4mm radials

[loz2754]

I have to agree with @westward10 on this one.

The use of conventional final circuits implies that we accept all of the conditions for conventional final circuits. This includes the fact that diversity cannot be applied in this case, because diversity has already been factored in.
So the design current for each of the 2 radials has to be taken as 32 amps.

I understand and perhaps even agree with @pc1966 and others, that in practical terms it seems likely that there will not be a problem with overloading of the cables. But this doesn't change the fact that the circuits have not been properly designed to take into account the installation conditions.

I would be getting the electrician who installed it to correct his mistake at his own expense.

 

[Mike Johnson]

What mistakes has the original electrician made?

 

[loz2754]

think P said cables in stud were loose.i.e. insulation moved away from cables.

The 2 options for cables in a stud wall are:
103 in insulation with the cable not touching the wall.
102 in insulation with the cable touching the wall.

So if the cable was clipped in such a way that it is in contact along its length with the wall, the current carrying capacity would be 27 amps for a 4mm² cable.

 

[loz2754]

What mistakes has the original electrician made?

He has not allowed for derating the circuit because of thermal insulation.

 

[telectrix]

nowhere does OP say that the cable is in contact with insulation . i quote.

All the cables from the consumer unit descend loosely through a void in an otherwise insulated stud wall.

 

[pc1966]

I wonder if the OP can post some photos of the cable run to take a look? Also a detailed photo of the Wylex board to see what it is using?

Certainly changing to a 25A RCBO would deal with most installation methods for 4mm, the question is if one can be sourced for the board. I'm willing to bet that @westward10 will know chapter & verse of what can be fitted!

 

[7029 dave]

This is the trouble with radial circuits for socket outlets, I like the flexibility of RFC any day, especially in kitchen.

 

[Deleted account]

4 mm radials are the future and are absolutely fine.

we are the only country in the world who do rings. What does that tell you.

in my opinion rings are potentially dangerous and I don’t do them any more. Radials every time for me.

personally I would have liked to put the oven on a separate circuit, but each electrician to there own.

ask 5 electricians what they think of an installation design you will get five different answers.

 

[pc1966]

we are the only country in the world who do rings. What does that tell you.

That we used fused plugs and no one else does?

 

[7029 dave]

4 mm radials are the future and are absolutely fine.

we are the only country in the world who do rings. What does that tell you.

in my opinion rings are potentially dangerous and I don’t do them any more. Radials every time for me.

personally I would have liked to put the oven on a separate circuit, but each electrician to there own.

ask 5 electricians what they think of an installation design you will get five different answers.

I agree with you statement about each to their own, talking about other countries, the radials are multiple just like we had before RFC, talking in general for instance 20A radial unlimited socket outlets is IMO ridiculous. I would never create such a circuit.
I remember at college in one of the craft principles book on craft theory (J F Whitefield) socket radials were limited cant remember the amounts between 15A and 30A circuits.