4mm half of circuit on 32a mcb

[rustynails]

Hi all,
I did some work on a house the other day that had a circuit for sockets which was cabled in 4mm to half way in the house the split of it to 2.5 up to the sockets. It had a 32a breaker. I'm aware that you can have a 32a 4mm radial but that the whole circuit must be in 4mm. Using 2.5 on any part of the radial is not really acceptable am I right?

 

[Richard3009]

You can only have one double socket on a 2.5mm cable @32A it's no different to a spur, change the breaker to 20A if any more than one on 2.5mm radial

 

[GLENNSPARK]

are you sure this wasn`t a hybrid circuit here...?

 

[7029 dave]

You can only have one double socket on a 2.5mm cable @32A it's no different to a spur, change the breaker to 20A if any more than one on 2.5mm radial

2.5mm radial on 32amp breaker you sure?.

 

[GLENNSPARK]

2.5mm radial on 32amp breaker you sure?.

if the 2.5 is feeding one double outlet...then yep...its OK..

 

[7029 dave]

if the 2.5 is feeding one double outlet...then yep...its OK..

Well how over 3 decades things have changed, still you won't get me doing It.!!lol (that don't sit well with me)

 

[GLENNSPARK]

Well how over 3 decades things have changed, still you won't get me doing It.!!lol (that don't sit well with me)

well 3 decades ago those 3 way breakout/splitter boxes for BS1363s were often unfused....

 

[jay sean]

Its amazing how many people don't know that 2.5mm cant carry 32a unless it is one spur

 

[stevethesparks]

3 decades ago you was allowed to spur two twin socket outlets on a 2.5mm unless my memory has failed me.

 

[GLENNSPARK]

Its amazing how many people don't know that 2.5mm cant carry 32a unless it is one spur

no...caus the max draw would be 26A

and as we all know a 2.5/1.5 flat twin is good for 27 1/2 A method C...

 

[jay sean]

spur from a ring final cct

 

[Richard3009]

2.5mm radial on 32amp breaker you sure?.

As far as I know you can't buy a bigger fuse than 13a for a plug top x 2 = 26A perfectly controlled cable rating, so many sparks afraid of the limits, if you're under you're under

 

[rustynails]

are you sure this wasn`t a hybrid circuit here...?

it was a radial circuit cabled with 4mm for about 5/6 metres which I could see under the floor of the bungalow. It was then branched off with 2.5 to the sockets above. All on a 32a mcb.

 

[7029 dave]

As far as I know you can't buy a bigger fuse than 13a for a plug top x 2 = 26A perfectly controlled cable rating, so many sparks afraid of the limits, if you're under you're under

Never liked the idea of relying on forward fusing, like to design a circuit fit for purpose, with your principle you might as well back it with a 45amp breaker.!!

 

[GLENNSPARK]

it was a radial circuit cabled with 4mm for about 5/6 metres which I could see under the floor of the bungalow. It was then branched off with 2.5 to the sockets above. All on a 32a mcb.

well its the I N of the MCB that fails here...not the circuit...(assuming it tests OK that is).....

 

[rustynails]

are you sure this wasn`t a hybrid circuit here...?

I suppose it was kind of hybrid. It was a bungalow with one socket circuit which included all sockets and the kitchen... So the circuit does have a fair amount of 2.5 in it but also has quite a lot of 4mm as well. It's not burnt down so far, I told the customer they didn't seem that bothered.

 

[Knobhead]

You sure the 2.5’s are spurs? Sounds like a lollipop to me.

 

[rustynails]

You sure the 2.5’s are spurs? Sounds like a lollipop to me.

It might have been. I only had to work on one socket which had only one piece of 2.5 going to it from the piece of 4mm from the board. I since changed that one to 4mm I could see under the floor another junction box with another spur in 2.5 going up. Just never seen this before. Wasn't able to check any of the other sockets.

 

[Richard Burns]

From that description it may possibly be a lollipop radial, i.e. each socket is a single radial out from the 4mm, but I think you would have seen that.

 

[Knobhead]

Quite handy for largish buildings. Run a 4/6mm from the CU to where the ring is needed. Great for confusing the youngsters.

I think we used 6mm when we got around to rewiring the brothers 4 floor + basement house. Both of us electricians, it only took three years to finish.