cooker circuit

[thomaswht2]

hi there,
just moved into a new house that has a 4 way cu with rcd protection, problem is i need to install a cooker circuit as the old one is fed seperately via a 40amp rewireable outside of the cu. I dont want to change the existing board as it is sufficient and is to 16th edition, i just want to add a cooker circuit, but I have no spare ways. i dont know the rating of the cooker as it was second hand, but it has a 10mm cable attached from the previous owner. my questions are, can i feed the cooker unit seperately via a small 2 way cu next to the board or cooker? would this need rcd proection, and what rating breaker would be best to use to feed the small board?
the current board is rcd protected and feeds 2x ring main 32A breaker and 2 x lighting circuits 6 A. can I remove one of these and put it one the smaller 2 way cu, therfore freeing up the way for the feed to the smaller cu?
thanks for any advice
A

 

[mikhailfaradayski]

there should be a power rating on a label on the cooker somwhere. Either near the electrical connection on the back, or on a small label just inside the oven door.
If not, do you know the make/model of the cooker?
A bit of googling will give the power rating if you know the model.

It would be easier to comment on fuses/cables if we knew this.

So you have a RCD'd 4 way MCB board, plus another single way rewireable board, not RCD'd, supplying the cooker?

 

[peterduckett]

It might need RCD protection depending on how deep the cables are buried in walls ect i think you need RCD protection if the cable depth is less than 50mm any where on its journey.

To work out the what size MCB you will need you can do a little formula:
Watts / Voltage = Amps
Though you need to know the total wattage from the oven and then you will need to apply any de-rating factors to the cable for running in insulation or next to other cables

As for the fuse why don't you buy a little Two way broad and replace the existing external seems most logical

 

[ColJack]

you need a bigger fuse board.. ..

you feed the second board by splitting the tails with a henley block.
it's best to install a larger CU than you need as no doubt at some point you'll need another circuit for something.. ( shower, immersion heater etc.. )

if you already have a 40A feed, then why do you need a new one?

this is not a job for a DIYer as the circuits will need testing and as you don't mention where you are, it falls under Part-P of the building regulations if you are in england and wales, or under the scotish building regs if you're north of the border... both of which require you to inform the LABC ( or scotish equivalent ) before you start ( and obtain a warrant in scotland ) ..

 

[thomaswht2]

I already have a henley block feeding the cu and the cooker seperately, as i said the current cooker circuit is next to the cu by way of a 40A rewireable fuse. I wanted to rewire the circuit as the cable is old and get rid of the rewireable fuse. as i said i would like to avoid fitting a new board as we dont intend on adding anything else.
A

 

[bongos]

I already have a henley block feeding the cu and the cooker seperately, as i said the current cooker circuit is next to the cu by way of a 40A rewireable fuse. I wanted to rewire the circuit as the cable is old and get rid of the rewireable fuse. as i said i would like to avoid fitting a new board as we dont intend on adding anything else.
A

Once you know the power of the new cooker then you can work out what protective devices and cable to use.

Bear in mind this work is notifiable to your LABC (in England & Wales). You need to speak to them before starting work.

More info here.

 

[mikhailfaradayski]

if you are re-wiring the circuit with anything other than like-for-like then i think the new cable will require some form of additional protection (e.g. RCD)

What makes you think the cable needs replacing?

Have you found the power of the cooker?

How do you intend to test the new circuit?

How do you intend to deal with notification of this job?