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-   -   Any sparky's on here, need advice. (https://www.the75andztclub.co.uk/forum/showthread.php?t=173928)

petespieces 16th February 2014 21:38
Any sparky's on here, need advice.
 
I have an induction hob which I am connecting to two phases of my three phase supply.

The unit has five wires, two live, two neutral and one earth.

As per the installation diagram I will be connecting the two neutrals together at the unit.

The question I have is does the neutral from the fuse box need to be (approx) twice the size of one phase, for instance if the phases are 2.5mm should the neutral be 6mm.

I think the answer is no, 2.5 the same as the phases but need to be sure.

I have rewired the whole house and balanced the three phases so I'm quite OK handling the system (passed by EDF), just this one thing I need to know.



Thanks

Pete

Steve916 16th February 2014 21:47
The size of cable is determined by the load you are putting on it

petespieces 16th February 2014 21:53
Quote:
Originally Posted by Steve916 (Post 1579459)
The size of cable is determined by the load you are putting on it
The instructions state 2.5mm with 16a fuse for each live but does the neutral need to be twice the capacity of each live?

Thanks.

Pete.

Steve916 16th February 2014 22:03
Ah, I see.
The neutral can be 2.5mm also. Think about your incoming supply to your house. You probably have something like 25 square mm for each phase, and 25mm for neutral too.

petespieces 16th February 2014 22:08
Quote:
Originally Posted by Steve916 (Post 1579479)
Ah, I see.
The neutral can be 2.5mm also. Think about your incoming supply to your house. You probably have something like 25 square mm for each phase, and 25mm for neutral too.
Thanks Steve, that's what I thought, as I already have a spare supply to the kitchen it will save me a lot of time pulling another cable through the gaine, even if that's possible :}

Pete.

maintenanceman 17th February 2014 19:52
Quote:
Originally Posted by petespieces (Post 1579446)
I have an induction hob which I am connecting to two phases of my three phase supply.

The unit has five wires, two live, two neutral and one earth.

As per the installation diagram I will be connecting the two neutrals together at the unit.

The question I have is does the neutral from the fuse box need to be (approx) twice the size of one phase, for instance if the phases are 2.5mm should the neutral be 6mm.

I think the answer is no, 2.5 the same as the phases but need to be sure.

I have rewired the whole house and balanced the three phases so I'm quite OK handling the system (passed by EDF), just this one thing I need to know.



Thanks

Pete

Are you are in a farm or an industrial building/large or multi-floorhouse to have 3 phase supply.

Any link to the wiring diagram or a scan of it. Have you actually got 2 phases on the same floor or in the same room?

galaxyclass 17th February 2014 20:08
As above, 2.5mm neutral is ok, must be some size house you have there.

petespieces 17th February 2014 20:27
Not a large house, three beds, two reception etc.

Out here in the French countryside 3 phase is common, ERDF will change to single phase but apparently I would have to pay the cost of replacing the overhead cables from the village to our place, believe me that is not going to happen:}

basically the current setup has one phase to feed upstairs and the water tank heater, one phase for cooker and dishwasher and one phase for original hob and clothes washer, the sockets and lights etc are split by the various rooms depending on power usage.

The kitchen is the only room where all three phases will be in use, one for the cooker and two for the new hob.

The earth is provided through spikes driven into the ground, when we first moved into here there was only one ground earth point and the cable was actually broken (so NO earth), my wife kept getting a small shock whenever she used the washing machine:eek:

http://i56.photobucket.com/albums/g1...ps92d242c9.jpg

galaxyclass 17th February 2014 20:46
Quote:
Originally Posted by petespieces (Post 1580474)
Not a large house, three beds, two reception etc.

Out here in the French countryside 3 phase is common, ERDF will change to single phase but apparently I would have to pay the cost of replacing the overhead cables from the village to our place, believe me that is not going to happen:}

basically the current setup has one phase to feed upstairs and the water tank heater, one phase for cooker and dishwasher and one phase for original hob and clothes washer, the sockets and lights etc are split by the various rooms depending on power usage.

The kitchen is the only room where all three phases will be in use, one for the cooker and two for the new hob.

The earth is provided through spikes driven into the ground, when we first moved into here there was only one ground earth point and the cable was actually broken (so NO earth), my wife kept getting a small shock whenever she used the washing machine:eek:
Ahh, I never noticed your location, I contemplated mentioning about part p etc in my original reply but I see that is irrelevant in your case.
Enjoy.

maintenanceman 18th February 2014 19:09
Quote:
Originally Posted by galaxyclass (Post 1580502)
Ahh, I never noticed your location, I contemplated mentioning about part p etc in my original reply but I see that is irrelevant in your case.
Enjoy.
Neither did I clock the location! A few questions; How many amps per phase? Do local regs require warning signs when two phases are present? Is it a 'TT' type supply ie overhead cables on a post or underground cable?

Re the earth spike. Nasty!


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