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MCB & Cable Size for 3 Phase Star (Wye) with Neutral

Nano Brewery
Hi, I'm trying to understand/figure out what MCB & Cable Size would be required for a 3 Phase 9kW Immersion Element wired in Star using Neutral?  I have been a little confused by the results when using various online calculators. One example here: https://www.watlow.com/resources-and-support/engineering-tools/3phase-delta-wye-calculator

i.e. Using a Line Voltage of 400V equals a Phase & Line Current of 12.99A.  Where as using a Phase Voltage of 230V equals a Phase & Line Current of 22.59A?


My questions are:

1. Are these calculations correct?

2. What Amperage MCB would be required?

3. Would the MCB required need to be 3P, 3P+N or 4P?

3. Would 1.5mm2 cable at a 6 meter run be adequate?


Thanks in advance for your feedback and help.
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    3. According to BS7671:2018 554.1.2, "The supply to the electrode water heater or electrode boiler shall be controlled by a linked circuit-breaker arranged to disconnect the supply from all electrodes simultaneously and provided with an overcurrent protective device in each conductor feeding an electrode.". I would interpret this as needing a 3P breaker.

    As an aside, electrode heaters are quite a different kind of beast - literally just a few rods exposed to the water - no metallic heating "element" as such - the current passes through the water and the resistance of the water produces the heat.


    Normal immersion heaters don't fall into that category at all.


       - Andy.
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    3. According to BS7671:2018 554.1.2, "The supply to the electrode water heater or electrode boiler shall be controlled by a linked circuit-breaker arranged to disconnect the supply from all electrodes simultaneously and provided with an overcurrent protective device in each conductor feeding an electrode.". I would interpret this as needing a 3P breaker.

    As an aside, electrode heaters are quite a different kind of beast - literally just a few rods exposed to the water - no metallic heating "element" as such - the current passes through the water and the resistance of the water produces the heat.


    Normal immersion heaters don't fall into that category at all.


       - Andy.
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