Induction hob.

Am about to install an induction hob and can either use single phase or three phase. Will use singles in conduit. Maximun load is 11Kw so either single phase in 6mm or 3phase using 2.5mm. If I use 3 phase I will get a normal cooker isolation switch to operate a 4 pole contactor, as am not too keen on an industrial looking switch by the hob!

Is there any overiding reason I should use one over the other?

Singles in conduit ?    AH !   So this is a commercial job  so probably better in 3Ph  . Not such a big load unbalancing the supply on SP.     Don't worry about the isolator just use whatever, its a commercial job  not your house . 

Hi

Not a commercial job is my kitchen at home.

Just use a rotary isolator.

But do you actually have a three-phase supply? And should you be DIYing this?

Yes I do and why should I not be doing it?

DIY is one thing .....working with 415V  is another .     It must be a very large house to have a 3ph feed .   As you say you will use a contactor if 3ph  then you only need a 6A  1way  switch as isolator. 

Not sure about the Forum advising a DIY  on 3Ph  . 

Bogart said:

Yes I do and why should I not be doing it?

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the fact youre asking suggests youre not competent to do it

best have a look through BS7671 to see if what you are suggesting complies

Evans Electric said:

DIY is one thing .....working with 415V  is another .     It must be a very large house to have a 3ph feed .   As you say you will use a contactor if 3ph  then you only need a 6A  1way  switch as isolator. 

Not sure about the Forum advising a DIY  on 3Ph  . 

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Was originally 3 seperate cottages and assumption made each on different phases.

Andy™ said:

the fact youre asking suggests youre not competent to do it

best have a look through BS7671 to see if what you are suggesting complies

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How can it not comply as there is no requirement to have any sort of local isolation for an appliance?

Bogart said:

Was originally 3 separate cottages and assumption made each on different phases.

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That's a big assumption to make ..... how many fuseboards do you have?

Bogart said:

Was originally 3 seperate cottages and assumption made each on different phases.

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never assume anything

Bogart said:

How can it not comply as there is no requirement to have any sort of local isolation for an appliance?

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then why are you asking if you already know if it complies or not?

So this 3ph supply you have is it split to three 1ph boards or have you a 3ph board?  

Are all three phases still live to the property? 

Customer of mine knocked 3 properties into 1

he assumed 3 phase

he even 'tested' and told me he got 415v

he basically stopped his 'testing' when he got the answer he wanted which was 415v

if he had carried on a bit more the two phases would have been apparent

2 properties on red phase

1 property on blue phase

......... took a while for the laughter to subside

Bogart said:

How can it not comply as there is no requirement to have any sort of local isolation for an appliance?

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Have the Regs been changed then ?    As far as I know  , all appliances require local isolation  .    

Murdoch said:

That's a big assumption to make ..... how many fuseboards do you have?

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3

Sharpend said:

So this 3ph supply you have is it split to three 1ph boards or have you a 3ph board?  

Are all three phases still live to the property? 

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3 seperate CU each on its own phase.

Andy™ said:

never assume anything

then why are you asking if you already know if it complies or not?

Hard work at times. I posted the question to run it past you folks, not to receive comments such as yours!

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Evans Electric said:

Have the Regs been changed then ?    As far as I know  , all appliances require local isolation  .    

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When were they changed then to require local isolation?

requirement for local point of isolation has been standard for many years, so long I can't remember when it came in to force. On top of that is a Building regs requirement that the isolator should be within 2 m of the appliance. 

So you have a single phase supply, so 3 phase wiring is not an option.

Bogart said:

3 separate fuseboards

Evans Electric said:

Have the Regs been changed then ?    As far as I know  , all appliances require local isolation  .    

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If you have separate phases in separate fuseboards you can't install anything 3 phase .............. its that simple

Local isolation is down to interpretation BUT good practice says each fixed appliance should have multiple pole isolation

Bogart said:

3

3 seperate CU each on its own phase.

When were they changed then to require local isolation?

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Me thinks bogart needs to call an electrician as their knowledge and understanding is flawed. 

Sharpend said:

Me thinks bogart needs to call an electrician as their knowledge and understanding is flawed. 

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me thinks that's very unlikely ...........

Bogart said:

When were they changed then to require local isolation?

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It has always been the case ,  as far as I know there is no argument to the contrary .  

It was an addendum to the Ten Commandments ....Moses got halfway down the mountain  humping the tablets of stone  with him and he was called back  to be told ..."Oh and by the way  all electric devices & machines shall have a local isolator attached within 2  cubits and always shall it be so "   

Murdoch said:

If you have separate phases in separate fuseboards you can't install anything 3 phase .............. its that simple

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If I'm reading this thread right the 3 single phase supplies / fuseboards are in different parts of the property making it difficult to provide any single point of isolation for the whole property let alone a three phase cooker

This really sounds like a wind up although I'm not sure you could make this up