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I've wired a new induction hob in and looking for confirmation on cabling.

Instructions state you can wire it as follows:

A)3 x 4 mm² three-core L1 N G (bridge L1,L2,L3 inside on hob terminal if using 3 core cable) or B)5 x 2.5 mm² five-core L1 L2 L3 N G http://productdocs.smeg.it/st/PI964X/userManual/GB

It came pre wired with a 5 core cable. I have 3 terminals available on a 45A outlet.

I have connected L1 L2 L3 into L terminal on the 45A outlet. All appears to work well. Is this ok?

Alternatively I have a 3 core cable from old hob I could use but would prefer not to unscrew terminal box on the new hob. Not sure if there are bridge connectors for L1 L2 L3 which I would need with a 3 core cable, as it already has a pre wired 5 core cable.

Thanks

  • Where are you on this planet? – ThreePhaseEel Nov 17 '18 at 18:24
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    I am in the UK. – James M Nov 17 '18 at 18:58
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The L1, L2 and L3 terminals are separate for a specific reason: many countries in Europe (and some homes in the UK) have access to two-phase or 3-phase power, and 16A is a common breaker size on the continent. So in a larger home in Germany, for instance, this same hob would be connected to all three phases via a 3-phase, 16A breaker. In that case 5-wire cable would supply all three phases, neutral and ground, that would hook up in the obvious manner.

If your home has 3-phase, you too can split load like that, with appropriate breakers. It really doesn't matter which of the 3 is connected to which phase, as long as the wire size and breaker is correct.

Or in a 1-phase home, you can connect all 3 terminals to your one supply phase. You will need to use a 45, 48 or 50A breaker, of course.

  • Based on your response I believe I have correctly wired the new hob using a 1 phase 45A breaker therefore I believe I am correct to wire 3x 2.5mm wires to the single phase on a 45A breaker + a N + a G. I think this seems safer than re wiring the hob to a 3 core or adding an additional junction box. Therefore thank you for your confirmation unless anyone can correct me otherwise :) – James M Nov 18 '18 at 1:09
  • Keep in mind that your neutral (N) wire must be rated for 45 amps. A 2.5mm neutral will not suffice, and will burn up. It is very important to get neutral right, becuase it is not fused (no OCP/breaker). – Harper - Reinstate Monica Nov 18 '18 at 1:12
  • Interesting so why is the N provided prewired as 2.5mm wire ? – James M Nov 18 '18 at 1:15
  • @JamesM because a 2.5mm wire would be appropriate for a 3-phase connection, due to the way phases balance, diminishing flow on neutral. In your case, all your supply wires are on the same phase, so currents do not partially cancel each other out, they sum up! So the neutral must be able to return all the current for all 3 supply wires. – Harper - Reinstate Monica Nov 18 '18 at 1:19
  • Ok that sums up. So I should really re wire it using a 3 core 4mm and bridge the connections on the hob block to be safe . – James M Nov 18 '18 at 1:26

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