16 amp oven wiring

Hello to you all and Merry Christmas first of all. I'm hoping the Christmas days after-celebrations boredom will provide me with some answers .

Before I start I appreciate everyone will advise me to call an electrician and have it done by them. This is what I might do unless it's a very simple solution but even if I have to call an electrician I need to know exactly what I need to get done. In my experience the more tradesmen I call the more options and opinions I get for the same problem. Also I have searched the forum for answers but could not find one.

So here is my question:
We are doing our house up refurbishing everything from top to bottom. This involved the whole house being rewired. It has been done by a qualified electrician all certified and legal.
When he wired our oven because of my stubbornness we used a grid switch for all the kitchen appliances. I did not want unsightly switches all around the kitchen wall. Long story short what I have installed from the consumer unit (sorry if I'm not using the right terms I am not a qualified electrician) 16A RCBO, then 6mm2 cable to the grid switch. The grid switch is 20A MK switch. From the grid switch 2.5 mm2 cable to a 13 amp regular socket. As far as I understood the electrician said he had to install the socket instead of an FCU so that in the future no one can connect a larger than 13 amps oven to the wiring. I was ok with it because that time we wanted to install a small 13 amp oven to it so I said it's fine. As it happens now we have changed our mind and found quite a few nice 16 amp ovens.

Question is what is the easiest safe and legal way to connect a 16 amp oven to this setup.
Any help or advice is much appreciated. Thanks

lazlow said:

We are doing our house up refurbishing everything from top to bottom. This involved the whole house being rewired. It has been done by a qualified electrician all certified and legal.
When he wired our oven because of my stubbornness we used a grid switch for all the kitchen appliances. I did not want unsightly switches all around the kitchen wall.

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You did not have to have any switches if you didn't want them.

Long story short what I have installed from the consumer unit (sorry if I'm not using the right terms I am not a qualified electrician) 16A RCBO, then 6mm2 cable to the grid switch. The grid switch is 20A MK switch. From the grid switch 2.5 mm2 cable to a 13 amp regular socket.

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That doesn't really make much sense.

As far as I understood the electrician said he had to install the socket instead of an FCU so that in the future no one can connect a larger than 13 amps oven to the wiring. I was ok with it because that time we wanted to install a small 13 amp oven to it so I said it's fine. As it happens now we have changed our mind and found quite a few nice 16 amp ovens.

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FCUs use the same fuses as plugs so that doesn't make any difference or sense either.

A usual cooker circuit is 32A MCB or RCBO - 6mm² cable - 45A cooker switch - cooker outlet .
To this you may connect virtually any domestic cooking appliance you may buy.
A 20A switch would be insufficient for a cooker circuit.

Conversely if you have a 16A circuit then 6mm² cable is way OTT.

Question is what is the easiest safe and legal way to connect a 16 amp oven to this setup.

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It's hard to say because of the uncertainty of what you actually have.

Thanks for taking time to reply. The reason for the OTT cable is that this is a VERY slow moving renovation project and when he did the first fix he wanted to make sure it will accommodate any scenario. Connecting a smaller than 32A or 45A unit to it should not make any harm. I do not need that amperage because of the setup of the kitchen I will not connect a cooker unit to it. The hob is a gas hob and the microwave is a plug in 13 amps regular one I only want to connect a single built in oven to this dedicated circuit. Worst case scenario I'll buy a plug in oven but I found I have far more choices if I go for a 16 A one. No higher than that. I understand that the usual cooker circuit is to accommodate much higher amperage but I do not need that. I also understand that what I have is everything but usual but this is what I have now.
What I need to know is that (I might be wrong but as far as I understand) if all the cables and RCBOs and grid switches are large enough to run a 16 A unit from them how can I connect one. In theory if a 16 A FCU existed I think I could use one. Am I right thinking that? I know there is no such thing but there might be a substitute.
Thank you again

Don't take this as the last word, but it sounds as though you need to change the socket for a cooker unit, then change the 2.5mm cable for 6mm, back to the grid switch, and then change that for a 45amp one.

If you mean that you have the cooker cable AND separate socket cable(s) both going to the grid switch with a separate cable going to the oven FCU/socket then, as above, change the FCU/socket to a cooker outlet and just connect the oven to it.

As it is protected by a 16A RCBO then the 2.5mm² cable will be fine.

I would say that if you wanted a cooker in the future then it will be a bit of a job to alter.
If you do not want a cooker in the future then running a 6mm² cable to a grid switch is unnecessary.

Thank you again EFLImpudence, this is exactly what I meant. From the 16A rcbo the only thing is fed is the oven nothing else. I think it's called a radial circuit, basically a dedicated cable running from the consumer unit to the one appliance and nothing else. Everything else is fed from a different circuit in the kitchen. I also understand that it is not future proof for a cooker and if we change the oven in the future for a more power hungry one we need to change (have it changed by a professional) the RCBO to a larger capacity one and also the cable going from the switch in the kitchen and the switch itself.
My final question is that if I change the 13 amp socket to a cooker outlet will it be legal? Since it involves as much work as changing a socket can I do that or it needs to be done by someone qualified. Also would you be kind enough to send me a link to an appropriate cooker outlet.
It's so good to have someone knowledgeable answer my questions. Thank you

lazlow said:

My final question is that if I change the 13 amp socket to a cooker outlet will it be legal?

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Yes.

Since it involves as much work as changing a socket can I do that or it needs to be done by someone qualified.

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Yes, you may do it if you can.

https://www.tlc-direct.co.uk/Products/AA45COP.html

Same thing but innards not visible.
http://www.toolstation.com/shop/p87053?table=no

You are an absolute star, thank you.
One last question. I understand that the circuit is protected by the RCBO but legally does it have to have a fuse somewhere along the line or is it ok if it does not have one?

The 6mm² and the 2.5mm² will both take the load, so there is no safety problem, but there is a problem complying with regulations, it states there should be a overload device where the current carrying capacity of the cable changes, where there is a cable of less than 3 meters that overload device can be at destination rather than origin as long are the cable is unlikely to be damaged.

So options
1) replace 2.5mm² with 6mm² and ensure the RBCO or MCB is no larger than weakest link, in this case 20A the switch. And fit a cooker connection unit.
2) Replace the grid switches with a consumer unit with MCB's for each item supplied.

Of course you could use a 13A FCU and cross your fingers and hope the fuse does not blow, in real terms it is unlikely to blow.
Also you can retain the 2.5mm² cable as long as the MCB/RCBO is 20A or less it is not going to cause a problem, however strictly to rule book it will not comply, however there are very few houses which comply to every regulation, the person filling in the paperwork has to decide if he is happy with what you have.

Regulations and what makes sense don't always go hand in hand.

ericmark said:

The 6mm² and the 2.5mm² will both take the load, so there is no safety problem, but there is a problem complying with regulations, it states there should be a overload device where the current carrying capacity of the cable changes, where there is a cable of less than 3 meters that overload device can be at destination rather than origin as long are the cable is unlikely to be damaged.

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The protection is at the supply end so that does not apply.

So options
1) replace 2.5mm² with 6mm² and ensure the RBCO or MCB is no larger than weakest link, in this case 20A the switch. And fit a cooker connection unit.

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It is a 16A RCBO so that is not necessary.

2) Replace the grid switches with a consumer unit with MCB's for each item supplied.

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Not necessary.

Of course you could use a 13A FCU and cross your fingers and hope the fuse does not blow, in real terms it is unlikely to blow.

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It has a 16A RCBO so that is not necessary.

Also you can retain the 2.5mm² cable as long as the MCB/RCBO is 20A or less it is not going to cause a problem, however strictly to rule book it will not comply, however there are very few houses which comply to every regulation, the person filling in the paperwork has to decide if he is happy with what you have.

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It is a 16A RCBO so that does not apply.

Regulations and what makes sense don't always go hand in hand.

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However, in this case they do.

All irrelevant.

lazlow said:

I understand that the circuit is protected by the RCBO but legally does it have to have a fuse somewhere along the line or is it ok if it does not have one?

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No fuse needed.

It is all fine and correct.

Thank you ericmark. I have assumed that what I have would be safe in theory I was more worried about complying with the regulations. With regards to changing the grid switches I'm only talking about his one switch all the others end in single 13A sockets and I don't need them to be changed since those are more than adequate for what I'm using them for. I am trying to retain the 2.5mm cable since the rcbo is a 16A one so the cable is protected as far as I understand it but as you said it might not comply with regulations fully. It's a shame that there is no simple solution to accommodate 16A European appliances (and strictly no more than 16A) there are so many of them on the market and as future-proof it might be it is sometimes an over the top solution to use 32 or 45A circuits to feed them as EFLImpudence said.

lazlow said:

I am trying to retain the 2.5mm cable since the rcbo is a 16A one so the cable is protected as far as I understand it but as you said it might not comply with regulations fully.

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It does comply; there is no doubt.

It's a shame that there is no simple solution to accommodate 16A European appliances (and strictly no more than 16A) there are so many of them on the market

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That's what they make in Europe because they have 16A circuits - as do you.