Cable Size Advice

[BES SPARK]

Hi all, we first fixed a extension a couple of weeks ago and they were going to have a 10.5 kw convection oven so we ran a 10mm cable to it... we have gone back to second fix today but they are not having that oven anymore instead they are now having a 4.6kw oven so 20A, now the guy I was working with is saying that the cable is now too big and needs replacing, I might be wrong but am I right in thinking that we can just down rate the MCP and keep the 10mm cable? or does the cable need to be smaller?
thanks guys.

 

[Bobster]

Keep the cable in place.

Job done.

 

[Pete999]

You are the Electrician mate, whats your take?

 

[Andy78]

Tell the guy who told you to swap the cable to stick to plumbing.

 

[shanky887614]

the mcb is to protect the cable not the device, why do you think fan manufacturer's say it needs to be fed from a fused spur

 

[BES SPARK]

Thanks guys thought I was right when you got another electrician saying something else you start to doubt yourself a little

 

[LeeH]

I bet you 10p he's not a spark

 

[Simonslimline]

What were the other sparks reasons for wanting to downsize the cable?

 

[Silly Sausage]

In situations like this, always get them to justify/prove their case.
They'll soon crawl away!

 

[Andy78]

What was the reason for the 10mm cable in the first place ?

 

[telectrix]

What was the reason for the 10mm cable in the first place ?

shower in the kitchen, obviously. :ack2:

 

[BES SPARK]

well he wanted to down grade it because this new oven was only going to pull 20A and we have10mm cable that's why I was having the argument that we can keep the cable and down rate to a 20A MCB

 

[Leesparkykent]

This can't be an electrician asking this surely?

 

[LeeH]

This can't be an electrician asking this surely?

Nope....

 

[Pete999]

This can't be an electrician asking this surely?

It is Leesparkykent

 

[Leesparkykent]

No disrespect but this is even basic for a DIY question.

 

[Leesparkykent]

It is Leesparkykent

Blimey.

 

[davesparks]

If using a cable that is too big was a problem then that 10mm would have been no good for the original appliance !

 

[BES SPARK]

the cable would have been too big for original appliance as you are probably allowing for diversity, if your allowing for diversity yes the calculation only comes to 20.68A or 25.68A If theres a socket, but personally I don't like using diversity for cookers as for peace of mind at Christmas when they are probably using all hobs and oven so I go to manufacturers spec which is 10.5kw so 45.6A and for the reference method how we installed it 10mm takes 45A, little bit more expensive yes but nice to know cable size takes total demand, im a young spark finished last year and as for me asking the question this was because another spark who is older than me so more experienced was arguing that cable was too big, where I said we can just change breaker so I guess him saying that baffled me a bit don't know why so sorry for stupid question

 

[ferg]

Rip out the cable and put a smaller one in.

Don't listen to any of the idiots above who think that you can chop and change the standard circuits in the OSG as they fancy.

How on earth do you think a 10mm cable will manage to carry 20A?