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.

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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

As Phil says the neutral current is a vector sum of the currents in the three phases.
As the phases are 120 degrees out of phase if the phase currents are balanced then the neutral current is zero.
Depending on how out of balance the phase loads are the neutral current will vary.
There are online calculators available to calculate the current, or you can go back to the old method of drawing up vector diagrams and working out the current from there.
pete