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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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    Well any one immersion heater element only has 2 ends. so is intrinsically a single phase item. You may elect to run it on 400V of course if you want it to boil faster, and have 400v available 230V insulation to earth should be up to it ?.

    A 3 phase electrode boiler has all 3 phases in the water and no element as such. Same idea as these nasty devices not permitted in the UK. (nasty also in that your tea tastes sort of metallic )


    Not to be confused with the un-insulated element devices like this popular in less affluent countries. (skip to 5 mins in to see the elements,  and how the CPC earths the waterflow, after a fashion.) I have been assured these are perfectly safe on 30mA RCD so long as the water is reasonably pure. (and we worry about sockets in bathrooms....)
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  • 0
    Well any one immersion heater element only has 2 ends. so is intrinsically a single phase item. You may elect to run it on 400V of course if you want it to boil faster, and have 400v available 230V insulation to earth should be up to it ?.

    A 3 phase electrode boiler has all 3 phases in the water and no element as such. Same idea as these nasty devices not permitted in the UK. (nasty also in that your tea tastes sort of metallic )


    Not to be confused with the un-insulated element devices like this popular in less affluent countries. (skip to 5 mins in to see the elements,  and how the CPC earths the waterflow, after a fashion.) I have been assured these are perfectly safe on 30mA RCD so long as the water is reasonably pure. (and we worry about sockets in bathrooms....)
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