Do MCB's need to be in size order in the CU?

[Bonce]

Thinking of having a new cooker (range sort of thhing) and may want to go for duel fuel. At present my cooker is gas only so understand this would mean running a new cable 6mm2 (most likely from the CU) to the cooker.

I have one spare way in my CU (at the end after the 6A mcb for my downstairs lights. As the cooker circuit would be a high value MCB (40A) can it just be 'plugged' in that spare way or should they all be moved along.

Just tryng to judge if it's worth it in terms of getting a spark in if its too much work then I think I will do more digging and perhaps just go for a gas only range (though I think dual fuel is better for making cakes - apparently - so the missus says!!).

Thanks in advance

 

[Taylortwocities]

In the "good old days" of CUs with a lower current-carrying capacity the convention was to have the big ones next to the main switch, with the values getting smaller as you get further along.

But more up-to-date CUs have substantial distributed main feeds and chunky busbars. So, assuming you have a newish board, you should be OK.

I say "assuming" because your new circuit will need to be
1. notified to the local authority and
2. be RCD protected

 

[EFLImpudence]

As above.

32A will be adequate for the cooker circuit.
Are you sure there isn't a cooker circuit there already?

 

[JohnW2]

A photo of your existing CU might be helpful.

Kind Regards, John

 

[Bonce]

Hi TTC, I think it is an 'up to date board' certainly 17th edition.

It has 2 rcd's split bus bar etc so I think I am goodd. Just when thinking about it I had always noticed that they were placed in size order across the split i.e. shower (40A) then sockets (16A) the lights (6A0 from memory and same on the other side but without the shower.

I wont be doing myself but if it was going to require the whole board to be buggered about I don't think I wwould bother.

 

[flyingsparks]

I always fit mcbs in size order largest to smallest from main switch on a new install or cu change. It won't matter though to have the 32A one on the end if it's too much effort to swap things around.

 

[JohnW2]

I wont be doing myself but if it was going to require the whole board to be b*****r about I don't think I wwould bother.

If it's a fairly modern CU, then it probably would not take much effort to 'shift everything along' if you really wanted that done (there would very probably be enough slack in the wires) - but, as others have said, it isn't really necessary.

Kind Regards, John

 

[JohnW2]

In the "good old days" of CUs with a lower current-carrying capacity the convention was to have the big ones next to the main switch, with the values getting smaller as you get further along. ... But more up-to-date CUs have substantial distributed main feeds and chunky busbars. So, assuming you have a newish board, you should be OK.

All agreed - except that, ironically, the Wylex Standard CUs which were so common in the good-old-days when that convention was strictly adhered to probably had busbars the chunkiness of which would probably put those in a modern CU to shame!

Kind Regards, John

 

[ban-all-sheds]

And for contrary advice, IIRC I've seen it recommended to mix them up, so that you don't end up with high-load ones adjacent, and thus avoid mutual heating effects.

 

[JohnW2]

And for contrary advice, IIRC I've seen it recommended to mix them up, so that you don't end up with high-load ones adjacent, and thus avoid mutual heating effects.

Indeed, and that makes good sense. ... and, as I've pointed out before, at least Wylex seem to say that some sort of 'de-rating' is required if adjacent MCBs are run at currents approaching their rating, which presumably becomes more of an issue the higher that rating.

Kind Regards, John

 

[stevey1983]

Mix them up as said above or put them in order, doesnt matter in a house which doesn't draw much. If you were to run close to the ratings of mcb then you should mix them up

 

[333rocky333]

Just because you have 1 spare way does not always mean theres a bus bar prong to supply it.

If it has been reconfigured and cut by the installer you may require a new bus bar