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Forum Index : Other Stuff : 3 phase to neutral Loads.

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Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 1585

Posted: 04:47am 11 Jan 2026

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I am trying to get some clarification on this as I get a lot of conflicting opinions so maybe the knowledgeable people I trust can give me a consensus.

With 3 phase power, if connections are from each live back to neutal for 3 single phase connections/ loads, What is the load Limit PER PHASE when all are used together AND if only 2 phases are in use?

Lets say the cables are 6mm / 32 Amp.

Is the power that can be pulled 32 A total across / divided by the 3 phasese or 32 per phase?

If only 2 of the 3 phases are being used, does that change the per phase load limit?

Again, I am talking specificaly each live to neutral for 230V, NOT phase to phase 415V.

I won't give anymore background to my thoughts and what I have been told which may confuse the question, I'll leave the question as that as I'm interested to see what people here say.

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2921

Posted: 07:39am 11 Jan 2026

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The basic limit for a 32A 4 core + earth cable is 32A per phase, regardless of whether 1, 2 or 3 phases are drawing that current. The worst-case neutral current will be 32A. If the 3 actives carry the same current the neutral current is 0 as it is the vector sum of the active currents.

The exception is if the temperature is likely to approach the limit for the cable insulation.
There are de-rating tables that set a lower current in such situations.
Edited 2026-01-11 17:40 by phil99

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