Any sparky's on here, need advice. - Page 4

HarryM1BYT · 8th May 2014, 09:51

On a multi-phase system, it is best to consider the neutral as a 'balancing conductor', with the aim to have the minimum imbalance current flowing through it. Which is why you should try to balance the load on each phase.

The current flows between phases, even on a single phase supply.

On a street of houses, each with a single phase, the first house will be P1, then P2, then P3, then back to P1. The idea is to balance the load on each phase, so there is minimum current flowing on the neutral. The current flows from from one house another via the phase, then the neutral, then back via the other house's phase. So the neutral back at the substation will, if the system is well balanced will be carrying very little current. Often the neutral can be half the size of the phase conductors.

So to answer your neutral sizing question...

It needs to be big enough to carry the larger of the two oven loads, but it will never be asked to carry both loads, because one will balance out the other. So if 2.5mm is big enough for each phase, 2.5mm will be big enough for the neutral.

Sorry for the ramble, but I think it important to understand why 2.5mm is adequate.

8th May 2014, 09:51	#31
HarryM1BYT This is my second home 75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD Join Date: May 2010 Location: Leeds Posts: 17,273 Thanks: 2,160 Thanked 2,061 Times in 1,586 Posts	On a multi-phase system, it is best to consider the neutral as a 'balancing conductor', with the aim to have the minimum imbalance current flowing through it. Which is why you should try to balance the load on each phase. The current flows between phases, even on a single phase supply. On a street of houses, each with a single phase, the first house will be P1, then P2, then P3, then back to P1. The idea is to balance the load on each phase, so there is minimum current flowing on the neutral. The current flows from from one house another via the phase, then the neutral, then back via the other house's phase. So the neutral back at the substation will, if the system is well balanced will be carrying very little current. Often the neutral can be half the size of the phase conductors. So to answer your neutral sizing question... It needs to be big enough to carry the larger of the two oven loads, but it will never be asked to carry both loads, because one will balance out the other. So if 2.5mm is big enough for each phase, 2.5mm will be big enough for the neutral. Sorry for the ramble, but I think it important to understand why 2.5mm is adequate. __________________ Harry How To's and items I offer for free, or just to cover the cost of my expenses... http://www.the75andztclub.co.uk/foru...40#post1764540 Fix a poor handbrake; DIY ABS diagnostic unit; Loan of the spanner needed to change the CDT belts; free OBD diagnostics +MAF; Correct Bosch MAF cheap; DVB-T install in an ex-hi-line system; DD install with a HK amp; FBH servicing. I've taken a vow of poverty. To annoy me, send money.