Wiring Double oven/ induction hob

julie8314dave

Hi
We have just brought a Zanussi double oven and zanussi induction hob.

The oven requires 30 amp fuse as is
this is already in place.

The induction hob is 7 .4 kw and we are not sure what mm cable is needed to wire it in, also what ampage it needs.

We are not doing this ourselves but have had (we think) a really dodgy bloke in that wants us to pass over a large sum of money and we just wanted some advice before we go ahead and look for some one else.

Thanks.

ryder72

Your hob will also need a 30A dedicated supply

Ectophile

7400W/230V = 32A. So it should be on a 32A supply as well. So that would normally be 6mm, maybe 10mm if run in insulation.

julie8314dave

Ectophile wrote: »

7400W/230V = 32A. So it should be on a 32A supply as well. So that would normally be 6mm, maybe 10mm if run in insulation.

Would surface trunking be ok ?

Thanks

f1r31c3r

julie8314dave wrote: »

Hi
We have just brought a Zanussi double oven and zanussi induction hob.

The oven requires 30 amp fuse as is
this is already in place.

The induction hob is 7 .4 kw and we are not sure what mm cable is needed to wire it in, also what amperage it needs.

We are not doing this ourselves but have had (we think) a really dodgy bloke in that wants us to pass over a large sum of money and we just wanted some advice before we go ahead and look for some one else.

Thanks.

Power = Volts x Amps

So

Current (I) = Power / Voltage

Although this is simple, resistance has to be taken into consideration and this is where cable specs can make things complicated.

Electricians rule of thumb, a single NON ring main run of 2.5mm2 twin and earth must be placed on a 16amp RCBO. Although new regs in January of this year with Amendment 3 states MCB's are still allowed it is recommended for future regulations to only use RCBO's throughout the consumer unit instead. A 32Amp ring works because it is in a ring, current can flow either way around the ring, you effectively have two cables in a parallel circuit which can handle a 32Amp and is called a ring main.

So if you want 32A on a single radial(one wire that does NOT return to make a ring in the consumer unit) type circuit then ideally you should use 6mm2 if cable is to be cliped to the wall open and not concealed. Also new regs state you have to have an isolator(dedicated switch) above the work top to isolate the cooker. Also if the cable is to be placed in trunking or within a wall then you probably be better using 10mm2 especially if it is a long run of cable. Wire has a resistance of its own, it is not a superconductor so the cable can get hot especially with the higher the current passed through it. If the cable is trunk or placed in a wall or even under loft insulation then the cable can rise in temperature and have difficulty cooling therefore melting and causing a fire. As a cable gets hot, it's resistance increases and therefore creates even more heat as it begins to fail and becomes more a heating element.
So we have an open air spec for using a size of cable and a concealed rating, trunking affects the cables cooling so you are better to use 10mm2

So 7400W/240V is 30.8Amps

You will need two feeds and two RCBO's in you consumer unit with two isolation switches above your counter top leading to a junction box bellow the counter top connecting to one your hob and another for your oven.

You could run one 65Amp RCBO but you have to use 16mm2 twin and earth and trust me that cable is seriously hard to work with. It is also very expensive.

It is amazing how many people install a shower in concealed installation to a 12KW++ shower using 6mm2 or 10mm2 cable even through loft insulation. God forbid they use 2,5 or 6mm2 for this and it has been known.

Don't forget to run residual current test. Push the damn test button lol. I don't expect a DIY person to have a megger in their toolkit but call in a friend to test your circuit after you done.

chappers

f1r31c3r wrote: »

Power = Volts x Amps

So

Current (I) = Power / Voltage

Although this is simple, resistance has to be taken into consideration and this is where cable specs can make things complicated.

Electricians rule of thumb, a single NON ring main run of 2.5mm2 twin and earth must be placed on a 16amp RCBO. Although new regs in January of this year with Amendment 3 states MCB's are still allowed it is recommended for future regulations to only use RCBO's throughout the consumer unit instead. A 32Amp ring works because it is in a ring, current can flow either way around the ring, you effectively have two cables in a parallel circuit which can handle a 32Amp and is called a ring main.

So if you want 32A on a single radial(one wire that does NOT return to make a ring in the consumer unit) type circuit then ideally you should use 6mm2 if cable is to be cliped to the wall open and not concealed. Also new regs state you have to have an isolator(dedicated switch) above the work top to isolate the cooker. Also if the cable is to be placed in trunking or within a wall then you probably be better using 10mm2 especially if it is a long run of cable. Wire has a resistance of its own, it is not a superconductor so the cable can get hot especially with the higher the current passed through it. If the cable is trunk or placed in a wall or even under loft insulation then the cable can rise in temperature and have difficulty cooling therefore melting and causing a fire. As a cable gets hot, it's resistance increases and therefore creates even more heat as it begins to fail and becomes more a heating element.
So we have an open air spec for using a size of cable and a concealed rating, trunking affects the cables cooling so you are better to use 10mm2

So 7400W/240V is 30.8Amps
Current is always quoted at the lower range of the supply voltage so in this case 7400/230v=32.17amps and also you haven't taken account of any diversity

You will need two feeds and two RCBO's in you consumer unit with two isolation switches above your counter top leading to a junction box bellow the counter top connecting to one your hob and another for your oven.

You could run one 65Amp RCBO but you have to use 16mm2 twin and earth and trust me that cable is seriously hard to work with. It is also very expensive.

It is amazing how many people install a shower in concealed installation to a 12KW++ shower using 6mm2 or 10mm2 cable even through loft insulation. God forbid they use 2,5 or 6mm2 for this and it has been known.

Don't forget to run residual current test. Push the damn test button lol. I don't expect a DIY person to have a megger in their toolkit but call in a friend to test your circuit after you done.

What's the rating for the oven, a double oven would run somewhere in the 4-5kW range so a total load of say 12.4kW including the hob

But you don't simply take the load against the voltage as 12400/230=53.9amps.

You have to allow for diversity, which allows for the fact that the appliances won't be running at full tilt at anyone time and for cooking appliances that equates to the first 10amps plus 30% of the remaining plus 5amps if your cooker switch has an outlet.

So in this case 10amps plus 30% of the remaining 43.9amps(13.17amps) equals 23.17amps, then maybe the additional 5 amps so a possible total of 28.17amps.
Under most installations a single 6mm cable will be fine protected with a 32amp mcb.
Surface trunking would be OK
It's possible you might get the odd trip on say something like Christmas day or the like when you have everything running at once for extended periods.

julie8314dave

chappers wrote: »

What's the rating for the oven, a double oven would run somewhere in the 4-5kW range so a total load of say 12.4kW including the hob

But you don't simply take the load against the voltage as 12400/230=53.9amps.

You have to allow for diversity, which allows for the fact that the appliances won't be running at full tilt at anyone time and for cooking appliances that equates to the first 10amps plus 30% of the remaining plus 5amps if your cooker switch has an outlet.

So in this case 10amps plus 30% of the remaining 43.9amps(13.17amps) equals 23.17amps, then maybe the additional 5 amps so a possible total of 28.17amps.
Under most installations a single 6mm cable will be fine protected with a 32amp mcb.
Surface trunking would be OK
It's possible you might get the odd trip on say something like Christmas day or the like when you have everything running at once for extended periods.

Energy consumption
0.79 kWh for Electric Double Oven.

Induction 7.4 kW hob

Am i right in thinking i can put in a
Dual Cooker / Appliance Outlet Plate/plug i had someone say this would be fine as 6mm cable will take up to 15kw

Risteard

One word:

Diversity.

thescouselander

You could just use 6mm cable with 32 amp breaker for both the hob and oven - thats whats been used up and down the country since the beginning of time with no issues.

Alternatively you could run the hob on the existing cooker circuit and run a 20A spur with 2.5mm or 4mm cable (depending on routing etc) for the oven.

chappers

julie8314dave wrote: »

Energy consumption
0.79 kWh for Electric Double Oven.

Induction 7.4 kW hob

Am i right in thinking i can put in a
Dual Cooker / Appliance Outlet Plate/plug i had someone say this would be fine as 6mm cable will take up to 15kw

Really need the absolute rating of the oven, Model ?

I suspect that yes you will be OK with a dual outlet 15kW is over the top for a 6mm cable, the maximum capacity is around 45amps or just over 10kw and that is in an ideal situation in free air. depending on the installation and what the cable runs through on it's route this could be de-rated by up to 50%