Single phase to Three phase connection


I recently sold my 30 amp electric aga and replaced it with a second hand Lacanche gas/electric cooker.

The aga connections have 5 wires ( 3 red, blue, and earth ) which I assume is 3 phase.

My Lacanche has 3 wires ( black, blue and earth ) and I assume the black is the live.

I have two questions : can I connect the Lacanche directly to the 3 phase wiring; and if so which red wire do I pick? When I put a mains tester on the red wires one is clearly live, whilst the one next to seems to have some current but glows dimly on the tester.

Thanks in advance.


three phase can be quite simply converted to single phase.

each phase to neutral will produce a voltage of 220v.

phase to phase will produce a voltage of 415volts.

so when making a three phase conversion you wire each socket to a neutral to get 220v

just as edf do from their supply cables, they tap of to each house from one of the phases to supply 220v

3 phase simple, each phase to neutral will produce 220v and each separate phase will supply a bank of heater elements.

for 3phase, using each red wire connect to terminals L1, L2, L3, neutral connects to neutral and earth wire connects to earth wire.

single phase is slightly different as each terminal L1,L2,L3 can be connected to a single phase power supply, but the total output of the elements has to be taken into account, ie for example each heating element may be 3Kw, so each element will draw a current of 14amps, this is fine on 3phase as the cable of 2.5mm can carry this current. But when connected to single phase you have three banks of 3Kw drawing 9Kw in total this means your supply cable will have to be rated at 45amps ie 10mm cable.

I would advise you to get an electrician in if you are not sure.

Thanks everyone. I'm clearly out of my depth here so I will take the unanimous advice and call the electrician.

Seek an electrician's advice.

It sounds like you have a three phase electricity supply, and yes, it is more common than one would think, especially in old houses, even today in France.

The house I'm in at the moment originally had a three-phase supply and I learnt to my cost the joy (sic) of plugging in a 230V 16a appliance into a 380-400V supplied socket - it was a flatbed scanner and literally, it went up in smoke. Also having had multiple shocks from testing circuits that I thought I'd cut off at various Bakelite trip switches, it was decided to refit the whole house and switch the supply over to single phase before I had one shock too many.

Are you sure you still have a tri-phase supply to your house? There should be ~230V between each live wire & neutral, and ~415V between any pair of live wires (LETHAL).

Presumably you just have electric ovens (gas hobs)? In which case you should get away with a 13A monophase supply (check your oven's rating).

If your house is now monophase, but you still have triphase sockets, then perhaps you can continue to use the old triphase socket. Being correct about it, you'd rip 'em all out and put in the appropriate monophase wiring & sockets.

I disagree Gerald. The Aga could be 3 phase. I bought an electric hob that could be connected either 415v or 220 and although I had 3 phase into the house I couldn’t find an electrician qualified to work on it so I connected it at 220v. I agree with your final advice though. Call an electrician.

You don't really want to take one phase from a three phase supply. Your house must be single phase so there must be a junction from the three phase into the house and the single phase that the house uses. You need to tap into that. I am not an electrician but your house does not run on three phase unless separate phases are balanced out in supplying different parts of the house... My advice - call in an electrician.