2.5mm Ring wired off a 4mm Radial | Page 2 | on ElectriciansForums

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Chris

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Hi,
I have been testing a domestic property today and when i started to look into the kitchen sockets there is a 4mm radial from the DB going to one socket on one side, the 4mm radial is cut into and JB'd and 2x2.5mm cables run out forming a ring for the other 4 sockets...

Does this obey regs? I know you can run 2.5mm spurs off 4mm but havent seen or heard of this before?
 
Hi,
I have been testing a domestic property today and when i started to look into the kitchen sockets there is a 4mm radial from the DB going to one socket on one side, the 4mm radial is cut into and JB'd and 2x2.5mm cables run out forming a ring for the other 4 sockets...

Does this obey regs? I know you can run 2.5mm spurs off 4mm but havent seen or heard of this before?
One would think if you do what you suggest you would need to reduce the size of the OCPD at or near the change of cable size, wouldn't you????
 
One would think if you do what you suggest you would need to reduce the size of the OCPD at or near the change of cable size, wouldn't you????

Are you talking about a 2.5mm spur off a 4mm radial? It is compliant if you only have 1 socket outlet as they are rated 13a so if any higher load was placed on the cable the socket would fail.
 
Is it simply a case of "get some power in there, 4mm will do it...then get some sockets off that, 2.5 rfc will do?"
I ask this as a complete novice, but I can see some logic in such a lollipop arrangement...
However, I have no clear idea what circuit protection would be appropriate, given I have no idea what the final load might be...
maybe one level at the CU, and another at the junction with the rfc?
Or maybe just assume that the final load will never be enough to cause a fire?
Hmmm...
think I need to get an electrician in!
 
Whether a 4mm radial, or a 2.5 rfc from source, it would still be generally a 32A OCPD.
I just think it over complicates matters and makes it more confusing for the next spark to work on the circuit.
It shouldn't be done, but its compliant, so hey.
 
If it's compliant, why shouldn't it be done? Again, I ask as a novice.

It's a bit like laying a watering hose system in a garden. Send the big hose in, then split it into a ring through smaller pipes. Obviously the water won't kill you!
 
If it's compliant, why shouldn't it be done? Again, I ask as a novice.

It's a bit like laying a watering hose system in a garden. Send the big hose in, then split it into a ring through smaller pipes. Obviously the water won't kill you!

Technically nothing wrong with it. No different than your meter tails or other sub distribution.
However it may cause problems or confusion for the next guy who comes to test or make alterations.
 
Nines times out of ten its generally an old perhaps cooker circuit that has been adapted as a ring circuit.
Cant imagine anyone would deliberately install a hybrid (or lollipop) circuit.
If only the kitchen as per OP may have just carried on as a 4mm radial!
 
In domestic it tends to be done when only the kitchen is refurbed, usually repurposing the 6mm^ feed that was formerly used for the electric cooker circuit , save ripping the rest of the house apart.

In Industrial/commercial it may be done for volt drop/max Zs reasons using a larger feeder cable and to save what may be just a 'local' RFC from needing two long runs back to a DB.

It is compliant btw, and in the OP it is more likely a 6mm^ as said above
 

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