Wiring oven and hob - pics & questions

[des606]

Hello,

I'm replacing an oven and found that the old oven and the hob were both plugged in to the same connector terminal which is wired to the large red oven isolator switch

The wire plugged in goes to the hob and the one on the left was the old oven and was wired in here along with the hob.Both sets of wires in together.
Is it ok to do the same in wiring the new oven ??

The hob is rated 6600watts and the new oven is 2.5-3kw

Cheers

 

[Diyisfun]

No..
The sparks will tell you what you need.
That wiring dosnt look heavy enough & should be using a choc block.

 

[riveralt]

You will need one of these cooker connection units.

http://www.alertelectrical.com/prod/1022/click-45a-easyfit-dual-appliance-outlet-plate

However, you will need to check the size of the cables is protected by a suitably sized MCB. It is difficult to see the size of the cables from your photograph.

Generally speaking the cable coming into the cooker switch then leading to the cooker connection unit will be 6mm protected by a 32 Amp MCB. If the ratings you have given are correct and the cable and MCB are these sizes then you should be okay.

You will need to be guided by what your cooker and hob Manufacturers instructions say - at least one of the cables to cooker or hob looks like it is 4mm which will probably be okay.

 

[michaelcouper]

id personally have 2 circuits! you could argue if its a short run, but just good practice

don't re use the connector block use one of these

http://www.screwfix.com/p/volex-cooker-outlet-plate/50538

 

[echoes]

id personally have 2 circuits! you could argue if its a short run, but just good practice

That would be a perfectly good solution but, since the OP already has a cooker circuit of ample size for probably 15kW of cooking appliances, unnecessary.

 

[michaelcouper]

id personally have 2 circuits! you could argue if its a short run, but just good practice

That would be a perfectly good solution but, since the OP already has a cooker circuit of ample size for probably 15kW of cooking appliances, unnecessary.

you wouldnt wire a 10kw shower in 6mm, just saying good practice

 

[EFLImpudence]

you wouldnt wire a 10kw shower in 6mm, just saying good practice

Not the same. No diversity on a shower.

 

[riveralt]

you wouldnt wire a 10kw shower in 6mm, just saying good practice

While that may be true it is an extemely poor comparison considering what the OP has. No account is taken for diversity in a water heater (shower) but there is for cookers/hobs.

So in the scenario outlined by the OP you would have him introduce a new circuit to the installation - one which, in most instances, will need to be chased in and run back to the main board and must be additionally protected by an RCD.

So a simple £10-20 job could shoot up ten fold in price - where is the good practice in that.

To me that sounds like an electrician ripping a customer off - maybe good practice for the spark but not for the customer.

 

[ericmark]

This raises an interesting point. The duel unit shown

does join two cables but it does not fuse the oven and often but not always the oven manufacturer stipulates a 13A supply. In fact often provided with 13A plug.

Duel boxes like these

are available and a cooker outlet and fused connection unit could be mounted along side each other.

But the duel connection unit is not designed for one flex out and one out into a second unit along side. We regularly connect two cables into 13A sockets so I would think there is nothing to stop one using a standard cooker outlet.

Although one can buy a standalone cooker with double oven with multi-elements and four induction areas which the manufacturer recommends a 32A supply. When the two are separated there is no interconnection between the units to stop overload. I assume there is with standalone but I am not stripping it down to find out.

So the question is should we connect two independent units to a 32A supply when so easy this limit could be exceeded?

The problem as I see it is should the fuse/MCB open then cooling fans will stop. However the same applies with any power cut however caused and one would hope a power cut will not damage equipment. But I have had equipment (although not domestic) fail due to cooling fan failure in turn due to power cut.

I think likely the only problem would be having to reset the trip or renew fuse. But not really sure if there would be a problem or not if cooling fans are lost.

As to if a oven really needs it's own fuse is also open to debate. I would say unless the supply cable was 4mm min then it would need a fused protection unit! So with consideration of that I would say yes they do need a fuse or a supply of no more than 20A.

 

[echoes]

So the question is should we connect two independent units to a 32A supply when so easy this limit could be exceeded?

If we accept that diversity means that it is unlikely that > 32A will be drawn for any significant period, then it seems sensible that a circuit designed to carry 32A is sufficient.

As to the overload protection for the appliance's cable/flex, then if we accept that the nature of the fixed load is such that it cannot overload that cable/flex, and that the connection is short enough, then overload protection may be omitted with no detriment to safety; not so different to an unfused spur on a ring final. Provided of course that fault protection is adequate.

I'm not trying to promote deliberately wriggling into a situation that has the bare minimum protection where it would be trivial to provide more, nor stridently arguing against separate circuits or individual fusing down, but if one found such a situation, or to do otherwise would be uneconomic or impractical, the required degree of safety would still be there.

And the manufacturers' instructions are often pitiful - there was one recently where it was clear cut & paste job requiring a 32A PLUG(top) or a 16A FCU or somesuch.

 

[EFLImpudence]

Whilst you may be correct in what you wrote-

the required degree of safety would still be there.

Probably not for the flex supplied by the manufacturer of an oven.

As the OP is unlikely to (definitely won't) have the equipment to carry out the necessary measurements nor the knowledge to calculate if this would be safe or not I feel it unwise on a forum to suggest that overload protection be omitted.

 

[echoes]

Whilst you may be correct in what you wrote-

the required degree of safety would still be there.

Probably not for the flex supplied by the manufacturer of an oven.

As the OP is unlikely to (definitely won't) have the equipment to carry out the necessary measurements nor the knowledge to calculate if this would be safe or not I feel it unwise on a forum to suggest that overload protection be omitted.

I agree.

 

[des606]

Hello, cheers for replies.

The Fuse board / CU is rated 63A. The fuse for the oven switch says MBN 132A

Switch below is about 5m from CU

Cable from this switch to terminal block below is 6mm ( flat wire measuring 6.8 x 13.1 accross outer sheath) and travels 1m from switch above.

Two other wires are also 6mm and as said were both doubled up in this terminal block, The hob is rated 6600watts and the new oven is 2.5-3kw


So can I go ahead and wire it up as was ? Or is there a need for dual connector unit as ericmark has shown in pic above??

Thanks

 

[sparkybird]

Allowing for diversity the oven and hob will draw just under 30A. Ideally the oven should have a separate circuit being over 2kW, but as it's an existing set up, I can't see how it would be wrong to install a cooker outlet for the hob and a fused connection unit for the oven - so a dual box would be required

You've been told all this information in previous posts - so don't just re connnect the exisitng lash up!

 

[riveralt]

Allowing for diversity the oven and hob will draw just under 30A. Ideally the oven should have a separate circuit being over 2kW, but as it's an existing set up, I can't see how it would be wrong to install a cooker outlet for the hob and a fused connection unit for the oven - so a dual box would be required

You've been told all this information in previous posts - so don't just re connnect the exisitng lash up!

Sparkbird not sure how, after diversity, you arrived at 30Amps - no evidence of a cooker socket switch - I get just under 20Amps.

9600/230 = 41.73Amps applying diversity 10 + (0.3*31.73)= 19.52Amps.

Also you have to be guided by the Manufacturers instructions whether you use a plug or hardwire oven - cooker will definitely need hard wire.