Sub db from 3 phase db

**Die sparky** · 18-Nov-23, 08:38 AM

Hi so the original idea was to run a single phase sub db 32 amp for a kitchen from a 3 phase 32 amp db so the guy installed 3 core swa cable but then i told him i dont think 32 amp is going to be enough for the kitchen i would rather go with 3 phase 32 amp. I believe he then added another 2 wires earth and a blue wire in plastic corrugated pipe. I will just flag the other ones the correct collours. Wil i need to have a circuit breaker for 3 phase plus neutral in the main db and wil they need a 3 phase plus neutral earth leakage in the main db becuase of the wires in the corrugated plastic pipe? I will probably put 3 seperate single phasw earth leakages in the sub db.

**Thys LOW Elektries** · 18-Nov-23, 11:13 AM

Safest option is the 4-pole breaker, you can then isolate everything in that db with the main breaker. After the main breaker you can put three earth leakages for the three single phase or a main breaker and earth leakage for each phase, these mains can be one pole mains.

**Dylboy** · 18-Nov-23, 08:59 PM

Also just a flag of something to look into is that the power supply must have the same wireway.

The exact reg and the terminology I didn't know and can't look up as I am away.

But my process of thought is you can't have the line in one conduit and the neutral in another, so 3 phase all the phases need to be in the same wireway.

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**Die sparky** · 19-Nov-23, 12:01 AM

Ugh that also. Probably has to do with eddy currents wonder if i can just cut a slot between the knock outs for the swa and the two wires

**Thys LOW Elektries** · 19-Nov-23, 07:29 AM

6.4.3.5 Each a.c circuit shall be so arranged that
a) all live cores are in the same wireway, P139
Not sure if there is any other regs though

**Thys LOW Elektries** · 19-Nov-23, 07:33 AM

Other than the regs I'm sure that if all the wires that belong together exit the wireway together it is easier to know its purpose and safe to assume they have the same source.
If one wire is here and another there, it makes problem tracing hard. So keep the cables that belong together, together and make it easier and safer for you and the next electrician.