Builtin Electric oven install

[Jack W]

Hi all,
I’ve purchased samsung built-in single oven
Samsung nv7b57550tak.

I have dedicated ring directly from consumer unit, buried into mortar, on a 40a mcb with 6mm cable to connect the oven with.
As installed by my builder.

My questions are,
1)Is the mcb/cable setup acceptable (can 40A be used with 6mm cable)

2)what isolation switch do i need to add, in the kitchen? Does it have to be 40A or 45A because of the mcb size or can i have smaller one for example 20A.

(Spec says that oven has max 3950w power output and it seems to have 16A rating)

Appreciate an advice
Regards

 

[EFLImpudence]

I have dedicated ring directly from consumer unit, buried into mortar, on a 40a mcb with 6mm cable to connect the oven with.
As installed by my builder.

It won't be a ring. Ring is not another word for circuit.

My questions are,
1)Is the mcb/cable setup acceptable (can 40A be used with 6mm cable)

Yes.

2)what isolation switch do i need to add, in the kitchen? Does it have to be 40A or 45A because of the mcb size or can i have smaller one for example 20A.

A 45A one is normal for a cooker circuit and could include another socket on the switch.
You could reduce the MCB to a 20A or 16A one and have a 20A switch.

(Spec says that oven has max 3950w power output and it seems to have 16A rating)

Ok.

 

[Taylortwocities]

Who says you need a switch?

 

[EFLImpudence]

You might have if I had said it is not required by the regulations.

 

[Taylortwocities]

You might have if I had said it is not required by the regulations.

If only…

 

[Jack W]

It won't be a ring. Ring is not another word for circuit.

@EFLImpudence genuine question. would radial be better term to use here? Since it’s a straight to CU line?

Yes.

@EFLImpudence
My understanding is that if i have 4mm then 32A Mcb is max?

A 45A one is normal for a cooker circuit and could include another socket on the switch.
You could reduce the MCB to a 20A or 16A one and have a 20A switch.

Ok great. Thanks for confirmation.

 

[Taylortwocities]

would radial be better term to use here?

In domestic installations there are two types of final circuits: RING and RADIAL. If your circuit has one cable that goes from the consumer unit to the oven then that is a radial circuit.

My understanding is that if i have 4mm then 32A Mcb is max?

The MCB size is set relating to a number of criterea. the size of cable is one. Other factors such as installation method, environment, etc all have a bearing on the size of the protective device (MCB in this case). In ideal conditions, the maximum rated current for 4mm² twin and earth cable is 32amp, so it can never be more than 32amp, in some situations it may need to be less!

 

[EFLImpudence]

In ideal conditions, the maximum rated current for 4mm² twin and earth cable is 37amps.

 

[Taylortwocities]

@Jack W
I'm a little lost. You started this off by saying

I have dedicated ring directly from consumer unit, buried into mortar, on a 40a mcb with 6mm cable to connect the oven with.
As installed by my builder.

and now you are asking

My understanding is that if i have 4mm then 32A Mcb is max?

I just noticed that after I spent quite some time creating the following
What size cable are you talking about??

In ideal conditions, the maximum rated current for 4mm² twin and earth cable is 37amps.

When designing the circuit, the protective device chosen is the next lowest value available following the cable size calculations.
There are very very few MCBs available between 32 and 40amp (Square D and Dorman used to have a 35amp MCB, those are as rare a rocking horse poo, even if you had such a consumer unit).

So the usual (subject to calculations) MCB choice for 4mm² T&E is 32amp.

@Jack W all this is academic as your oven load will be way less than 32amp. Anyways, your builder's electrician is the person for all of this.

As this will be a new circuit you must ask your builder if his electrician is a member of one of the Competent Person Schemes (NICEIC, NAPIT, etc) and that this NEW CIRCUIT will be NOTIFIED in accordance with the requirements of Building Regulations.
Many builders have always done their own electrics and ignore the regs. The legalities of this changed 20 years ago, so make sure he is working for you within the legal requirements or you may have issues when/if you come to sell the property. That's if you forget the possible safety aspects!

 

[blup]

I have dedicated ring directly from consumer unit

We know what you mean

1)Is the mcb/cable setup acceptable (can 40A be used with 6mm cable)

yes

2)what isolation switch do i need to add, in the kitchen? Does it have to be 40A or 45A because of the mcb size or can i have smaller one for example 20A.

An isolator is not a fuse so 40amp

 

[EFLImpudence]

So the usual (subject to calculations) MCB choice for 4mm² T&E is 32amp.

Obviously - but that does not alter the fact that "the maximum rated current for 4mm² twin and earth cable is 37amps".

 

[Jack W]

@Jack W
I'm a little lost. You started this off by saying

and now you are asking


I just noticed that after I spent quite some time creating the following
What size cable are you talking about??

@Taylortwocities apologies. The 4 mm cable ,question was purely for learning purposes.
To confirm i have is 6mm cable.

When designing the circuit, the protective device chosen is the next lowest value available following the cable size calculations.
There are very very few MCBs available between 32 and 40amp (Square D and Dorman used to have a 35amp MCB, those are as rare a rocking horse poo, even if you had such a consumer unit).

So the usual (subject to calculations) MCB choice for 4mm² T&E is 32amp.

@Jack W all this is academic as your oven load will be way less than 32amp. Anyways, your builder's electrician is the person for all of this.

As this will be a new circuit you must ask your builder if his electrician is a member of one of the Competent Person Schemes (NICEIC, NAPIT, etc) and that this NEW CIRCUIT will be NOTIFIED in accordance with the requirements of Building Regulations.
Many builders have always done their own electrics and ignore the regs. The legalities of this changed 20 years ago, so make sure he is working for you within the legal requirements or you may have issues when/if you come to sell the property. That's if you forget the possible safety aspects!

Correct. I’ll def make sure of that. They have just done the initial cable layout and i am researching to make sure i understand what the builders are saying to me .
Cheers for your advice