusing if, as you state, the normal electrical person will be assuming that they are the same phase.

If they are truly the red phase, yellow phase etc, segregated into their own conduits, then all the circulating issues mentioned, in addition to a real problem with balancing the loads and running a lot of extra neutral wires will be encountered.

As for the UPS and raw power issue, that is simply to delineate which is which, and no interference would be caused if they ran together. Again, organizational in nature.

Regards, CJM

This doesn't seem to make sense because if the same phase were ran in a conduit then the hysterisys would result in overheating.

Here in the States we run a "full boat" (phase A,B,& C along with a neutral) or multiple "full boats" or the largest portion thereof. with this configuration the phases effectively cancel out the heat generated by one another.

Surly you mean cancel out the magnetic field.

true but the resultant heat is the major problem.

For ref, see NEC 300.20 "Induced Currents in Ferrous Metal Enclosures or Ferrous Metal Raceways" Also, 215.4(B) under Feeders with Common Neutral Conductor. Other sections that have a bearing: 250.102(E), 250.134(B), 300.3, 300.5(1) and 300.20. All refs pertain to the 08 code.

What happens when you pass a magnetic field through a metal object? Answer, It tries to move. This is what causes the conduit to heat up when you put opposing phases in separate conduits and they are too close together. This is why we run three phases in a single conductor in feeder circuits, each phase cancels the others out. In branch wiring we have a neutral in each conduit and it achieves the same effect.

There is much more to this but I am not going to go any farther.

In answer to the second part of your question. A UPS is usually installed as an emergency power supply during a normal power interruption. If this interruption was caused by the conductors shorting out in the same conductor you ran your UPS conductors in, you would effectively take out your emergency power also. So no it is not a good idea to run your UPS power with the building supply power.

Actually there is no problem running R phase ,Yphase ,B phase in different conduits if you do wiring for house/building etc and more over it is good practice to divide circuit on different phases for different rooms

but it is not acceptable in case you have no. of single core cable say 2 single core per phase and heavy load say 1000Amp .in such cases you should run cable in trefoil(triangular) format ,if you dont do this chances r there that cable life will be shorter because in trefoil format electomagnetic field develop by each cable nullify each other and hence cable does not heat up unnecessarily.hope it it clear now

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